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A Phenomenology of Meditation-Induced Light Experiences: Traditional Buddhist and Neurobiological Perspectives

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Abstract

The scientific study of Buddhist meditation has proceeded without much attention to Buddhist literature that details the range of psychological and physiological changes thought to occur during meditation. This paper presents reports of various meditation-induced light experiences derived from American Buddhist practitioners. The reports of light experiences are classified into two main types: discrete lightforms and patterned or diffuse lights. Similar phenomena are well documented in traditional Buddhist texts but are virtually undocumented in scientific literature on meditation. Within Buddhist traditions, these phenomena are attributed a range of interpretations. However, because it is insufficient and problematic to rely solely upon the textual sources as a means of investigating the cause or significance of these phenomena, these qualitative reports are also considered in relation to scientific research on light-related experiences in the context of sensory deprivation, perceptual isolation, and clinical disorders of the visual system. The typologies derived from these studies also rely upon reports of experiences and closely match typologies derived from the qualitative study of contemporary practitioners and typologies found in Buddhist literary traditions. Taken together, these studies also provide evidence in support of the hypothesis that certain meditative practices - especially those that deliberately decrease social, kinesthetic, and sensory stimulation and emphasize focused attention - have perceptual and cognitive outcomes similar to sensory deprivation. Given that sensory deprivation increases neuroplasticity, meditation may also have an enhanced neuroplastic potential beyond ordinary experience-dependent changes. By providing and contextualizing these reports of meditation-induced light experiences, scientists, clinicians, and meditators gain a more informed view of the range of experiences that can be elicited by contemplative practices.
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ORIGINAL RESEARCH ARTICLE
published: 03 January 2014
doi: 10.3389/fpsyg.2013.00973
A phenomenology of meditation-induced light experiences:
traditional Buddhist and neurobiological perspectives
Jared R. Lindahl1, ChristopherT. Kaplan 2, Evan M. Winget 2and Willoughby B. Britton2*
1Department of Religious Studies, Warren Wilson College, Asheville, NC, USA
2Department of Psychiatry and Human Behavior, Warren Alpert Medical School at Brown University, Providence, RI, USA
Edited by:
Zoran Josipovic, NewYork University,
USA
Reviewed by:
Zoran Josipovic, NewYork University,
USA
Donna Marie Lloyd, University of
Leeds, UK
*Correspondence:
Willoughby B. Britton, Department of
Psychiatry and Human Behavior,
Warren Alpert Medical School at
Brown University, Biomed 232,
171 Meeting Street, Providence,
RI 02912, USA
e-mail: willoughby_britton@brown.edu
The scientific study of Buddhist meditation has proceeded without much attention to
Buddhist literature that details the range of psychological and physiological changes thought
to occur during meditation. This paper presents reports of various meditation-induced light
experiences derived from American Buddhist practitioners.The reports of light experiences
are classified into two main types: discrete lightforms and patterned or diffuse lights.
Similar phenomena are well documented in traditional Buddhist texts but are virtually
undocumented in scientific literature on meditation. Within Buddhist traditions, these
phenomena are attributed a range of interpretations. However, because it is insufficient and
problematic to rely solely upon the textual sources as a means of investigating the cause or
significance of these phenomena, these qualitative reports are also considered in relation
to scientific research on light-related experiences in the context of sensory deprivation,
perceptual isolation, and clinical disorders of the visual system. The typologies derived
from these studies also rely upon reports of experiences and closely match typologies
derived from the qualitative study of contemporary practitioners and typologies found in
Buddhist literary traditions. Taken together, these studies also provide evidence in support
of the hypothesis that certain meditative practices – especially those that deliberately
decrease social, kinesthetic, and sensory stimulation and emphasize focused attention –
have perceptual and cognitive outcomes similar to sensory deprivation. Given that sensory
deprivation increases neuroplasticity, meditation may also have an enhanced neuroplastic
potential beyond ordinary experience-dependent changes. By providing and contextualizing
these reports of meditation-induced light experiences, scientists, clinicians, and meditators
gain a more informed view of the range of experiences that can be elicited by contemplative
practices.
Keywords: meditation, buddhism, concentration, light, hallucinations, neuroplasticity
INTRODUCTION
Meditation practices that were previously taught within the
context of religious traditions are now increasingly being prac-
ticed in non-traditional and secular contexts. Since the rise of
mindfulness-based interventions (MBIs) such as mindfulness-
based stress reduction (MBSR), “meditation” is also being pre-
scribed in a clinical context as treatment for a variety of psycho-
logical and physiological ailments (e.g., Kabat-Zinn et al., 1985;
Kristeller and Hallett, 1999;Goldin and Gross, 2010). Current
research has focused almost exclusively on the beneficial effects
of meditation, such that the scientific community has not thor-
oughly investigated the full range of experiences that can arise as
a result of meditative practices. It is important to recognize that
the trajectories of practice outlined in the traditional literature of
contemplative traditions include a wide range of experiences that
fall outside the commonly reported positive health effects, includ-
ing unusual affective, perceptual,and somatic changes (Kornfield,
1979). Especially as practitioners move into more advanced stages
of practice, a number of experiences may arise that can be bewil-
dering to those who are not expecting them and who are not
prepared to manage them.
Part of the reason for this lacuna in the scientific under-
standing of meditation derives from the fact that scientific
research on meditation, especially at the clinical level, has
become increasingly divorced from the study of the literature
and practitioners from contemplative traditions. Consulting tra-
ditional sources is an essential and important step in furthering
the scientific understanding of meditation. The literature on
Buddhist meditation not only clearly delineates the stages of
practice that comprise contemplative disciplines, it also details a
range of psychological and physiological experiences that might
be expected from undertaking such practices (e.g., Nanamoli,
1997;Buddhaghosa, 1999;Dalai Lama, 2001;Namgyal, 2006;
Wallace, 2011). Without adequate knowledge of the range of
possible meditation-related experiences, there is a risk that in
the clinical application of meditative practices – where medi-
tation training is divorced from its traditional religious, social,
and cultural contexts – reports of such experiences could be
misdiagnosed as a more serious physiological or psychological
disorder. In order to have realistic and accurate expectations
of the possible outcomes of meditative practices, clinicians and
researchers in this field should be aware of the trajectories of
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Lindahl et al. Meditation-induced light experiences
practice and experience detailed in traditional religious litera-
ture.
The data in this study are derived from a larger on-going project
that is investigating the full range of contemplative experiences.
In this paper, we focus in particular on addressing experiences
described as lights or as having luminous characteristics. We
have selected these experiences from among the possible range of
meditation-induced experiences for three primary reasons. First,
with the exception of one study that included lights among dozens
of different meditation-related symptoms (Kornfield, 1979) and
one study in which light-related metaphors are used to describe an
experience of “inner energy” (Lo et al., 2003), lights are fairly com-
mon meditation experiences that have gone undocumented in the
scientific research on meditation. Second, reports of light-related
experiences are well documented in scientific literature on visual
hallucinations, and their neurobiology is fairly well understood.
Third, traditional Buddhist literature provides a rich typology
of meditation-induced light experiences that contextualizes these
experiences within the trajectories of meditative progress.
The qualitative data for this paper are derived from first-
person reports of meditative experiences provided by contem-
porary American Buddhist practitioners in a variety of lineages.
These data are contextualized in relation to typologies of med-
itative experiences derived from traditional Buddhist literary
traditions. While Buddhist literature abounds with detailed ref-
erences to experiences of lights or luminosity (e.g., Nanarama,
1983;Dondrup, 1997;Chagme and Gyatrul, 2000;Wangyal, 2000,
2002;Gyatso, 2004;Wallace, 2011), to our knowledge, this is
the first study that attempts to connect historical, textual data
on meditation-induced light experiences with reports from living
practitioners of different lineages as well as with related data from
experimental scientific research.
Our analysis is restricted to assessing simple visual halluci-
nations – unstructured points of light, patterns of light, and
diffuse changes in the visual field – because these are the types of
experience emphasized both in the qualitative data derived from
our interviews with Buddhist meditators and in the typologies
of meditation-induced light experiences in Buddhist literature.
However, it is insufficient to rely solely upon traditional textual
sources as a means of investigating the cause or significance of
these phenomena. For this reason, our qualitative data are consid-
ered in relation to scientific research on sensory deprivation (e.g.,
Zubek et al., 1961;Zuckerman, 1969;Merabet et al., 2004), per-
ceptual isolation (homogenous stimuli; e.g., Wackermann et al.,
2002,2008;Pütz et al., 2006;Lloyd et al., 2012), and clinical disor-
ders of the visual system (e.g., Santhouse et al., 2000;Wilkinson,
2004;Vukicevic and Fitzmaurice, 2008;Ffytche et al., 2010). These
studies, discussed below, also provide evidence in support of the
hypothesis that certain contemplative practices – especially those
that deliberately decrease social, kinesthetic, and sensory stim-
ulation and emphasize focused attention – have perceptual and
cognitive outcomes similar to sensory deprivation. Finally, we sug-
gest that since sensory deprivation has been shown to introduce a
period of enhanced neuroplasticity (Boroojerdi et al., 2000;Fierro
et al., 2005;Pitskel et al., 2007;Maffei and Turrigiano, 2008), med-
itation may also have an enhanced neuroplastic potential beyond
ordinary experience-dependent changes.
MATERIALS AND METHODS
PARTICIPANTS
Twenty-eight meditators (39% female, 61% male, mean
age =43.3, SD =14.1, range =21–74) participated in the “Vari-
eties of Contemplative Experience” study. The subject pool was
recruited via snowball sampling (Faugier and Sargeant, 1997).
General inclusion criteria required a minimum age of 18 years,
a regular meditation practice in one or more recognized Buddhist
traditions, and a meditation-related experience that was signifi-
cant, unexpected, challenging, or was associated with physiological
or psychological changes. Twenty (71%) participants practiced in
an American Vipassan¯a or an Asian Therav¯ada Buddhist tradition,
seven (25%) in a Tibetan Buddhist tradition, and seven (25%) in
a Zen Buddhist tradition1. Nearly half (46%) of the sample were
meditation teachers. The average number of prior years of practice
before the onset of unexpected experiences was 10.33 (SD =10.88,
range =0.25–41).
PROCEDURE
The project was approved by the Brown University Institutional
Review Board, and all participants provided informed consent.
Interviews were conducted via telephone and in person either by
the PI (WB) or by other study personnel (CK, EW). After pre-
liminary demographic information was collected, subjects were
interviewed in a semi-structured, open-ended format.
Since the primary data are narratives and the aim of the study
is to generate descriptions of the participants’ meditation experi-
ences, qualitative methodology is the most appropriate approach.
Thus, interviews were conducted, recorded, transcribed, and
coded in line with qualitative methodology standards (Miles and
Huberman, 1994;Patton, 2002;Flick, 2006;Fonteyn et al., 2008;
DeCuir-Gunby et al., 2011;Miles et al., 2013). Content analysis
is a systematic and objective means of describing and quantify-
ing phenomena (Krippendorff, 1980;Downe-Wamboldt, 1992;
Elo and Kyngas, 2008), and may be either inductive or deductive.
We chose to use inductive content analysis, where categories are
derived from the data, because this is the method that is recom-
mended if there is little former knowledge about a phenomenon
(Elo and Kyngas, 2008).
Because the varieties of meditation-related experiences have
not been well documented in scientific literature, it was crucial
that the interview content was driven by the subject, not the
researcher. Subjects were allowed to respond freely to the initial
open-ended prompt “What was your experience with meditation?”
Additional queries included non-specific prompts for elaboration
such as “Can you tell me more about that?” In order to minimize
researcher’s influence on interview content, directed queries about
specific experiences or queries that interrupted the narrative were
discouraged.
A total of 2157 min of audio recording were transcribed into 605
pages and separated into 6594 separate units of analysis. Within
the transcripts, a new unit of analysis was created for each change
in speaker, concept, or event, and each unit was allocated to a
1The total percentage surpasses 100% due to some participants practicing in
multiple traditions.
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separate row in an excel spreadsheet (Cavanagh, 1997;Graneheim
and Lundman, 2004;Elo and Kyngas, 2008).
The qualitative content analysis followed a grounded theory
approach (Glaser and Strauss, 1967) using open coding techniques
(Strauss and Corbin, 1998), which are intended to “open up” the
text in order to uncover its content and meaning. Following the
methodology of open coding, coders assign a tentative heading or
category to each unit of analysis. They then read and code the tran-
script repeatedly until all aspects of the content are categorized.
As the coding structure evolved from the initial open coding, the
research team met repeatedly to create and revise a list of stan-
dardized definitions for each type of experience with inclusion
and exclusion criteria, supported by example texts (MacQueen
et al., 1998;Fonteyn et al., 2008). To establish reliability for the
codebook, an interview was chosen at random and was coded inde-
pendently by each of the researchers. All interviews were coded by
pairs of researchers with the finalized manual, and any disagree-
ments led to iterative discussions that refined coding criteria until
consensus (80%) was achieved.
More than forty categories of experience were aggregated into
six higher-order clusters: cognitive, perceptual, sense of self, affec-
tive/emotional, somatic/physiological, and social/occupational.
“perceptual” is defined as pertaining to the senses, i.e. the visual,
auditory, gustatory, olfactory, and tactile systems. “Light expe-
riences” emerged as a sub-category of perceptual experiences
in the visual domain. Inclusion criteria for light-related visual
experiences included use of the word “light” or description of
an experience either directly linked to visual perception with
the phenomenal quality of luminosity or brightness. Exclusion
criteria were metaphorical uses of light that were not directly
linked with visual perception or that had ambiguous phenom-
enal quality (cf., Lo et al., 2003). Complex involuntary mental
images involving objects, figures, and scenes that were not linked
to a light-related experience were included in another category
and therefore are not addressed in this paper. Because the pur-
pose of this paper is to discuss light-related experiences from
traditional Buddhist and neurobiological perspectives, only cells
that received the <Perceptual.Visual.light>code are included
below.
RESULTS
Nine individuals (32% of total participants) voluntarily reported
lights or other forms of luminous experiences [mean age =41,
SD =9.7, range =31–60, two females (22%), seven males (78%)].
Six (67%) of these participants practiced in an American Vipassan¯a
or Burmese Therav¯ada tradition, two (22%) in a Zen Buddhist
tradition, and one (11%) in a Tibetan Buddhist tradition. Five
(56%) of the meditation-induced light experiences appeared on
retreats, and the remaining four (44%) arose in the context of
daily practice. Among these reports, the level of light of the med-
itation environment varied according to setting and time of day
and was not intentionally manipulated. None of the practition-
ers engaged in a “dark retreat” practice where the level of light is
deliberately attenuated. Practitioners who reported lights had been
practicing within one or more Buddhist traditions for an average
of 5.0 years (SD =2.0, range =2–8) before these experiences arose
(Ta b l e 1 ).
DISCUSSION
Our discussion begins by presenting a basic typology of
meditation-induced light experiences based upon the data derived
from the coded interviews from our subject pool. Data from
these first-person reports of meditation-induced light experiences
are then compared to typologies of related phenomena derived
from traditional Buddhist literary sources. We also present tradi-
tional Buddhist interpretations of their significance in terms of the
practitioner’s progress in meditation.
The second main subsection discusses the neurobiology of
light-related experiences according to scientific research on sen-
sory deprivation, perceptual isolation, and clinical disorders of
the visual system. We draw upon this literature both to posit
the possible underlying mechanisms of meditation-induced light
experiences and in order to suggest a novel interpretation of medi-
tation that calls attention to its structural similarities with sensory
deprivation and perceptual isolation.
We end our discussion with the implications of our findings for
the scientific study and clinical application of meditation.
A TYPOLOGY OF MEDITATION-INDUCED LIGHT EXPERIENCES BASED
UPON QUALITATIVE DATA AND TEXTUAL SOURCES
Class one: discrete lightforms
Four practitioners reported discrete lightforms appearing as either
“globes,”“jewels,” or “spots.” These lights appeared in various col-
ors and were also described as being “very vivid” or “very distinct.”
Discrete lightforms could be either singular or multiple in num-
ber and were generally small, being described as “little stars” or
“small radiant bursts.” Some of these bright, luminous shapes
were characterized by some practitioners as being stable, or as
“hanging out in space,” whereas for others they were more ani-
mated. For example, one practitioner described spots of lights as
floating “together in a wave, sort of like a group of birds migrat-
ing.” Small lights – singular or multiple – that appear as generally
round points of colored light are the first group of phenomena
that can be linked with accounts derived from traditional Buddhist
literature.
Literature throughout the Therav¯ada Buddhist tradition
describes a particular mental phenomenon called a nimitta.The
nimitta arises once a preliminary mastery of concentration has
been established, and especially through developing concentra-
tion by focusing attention on the inhalation and exhalation of
the breath (Ledi Sayadaw, 1999). Although the particular men-
tal image or form of the nimitta varies across practitioners and
depends upon the object of concentration, the most common
Buddhist meditation practice involves taking the breath as a pri-
mary object of attention. A fifth century treatise entitled The Path
of Purification (Buddhaghosa, 1999, p. 277) describes the nimitta
that arises through concentration on the breath as follows:
It appears to some as a star or cluster of gems or a cluster of pearls,
[...] to others like a long braid string or a wreath of flowers or a puff
of smoke, to others like a stretched-out cobweb or a film of cloud or a
lotus flower or a chariot wheel or the moon’s disk or the sun’s disk.
Many of these initial descriptions of the nimitta are consonant
with the reports of small points of light described as “globes,
“jewels,” or “stars” discussed above. One practitioner from our
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Table 1 |Practitioner data and reports of meditation-induced light experiences.
Subject
no.
Sex Dominant practice
tradition
Duration of
practice before
lights (years)
Retreat or
daily
practice
Light experience excerpts
99000 M Vipassan¯a (Bur),
Shamatha (Bur)
7 Retreat I started getting these meditative states that were like seeing a curtain of light, so even in a dark room meditating at night
there would be a sense of – as if there were lights on in the room, and when I opened my eyes there wouldn’t be,
but...there was often a curtain, this internal curtain of light. I began to have very luminous imaginations where...if I
pictured something it was as if I was actually there, so when I pulled back a memory or a fantasy of being on a beach my
mind became so bright it was as if I was actually there, I could see all the details of all the trees and hear the birds calling
and... it was as if I was actually standing at the beach. So this very luminous mind... was coming a lot also when I was
sleeping; I was getting incredibly vivid dreams...I would be walking around my cabin, and after ten-fifteen minutes of this
I realized I was still dreaming, but it was so incredibly vivid as a first-hand experience.This is all talked about in the
developing of concentration.
99003 M Vipassan¯a (USA) 5 Retreat Even with my eyes closed, there would be a lot of light in the visual frame, so to speak. Diffuse, but bright...My eyes
were closed – there was what appeared to be a moon-shaped object in my consciousness directly above me, about the
same size as the moon if you lay down on the ground and look into the night sky. It was white. When I let go I was totally
enveloped inside this light...I was seeing colors and lights and all kinds of things going on... Blue, purple, red. They were
globes; they were kind of like Christmas tree lights hanging out in space except they were round. They were very distinct;
they weren’t fuzzy, they were very clear.
99005 M Zen 8 Daily So most people see that if they do eyes open meditation (they have) the sense that reality is pixelating a little bit and
becoming very very vivid... My personal experience of it... definitely the Christmas lights and definitely the
shimmering... my tendency is to perceive it that way. The Christmas lights (...were) almost like small radiant bursts.
99008 M Vipassan¯a (Bur) 2 Retreat The mind became very strong and bright. By the end of the retreat, it was just on, the lights were on all the time...The
last night, I sat the whole night (with) no effort just all kinds of stuff would be happening, energetic stuff, painful things,
it’s just the mind was totally unmoving.
99009 F Vipassan¯a (USA) 2 Retreat I was just bursting with light, I would just close my eyes and it was just brilliant light. I just felt like I was radiating, like
there were rays of light coming out of me. ...It felt like it was just emanating from my body and my system. But this
wasn’t my entire retreat by any means, it was just near the end.
(Continued)
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Table 1 |Continued
Subject
no.
Sex Dominant practice
tradition
Duration of
practice before
lights (years)
Retreat or
daily
practice
Light experience excerpts
99011 M Vipassan¯a (USA) 6 Daily And...I had the lights out, so I had this sensation of lights passing over my eyes, but they weren’t external. ...It seemed
to be something just happening to my inner eye, or maybe on my retina, or something when you close your eyes and
become deeply relaxed and you start seeing these sort of pleasant pulsations of color, of various forms of color. I think it
was that, but like times one hundred, it was just all sped up to a ridiculous degree...It created this perceptual distortion
which I felt like I was in a tunnel, or in some kind of train, and there were lights passing me as I moved forward. It was
almost as if I was being carried forward...lying on my back through some sort of...crazy roller coaster ride.
99019 F Shamatha (Tib) 5 Retreat Sometimes there were, oftentimes just a white spot, sometimes multiple white spots, sometimes the spots, or “little
stars” as I called them, would float together in a wave, like a group of birds migrating, but I would just let those things
come and go. All of a sudden this tremendous amount of bliss, the jet engine feelings of bliss, would come up while I
was sitting and meditating. Or the white lights, or sometimes blue lights, would come up while I was meditating. It was
not associated with an unpleasant feeling, or with any kind of palpitations, or rushes, other than this energetic jet engine
vibration feeling.
99021 M Vipassan¯a (USA) 5 Daily I’ve put all of these experiences more in the arising and passing part of the path...golden light that fills the sky and my
body feeling like the same nature as that, and the combining and unitive kind of experience, but also there was one
night...where my body just was breaking apart into sparkles and like electrical sparks being sent off everywhere in all
directions with...so that kind of light and physical...so that the sparks one is obviously more dynamic, the gold one is
more unitive, and then during meditation there’s plenty of states where you’ll see jewel lights or blues and greens and
oranges and that seems to be associated with being fairly concentrated at that point.
99022 M Zen 5 Daily I’ve seen ropes of shimmering...where it’s causing space behind it to shimmer a little bit and move. I’ve occasionally had
the visual field get much brighter than normal for no particular reason (and) I’d say that’s attached to concentration of
some sort... In concentration I’ve had rays of white light that go through everything. They’re either coming from behind
me somewhere or coming out of the object that I was concentrating on. ...I saw it with my eyes open and it wasn’t
really seeing it was something else, even though I still was perceiving that it was there.
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study also described a white light that appeared to be the size of
moon as seen in the night sky.
While Buddhaghosa suggests that the different lightforms of
the nimitta are idiosyncratic, Buddhist sources from other tra-
ditions present similar phenomena to the cluster of gems,
“puff of smoke,” and “film of cloud” as arising in a progres-
sive sequence.Extensive presentations of light-related signs of
attainment can be found in the Buddhist tantras – a vast body
of literature associated with ritual and contemplative practices
that developed and flourished in India between the seventh and
the eleventh century (Samuel, 2008). According to a traditional
commentary on the tantras, a typical trajectory for the light-
forms is as follows: The first is described as being “like seeing a
mirage,” the second as a “smoke-like vision,” the third a “vision
like flickering fireflies,” the fourth is like “the glow of a butter-
lamp,” and the fifth is “like a clear autumn sky pervaded by the
light of the full moon” (Dondrup, 1997, p. 85). Various tantras
present the progressive sequence of mental images in different
orders; Gyatso (2004) explains that this is due to the different
techniques that can be used to induce the involuntary mental
images.
While the reference in the tantras to lights “like flickering fire-
flies” closely resembles the reports of “Christmas lights”and “small
radiant bursts” discussed in the first class of light-related phe-
nomena, the depictions of a mirage-like light and an illuminated
autumn sky more closely correspond to phenomena we include in
the second class of meditation-induced light experiences.
Class two: patterned and diffuse lights
The second class of light-related phenomena includes patterned
and diffuse changes to the visual field, most commonly described
as shimmering, pixelation, or brightening. This class of phe-
nomena can be distinguished from the first class on account of
not having a distinct and circumscribed shape, size, color, or
spatial location. Instead, they are characterized as being super-
imposed on the practitioner’s perception of space, and often arise
in conjunction with the perception of external objects.
Shimmering. Like the tantric visions of seeing a mirage, one prac-
titioner described space as “shimmering,and alternately as seeing
“ropes” that would emerge from objects in space and cause the
space behind it “to shimmer a little bit and move.” Contempo-
rary authors in a Tibetan Buddhist lineage explain that “when you
meditate, many different lights can appear [including...] all kinds
of shimmering experiences,”and these are taken to be “good signs”
(Sherab and Dongyal, 2012, p. 94).
Pixelation. Another example of an alteration of the visual field
comes from a practitioner who described the visual field as
“pixelating a little bit and becoming very very vivid.” A simi-
lar cluster of phenomena that co-arise with the perception of
external objects include reports of “seeing energy instead of
seeing solid objects” and “seeing rays of light that go through
everything.” In a description strikingly parallel to “pixelating,
Tibetan author Dudjom Lingpa includes “the perception of all
phenomena as brilliantly colored particles” among the list of med-
itation experiences (nyams) that can arise from proficiency in
concentration practice (Wallace, 2011, p. 136). Full et al. (2013)
documented advanced meditators in a Burmese Therav¯ada tra-
dition, some of whom also reported perceiving both external
objects and their own body as small particles as a result of
directing a concentrated mind toward the investigation of the
body.
Brightening. In addition to the shimmering and pixelation
described above, six practitioners reported a homogenous bright-
ening of the visual field. Two of these practitioners reported that
the visual field was brighter when the eyes were open, including a
report of a “golden light that fills the sky,” which is quite similar to
the imagery used in the Buddhist tantras to characterize the fifth
sign of attainment.
Four other practitioners characterized the homogenous field
of light as a mental image arising behind closed eyes. For exam-
ple, one practitioner described an “internal curtain of light” that
would be most apparent when meditating in a dark room or with
eyes closed. On account of this curtain of light, this practitioner
reported being able to perceive memories and dream-like rever-
ies as clearly as external objects. This increasing brightness of the
visual field may again be related to the fifth, unstructured “sky-
like” sign of attainment presented in the tantras, or, it may be
closer to a phenomena described in the canonical sources of early
Buddhism as the “pure bright mind.” This “pure bright mind” is
associated with the fourth state of meditative absorption (jh¯ana)
attained through the cultivation of concentration. In one pas-
sage, this quality of awareness pervades the body in a manner
compared to a man “sitting covered from the head down with a
white cloth, so that there would be no part of his whole body
unpervaded by the white cloth; so too, a [monk] sits pervading
this body with a pure bright mind” (Nanamoli and Bodhi, 1995,
p. 369).
Two practitioners also reported a proprioceptive dimension
to their meditation-induced light experience. One practitioner
explained that “my body just was breaking apart into sparkles
and like electrical sparks being sent off everywhere in all direc-
tions”; the other “felt like I was radiating, like there were rays of
light coming out of me.” In contemporary Therav¯ada accounts
(Sayadaw, 2010, p. 122), concentration directed toward the body
is similarly associated with seeing “a smoky gray light [that will]
become whiter like cotton wool,and then brig ht white, likeclouds,”
and furthermore with seeing the body “sparkle and emit light.”
Experiences of light emanating from the meditator’s body are also
associated with a calm mind and with a particular stage of insight
called the “knowledge of arising and passing away” (Nanarama,
1983, p. 36), the significance which is discussed below.
Textual interpretations of meditation-induced light experiences
As suggested above, reports of meditation-induced light phenom-
ena can be found across Buddhist traditions, in both histori-
cal, textual accounts and among accounts from contemporary
practitioners. A survey of both historical and contemporary
accounts reveals that there is no single, consistent interpretation
of meditation-induced light experiences in Buddhist traditions.
Some types of light may signal that a particular discipline such
as concentration has reached a certain stage of development,
whereas other lights may be the result of imbalanced practice.
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Some interpret lights as a vehicle for investigating the constructed
nature of phenomenal appearances; other light experiences are
deemed unimportant side effects of meditation.
In the context of Therav¯ada and Tantric Buddhism, meditation-
induced light experiences are often deliberately sought as part of
the method of transforming consciousness or are interpreted as
a sign that such transformations have occurred. According to
typical Therav¯ada instructions on concentration practice, such
as those found Buddhaghosa’s The Path of Purification,oncea
nimitta arises, it is take as a sign that an initial stage of medita-
tive absorption has been reached. At that point, this involuntary
light experience can then replace the breath or an external object
as the new object of concentration (Ledi Sayadaw, 1999). Simi-
larly, in Tibetan traditions, the progressive sequence of signs that
are thought to manifest on account of tantric practices, including
both discrete lightforms and diffuse lights such as shimmering,
are interpreted as positive signs that the clarity and luminosity of
the mind is becoming apparent to the practitioner (Gyatso, 2004;
Sherab and Dongyal, 2012).
However, similar typologies of light-related experiences are
elsewhere treated as involuntary side effects of meditation. Some
Therav¯ada Buddhist authors from contemporary Burmese lin-
eages (Nanarama, 1983, p. 36; Sayadaw, 1994, p. 13–14) identify
the arising of a “brilliant light,” a“flash of lightning,” a“lamplight
in the distance,” or a “light [that] emanates from [the medi-
tator’s] own body” as “illumination” experiences – one of 10
“imperfections of insight” that can arise during a stage of practice
called the “knowledge of arising and passing away.” These light-
related meditation experiences, while still taken as signs of a calm
mind capable of carefully investigating present moment experi-
ence, are nevertheless treated as “corruptions” or “imperfections”
because they are so enticing that they can lead the meditator astray
from the practice instructions. Similarly, the phenomena classi-
fied in Tibetan Buddhism as “meditation experiences” (nyams)
also include light-related experiences among the range of phe-
nomena that can arise in meditation. Like the lights that arise in
the context of the imperfections of insight, light-related nyams
such as pixelation are to be left alone, and the practitioner is to
proceed without becoming attached to them (Wallace, 2011). In
Zen Buddhist traditions, the term makyo is used to refer to a
similar category of “side-effects” or “disturbing conditions” that
can arise during the course of practice (Austin, 1999, p. 373).
Consonant with Southeast Asian Therav¯ada and Tibetan Tantric
Buddhist sources, Sogen (2001, p. 84) associates the arising of
makyo with “proof of considerable maturity in Zen concentra-
tion.” However, “even if a glorious light shines, [...] they all
belong to makyo regardless of whether they are good or bad,” and
the practitioner should respond by “paying no attention to them”
(p. 87).
According to other traditional interpretations, especially
prominent in the Dzogchen tradition of Tibetan Buddhism, one
of the objectives of advanced meditation practices is to sta-
bilize the lightforms that arise and investigate them (Chagme
and Gyatrul, 2000, p. 159; Namdak, 2006, p. 197). Temple
wall paintings featuring both descriptions and representations
of these lightforms describe a trajectory beginning with “count-
less minor circles like pearls on a string” that develop into
visions of “luminous spheres, grids, and disk of light” (Baker,
2000, p. 119). Such meditation-induced light experiences are
not important in and of themselves; rather, they are valuable
only insofar as they assist the practitioner in recognizing the
way in which the mind constructs visual appearances and reifies
them as external objects (Wangyal, 2002, pp. 131–133; Namdak,
2006, p. 198). In this trajectory of practice, certain Buddhist
meditation traditions utilize visual hallucinations as a means of
gaining insight into the way in which perceptual experience of
the phenomenal world is constructed, rather than given. Some
contemporary theories in cognitive science have characterized
phenomenal consciousness as a process that simulates the relation-
ship between the body and its environment (e.g., Metzinger, 2003;
Revonsuo, 2006) in a manner compatible with certain Buddhist
approaches to insight (Waldron, 2006). As the following section
will demonstrate, the neurobiology of visual hallucinations and
veridical visual perceptions are closely related (Ffytche et al., 1998;
Lloyd et al., 2012).
NEUROBIOLOGICAL PERSPECTIVES ON LIGHT-RELATED EXPERIENCES
Scientific studies of light-related experiences tend to classify such
phenomena as visual hallucinations. This section presents findings
from sensory deprivation, perceptual isolation, and disorders of
the visual system.
Sensory deprivation
Sensory deprivation includes exposure to environments that
present the subject with minimal sensory input. Through dark-
ness, silence, isolation, and bodily stillness, respectively, the
subject’s visual, auditory, social, and kinesthetic experience is
reduced as much as possible (Zubek et al., 1961;Rossi, 1969;Mer-
abet et al., 2004;Kjellgren et al., 2008;Mason and Brady, 2009).
Sensory deprivation may include occlusion of individual sense
organs, such as with earplugs or blindfolds, or multiple senses at
once, such as through sitting alone in a dark and silent room.
Perceptual isolation
Perceptual isolation refers to exposure to homogenous, invariant,
or unstructured stimuli (Wackermann et al., 2002,2008;Pütz et al.,
2006;Lloyd et al., 2012). While sensory input is not technically
absent in perceptual isolation, the monotony leads to habitua-
tion where input is “filtered out,” which can mimic the effects of
decreased input of sensory deprivation (Pütz et al., 2006).
Visual impairment
Among disorders of the visual system, Charles Bonnet Syndrome
is classically associated with visual hallucinations and light-related
experiences. Charles Bonnet Syndrome is most commonly found
among elderly patients who have very poor vision or are blind on
account of an impairment of their visual system, ranging from eye
abnormalities to dysfunctions in the occipital lobe (Vukicevic and
Fitzmaurice, 2008;Kazui et al., 2009).
All three of these conditions – sensory deprivation, perceptual
isolation, and Charles Bonnet Syndrome – are characterized by
impaired sensory input to the visual system, and all result in the
rise of involuntary visual hallucinations, where “hallucinations”
are defined as a “percepts, experienced by a waking individual, in
the absence of appropriate stimuli from the extracorporeal world”
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Lindahl et al. Meditation-induced light experiences
(Blom, 2013, p. 44). Hallucinations are different both from illu-
sions, which are distortions of actual external stimuli, and from
intentionally constructed mental imagery, which remains under
volitional control and lacks perceptual vividness (Reichert et al.,
2013).
While the sensory loss that occurs at sleep onset may also result
in hallucinations, these “hypnagogic” hallucinations are more sim-
ilar – both neurologically and phenomenologically – to dreams
that occur during REM sleep than to visual hallucinations that
occur during wake (Wackermann et al., 2002;Collerton and Perry,
2011;Fenelon,2013). Like dreams, hypnagogic hallucinations tend
to occur in multiple sensory modalities at once, are panoramic or
“full screen” rather than circumscribed, and are associated with
lack of insight and strong, often negative affect (Cheyne et al.,
1999a,b;Ohayon, 2000;Collerton and Perry, 2011). Thus, our
typologies of visual hallucinations will focus on those that arise
during wake, as the phenomenology of waking visual hallucina-
tions is the most congruent with the reports from participants in
our study.
SCIENTIFIC TYPOLOGY OF VISUAL HALLUCINATIONS
Researchers of sensory deprivation (Zubek et al., 1961;Zucker-
man, 1969;Merabet et al., 2004), perceptual isolation (Wa c ke r-
mann et al., 2002,2008;Pütz et al., 2006;Lloyd et al., 2012), and
visual disorders (Santhouse et al., 2000;Wilkinson, 2004;Ffytche
et al., 2010) have developed similar typologies of visual hallucina-
tions. Documented visual hallucinations range from simple forms
or flashes of light or color to grid-like patterns to animated figures
or scenes. While “complex” hallucinations include faces, objects,
and landscapes, light-related experiences of both discrete light-
forms and patterned or diffuse lights fall into the category of
“simple hallucinations.” As explained above, our present analysis
is limited to “simple” visual hallucinations.
SIMPLE HALLUCINATIONS
Simple hallucinations often include circumscribed objects, pat-
terns, and diffuse changes across the visual field. Circumscribed
hallucinations include points of light, colored lights, or shapes
(phosphenes), or flashes of light (photopsia) sometimes described
as “dots” or “stars.”
Patterned hallucinations may include regular, overlapping pat-
terns (tessellopsia) like lattices, grids, and cobwebs, branching
forms (dendropsia) like vines, ropes or roads, and zigzag patterns
(teichopsia). Other patterns include the perception of visual snow
or television-like static. Diffuse hallucinations include a brighten-
ing of the visual field, descriptions of mist or fog, shimmering,
or bright sunsets (Ffytche and Howard, 1999;Merabet et al., 2004;
Wilkinson, 2004;Ffytche et al., 2010;Lloyd et al., 2012;Ta b l e 2 ).
Both circumscribed and diffuse simple visual hallucinations
arise as result of sensory deprivation (Zubek et al., 1961;Zuck-
erman, 1969;Merabet et al., 2004) and perceptual isolation
(Wackermann et al., 2008;Lloyd et al., 2012). In some cases of
perceptual isolation, the visual field may disappear entirely, leav-
ing subjects “uncertain whether their eyes were open or closed, or
even unable to control their eye movements. In the‘luminous fog’
of the (homogenous visual field) the subjects do not see anything;
in the ‘blank-out’ periods, they may experience the presence of
‘nothingness’ ” (Wackermann et al., 2008, p. 1367). The authors
also point out that natural environments, such as a uniformly
blue or cloudy sky, can function in a manner similar to intention-
ally constructed perceptual isolation environments (p. 1365), and
that depending upon the subject’s disposition, perceptual isola-
tion experiences and especially “blank out” episodes “may elicit
even mystical or religious interpretations” (p. 1368).
Simple hallucinations are much more common than complex
ones. Among those with disorders of the visual system, more than
50% of visually impaired individuals report simple hallucinations,
while only 15–25% report complex hallucinations (Menon et al.,
2003;Vukicevic and Fitzmaurice, 2008). Simple hallucinations can
be evoked with very brief exposure to attenuated input, whereas
complex hallucinations require more prolonged or more exten-
sive sensory deprivation or perceptual isolation (Wackermann
et al., 2002,2008;Pütz et al., 2006;Lloyd et al., 2012). Com-
plex hallucinations are thought to draw upon many brain areas,
including those involved in memory (Collerton et al., 2005), and
require more widespread and extensive neuroplastic modifications
(Ffytche et al., 2010). More prolonged or extensive deprivation
and brain changes may also begin to include cross-modal experi-
ences where visual phenomena are experienced proprioceptively
and incorporated into body schema and emotional meaning or
valuestructures(Ffytche et al., 2010).
Researchers have found that simple visual hallucinations are
associated with activity in the occipital cortex, the primary visual-
processing center of the brain (Boroojerdi et al., 2000;Merabet
et al., 2004). Ffytche et al. (1998, p. 740) presents fMRI-based evi-
dence of a specific “correlation between the location of activity
within a specialized cortex and the contents of a hallucina-
tion.” Visual hallucinations of grid-like patterns, for instance,
correlated with activity in the collateral sulcus, and color hal-
lucinations correlated with activity in the fusiform gyrus. This
led the researchers to conclude that in terms of their neurobi-
ology, visual hallucinations are more like ordinary perceptions
than they are like visualized mental images. Similarly, a percep-
tual isolation study (Lloyd et al., 2012) demonstrated that subjects
responded to and could modulate their attention in relation to
visual and auditory hallucinations as they would with ordinary
perceptions.
WHY SENSORY LOSS CAUSES HALLUCINATIONS
Attenuation of sensory input reliably leads to hallucinations, even
after a short time. Decreased sensory input leads to spontaneous
firing and hallucinations through homeostatic plasticity–asetof
feedback mechanisms that neuronal circuits use to maintain stable
activity and firing rates close to a set point (Desai, 2003). Home-
ostatic plasticity may include adjusting synaptic input strength
(synaptic homeostasis) or changing the intrinsic excitability of
the neuron (intrinsic plasticity) (Turrigiano, 2011). When sen-
sory inputs are attenuated or lost, the homeostatic plasticity
mechanisms increase neuronal excitability and firing thresholds
(Boroojerdi et al., 2000;Fierro et al., 2005;Pitskel et al., 2007),
which may be experienced as heightened sensory acuity or percep-
tual sensitivity (Suedfeld, 1975). In the case of sensory attenuation,
homeostatic mechanisms often overcompensate to the point of
generating spontaneous firing, which is experienced subjectively
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Table 2 |Comparative typology of visual hallucinations and meditation-related light experiences.
Typologies derived from sensory deprivation, perceptual
isolation, and disorders of the visual system
Typologies derived from qualitative reports from
contemporary practitioners of Buddhist meditation
Typologies derived from
Buddhist literary sources
Class 1: Discrete lightforms
Phosphenes: colored spots, dots, or points of light Blue, purple, and red globes Cluster of pearls
Jewel lights Cluster of gems
Christmas tree lights Luminous spheres
White or blue lights Lamplight in the distance
White spots or little stars A star
Photopsia: flashes of lights Small radiant bursts Flickering fireflies
Sun’s disk and sunset Moon-shaped object Moon’s disk
Sun’s disk
Class 2: Patterned and diffuse lights
Teichopsia: zigzag colors Stretched-out cobweb
Tessellopsia: lattice, nets, grids, or cobwebs Grids
Shimmering Ropes of shimmering Shimmering experiences
Mist Seeing energy instead of solid objects Mirage
Luminous fog Film of cloud
Smoke-like vision
Visual snow, television-like static Reality is pixelating All phenomena as brilliantly
colored particles
Electrical sparks in all directions Perceiving body and objects as
small particles
Rays of light that go through everything
Lighter visual field Brighter visual field Glow of a butter lamp
Lights always on
Curtain of light Clear autumn sky pervaded by
the light of the full moon
Golden light that fills the sky
Bright sunsets Body feeling like the same nature as light Pervading the body with a pure
bright mind
Bursting with light
Light emanating from the body Light emanates from his own
body
Bright mind
as hallucinations (Schultz and Melzack, 1991;Burke, 2002;Maffei
and Turrigiano, 2008;Reichert et al., 2013).
A wide variety of conditions of sensory attenuation or
monotony lead to increased cortical excitability, spontaneous fir-
ing, and hallucinations. Given that meditators are reporting visual
hallucinations in the context of meditation, it is worth considering
the sensory attenuating qualities of meditation practices.
BUDDHIST MEDITATION AS A FORM OF SENSORY DEPRIVATION AND
PERCEPTUAL ISOLATION
Structural components
While there are a variety of approaches to meditation, many
practices incorporate structural components analogous to sensory
deprivation and perceptual isolation, including sensory,social and
kinesthetic deprivation, or invariance. The practice of medita-
tion tends to be done in social isolation or in groups in which
social interactions are minimized. During a formal practice ses-
sion, practitioners adopt a stable, seated posture. The locations for
meditation practice also tend to be quiet environments removed
from excessive auditory stimuli. Through dimly lit environments
or through practicing with the eyes closed or open with a fixed
gaze, visual stimuli are restricted.
It is important to note that even when meditation is not prac-
ticed within such sensory minimal environments, the practice
of meditation functions in a manner analogous to percep-
tual isolation through restricting attention to monotonous or
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homogenous stimuli. In practices that involve movement, the
emphasis is on monotonous, repetitive movements, such as slow
walking. In concentration practice on the breath, other kinesthetic,
auditory, and visual stimuli are deselected in order to attend, again
and again, to the repetition of inhalation and exhalation. Even
when meditators practice with their eyes open, the gaze either
remains unfocused and on the entirety of the visual field or is
restricted to a single invariant object.
Thus, whether through practicing in environments with min-
imal sensory input, or through attending only to monotonous,
repetitive stimuli, the context and function of meditation is simi-
lar to both sensory deprivation and perceptual isolation (Ta b l e 3 ).
That advanced practitioners often deliberately choose to isolate
themselves further by practicing in remote caves or in sensory
deprivation environments demonstrates how Buddhist meditation
traditions have recognized the importance of practicing within
sensory minimal environments. For example, the Tibetan Bud-
dhist practice of “dark retreat” (mun mtshams) suggests that
deliberate and intensive sensory deprivation is thought to be
particularly effective in producing profound shifts in percep-
tion and cognition (Chagme and Gyatrul, 1998;Wangyal, 2000,
2002;Gyatso, 2004;Reynolds, 2011). Not surprisingly, discus-
sions of meditation experiences in dark retreat closely resemble
the typology of visual hallucinations discussed above. Tenzin
Wangyal Rinpoche, who undertook an extensive dark retreat when
he was a young boy, reports both simple and complex visual
hallucinations arising as a result of the prolonged sensory depri-
vation (Wangyal, 2000,2002, pp. 32, 132). Tibetan Buddhists
also prescribe a shorter-term technique of fixing the gaze upon a
cloudless sky as a means of inducing simple visual hallucinations
(Gyatso, 2004). As mentioned above, Wackermann et al. (2008)
suggest that a uniform sky serves as a natural perceptual isolation
condition.
Concentration as sensory deprivation
In addition to the structural aspects of meditation practices listed
above, it is possible that the intense attentional engagement of
Buddhist meditation practices also functions as a form of sen-
sory deprivation. By “guarding the sense doors,” some meditation
practices aim to limit the sensory input impinging on aware-
ness through restricting attention to a single object of perception,
such as a visual object or the breath (Buddhaghosa, 1999;Dalai
Lama, 2001). Whether in “focused attention” types of meditation,
where one object is continually selected, or in“open monitoring”
meditation, where many different objects are selected sequentially
(Lutz et al., 2008), attention facilitates the processing of relevant
information by suppressing irrelevant sensory inputs (Briggs et al.,
2013), and can therefore be viewed as a largely inhibitory process
(Kerlin et al., 2010;Foxe and Snyder, 2011).
The act of paying attention facilitates the processing of relevant
stimuli while inhibiting irrelevant stimuli. In terms of the brain’s
electrical activity, fast excitatory frequencies and slow inhibitory
frequencies interact to facilitate attention (Jensen and Mazaheri,
2010). The active processing of relevant stimuli is associated with
increased fast frequency (gamma) oscillations and decreased slow
frequencies (i.e., decreased alpha power or increased alpha desyn-
chronization) in the engaged areas (Pfurtscheller and Lopes da
Silva, 1999). In contrast, suppression or inhibition of irrelevant
stimuli is associated with the opposite pattern, decreased beta and
gamma and increased alpha power or alpha synchronization in
areas not related to the task (Pfurtscheller and Lopes da Silva, 1999;
Suffczynski et al., 2001;Lutz et al., 2007;Kerr et al., 2011). Alpha
activity is also associated with decreases in fMRI BOLD signal and
is thought to reflect the functional inhibition of neural activity in
task-irrelevant areas (Goldman et al., 2002;Feige et al., 2005). For
example, during visual tasks, information from non-visual (e.g.,
motor) areas is inhibited via increased alpha power (Pfurtscheller,
1992). Studies of spatial attention have shown decreases in alpha
power in areas related to active processing of target locations but
increases in alpha in areas related to non-target locations (Thut
et al., 2006;Rihs et al., 2007;Kerr et al., 2011). Although most early
research on attention focused on gamma activity in task-relevant
areas and ignored alpha activity in task-irrelevant areas, it now
appears that alpha inhibition is as important or more important
than gamma facilitation. Indeed, optimal task performance on a
number of cognitive tasks, including selective and sustained atten-
tion, is determined by the extent of alpha activity in task-irrelevant
areas rather than gamma in task-relevant areas (Dockree et al.,
2007;Jensen and Mazaheri, 2010). Similarly, widespread increases
in alpha power in meditators (Cahn and Polich, 2006) that were
initially viewed as “idling”(Pfurtscheller et al., 1996) or relaxation
(Fenwick et al., 1977) are now thought to reflect the active inhibi-
tion of irrelevant cortical inputs as a means of facilitating attention
(Jensen and Mazaheri, 2010;Britton et al., 2013;Kerr et al., 2013).
Various meditation practices, especially focused attention or
concentration practice, involve selecting target or relevant stimuli
Table 3 |Comparison of sensory deprivation, perceptual isolation, and meditation.
Sensory deprivation Perceptual isolation Meditation
Social Isolation from human interaction
and communication
Isolation from human interaction and
communication
Retreat environment temporary social isolation
Kinesthetic Immobilization, floatation tank Restricted to comfortable chair Stable, seated posture, monotonous movements
Auditory Silence, soundproof room, earmuffs Headphones with white noise monotonous
sound, consistent volume
Quiet retreat environment, redirection of attention
away from sound
Visual Darkness, blindfolds Eye shields and lighting create homogenous
visual field
Eyes closed, gaze fixed on single object, gaze
directed at space
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and deselecting non-target or irrelevant stimuli. Areas of the
body that are related to the sensations of breathing or walking
are a common target of focus in many forms of Buddhist med-
itation, and the ability to maintain focus on these target areas
and inhibit distracting non-target stimuli is considered to be a
hallmark of proficiency in focused attention forms of meditative
practice. Meditation-related increases in interoceptive accuracy
to frequently attended targets (Kerr et al., 2011;Silverstein et al.,
2011;Fox et al., 2012) are associated with longer lifetime medita-
tive experience (Fox et al., 2012) and are thought to be determined
by the extent of alpha-modulated inhibition in non-target areas
(Kelly et al., 2009;Jones et al., 2010;Foxe and Snyder,2011). Thus,
it could be argued that proficiency or expertise in focused attention
as a result of meditation can be indexed by the degree of cortical
inhibition.
Increased throughput of frequently attended-to “target” areas
(e.g., improved interoception) is a straightforward example of
experience-dependent neuroplasticity that underlies successful
skill acquisition. However, the model in this paper suggests that
inhibition of non-target sensory input can also result in a compen-
satory increase in neuronal excitability, which is often measured
either by a decreased sensory threshold or by increased firing rates
or spontaneous firings (hallucinations). In terms of decreased
sensory thresholds, studies of Tibetan Shamatha (MacLean et al.,
2010) and Therav¯ada Vipassan¯a(Brown et al., 1984) practition-
ers who were not using visual objects as their primary target have
found long-lasting (more than 5 months) decreases in visual per-
ception thresholds. In terms of increased firing rates, long-term
practitioners in both Therav¯ada Vipassan¯a(Cahn et al., 2010;Fer-
rarelli et al., 2013) and Tibetan Shamatha (Ferrarelli et al., 2013)
traditions were found to have unexplained increases in occipital
gamma during meditation and NREM sleep that was associated
with lifetime expertise in meditation. The reports of visual hallu-
cinations from this paper suggest that visual areas of the occipital
cortex have become hyperexcitable as a result of focused attention
on non-visual target areas.
While it is still unknown if meditation-related light experi-
ences are indeed caused by suppression of sensory input via alpha
inhibition leading to compensatory disinhibition, this model is
supported by perceptual isolation and sensory deprivation studies.
Visual hallucinations in perceptual isolation (Wackermann et al.,
2002;Pütz et al., 2006) and in sensory deprivation (Hayashi et al.,
1992) are preceded by increases in global alpha power, followed by
sudden high frequency EEG at occipital sites just before the hallu-
cination (Pütz et al., 2006). Although the relationship to a visual
hallucination is unclear, Lo etal. (2003) found a similar progres-
sion in EEG power among meditators who reported an experience
of “inner energy” or“inner light.”
In support of concentration playing a role, it is worth noting
that seven of the nine practitioners who reported lights (78%)
spontaneously connected their meditation-induced light expe-
riences with a period of increased concentration, a claim also
made in Buddhist literature across traditions. This association
fits with existing neurobiological models that suggest that hallu-
cinations can be related to alpha inhibition (Hayashi et al., 1992)
and to the “attentional spotlight” of concentrated attention (Ale-
man and Laroi, 2008, p. 173). Together these data suggest that
the attentional and structural components of meditation serve
to attenuate sensory input, which activates homeostatic forms of
neuroplasticity that lead to hyperexcitability, spontaneous firing,
and hallucinations.
IMPLICATIONS
Implications for clinical neuroscience
The possibility of viewing meditation practice as a form of sen-
sory deprivation has potentially profound implications. Current
medical technologies are combining non-invasive brain stimu-
lation techniques that alter neuronal excitability and enhance
cortical plasticity with training protocols to enhance outcomes
in neuropsychiatric patients, including dementia, pain, addic-
tion, anxiety, and depression (Nitsche et al., 2008;Halko et al.,
2011;Kuo et al., 2013). In addition to improving symptoms, this
enhanced neuroplasticity is also associated with improved learn-
ing, working memory, attention, and other cognitive improve-
ments (Guse et al., 2010). Similarly, the attenuation of sensory
inputs increases neuronal excitability and facilitates a period of
enhanced neuroplasticity (Ffytche et al., 1998;Boroojerdi et al.,
2000,2001). Whether through brain stimulation or sensory
attenuation, changes in neuronal excitability that accelerate neu-
roplasticity can be used to facilitate therapeutic changes beyond
usual training protocols. Since meditation training contains sen-
sory attenuation components, it is possible that this form of
cognitive training may have enhanced neuroplastic potential.
Furthermore, the appearance of visual lights or other hallu-
cinations could potentially serve as an indicator of a period
of enhanced neuroplasticity, during which the ability to make
a significant affective, perceptual, or cognitive shifts could be
maximized.
Implications for the scientific study of meditation
Current researchers assert that “the mental training of meditation
is fundamentally no different than other forms of skill acquisi-
tion that can induce plastic changes in the brain” (Davidson and
Lutz, 2008, p. 176). However, the meditation-induced light expe-
riences described in this paper suggest that meditation is a form
of sensory attenuation that is capable of activating an enhanced
period of neuroplasticity that may not occur in other forms of
skill acquisition. Visual hallucinations arising in the context of
meditation practice may serve as indicators that homeostatic plas-
ticity has been activated and that the brain may be more malleable
to learning and change. While still highly speculative, this sug-
gests that the sensory attenuation components of meditation may
enhance its neuroplastic potential beyond other forms of skill
acquisition.
Meditation researchers are also currently struggling with ways
to measure meditative proficiency or expertise. Current attempts
to measure expertise include self-reported “mindfulness” scales
and the estimated number of hours of practice, both of which
are problematic (Grossman and Van Dam, 2011;Van Dam
et al., 2012). Meditation-induced light experiences are worthy
of further consideration and study as a potential indicator of
meditative proficiency. Converging reports from our subjects,
Buddhist textual sources, as well as multiple scientific research
domains suggest that lights may, at least in some cases, be signs
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Lindahl et al. Meditation-induced light experiences
that the practitioner has attained a certain degree of concentra-
tion. Proficiency in concentration could be determined by the
degree to which a practitioner is able to inhibit irrelevant inputs
from impinging on attention. Meditation-related light experi-
ences may serve as a fairly consistent signpost of concentrative
attainment across Buddhist traditions because such visual hallu-
cinations tend to arise as a result of the attenuation of sensory
input. In addition, because the spontaneous firings that gen-
erate visual hallucinations are associated with the activation of
homeostatic plasticity, they may also herald entry into a time of
enhanced learning, progress, and insight. However, any tradi-
tional or well-known marker of progress potentially introduces
demand characteristics. Further research that triangulates self-
reports with both behavioral and neurobiological markers is
necessary.
Implications for clinical applications of meditation
While light-related experiences arising in the context of medita-
tion are well documented in traditional contexts, they are largely
unknown in clinical settings. In assessing meditators practic-
ing outside of traditional contexts, it is important to carefully
attend to the nuances of light-related discourses when evaluating
whether lights are signs of positive changes or inconsequential side
effects of meditation. In traditional contexts, meditation-induced
light experiences are frequently subject to scrutiny before they
are attributed either positive or negative value. Without the tra-
ditional safeguards of a student-teacher relationship, the clinical
application of meditation practices may be particularly susceptible
to misinterpreting lights and other meditation experiences, since
visual hallucinations are well-known indicators of both psychosis
and vision system impairment. It is important, therefore, not to
uncritically pathologize these anomalous perceptual experiences.
Light-related experiences are likely to be benign, but may cause
distress to the practitioner if they are unexpected or accompa-
nied by other psychological changes. By empirically studying and
documenting meditation-induced light experiences and describ-
ing them within their traditional Buddhist frameworks, we hope
to help educate clinicians and meditation teachers about some of
the common side effects of meditation in order to create more
appropriate support structures for practitioners.
Study limitations and suggestions for future research
The investigation of phenomena that has received little empiri-
cal attention requires inductive methods that are intended to be
free of both assumptions and hypotheses. Thus, our grounded-
theory-based approach, which is appropriate for this stage of
research, is both a strength and a limitation. As a strength, the
open-ended approach, which discourages researchers from asking
specific questions that would bias the subjects’ answers, helps to
minimize demand characteristics of the interview. As a limitation,
by not asking participants if they had certain experiences, such
as lights, the current report may have underestimated the actual
prevalence of light-related meditation experiences. Our current
approach can only answer the question“What types of experiences
arise in the context of meditation?” Many other important ques-
tions will need to be pursued through additional theory-driven
research.
This study has a number of other limitations. Demand char-
acteristics and subject expectations are an inherent limitation of
many types of studies, including nearly all intervention studies,
meditation studies, and pharmacology studies. In clinical med-
itation studies, the simple fact that the name of a meditation
program includes the phrase “stress reduction” sets up expec-
tations that the program will reduce stress. Similarly, certain
experiences may be more or less frequently reported depending
on the subject’s expectations of what is supposed to happen in the
context of meditation. There are several reasons why the influ-
ence of subjects’ expectations are minimized in this study. First,
lights are not commonly described in American Buddhist medi-
tation literature and are likely not well known to most American
practitioners. Participants in this study were deliberately recruited
on the basis that the experiences they had with meditation were
unexpected. In our sample, only one participant made an explicit
association between their own experience and Buddhist theo-
ries about the significance of lights. The subjects also tended
to describe their experience in non-Buddhist terms such as the
“curtain of light,” “Christmas lights,” “electrical sparks,” or “little
stars.”
It may seem plausible that the light-related experiences in our
sample were just hypnagogic hallucinations that were caused by
falling asleep and not by meditation practice. We find it unlikely
that sleep played a role in these experiences for several rea-
sons. First, hypnagogic hallucinations are extremely common
(Ohayon et al., 1996) and we would therefore expect the preva-
lence in our sample to be much higher and also much more
well known to the average meditator. Second, Buddhist medita-
tion practice, especially among more-experienced practitioners,
is associated with an increased alertness that is neurologically
distinct from and resistant to sleepiness (Britton et al., 2013).
Third, as described previously, hypnagogic hallucinations are
phenomenologically and neurologically different from waking
hallucinations that arise in the context of sensory deprivation
or perceptual isolation (Cheyne et al., 1999a,b;Ohayon, 2000;
Wackermann et al., 2002;Collerton and Perry, 2011;Fenelon,
2013). Finally, several of our subjects reported that their eyes were
open during these experiences, and mentioned them in conjunc-
tion with concentration, never drowsiness or sleep. Nevertheless,
future studies of meditation-induced light experiences should
include real-time measurements of brain activity to rule out this
possibility.
Now that some of the basic phenomenology of meditation-
related light experiences has been described, we can begin to
investigate follow-up questions in a hypothesis-driven experi-
mental design that uses quantitative statistical analyses. Future
studies would benefit from investigating light-related experiences
in larger sample of practitioners, with a range of practice types
and durations, including secular, clinical meditation practices
(e.g., MBSR). The hypothesized link between concentration and
meditation-induced light experiences could be empirically inves-
tigated with neuropsychological tests of attention (e.g., SART) and
concurrent neuroimaging (fMRI, EEG). Real-time neuroimag-
ing concurrent with reports of light experiences may be able to
determine neurological mechanisms as well as the possible rela-
tionship to hypnagogic hallucinations. Future studies should also
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Lindahl et al. Meditation-induced light experiences
make an effort to control for light exposure, both in terms of the
ambient light in the environment, and in terms of whether the
eyes are open or closed. Changes in light exposure can result in
compensatory changes in the retina (dark adaptation) that may
also cause short-lived changes in visual experience (Lamb and
Pugh, 2004). Similarly, visual after-effects are also brief adap-
tations in response to certain stimuli that may be mediated at
the level of the eye or brain (Rhodes et al., 2003). Because eye-
based changes are less enduring than brain-based changes, more
information about the duration of meditation-induced light expe-
riences may also help elucidate their underlying sensory and neural
mechanisms.
CONCLUSION
This paper demonstrates importance of engaging with traditional
Buddhist presentations of the states and stages of meditation, as
what is described in the texts in many cases is very closely linked
with reports of meditation experience derived from contempo-
rary practitioners. By investigating traditional Buddhist sources,
meditation researchers and clinicians will be more informed about
the varieties of meditation experiences and their possible signifi-
cance. Investigating meditation-induced light experiences suggests
that on account of restricting attention by deselecting sensory
stimuli, certain meditation practices may function in a manner
analogous to sensory deprivation and perceptual isolation. The
arising of lights may signal a period of enhanced neuroplasticity
and potential for important and enduring shifts. Further research
should investigate whether it is the unique configuration of sen-
sory deprivation, attentional training, and investigative processes
that accounts for why meditative practices tend to lead to enduring
perceptual and affective changes and cognitive insights.
ACKNOWLEDGMENTS
Funding for this research was provided by grants T32-AT001287,
MH067553-05, and K23-AT006328-01A1 from the National Insti-
tutes of Health, the Mind and Life Institute, the Lenz Foundation,
Hershey Foundation, the Bial Foundation,and the Brown Univer-
sity Contemplative Studies Initiative. We would also like to thank
the Clinical and Affective Neuroscience Laboratory for their time
and Jack Kornfield for his pioneering efforts and support of this
project.
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Conflict of Interest Statement: The authors declare that the research was conducted
in the absence of any commercial or financial relationships that could be construed
as a potential conflict of interest.
www.frontiersin.org January 2014 |Volume 4 |Article 973 |15
“fpsyg-04-00973” — 2013/12/30 — 17:16 — page 16 — #16
Lindahl et al. Meditation-induced light experiences
Received: 29 August 2013; accepted: 09 December 2013; published online: 03 January
2014.
Citation: Lindahl JR, Kaplan CT, Winget EM and Britton WB (2014) A phenomenol-
ogy of meditation-induced light experiences: traditional Buddhist and neurobiological
perspectives. Front. Psychol. 4:973. doi: 10.3389/fpsyg.2013.00973
This article was submitted to Consciousness Research, a section of the journal Frontiers
in Psychology.
Copyright © 2014 Lindahl, Kaplan, Winget and Britton. This is an open-access
article distributed under the terms of the Creative Commons Attribution License
(CC BY). The use, distribution or reproduction in other forums is permitted,
provided the original author(s) or licensor are credited and that the original pub-
lication in this journal is cited, in accordance with accepted academic practice. No
use, distribution or reproduction is permitted which does not comply with these
terms.
Frontiers in Psychology |Consciousness Research January 2014 |Volume 4 |Article 973 |16
... To learn about a meditation technique or experience, it is essential that researchers consider understandings of experts within the meditation tradition (Gyatso, 2016;Lindahl et al., 2014). Traditional understandings of experts, in written form, are a major source of information about meditation practices. ...
... Traditional understandings of experts, in written form, are a major source of information about meditation practices. Where researchers have regard to these expert accounts, they typically concentrate on a small subset of the total publications (e.g., Lindahl et al., 2014;Lutz et al., 2015;Wahbeh et al., 2018). There are often thousands of traditional publications for a particular practice, and it is not practicable to review them all. ...
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Booming Western interest in mindfulness and meditation has significantly mainstreamed breath and breathing practices, where focussed breathing is taken to be conducive to novel psychological states. Thanks to the regulation of breathing patterns, patterns in our thinking are not just affected but revealed, together with their entanglement with respiration (in a variety of looping effects here considered as ‘biocognitive feedback’). What makes this reciprocal feedback possible is the structural intimacy and co-dependency of breath and consciousness—a dyadic and dynamic relationship already conceptualised by William James, and today reappraised by contemporary, Buddhist-inspired cognitive sciences. Critically integrating psychological, cognitive, phenomenological, and narratological frameworks, this essay investigates the co-dependent intimacy between breath and cognition as represented, explored, and complicated in the narrative work of Samuel Beckett.
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Yoga, tantra and other forms of Asian meditation are practised in modernized forms throughout the world today, but most introductions to Hinduism or Buddhism tell only part of the story of how they developed. This book is an interpretation of the history of Indic religions up to around 1200 CE, with particular focus on the development of yogic and tantric traditions. It assesses how much we really know about this period, and asks what sense we can make of the evolution of yogic and tantric practices, which were to become such central and important features of the Indic religious scene. Its originality lies in seeking to understand these traditions in terms of the total social and religious context of South Asian society during this period, including the religious practices of the general population with their close engagement with family, gender, economic life and other pragmatic concerns.
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Hallucinations occur in a great variety of neurological conditions and are facilitated by sensory loss. The common end pathway of their pathophysiology involves the activation of cortical sensory areas implicated in normal sensory ­processing. Based on the presumed pathophysiology, we here classify the hallucinations in four main groups. In migraine aura and epilepsy, hallucinations result from spontaneous intrinsic overactivity in hyperexcitable sensory cortical areas. Deafferentation, i.e. the loss or impairment of sensory input, facilitates hallucinations in the corresponding sensory modality, probably by leading to chronic hyperexcitability of the corresponding cortical areas. The archetypal example of this mechanism is the Charles Bonnet syndrome, where hallucinations are associated with visual impairment. A third mechanism relies on the dissociation of dream and sleep mechanism, as illustrated by hypnagogic and hypnopompic hallucinations. Finally, in the course of neurodegenerative diseases such as Parkinson’s disease and dementia with Lewy bodies, hallucinations are frequent and probably result from a combination of factors, including dysfunction of both bottom–up sensory processing and top–down modulatory mechanisms, as well as dream intrusion phenomena and facilitating pharmacological factors.