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C
URRENT
O
PINION
Color synesthesia. Insight into perception, emotion,
and consciousness
Avinoam B. Safran
a,b
and Nicolae Sanda
a,c
Purpose of review
Synesthesia is an extraordinary perceptual phenomenon, in which individuals experience unusual percepts
elicited by the activation of an unrelated sensory modality or by a cognitive process. Emotional reactions
are commonly associated. The condition prompted philosophical debates on the nature of perception and
impacted the course of art history. It recently generated a considerable interest among neuroscientists, but
its clinical significance apparently remains underevaluated. This review focuses on the recent studies
regarding variants of color synesthesia, the commonest form of the condition.
Recent findings
Synesthesia is commonly classified as developmental and acquired. Developmental forms predispose to
changes in primary sensory processing and cognitive functions, usually with better performances in certain
aspects and worse in others, and to heightened creativity. Acquired forms of synesthesia commonly arise
from drug ingestion or neurological disorders, including thalamic lesions and sensory deprivation (e.g.,
blindness). Cerebral exploration using structural and functional imaging has demonstrated distinct patterns
in cortical activation and brain connectivity for controls and synesthetes. Artworks of affected painters are
most illustrative of the nature of synesthetic experiences.
Summary
Results of the recent investigations on synesthesia offered a remarkable insight into the mechanisms of
perception, emotion and consciousness, and deserve attention both from neuroscientists and from clinicians.
Keywords
cerebral disorders, color, consciousness, emotion, perception, synesthesia, vision
INTRODUCTION
Synesthesia is an extraordinary perceptual phenom-
enon, in which the world is experienced in unusual
ways. In this condition, a particular stimulation in a
given sensory modality (e.g., touch) or cognitive proc-
ess (e.g., computing) automatically triggers additional
experiences in one or several other unstimulated
domains (e.g., vision, emotion) [1]. An illustrative
presentation of the condition would be that of a given
person in whom hearing the sound of a trumpet
consistently elicits the vision of brightly colored
triangles dancing in front of his eyes, in association
with a sensation of pressure on his arms, letting him
feel uncomfortable to sit still. Stimuli generating
additional unusual experiences are termed ‘inducers’,
whereas internally produced synesthetic percepts are
termed ‘concurrents’ [2].
Synesthetic experiences have had over the cen-
turies far-reaching sociocultural implications. They
prompted philosophical debates on the nature of
perception, consciousness and even talent and
creativity, and significantly impacted the course
of art history, notably at the turn of the 20th Cen-
tury [3–6]. Moreover, favored by the emergence of
sophisticated tools for functional brain exploration,
they have generated a considerable interest among
neuroscientists [6,7]. Clinical significance of synes-
thesia, however, is still largely underevaluated.
Although some synesthetic phenomena express
the presence of a disease, developmental synesthesia
as a rule is considered an individual cognitive
a
Sorbonne Universite
´s, UPMC Univ Paris 06, UMR_S 968, Institut de la
Vision, INSERM, U968, CN RS, UMR_7210, Paris, France,
b
Department
of Clinical Neurosciences, Geneva University School of Medicine, Gen-
eva, Switzerland and
c
Neurology Department, Ho
ˆpital Foch, Suresnes,
Paris, France
Correspondence to Avinoam B. Safran, MD, 17 rue Moreau, Paris,
F-75012, France. E-mail: avinoam.safran@unige.ch
Curr Opin Neurol 2015, 28:36–44
DOI:10.1097/WCO.0000000000000169
This is an open-access article distributed under the terms of the Creative
Commons Attribution-NonCommercial-NoDerivatives 4.0 License, where
it is permissible to download and share the work provided it is properly
cited. The work cannot be changed in any way or used commercially.
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REVIEW
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variant in the normal population [8]. Unfortu-
nately, the astonishing features of these percepts
have too often led the entourage of affected per-
sons, including physicians, to wrongfully consider
them as confabulators, drug users, or schizo-
phrenics [7]. In this regard, the following history
reported by Vincent Van Gogh is representative.
While in 1885 the painter was taking piano lessons,
his teacher noticed that he was continually relating
the sounds of the piano keys with specific colors;
considering then that his pupil was insane, the
teacher sent him away [9]. It is therefore under-
standable that synesthetes (i.e., persons affected
by synesthesia) commonly avoid mentioning their
percepts and even tend to close on themselves in
psychological distress [10–12]. For that very reason,
scientific studies probably underestimate synesthe-
sia prevalence in the general population.
SYNESTHESIA VARIANTS
Synesthesia is commonly classified as developmen-
tal and acquired. Developmental synesthesia
appears to be the most frequent type of this con-
dition, with a 4.4% estimated prevalence rate [13]. It
can run in families and demonstrate Mendelian
transmission [14]. Different forms of synesthesia
can be observed in the same person or in the same
family [15]. The condition is occasionally associ-
ated with autism spectrum disorders, like Asperger
syndrome [16].
The following criteria have been proposed to
help establishing a diagnosis of developmental syn-
esthesia: induced percepts should be elicited by a
specific stimulus, they should be automatically
generated, and typically have percept-like qualities
[8,17,18]. Usually, pairings of inducers and concur-
rents are specific (i.e., a particular stimulus consist-
ently triggers the same synesthetic percept). They
tend to be stable over time in a given individual,
although this has recently been challenged by the
finding that synesthetic ability can disappear over
time [19
&
].
Acquired forms of synesthesia have also been
reported, essentially associated with neurologic dis-
orders or following psychotropic drug ingestion
[20–23]. In contrast to its developmental counter-
part, acquired synesthesia does not demonstrate
either idiosyncrasy or automaticity or stability
[3,24
&
].
So far, over 60 types of synesthetic phenomena
have been described. The apparently most common
form (with a 64.4% prevalence among synesthetes) is
grapheme– color synesthesia, in which achromatic
letters or digits automatically trigger an idiosyncratic
color perceptual experience (e.g., the letter ‘m’ indu-
ces blue color percepts) [25,26] (Fig. 1 [27]). The
second most prevalent form is time unit (e.g., Mon-
day, January)– color synesthesia (22.4%), followed by
musical sound– color synesthesia (18.50%) [26,28]
(Figs 2 and 3 [29,30]). Inducers and concurrents also
include smells, tastes, temperatures, personalities
and emotions [26], and can be multiple during a
single synesthetic experience. Thus, percepts
induced by grapheme–color synesthesia are
occasionally accompanied by shape, texture, move-
ment features, and even nonvisual percepts such as
smells and tastes, particularly emotions [31,32]. Syn-
esthetic colors generated in grapheme–color synes-
thesia are determined by systematic rules rather than
randomly occurring, and basedon the psycholinguis-
tic mechanisms of language processing. The same
occurs with both Latin characters and Chinese ideo-
grams [33,34
&
].
An additional type of colored synesthetic experi-
ence was recently described and termed ‘swimming-
style color synesthesia’. It is characterized by the
generation of specific colored percepts upon con-
ceptual representation of swimming in a particular
style (i.e., breast, backstroke, crawl, and butterfly)
[35,36]. This phenomenon could be triggered by
either presenting a picture of a swimming individual
or asking the tested individual to think about a
given swimming style. It was speculated that this
synesthetic type was caused by overactivity in the
mirror neuron system responding to the specific
representation [37].
Synesthetic experiences are labeled ‘lower’ when
triggered by elementary perceptual processes (e.g.,
texture) or ‘higher’ when involving a higher cogni-
tive process (e.g., semantic, computing) [7,38,39].
Synesthetes who experience the atypical percepts in
an internal space (‘in the mind’s eye’, as they some-
times describe it) have been categorized into ‘asso-
ciators’, whereas those for whom the additional,
KEY POINTS
!Persons presenting with synesthesia commonly avoid
mentioning their unusual percepts and even tend to
close on themselves in psychological distress.
!Developmental synesthesia predisposes to changes in
primary sensory processing and cognitive functions,
and heightened creativity.
!Affected individuals demonstrate distinct patterns in
cerebral activation and connectivity, compared
with nonsynesthetes.
!Acquired forms of synesthesia are commonly related to
drug ingestion or neurological conditions.
Color synesthesia Safran and Sanda
1350-7540 Copyright !2015 Wolters Kluwer Health, Inc. All rights reserved. www.co-neurology.com 37
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
atypical percept appears to be ‘out there’, overlaying
the actual, external surrounding, are designated as
‘projectors’ [40,41].
PAINTERS’ COMPREHENSION OF
SYNESTHESIA
Painters commonly demonstrate unique skills in
the observation of visual phenomena, in which
depiction offers an invaluable source of information
for neuroscientists investigating visual function in
health and disease [42–46]. Regarding our under-
standing of synesthesia, painters’ contribution is
particularly precious. Among this population, the
prevalence of synesthesia was found higher than in
general population; in addition, their percepts are
frequently represented in their artworks [47].
Indeed, synesthete prevalence among fine art stu-
dents was estimated to be 23% [48]. Among art
students, prevalence of grapheme–color synesthesia
alone was reported to be 7%, compared to 2% in
controls [49].
Interestingly, synesthetes’ personality profile
favors their involvement in creative, artistic activi-
ties [50]. Recently evaluated by a structured measure
of personality (the ‘Big Five Inventory’) and by
(a) (b)
FIGURE 1. Visual segregation test demonstrating improved digit identification performances by grapheme–color synesthetes.
(a) Pattern presented to the tested individuals and (b) same pattern as perceived by a grapheme–color synesthete. To identify
digits ‘2’, a person with regular visual perception must perfom a systematic search; in contrast, for a grapheme –color
synesthete, who links a specific color with a given number, digits ‘2’ instantly pop-out. Adapted with permission [27].
FIGURE 2. ‘Vision’ 1996, by Carol Steen, private
collection, represents a synesthetic visual experience elicited
in this synesthetic painter by a needle puncture during an
acupuncture session [29]. Reproduced with permission.
FIGURE 3. ‘Kondo’s Trumpet’ 2010, by Carol Steen, private
collection, depicts the synesthetic visual experience elicited by
the timbre of that trumpet [30]. Reproduced with permission.
Neuro-ophthalmology and neuro-otology
38 www.co-neurology.com Volume 28 !Number 1 !February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
questionnaires assessing empathy, synesthetes
exhibited higher levels of ‘Openness to Experience’,
considered to be related to imagination and artistic
tendencies, and higher levels of ‘Fantasizing’, con-
ceptually related to ‘Openness’ [51
&
]. Moreover, gra-
pheme–color synesthetes show a distinct cognitive
style, with a preference for processing information
in both verbal and vivid imagery styles [52
&
].
The peculiar world perception decisively
impacted the artistic work of numerous ‘synesthetic’
artists. Thus, Kandinsky’s nonfigurative paintings and
theory of synesthesia [53], prompted by his experi-
ence of extraordinary visions of lines and colors eli-
cited by the sound of musical instruments, paved the
way to abstract art and thus marked a turning point
in history of art [47]. A recent analysis of Kandin-
sky’s works using the Implicit Association Test
found no implicit association between the original
color–form combinations, and authors concluded
that these are probably not a universal property of
the visual system [44].
Most informative indications on the character
of percepts commonly observed by synesthetic
painters, as well as on the compulsive manner they
depict their visions, were provided by Carol Steen, a
remarkable synesthetic painter [54]. She emphasized
that synesthetes’ internal world differs tremendously
from what is commonly perceived by others. For
instance, colors can be perceived intensely bright,
‘similar to sunlight streaming through a stained glass
window’. Noteworthy, she felt that the ‘overwhelm-
ing beauty of what she has seen’ powerfully com-
pelled her to capture and reproduce her visions, and
that ‘urgency to paint needed to be expressed’. To
depict the brightness of colors perceived, synesthetic
painters reportedly often apply with speed, pure,
unmixed oil paint, or watercolor straight from the
tube. Faithfully representing their perceptions may
require breaking some long-standing rules, a feature
that – as underlined by Carol Steen – characterizes
modern art. The artist also specified that her visions
were never representational nor figurative. This is
apparently typical of many synesthetes’ experiences,
and probably explains why synesthetic artwork com-
monly looks abstract, even though it is a ‘ realistic’
depiction of the artist’s perceptions [54].
EMOTIONAL DIMENSION OF
SYNESTHESIA
Emotional reactions play a prominent role in synes-
thetic processes. They are commonly experienced in
such conditions [32,55], acting as either inducer,
concurrent, or modulator [32,56]. A conflict between
the actual color of a stimulus and synesthetically
induced percepts can generate discomfort, whereas
‘pleasantness’ is experienced when synesthetic and
actual stimulus features match. Some synesthetes
indicate that all disagreeable events generate same
color, specific for the given individual. Saturation of
evoked colors is susceptible to be altered by mood
[32]. In some personality–color type of synesthesia,
viewing known faces elicits emotionally mediated
color percepts, presenting either as colored faces or
colored auras around heads [1,32,57] (Figs 4 and 5
[58]), conceivably as a result of cross-activation
between right, face recognition area and neighboring
V4 color cortex [7,59]. In this regard, the following
delightful dedication by Julia Simner, a prominent
expert in synesthesia, is illustrative: ‘For my two
children: the blue one (Indigo) and the brown one
(Tommy Bruno)’ [60]. In the so-called ‘ordinal lin-
guistic personification’ synesthesia, letters have
emotional valences, as well as a sex and personality
[61,62]. Sexual arousalalso triggers synesthetic experi-
ences in some 2% of individuals [26]. These perceptual
phenomena mainly consist of colored shapes, less
commonly of flavors, smells, sounds,or temperatures,
and are associated with a higher degree of trance and
loss of environmental boundaries [63].
FIGURE 4. ‘I and the Village’ 1911, by Marc Chagall.
Museum of Modern Art, New York, USA. Reproduced with
permission, !Adagp, Paris 2014. Over decades, Chagall
repeatedly depicted using intense green or blue colors, the
faces of central characters in his paintings [58]. This most
probably reflected a variant of personality–color synesthesia.
Color synesthesia Safran and Sanda
1350-7540 Copyright !2015 Wolters Kluwer Health, Inc. All rights reserved. www.co-neurology.com 39
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
Cerebral structures processing emotion are
altered in developmental synesthestes. MRI explora-
tion of associator grapheme–color synesthetes
recently brought further evidence of structural
changes in emotional areas both at cortical and at
subcortical levels [64
&&
]. Acquired cerebral disorders
are also susceptible to cause emotional synesthetic
percepts. Thus, a patient who had sustained a post-
erolateral thalamus hemorrhage [24
&
] experienced
blue photisms, intense extracorporeal sensation,
and ‘orgasmic’ ecstasy when hearing brass instru-
ments, or severe disgust sensations when reading
words printed in blue characters. Occurrence, expres-
sion, and the underlying mechanisms of affect-
related forms of synesthesia have recently been
reconsidered [56].
IMPACT OF SYNESTHESIA ON COGNITIVE
FUNCTIONS
Synesthetic experiences impact the cognitive func-
tions to a larger extent than believed in the
past [65,66
&&
,67,68]. Constitutional synesthesia
predisposes to better performances in certain aspects
and worse in others. Although having better color
perception compared with nonsynesthetes [69,70],
synesthetes present impaired motion [66
&&
,67] and
speech perception [71]. Speech perception deficit
could be a consequence of the impaired motion
perception, namely the biological movement of lips
or of a much wider deficit in multisensory integration
[71]. In grapheme– color and tone–color synesthetes,
increased gray matter volume in the left posterior
fusiform gyrus and decreased gray matter volume
of the anterior part of the same gyrus and in the left
MT/V5 support these hypotheses [72]. Improved
perception can occur within both inducing stimulus
and concurrent domains [68]. Memory was also
found enhanced when using synesthetic percepts
[25,73].
Improved performances depend partly on
preconscious mechanisms, operating early in sen-
sory processing [74]. Thus, a recent investigation
using pictures containing hidden letters found
that grapheme–color projectors recognized the
letters faster than nonsynesthetes; interestingly,
tested individuals noted that concurrent colors
were generated before conscious letter recognition
[75
&
]. Grapheme– color synesthesia even allows com-
puting via synesthetically perceived colors [68] and as
expected, emotional experience modulates synes-
thetes’ performances [55].
CEREBRAL DISORDERS CAUSING
SYNESTHESIA
Acquired forms of synesthesia have been related to
a variety of neurological conditions, including
migraine [76,77], multiple sclerosis – radiologically
isolated syndrome [34
&
], posthypnotic suggestion
[78], and drug ingestion [20,79]. In recent years,
secondary synesthesia has been reported following
thalamic stroke [24
&
,80–83]: two of these affected
individuals experienced colored synesthetic per-
cepts [24
&
,83]. Thalamic insult may induce large-
scale reorganization of the brain, modify the bal-
ance between excitatory and inhibitory connections
in high-order visual areas, and favor the develop-
ment of synesthesia [80].
Sensory deprivation favors the occurrence of
synesthetic phenomena. With blind people, non-
visual stimuli tend to elicit various percepts in the
suppressed sensory modality, including colored
photisms [84,85] presumably by cross-modal acti-
vation of the deafferented cortex [86]. Sound-
induced photisms in visually affected people are a
well recognized phenomenon [87]. Six late-blind
individuals were recently reported experiencing
colored phenomena when hearing or thinking
FIGURE 5. ‘Half-Past Three’ (‘The Poet’) 1911, by Marc
Chagall. Philadelphia Museum of Art, The Louise and Walter
Arensberg Collection, Philadelphia, PA, USA. Reproduced
with permission, !Adagp, Paris 2014. For comments, see
the legend of Fig. 4.
Neuro-ophthalmology and neuro-otology
40 www.co-neurology.com Volume 28 !Number 1 !February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
about letters, numbers, and time-related terms
[88,89]. In one of these individuals, touching Braille
characters induced colored photisms. A patient of
ours, blinded by bilateral arteritic anterior ischemic
optic neuropathy, reported perceiving colored
photisms when brushing his teeth or hearing a hand
clap (personal observation). We also recently
observed an unusual case of a late-blind individual
suffering from retinitis pigmentosa who volun-
teered consistently ‘seeing’ his limbs when moving
them, a phenomenon presumably related to cross-
modal activation of his visual cortex by propriocep-
tive inputs [90
&
].
Brain lesions disrupting canonical networks
and sensory input to associative areas are also
susceptible to induce synesthetic-like hallucina-
tory syndromes. A right monophtalm patient
with right parosmia reported intricate visual and
olfactory hallucinations following a right occipi-
totemporal stroke [91]. The patient described
seeing people with strong odors. The presumed
mechanism of these hallucinations was the desin-
hibition of the connections from the visual associ-
ation areas to perirhinal and parahippocampal gyri
[92].
ARTIFICIALLY ELICITED SYNESTHESIA
Sensory substitution devices (SSDs) have been devel-
oped to provide blind individuals with information
on their visual surrounding. They convey visual
information through another sensory modality, like
audition [93]. Visual-to-auditory SSDs proceed by
online translation of camera-captured views into
sounds, which represent the visual features of the
scene [93,94]. Users of such devices commonly claim
to ‘see’ the objects figured by sounds, and therefore
sensory substitution has been considered a kind of
synthetic synesthesia [93]. Interestingly, functional
magnetic resonance imaging (fMRI) investigations
using a visual-to-auditory SSD, both in blindfolded
healthy individuals [95] and in congenitally blind
individuals [96
&
], showed activation of visual areas.
Whether – and to what extent – SSD users also
perceive the auditory stimulus as a sound is debated
[97,98].
Sensory substitution, however, differs in some
respect from the naturally occurring synesthesia.
Indeed, intended to reliably figure the visual sur-
rounding, percepts elicited by SSDs are elaborated,
whereas regular synesthetic phenomena exhibit
essentially idiosyncratic features [8]. Further, in
contrast to SSD-provoked synesthetic experiences,
in developmental synesthesia, inducers do not
conform to sensorimotor contingencies of the con-
current modality [98].
NEURAL FOUNDATIONS OF SYNESTHESIA
Assumptions have been made on the mechanisms
underlying synesthesia, including hyperconnectiv-
ity between cortical areas [99], reduced level of feed-
back from inhibitory cerebral structures [2], learned
association in early life [100], and a normal percep-
tual mechanism incompletely suppressed in synes-
thetes [17]. Neurocognitive models have been
elaborated [101–105].
In recent years, brain-imaging studies brought
further evidence that synesthetes connect more
inside and between sensory regions and less with
remote areas, especially the frontal cortex. Indeed,
these individuals exhibit increased intranetwork
connectivity in medial visual, auditory and intra-
parietal networks, and internetworks connectivity
between the medial and lateral visual networks,
the right frontoparietal network and between the
lateral visual and auditory networks. In contrast,
nonsynesthetes have more intranetwork connec-
tions within frontoparietal network [106]. When
presented with inducers, synesthetes exhibit a
clustering pattern of activated brain areas uniting
more visual regions, whereas nonsynesthetes acti-
vate particularly frontal and parietal regions [107
&&
]
(Fig. 6).
Involvement of the bottom-up and top-down
mechanisms has further been considered [105,108 –
111]. The bottom-up model stipulates that the con-
current representation is prompted by the inducer
representation via over represented and overactive
horizontal connections, whereas the top-down
model proposes that the inducer stimulates the
concurrent percept via an input from a convergent,
higher order integrator [2].
Using dynamic causal modeling, Van Leeuwen
et al. [106] have shown that projectors exhibited
effective connectivity patterns involving a bottom-
up mechanism, whereas associators used a top-down
mechanism. However, a recent electroencephalo-
graphic (EEG) study found evidence favoring the
top-down disinhibited feedback model as the
core of the synesthetic phenomenon [112
&&
].
Reduction of long-range couplings in the theta
frequency band could facilitate the top-down feed-
back. An fMRI study demonstrated that, in contrast
with projectors, associators’ synesthetic experience
was related to areas linked to memory processes,
including hippocampus and parahippocampal gyrus
[113,114].
THALAMUS AND DEVELOPMENTAL
SYNESTHESIA
It was suggested that congenital alterations
in thalamic circuitry might be responsible for
Color synesthesia Safran and Sanda
1350-7540 Copyright !2015 Wolters Kluwer Health, Inc. All rights reserved. www.co-neurology.com 41
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
atypical cortical morphology and connections,
found with different synesthetic phenotypes
[64
&&
,115]. Cytoarchitectonic maturation of the
primary sensory areas and the development of
their specific connections are highly dependent
on the thalamic input [116]. Enucleation in pre-
natal macaque drastically alters the equivalents of
V1 and V2 visual cortices, and induces rich non-
canonical connections with somatosensory, audi-
tory, and frontal areas [117], resembling transient
fetal connections [118]. Thus, the visual cortex
ends up treating other types of information. Like-
wise, congenitally blind humans exhibit occipital
cortex activation following auditory or somatosen-
sory stimulation [96
&
]. It is therefore conceivable that
in developmental synesthesia, congenitally anoma-
lous sensory input leads to abnormal synaptic
pruning and differences in brain connectivity. In
grapheme– color synesthetes, low white matter
densities in pulvinar, medial and lateral ventral
posterior nuclei, and low fractional anisotropy in
medial dorsal and ventral anterior nuclei suggest a
constitutional disconnection and hypoconnection
between thalamus and cerebral cortex [64
&&
]. The
concerned white matter tracts project to the left
prefrontal cortex and bilateral temporal and posterior
parietal cortex, regions that in synesthetes are dis-
tinct both in structure and function. Secondary syn-
esthesia after thalamic stroke also support the
involvement of thalamic output in synesthetic
phenomena [24
&
,80– 83].
CONCLUSION
Over the last few years, substantial advances have
been made in the understanding of synesthesia,
and hence more globally in the comprehension of
perception and consciousness. Fortunately, aware-
ness of this condition in the societal environment
also significantly improved, finally allowing syn-
esthetes to feel relieved by the so badly needed
recognition of their particular situation. In a near
future, in addition to the expected deepening of
the explorations undertaken, elaborating a more
comprehensive definition of synesthesia would be
welcomed. Currently used criteria are rather
restrictive for a condition that is quite polymor-
phic in nature. This process, however, is customary
in the history of medicine, which consists of
initially establishing a restricted definition to
encapsulate the core of the condition and then
broadening it, taking into account the numerous
subtle presentations encountered.
Acknowledgements
The authors thank Katia Marazova, MD, PhD, for
editorial assistance.
Financial support and sponsorship
Funding: This study was supported in part by grants from
LABEX and Humanis.
Conflicts of interest
There are no conflicts of interest.
Graphemes
All
Pseudographemes
3
D
S
Synesthetes
Control
FIGURE 6. Cerebral activation revealing distinct activity patterns for controls and synesthetes during grapheme and pseudo-
grapheme presentation. Synesthetes demonstrate the most significant activity in the bilateral posterior inferior temporal gyri.
Reproduced with permission [107
&&
].
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42 www.co-neurology.com Volume 28 !Number 1 !February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
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