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Citation: Jin, F.; Hsu, S.-M.; Li, Y. A
Systematic Review of Aphantasia:
Concept, Measurement, Neural Basis,
and Theory Development. Vision 2024,
8, 56. https://doi.org/10.3390/
vision8030056
Received: 11 July 2024
Revised: 11 September 2024
Accepted: 18 September 2024
Published: 22 September 2024
Copyright: © 2024 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
vision
Review
A Systematic Review of Aphantasia: Concept, Measurement,
Neural Basis, and Theory Development
Feiyang Jin 1,2, Shen-Mou Hsu 3and Yu Li 1,4,*
1Applied Psychology Program, Department of Life Sciences, BNU-HKBU United International College,
Zhuhai 519087, China; sofiajin0830@gmail.com
2Department of Applied Social Sciences, The Hong Kong Polytechnic University, Hong Kong, China
3Imaging Center for Integrated Body, Mind and Culture Research, National Taiwan University,
Taipei 10617, Taiwan; smhsu@ntu.edu.tw
4Guangdong Provincial Key Laboratory of Interdisciplinary Research and Application for Data Science,
BNU-HKBU United International College, Zhuhai 519087, China
*Correspondence: yuli@uic.edu.cn
Abstract: People with aphantasia exhibit the inability to voluntarily generate or form mental imagery
in their minds. Since the term “aphantasia” was proposed to describe this, it has gained increasing
attention from psychiatrists, neuroscientists, and clinicians. Previous studies have mainly focused
on the definition, prevalence, and measurement of aphantasia, its impacts on individuals’ cognitive
and emotional processing, and theoretical frameworks synthesizing existing findings, which have
contributed greatly to our understanding of aphantasia. However, there are still some debates
regarding the conclusions derived from existing research and the theories that were constructed from
various sources of evidence. Building upon existing endeavors, this systematic review emphasizes
that future research is much needed to refine the definition and diagnosis of aphantasia, strengthen
empirical investigations at behavioral and neural levels, and, more importantly, develop or update
theories. These multiple lines of efforts could lead to a deeper understanding of aphantasia and
further guide researchers in future research directions.
Keywords: aphantasia; visual imagery; mental imagery; vividness; cognitive functioning; mental health
1. Introduction
In 1880, Galton first systematically elucidated and studied individual differences in
visual imagery, designing specific questions to investigate related phenomena [
1
]. Visual
imagery ability refers to the capacity of individuals to create mental images of objects
or scenes that are not in front of their eyes [
2
], such as closing one’s eyes and imagining
a brightly colored apple. Visual imagery has been shown to be closely associated with
various cognitive functions and everyday activities. The active generation of visual imagery
is an important cognitive ability of humans. However, the human capacity for visual
imagery can be considered a spectrum, with some individuals exhibiting exceptionally
vivid visual imagery, which is referred to as hyperphantasia [
3
,
4
], while other individuals
can only produce limited or even deficient visual imagery. In 2015, Zeman and colleagues
introduced the term “aphantasia” to describe absent or marked reduced mental imagery in
individuals [5].
Presently, investigations into aphantasia concentrate on delineating its nature, assess-
ing its frequency, devising measurement methods, examining its influence on cognitive
and emotional functions, identifying related disorders, probing its neural underpinnings,
and developing conceptual models. In particular, studies examining cognitive functions
primarily explore how aphantasia impacts memory, atemporal and future imagination, spa-
tial imagery, mental rotation abilities, and visual search abilities (e.g., [
6
,
7
]). Neuroimaging
Vision 2024,8, 56. https://doi.org/10.3390/vision8030056 https://www.mdpi.com/journal/vision
Vision 2024,8, 56 2 of 20
studies indicate a possible link between the lack of visual imagery and the visual cortex
(e.g., [2,7,8]).
Aphantasia is still a relatively new topic in psychological research and has not received
widespread attention from researchers. This review aims to summarize the existing empiri-
cal studies and theoretical viewpoints on aphantasia. First, our discussion will concentrate
on the definition, prevalence, heritability, and assessment of aphantasia. Second, we will
synthesize the findings regarding aphantasia’s influence on cognitive functions. Third, we
will examine its potential associations with related disorders. Fourth, we will summarize
existing evidence on the neural basis of aphantasia. Fifth, we will critically appraise the
principal theoretical models. Last, we provide future research prospects for aphantasia,
aiming to further guide researchers in possible research directions.
2. Literature Retrieval and Screening
This study undertook a systematic search of English-language articles published be-
tween 2015 and the present (Figure 1). The commencement year of 2015 was selected due to
its significance as the year in which Zeman et al. first coined the term “aphantasia” to char-
acterize the absence and marked reduction of visual imagery. The databases used include
Scopus, PubMed, ProQuest, and Web of Science. All the relevant journal articles, master’s
and doctoral theses, conference papers, and preprints were included in the search. As of 14
August 2024, an initial retrieval yielded 255 literature sources, from which 113 duplicates
were removed. Other screening methods and a careful examination of the references cited in
pertinent articles added 28 more literature sources to the pool. An in-depth review of titles,
abstracts, and full texts for these 170 literature sources led to the exclusion of 10 inaccessible
papers, 76 papers not centrally concerned with aphantasia, and 19 non-empirical studies,
finally resulting in a curated collection of 65 pertinent literature sources.
Vision 2024, 8, x FOR PEER REVIEW 3 of 20
Figure 1. Flow diagram illustrating the research searching and screening.
3. Definition, Measurement, and Prevalence of Aphantasia
Aphantasia is conceptually defined as the inability to generate mental imagery.
However, variations exist in the details of the conceptual definitions [11,12]. Blomkvist
reviewed various definitions of aphantasia [4–7,13–19] and identified three primary areas
of disagreement: whether aphantasics exhibit impairments solely in visual imagery,
whether a distinction is made between the absence of voluntary and involuntary imagery,
and whether aphantasia primarily concerns the generation of imagery [11]. Regarding the
first aspect, aphantasia has also been associated with deficits in non-visual modalities (see
Section 4.1). Some studies do not emphasize “visual imagery” when describing its absence,
instead using the broader term “mental imagery” to refer to various modalities [7,15,18].
It is recommended that the consistent term “aphantasia” be used and that the modality be
specified when necessary, such as “auditory aphantasia” [20]. Concerning voluntariness,
some researchers explicitly defined aphantasia as the lack of voluntary visual imagery
[6,7,17], while others did not specifically address this aspect [14,16]. Krempel and Monzel
call for simply using a broader characterization of aphantasia in the field as there is no
solid evidence of preserved involuntary imagery in aphantasics [21]. Regarding the third
aspect, increasing evidence suggests that aphantasia is linked to other deficits in cognitive
and emotional processes (see Section 4).
In measuring visual imagery deficits, most research utilizes scores from the Vividness
of Visual Imagery Questionnaire (VVIQ, [22]) as the primary identification and diagnostic
tool [12]. The VVIQ comprises 16 questions and employs a 5-point Likert scale.
Participants are asked to rate their visual imagery ability on a scale ranging from “No
imagery at all, you only ‘know’ that you are thinking of the object” to “Perfectly clear and
as vivid as real seeing”, to differentiate between individuals with visual imagery deficits,
those with normal imagery abilities, and those with excessive visual imagery [22].
According to the criteria, a score of 16 denotes a complete absence of visual imagery, with
a score of 17‒32 indicating vague/dim imagery. In recent years, a new reliable method for
identifying visual imagery deficits has emerged, known as the binocular rivalry task
Figure 1. Flow diagram illustrating the research searching and screening.
We evaluated the quality of these studies and classified their evidence. A study quality
evaluation was conducted based on the criteria used in previous works [
9
,
10
]. The details of
the criteria for the quality assessment are presented in Table S1 (Supplementary Materials).
Vision 2024,8, 56 3 of 20
Out of the 65 studies included, 58 studies were cross-sectional or case-control studies.
Seven studies were case reports or ecological studies. The overall quality scores (%) were
categorized as follows: excellent quality (score
≥
81%), good quality (between 61 and 80%),
fair quality (between 41 and 60%), poor quality (between 21 and 40%), and very poor
quality (
≤
20%). The evaluation results showed that 58 studies were assessed as “excellent”
(N = 22) or “good” (N = 36), 8 studies were assessed as “fair”, and only one study was
identified as of “poor” quality (Table S2 in Supplementary Materials).
Based on these 65 papers, this review provides a detailed analysis, evaluation, and
summary of the existing empirical research on aphantasia. It should be emphasized that the
key studies published before 2015, though not using the term “aphantasia”, have also been
considered in discussions if necessary. Reviews and commentaries are further incorporated
into this study. In this review, we used “aphantasia” to refer to an absence of mental
imagery in any modality for consistency, although the majority of the reviewed studies
focused on visual imagery deficits. The detailed content is summarized as follows (see
Tables S3–S15 in Supplementary Materials for the details of each study included).
3. Definition, Measurement, and Prevalence of Aphantasia
Aphantasia is conceptually defined as the inability to generate mental imagery. How-
ever, variations exist in the details of the conceptual definitions [
11
,
12
]. Blomkvist reviewed
various definitions of aphantasia [
4
–
7
,
13
–
19
] and identified three primary areas of dis-
agreement: whether aphantasics exhibit impairments solely in visual imagery, whether
a distinction is made between the absence of voluntary and involuntary imagery, and
whether aphantasia primarily concerns the generation of imagery [
11
]. Regarding the
first aspect, aphantasia has also been associated with deficits in non-visual modalities
(see Section 4.1). Some studies do not emphasize “visual imagery” when describing its
absence, instead using the broader term “mental imagery” to refer to various modali-
ties [
7
,
15
,
18
]. It is recommended that the consistent term “aphantasia” be used and that
the modality be specified when necessary, such as “auditory aphantasia” [
20
]. Concerning
voluntariness, some researchers explicitly defined aphantasia as the lack of voluntary visual
imagery [
6
,
7
,
17
], while others did not specifically address this aspect [
14
,
16
]. Krempel
and Monzel call for simply using a broader characterization of aphantasia in the field as
there is no solid evidence of preserved involuntary imagery in aphantasics [
21
]. Regarding
the third aspect, increasing evidence suggests that aphantasia is linked to other deficits in
cognitive and emotional processes (see Section 4).
In measuring visual imagery deficits, most research utilizes scores from the Vividness
of Visual Imagery Questionnaire (VVIQ, [
22
]) as the primary identification and diagnostic
tool [
12
]. The VVIQ comprises 16 questions and employs a 5-point Likert scale. Participants
are asked to rate their visual imagery ability on a scale ranging from “No imagery at
all, you only ‘know’ that you are thinking of the object” to “Perfectly clear and as vivid
as real seeing”, to differentiate between individuals with visual imagery deficits, those
with normal imagery abilities, and those with excessive visual imagery [
22
]. According
to the criteria, a score of 16 denotes a complete absence of visual imagery, with a score of
17–32 indicating
vague/dim imagery. In recent years, a new reliable method for identifying
visual imagery deficits has emerged, known as the binocular rivalry task [
13
,
23
]. Prior
instructions to imagine one of the images increase the likelihood of perceiving that image
during the subsequent binocular rivalry task. Participants with visual imagery deficits
exhibit minimal evidence of image-based binocular rivalry priming [
13
,
23
]. The VVIQ-2,
an extended version of the VVIQ containing 32 items [
24
], and a variant of the VVIQ have
also been used in the field [
4
]. Recent research has also found that pupillary responses to
light can indicate visual imagery deficits, as affected individuals lack an imagery pupillary
light response but still exhibit a perceptual pupillary light response [
25
]. Additionally,
rhythmic visual flickering typically induces illusory percepts, and compared to control
groups, individuals with visual imagery deficits are less likely to experience complex
and vivid illusions [
26
,
27
]. These findings further highlight the physiological differences
Vision 2024,8, 56 4 of 20
between individuals with visual imagery deficits and control groups, offering an objective
measure for assessing visual imagery intensity.
The vividness of the image can be viewed as a continuous characteristic forming a normal
distribution curve with aphantasia occupying the left tail and hyperphantasia occupying the
right tail. Before the term “aphantasia” was introduced, the most cited work based on a single
question about visual imagery indicated a prevalence rate of 2.1–2.7% for a total absence
of visual imagery in the general population [
28
]. In the field, the VVIQ was widely used
for measuring the vividness of visual imagery. Different operational definitions have led to
varying prevalence rates. Zeman et al. found that the prevalence rate of aphantasia, where
imagery is completely absent, was 0.7% (VVIQ = 16), and that of moderate aphantasia with
a VVIQ score of 16–23 was 2.6% [
4
]. Using a VVIQ score of 16–32 covering “totally absent”
to “vague/dim” imagery ratings, Dance et al. found a prevalence rate of 3.9% across two
separate samples [
29
]. When using a score of 16, the rate was only 0.8%. Later, Monzel,
Vetterlein, and Reuter conducted meta-analyses and found a prevalence rate of 4.8% across all
the included studies and 3.5% in studies using the VVIQ [
30
]. Recently, Takahashi et al. found
in a large sample of Japanese individuals that the rate was 0.07% when using a score of 16 and
3.6% when using a score of 17–32 [
31
]. A study with a large sample of Brazilian university
students reported a prevalence rate of 5.9% based on VVIQ scores of 16–32 [
32
]. However,
another study noted a self-reported prevalence rate of 8.9% in the general adult population,
but not all self-reported aphantasics showed low imagery scores on the VVIQ, resulting in
only 1.5% [
33
]. Overall, the prevalence rates of aphantasia are inconsistent due to the use of
different criteria across studies. If the strictest criterion is used, the rate would be extremely
low. It is important to use consistent standards when discussing the prevalence rates.
For the effects of gender, studies have not found any gender differences in the preva-
lence of aphantasia [
29
,
34
]. Although previous studies found that women tend to score
higher on object imagery measures compared to men [
35
,
36
], this difference is not statisti-
cally significant enough to conclude that men are more likely to be aphantasics. Age has
also been considered as a factor influencing aphantasia. However, there is no consensus
on how age affects aphantasia [
34
,
37
]. Additionally, whether the prevalence of aphantasia
varies across different professions remains controversial [
4
,
37
,
38
], despite Galton’s initial
suggestion that scientists might have weaker visual imagery abilities as a group [
1
]. This
controversy could be explained by Blajenkova et al.’s opinion that scientists may not lack all
types of visual imagery but may be specifically deficient in object imagery [
39
,
40
]. Similarly,
visual artists tend to excel in spatial imagery rather than object imagery [40].
Aphantasia can be either congenital or acquired [
41
,
42
]. It is more common in individ-
uals with a family history of lacking visual imagery, suggesting a genetic basis. However,
a recent study found no significant genetic association, indicating the need for further re-
search to explore the genetic evidence of aphantasia [
43
]. Acquired aphantasia can provide
insights into the causes and mechanisms of aphantasia. This form of aphantasia can be
triggered by various events, including craniocerebral injuries, emotional disorders, stroke,
and postoperative complications [
41
,
42
,
44
]. A case study reported a female who developed
aphantasia after contracting COVID-19 [
45
]. Psychological and psychiatric factors should
be carefully considered in the assessment of aphantasia [
46
,
47
] as mental illnesses such as
depression and anxiety can significantly impact the vividness of visual imagery [46].
4. Aphantasia and Cognitive Processing
4.1. Visual and Non-Visual Imagery Ability
Visual imagery ability is associated with other forms of imagery, such as olfactory and
auditory imagery. In a pioneering study by Zeman et al., 10 out of 21 individuals with
visual imagery deficits reported impairments in all forms of imagery, including auditory,
olfactory, gustatory, tactile, motor, and bodily imagery, to some extent [
5
]. A certain number
of aphantasics reported a lack of all forms of mental imagery, while some only have deficits
in visual imagery [
31
]. In a large-scale study, 54.2% of aphantasics with visual deficits
reported deficits in all types of imagery [
4
]. Similar findings have been confirmed in
Vision 2024,8, 56 5 of 20
other studies, revealing that some aphantasics with visual deficits also reported deficits
in other forms of mental imagery (34%, [
48
]; 26%, [
6
]). Takahashi and Gyoba reported a
person with aphantasia who exhibited a complete deficit in various types of images (e.g.,
visual, olfactory, pain, tactile, gustatory, and somatic images) in vividness and a substantial
deficit in auditory images [
49
]. Furthermore, individuals with hyperphantasia, who exhibit
exceptionally vivid visual imagery, tend to experience more vivid imagery in other types of
imagery as well [
4
]. There may be overlapping mechanisms underlying visual and auditory
imagery, as many aphantasia participants report weak or absent auditory imagery [
50
–
52
]
and individuals who lack auditory imagery, which is termed “anauralia”, often show visual
imagery deficits [
51
]. However, some aphantasics self-reported higher auditory imagery
than the mean score of the control group [
53
]. Using cluster analysis, Dawes et al. recently
found that aphantasia is heterogeneous and has two subtypes: visual aphantasia, which
selectively shows an absence of visual imagery, and multisensory aphantasia, which shows
an inability to generate any sensory modality of mental imagery [54].
Overall, some individuals with aphantasia may also experience deficits in all types of
mental imagery. However, there is still a lack of large-scale studies to establish a reliable
and consistent picture, as well as plausible explanations of the neural mechanisms for
understanding these phenomena. It is worth noting that most of the previous measure-
ments of visual and other forms of mental imagery in research have relied on self-report
questionnaires (e.g., the VVIQ, the Auditory Imagery Questionnaire, and the Questionnaire
upon Mental Imagery). The latest research revealed no significant difference between
aphantasics and the control group in an auditory imagery task, even though most of the
aphantasic participants reported an impairment in auditory imagery [
53
]. This suggests
that, although self-report questionnaires are convenient for large samples, there may be
a meta-cognitive effect in the data. Participants may not actually lack genuine mental
imagery but rather report deficits based on cognitive differences and misunderstandings
of the questionnaire items. More precise, reliable, and objective measurement methods
could help clarify the relationships between different forms of mental imagery deficits
by mitigating the risks of participants’ meta-cognitive influences. Alternatively, when
using self-report questionnaires, participants should be provided with clear explanations
and clarifications of the items to minimize misunderstandings about the content of the
questionnaires.
4.2. Aphantasia and Memory
Existing research on the impact of visual imagery impairment on memory has mainly
focused on working memory, episodic memory, autobiographical memory, and object and
spatial memory. Overall, aphantasics do not exhibit deficits in simple working memory
tasks [
55
–
58
]. However, it has been reported that aphantasics perform worse than control
groups in tasks requiring fine-grained visual working memory, which are cognitively more
demanding and require participants to remember smaller differences [
55
,
56
,
58
]. Jacobs et al.
reported an aphantasia individual who performed worse than the controls only on the most
difficult visual working memory trials requiring a high level of precision [
15
]. The difficulty
level appears to be a crucial factor in visual working memory tasks. In terms of episodic
memory, individuals with aphantasia demonstrated significantly lower performance than
the control group [
6
,
59
,
60
]. Similarly, aphantasia individuals have been reported to experi-
ence difficulties in autobiographical memory [
4
–
6
,
16
,
55
,
60
–
62
]. Regarding spatial memory,
which involves the processing of an object’s location information, two recent studies did
not find any deficits in aphantasics [
6
,
17
]. For object memory, aphantasics showed poorer
performance in object memory in a drawing task requiring object processing [
17
]. Siena
and Simons used both subjective and objective measures of object and spatial memory
and found that aphantasia participants showed no objective deficits in memory perfor-
mance, indicating that some aphantasics might show a deficit in the awareness of mental
imagery [63].
Vision 2024,8, 56 6 of 20
It should be noted that new measurements of memory performance have been used in
existing research, deviating from traditional scales and experimental tasks. For instance,
drawing has been used to complement the assessment of memory performance in partici-
pants [
17
]. In the case of drawing, aphantasics and control groups were instructed to draw
scene images from real-world memory. It was found that aphantasics remembered fewer
objects and used fewer colors to draw, and relied more on verbal scaffolding to compensate
for the lack of visual imagery [17].
Overall, memory is a relatively well-researched aspect in the field of aphantasia. Many
studies have employed questionnaires and experiments to measure participants’ memory
performance. In visual working memory, aphantasics exhibit similar performance to control
groups, which could be explained by their potential use of semantic encoding or other
representational strategies to aid them in completing working memory tasks [
7
]. However,
some studies indicate that aphantasics perform worse in these visual working memory
tasks [
15
]. The inconsistency of these findings may be attributed to task characteristics,
measurement methods, and individual differences among participants. For instance, the
heterogeneous outcome included only one individual with aphantasia, suggesting that
the observed differences in working memory could be influenced by sample size or the
unique characteristics of the case study [
15
]. As for autobiographical memory, all the
results seem to converge on the conclusion that individuals with aphantasia have poorer
autobiographical memory. Differences in object memory and spatial memory performance
between the aphantasics group and the control group may be related to their abilities
in object imagery and spatial imagery. These differences may be explained through the
neural mechanisms of the ventral and dorsal pathways of visual processing, which will be
discussed more comprehensively later.
4.3. Aphantasia and Object and Spatial Imagery
Object imagery refers to visualizing the image appearance of objects and scenes,
such as their shape, color, and brightness, while spatial imagery refers to visualizing
the spatial relationships and movements of objects and their components, and spatial
transformation [
64
]. Existing research on the performance of individuals with aphantasia in
object and spatial imagery abilities has not reached a consensus and can be categorized into
three types of studies. The first type of study indicates that aphantasia individuals score
lower in object imagery abilities but show no significant differences from control groups in
spatial imagery performance [
6
,
17
,
52
,
60
]. The second type of study shows that aphantasics
score significantly lower in object imagery than control groups but perform better in
spatial imagery tests [
13
,
55
]. In the last category of results, individuals with aphantasia
demonstrate poorer performance in both object and spatial imagery abilities [
65
,
66
]. Based
on these findings and a review of the literature, researchers have proposed two types of
visual imagery impairments: object aphantasia and spatial aphantasia [39,67].
The finding that object imagery is impaired while spatial imagery remains unaffected
can be also explained by the functional division of visual pathways. Aphantasics’ ventral
pathway for object processing may be impaired, while the dorsal pathway for spatial
processing remains intact ([
7
,
68
], also see below). To better explain spatial aphantasia,
researchers have proposed that this type of aphantasia may be related to functional changes
in the visual dorsal stream projecting to the frontal lobe [
67
]. However, this explanation
still lacks further support from neuroimaging studies.
4.4. Aphantasia and Atemporal and Future Imagination
Atemporal and future imagination are related to voluntarily imagining general events
and future events, respectively. Autobiographical interviews on atemporal and future
imagination show that aphantasia participants have poorer abilities in atemporal and future
imagination, with fewer details in their imagined scenarios [
16
,
60
]. Evidence suggests that
atemporal and future imagination abilities are related to autobiographical memory [
16
].
This may help explain why aphantasics show poorer abilities in atemporal and future
Vision 2024,8, 56 7 of 20
imagination, as their autobiographical memory abilities are also lower compared to control
groups.
4.5. Aphantasia and Mental Rotation Task Performance
The mental rotation task has been widely used to investigate individuals’ spatial abili-
ties [
69
]. It has been reported that, compared to control groups, individuals with aphantasia
showed equal [
16
,
53
,
70
] or even higher accuracy in mental rotation tasks [
55
,
65
,
66
,
71
]. However,
aphantasics also required longer response times in these tasks [58,65,71].
Aphantasia and control groups performed similarly in mental rotation tasks, possibly
due to the use of different strategies to solve the tasks [
66
,
71
]. Pounder and his colleagues
suggested that aphantasics may employ non-visual processes in these tasks [
58
]. For
example, the patient in Furman et al.’s study self-reported using a spatial and kinesthetic
strategy instead of low-level visual object imagery in the mental rotation task [
13
,
66
].
Specifically, he used a first-person path-following strategy (i.e., spatial strategy) containing
kinesthetic features, using his body as a reference. This hypothesis is supported by the
performance of congenitally or early blind individuals in mental rotation tasks, as they did
not show differences from control groups in completing complex spatial tasks, indicating
that mental rotation tasks can be completed independently of visual processes [
72
]. Kay
and his colleagues suggested that aphantasics are more likely to use analytic strategies,
which do not depend on features and orientation [
71
]. Additionally, the mental rotation
task is considered to rely on an individual’s spatial imagery ability, and many individuals
with aphantasia report having similar or even better spatial imagery abilities compared to
control groups [13,60].
4.6. Aphantasia and Visual Searching Ability
Visual search is a commonly used skill in everyday life that helps us find the things
we need, even if the desired target is within our current field of vision. When performing
visual search tasks, aphantasics exhibit significantly slower speeds compared to control
groups [
73
,
74
]. This difference could be explained by the varying involvement of visual
imagery in top-down strategies between the two groups [
74
,
75
]. However, in the Moriya’s task,
which examines participants’ attentional guidance in visual search tasks ([
76
]; participants
are first asked to imagine a color primed by a color word such as “blue” and then to indicate
whether one of the two colored squares presented on the left and right sides has an opening
at the top or bottom), the priming process seems to be similar between the aphantasia
group and the control group [
73
]. This can be explained by the characteristics of the task,
where the instructions in the Moriya’s task are overly complex, resulting in a lack of visual
priming and only non-visual priming [
73
]. These findings suggest that visual imagery could
affect the way people perceive the world. Future research would benefit from designing
materials that are more ecologically valid, such as incorporating environmental cues into the
experimental design.
5. Aphantasia and Disorders and Emotional Processing
5.1. Emotion
Mood may influence the vividness of mental imagery [
4
]. By contrast, mental imagery
was also found to affect individuals’ emotion experience. Due to absent or reduced visual
imagery, aphantasics experience reduced emotional engagement and less sympathy for
characters in stories [
77
] and exhibit lower levels of fear response when reading scary
materials [
78
]. Mental imagery ability was found to be positively associated with empathy
elicited by descriptions, but not associated with empathy elicited by pictures [
79
]. Addition-
ally, aphantasics seem to experience lower emotional intensity when listening to music [
80
].
This may be because vivid imagery makes thoughts more realistic, triggering stronger
responses in the brain’s emotional circuitry and thereby amplifying emotions [
81
]. Future
research can continue to explore different types of emotions and incorporate neuroimaging
methods to validate previous findings.
Vision 2024,8, 56 8 of 20
5.2. Mental Health
Although aphantasia may impact individuals’ cognition and emotional processing and
potentially cause some personal distress, it is not currently included in any common clinical
diagnostic systems. Furthermore, the impact of aphantasia on individuals’ daily lives and
personal distress is relatively minimal and not sufficient to classify it as a psychological
disorder [
30
,
82
]. However, research has found associations between aphantasia and certain
conditions or diseases [
83
]. Moreover, scientists have proposed that progressive aphantasia
may be a precursor to dementia [84].
Existing research has focused on the impact of aphantasia on mental health, such as
depression, anxiety, distress, and well-being. Research has revealed that the aphantasia
group showed no significant differences compared to the control group in terms of de-
pression, anxiety, and state-trait anxiety [
16
,
81
]. However, Monzel, Vetterlein, and Reuter
found that 34.7% of aphantasia participants reported distress caused by the lack of visual
imagery [
30
]. Nevertheless, the researchers also suggested that these negative emotions
were relatively weak and did not significantly affect individuals’ daily lives [30].
5.3. Post-Traumatic Stress Disorder (PTSD)
Previous research has established a link between mental imagery and PTSD, a condi-
tion characterized by re-experiencing traumatic events through unwanted and recurring
intrusive memories and nightmares [
85
,
86
]. Aphantasics have been found to experience
fewer intrusions and exhibit less avoidance behaviors following trauma [
6
], both of which
are predictors of PTSD. Additionally, the aforementioned lack of visual imagery and its
association with reduced emotional intensity may also contribute to their lower likelihood
of developing PTSD. However, it is important to note that researchers emphasize the lim-
ited protective effect of visual imagery deficits when individuals with such deficits face
stressful events in their daily lives [6].
5.4. Autism
Individuals with aphantasia frequently score higher on the Autism Quotient Ques-
tionnaire (AQ) and are more likely to be classified within the autism spectrum [
16
,
87
]. This
association may be related to the connection between imagery and mentalizing. Compared
to control groups, aphantasics exhibit slightly reduced atemporal and future imagination,
as well as episodic memory [
6
,
16
,
60
], which are also characteristics of autistic spectrum
disorder [
88
,
89
]. Additionally, limited or absent visual imagery can impair the theory of
mind ability in aphantasics, leading to difficulties in social skills [
87
]. These factors may
explain why individuals with aphantasia tend to have higher scores on the AQ, indicating
a potential connection between visual imagery deficits and autistic spectrum disorder.
5.5. Prosopagnosia
Aphantasia has been associated with reduced facial recognition ability [
31
]. In a re-
cent study, 5.9% of participants in the spatial aphantasia group were identified as having
prosopagnosia [
67
], and face recognition difficulties were found to be more common in
individuals with aphantasia [
16
,
90
]. Aphantasics also reported difficulties with facial recog-
nition tasks [
41
]. Additionally, aphantasics have been associated with lower confidence in
tasks involving facial perception [
91
]. In a study of developmental prosopagnosia, about
20% of participants with developmental prosopagnosia reported a comorbidity with aphan-
tasia [
92
]. However, aphantasia does not significantly impact accuracy in tasks involving
the construction of facial composites and face recognition tasks [
93
], as individuals with
aphantasia can still create facial composites from memory similarly to control groups [
90
].
Nevertheless, some researchers have argued that the scores of aphantasics in tests are not
sufficient to diagnose them with prosopagnosia [
66
]. Overall, individuals with aphantasia
tend to exhibit poorer face recognition abilities. However, this may be influenced by the
scales used in experiments, as these scales may elicit meta-cognitive effects [
16
]. In other
words, individuals with aphantasia may have reduced confidence in their own facial recog-
Vision 2024,8, 56 9 of 20
nition abilities due to their lack of vivid facial imagery, which can manifest as relatively
lower scores on self-report measures.
6. The Neural Basis of Aphantasia
Although numerous studies have focused on the neural basis of mental im-
agery [
7
,
8
,
94
,
95
], there are limited studies utilizing modern neuroimaging techniques
such as magnetic resonance imaging (MRI) and electroencephalography (EEG) to explore
the neural basis of visual imagery deficits. Using resting-state and task-based MRI, Milton
et al. recently compared the brain activities of three groups: aphantasics, typical controls,
and hyperphantasics [
16
]. The results showed that individuals with hyperphantasia ex-
hibit stronger connectivity between the prefrontal regions and visual-occipital network
compared to the aphantasia group. When comparing the visualization and perception of
famous faces and places, individuals with hyperphantasia and the control group exhibited
greater frontal and parietal activation compared to the aphantasia group [
16
]. Another
functional MRI study showed that the aphantasic group exhibited decreased activation
in the hippocampus and increased activation in the visual-perceptual cortex during an
autobiographical memory task [
96
]. However, the control group displayed strong negative
task-based functional connectivity between the hippocampus and the visual cortex during
the task, and the resting-state functional connectivity between these two areas could predict
visualization skills [
96
]. Furthermore, using transcranial magnetic stimulation to induce
changes in brain activity, Dupont, Papaxanthis, Madden-Lombardi and Lebonet found that
there was no increase in the amplitude of motor-evoked potentials triggered in the target
right index finger in the aphantasia group, indicating a lack of corticospinal excitability
in individuals with aphantasia during motor simulation [
97
]. Similar findings were also
observed in an action reading task, which involved motor simulation [98].
Case studies are also a crucial source of neural evidence. Lesion studies have found
that patients showed intact visual imagery after brain lesions restricted to the occipital
cortex [
99
–
102
], suggesting that early visual areas are not involved in visual imagery. More-
over, patients with damage to the anterior part of the temporal lobe, particularly in the left
hemisphere, often report an inability to generate visual images [
103
–
105
], which is consis-
tent with observations of a left hemisphere bias [
106
]. Zeman et al. reported a patient who
showed reduced activation in the occipitotemporal regions during an imagery task [
107
].
In a recent study, a patient with an absence of visual imagery ability showed selective
lesions in a specific area of the left fusiform gyrus and a portion of the right lingual gyrus,
demonstrating a causal role of the left fusiform gyrus in visual imagery [
41
]. Therefore, the
fusiform region “might act as a neural interface between sensory information coming from
the occipital cortex and semantic processing in the anterior temporal lobe” during visual
perception, and “could endow semantic memories with visual information during visual
imagery” ([100], p. 517). An EEG study with source reconstruction reported that during a
visual imagery task, an aphantasic begins the evoking phase from the left temporal area
while lacking activation of the occipital and parietal lobes, which are associated with visual
image vividness [66].
Due to the limited evidence in these studies, it is challenging to draw a consistent
picture of the aberrant brain activity in aphantasia. However, we can still draw inspiration
from neuroimaging studies based on individual differences in mental imagery. Spagna
et al. recently conducted a meta-analysis of fMRI studies of visual imagery and found
that visual imagery recruits several fronto-parietal areas and a specialized area in the left
fusiform gyrus [
94
]. The specialized area was labeled the fusiform imagery node (FIN),
referring to a brain network node specifically responsible for voluntary visual mental
imagery [
94
,
108
,
109
]. Liu et al. found that imagery tasks activated the left frontal–parietal
regions, the FIN, and areas in the ventral temporal cortex, which were similarly activated
in the aphantasia and control groups [
110
]. However, the connectivity between the FIN and
the frontoparietal regions is reduced in aphantasics [
110
]. Together, these brain-lesion cases
and fMRI studies demonstrate that the fusiform gyrus is a core area for visual imagery,
Vision 2024,8, 56 10 of 20
and damage to or impairment of it could lead to deficits in visual imagery. Additionally,
abnormalities in the fusiform gyrus have been associated with prosopagnosia, which
may explain the facial recognition deficits observed in individuals with visual imagery
disorders [111,112].
A related debate concerns the involvement of the early visual cortex in (impaired)
visual imagery [
100
,
113
]. Using stimulation, Kosslyn et al. found that the early visual cortex
is causally involved in visual imagery [
114
]. Bergmann et al. documented that a smaller V1
size is associated with stronger but less precise imagery, indicating an anatomical basis [
115
].
Keogh et al. suggested a causal relationship between cortical excitability in the early visual
cortex and the intensity of visual imagery [
116
]. However, Meng et al. suggested that an
imagery-related representation exists in the primary visual cortex of aphantasics, despite
the absence of visual imagery, though the representation contains less or transformed
sensory information [
117
]. The results from Cabbai et al. showed a dissociation between V1
representations and subjective imagery [
118
]. Bartolomeo et al. [
100
] argued that the left
fusiform gyrus plays a crucial role in visual imagery, rather than the early visual cortex, and
that the involvement of the early visual cortex [
114
] might be modulated by downstream
areas. Dijkstra recently reviewed existing evidence and proposed that “imagery can recruit
the early visual cortex, but that does not mean that it always does so” [95].
7. Theory Development
Individuals with imagery deficits can still have imagination capabilities similar to
those without such deficits, such as creating novels and movies. Based on this, Arcangeli
attempts to distinguish between mental imagery and sensory imagination [
119
]. Mental
imagery can be considered a type of mental content (e.g., the appearance of an apple). In
contrast, sensory imagination is a special psychological attitude that involves the recreation
of perceptual experiences. According to this theory, most individuals previously defined as
having aphantasia in past research may actually have a deficiency in sensory imagination
rather than in mental imagery, which could explain why individuals with visual imagery
deficits can still perform imaginative tasks.
Nanay explains aphantasia from the perspective of both conscious and unconscious
visual imagery [
18
]. Previous research has found that individuals with aphantasia do not
exhibit the imagery priming effect in binocular rivalry tasks; yet some participants can
generate vivid dreams and perform visual imagery tasks similarly to control groups. To
explain this phenomenon, Nanay distinguishes between conscious and unconscious visual
imagery abilities, both of which could be generated voluntarily or involuntarily [18]. One
type of aphantasia involves a fundamental lack of visual imagery, while the other type
involves the ability to generate visual imagery without conscious awareness [
73
]. However,
this theory is challenged by Blomkvist [
11
], who argues that it does not fully explain
the issues of episodic memory or imagination of atemporal and future events in visual
imagery deficits, as it does not provide a link between mental imagery and the episodic
processes in episodic memory and episodic imagination. Additionally, there is research
suggesting that imagery tasks can be accomplished through cognitive strategies that do
not rely on imagery [
91
,
120
–
122
]. A recent study using both implicit and explicit priming
tasks found that participants with aphantasia did not show priming effects, suggesting
that aphantasia is an inability to generate visual imageries rather than an impairment in
conscious awareness of images [123].
To provide a better explanation for aphantasia, Blomkvist proposed enhancements
to the Constructive Episodic Simulation Hypothesis (CESH) model [
11
]. The original
CESH posits that memory and imagination involve three key processes: the semantic
retrieval process, episodic retrieval process, and (re)combination process [
124
]. Blomkvist
expanded on this model by adding three new components: “memory indices, differing
episodic retrieval mechanisms for all kinds of sensory information, and spatial retrieval
mechanisms” [
11
]. These additions aim to provide a new theoretical explanation for visual
imagery deficits. According to this updated theory, the mechanism of the episodic system
Vision 2024,8, 56 11 of 20
is deficient, resulting in the loss of visual imagery. However, this theory still lacks empirical
research data to support it further.
The theoretical framework of the ventral and dorsal pathways in the visual system has
been proposed for many years [
125
–
127
] (although there are ongoing debates about this
framework, [
128
,
129
]. Pearson proposed that the ventral (or “what”) pathway is associated
with object information, while the dorsal (or “where”) pathway is associated with location
and spatial features [
7
]. The two aspects of visual imagery, object imagery and spatial
imagery, are also likely generated through the ventral and dorsal pathways [
39
]. Damage to
the ventral pathway could impair individuals’ ability to visualize the appearance of objects,
while damage to the dorsal pathway is associated with a disrupted ability in spatial imagery.
These processes can be dissociated in aphantasia, which may explain why individuals
with visual imagery deficits perform similarly to, or even better than, control groups
in spatial imagery tasks [
7
,
68
]. Bergmann and Ortiz-Tudela also suggested that visual
feedback pathways used during episodic and schematic memory retrieval may be different
depending on the two visual processing streams: episodic memory retrieval involves both
the “what” and “where” streams, while schematic memory retrieval primarily involves the
“where” stream [
130
]. In other words, aphantasia may be associated with differences in the
“what” stream.
Inspired by neural models of mental imagery [
7
,
8
] and existing sources of neural evi-
dence, Zeman tried to depict candidate neural mechanisms of extreme imagery, aphantasia,
and hyperphantasia [
2
]. In the brain mapping picture, there are five functional clusters,
each involved in a unique role in mental imagery: the frontal cortex for initiating imagery
generation, the parietal cortex for interacting with the frontal cortex to generate imagery
during which attentional and spatial aspects of imagery are mediated, the temporal cortex,
including limbic structures for enabling access to the semantic and episodic memories that
determine what to visualize, and higher-order visual areas (e.g., the FIN) for visualizing
imagery. The extent to which activity in the early visual cortex (e.g., the V1) is required
for imagery is still debated. Moreover, the connections between these clusters are also
essential for imagery generation. From this mapping picture, Zeman [
2
] proposes five
candidates showing neural atypicality in extreme imageries: variations in the strengths
of the top-down feedback connection between higher-order regions (the frontal cortex)
serving as cognitive control and modality-specific areas (e.g., the visual cortex) activated
by sensory imagery; variations in the structure and function of the frontal cortex involved
in generating imagery; variations at the level of higher-order visual areas, including the
FIN proposed by Spagna et al. [
94
]; variations in the anatomical structure of the early
visual cortex, including the V1; and variations in the saliency involving the parietal areas
of the frontoparietal control system. In this proposal, Zeman provided future directions
for researchers in the field [
2
]. A neural model constructed and refined from accumulated
evidence would add to a better understanding of aphantasia.
8. Summary and Future Directions
This review primarily examines the definition, prevalence, and measurement methods
of aphantasia, as well as its impacts on individual cognitive and emotional processing,
associated disorders, neural basis, and theory development. Research on aphantasia is
continuously progressing, and its descriptions are becoming increasingly clear. However,
several debated areas remain, and the study of its impacts on individuals and underlying
mechanisms faces several challenges. Future investigations into aphantasia should focus
on the following aspects.
8.1. Clarify Definition and Diagnosis
It is evident that the current research on aphantasia is still in its early infancy. One of the
primary concerns is the definition of aphantasia. Clear definitions serve as the foundation
for advancing further research and facilitating effective communication among researchers.
The existing literature presents variations in the definition of aphantasia [
12
]. For example,
Vision 2024,8, 56 12 of 20
some definitions do not explicitly distinguish between voluntary and involuntary imagery
(see a review by [
21
]). The cut scores for the diagnosis of aphantasia vary across studies
(see Section 3). The inconsistent use of the arbitrary cut scores is considered a hindrance
to cross-study comparison and communication among researchers. Moreover, the use
of cut scores may also discourage efforts to examine individual differences in imagery.
Additionally, more effective, objective tools for non-clinical and clinical purposes should be
developed [131,132] rather than relying predominantly on the VVIQ or its variants [133].
The terminology in the field has recently been debated [
20
,
134
–
136
]. While the debate
continues on whether the term “aphantasia” specifically refers to the absence of visual
mental imagery or encompasses a deficit of all types of mental imagery (see Section 3), most
current research on aphantasia focuses on visual imagery. Other terms have been proposed
to refer to an absence of other modalities of imagery. For auditory imagery, Hinwar
and Lambert introduced the term “anauralia” to refer to an absence of auditory imagery
and “hyperauralia” to refer to the experience of extremely vivid auditory imagery [
51
].
Dance, Ward, and Simner proposed the term “dysikonesia” to refer to multisensory or
global aphantasia [
48
]. In this context, Monzel, Mitchell et al. believe that these new
terms complicate the field, making communication less effective for researchers and the
public, and therefore advocate for the use of the simple term “aphantasia,” which is widely
known [
20
]. When referring to an absence of a specific modality of imagery, it is easy to use
modality-specific terms (e.g., “visual/auditory/multisensory aphantasia”).
These divergencies across studies create difficulties in the classification of participants
and scientific communications among researchers and the public, therefore hindering
progress toward a better understanding of aphantasia. Researchers in the field should reach
a consensus on these issues to facilitate further development.
8.2. Strengthen Behavioral Research
Aphantasia research is still at its early stages, and there is limited literature in several
research directions. Future studies should build upon existing efforts to systematically
examine this phenomenon to better understand aphantasia. At the behavioral level, more
research is urgently needed within and beyond existing research directions. First of all,
together with a clear and consistent definition of aphantasia, researchers should focus on
examining the nature of aphantasia, including but not limited to investigating effects of
demographic variables (e.g., age and gender) and their interactions in large datasets, de-
veloping new assessment or diagnostic tools with high reliability and validity, elucidating
perceptual and cognitive processes required by tasks used to elicit mental imagery, and
determining the comorbidity rate of two or more subtypes of aphantasia in large samples.
Second, researchers should investigate how aphantasia is associated with other psycho-
logical aspects (e.g., conscious experience, [
18
,
137
–
139
], the influences of aphantasia on
emotional processing and disorders (see Section 4), and possible mechanisms underlying
these relationships (e.g., [
140
]). Third, research on hyperphantasia, the opposite extreme
characterized by vivid mental imagery, can also help contribute to a better understanding
of aphantasia. Viewing mental imagery ability as a continuum could be more realistic and
scientifically useful in understanding the absence of or reduction in imagery in people
with aphantasia. Fourth, researchers should use these different sources of evidence as a
foundation to propose or create intervention programs for people with aphantasia. The
effectiveness of these interventions can also help researchers better understand the nature
of this phenomenon, fostering further advances.
8.3. Discover Neural Bases
Unraveling the neural bases of aphantasia has recently become a prominent research
topic. Neuroimaging evidence has been instrumental in understanding the manifestations
of aphantasia and in constructing neural models. Employing neuroimaging methods,
future research can explore various variables to gather more neural evidence. Specifically,
researchers can utilize the high spatial resolution of MRI techniques to investigate regional
Vision 2024,8, 56 13 of 20
activation and inter-regional connections (structural and functional connectivity) involved
in the absence or reduction of mental imagery. Previous functional MRI studies have
identified areas involved in mental imagery, based on which neural models have also been
proposed (e.g., [
14
,
115
,
116
]; see a review by [
7
]). Although some studies of aphantasia have
been conducted [
16
,
107
,
110
], it is difficult to accumulate convergent evidence for localizing
aberrant brain regions and connections. Using EEG and magnetoencephalography (MEG)
techniques with high temporal resolution [
141
,
142
], researchers can examine the neural
dynamics of the processes involving mental imagery in people with and without aphantasia
(e.g., [
66
]). For example, Xie et al. found shared alpha-band neural representations in
visual imagery and perception [
143
]. Combining spatial and temporal neural evidence
across different studies, or even using fusion techniques (e.g., EEG-MRI fusion, [
144
]) can
contribute to a better understanding of aphantasia by incorporating different types of
information into a single picture, further facilitating the construction of neural models.
Recent technical advances in multi-variate pattern analysis (e.g., [
145
,
146
]) may also be
powerful in understanding the neural correlates of aphantasia, as demonstrated in previous
studies of mental imagery [
111
,
117
,
143
]. Non-invasive brain stimulation techniques [
147
]
can be powerful tools for discovering causal evidence of the involvement of brain areas
in mental imagery. Together, the convergence of behavioral and neural evidence not only
helps elucidate various aspects of aphantasia but is also useful in building behavioral
and neural models that explain this phenomenon [
2
]. In addition, evidence from other
sources of investigation should also be encouraged. It has been reported that aphantasia
has a genetic basis [
4
] and that dopamine plays an important role in generating mental
imagery [148].
8.4. Construct and Refine Theories
Good theories help humans systematically and scientifically understand their
minds [
149
,
150
]. Although aphantasia has garnered increasing attention over the
past decade, and has also gained interest in art, philosophical, and theoretical discus-
sions [
80
,
83
,
151
–
160
], empirical studies examining this phenomenon remain limited. The
field is still in its early stages. A lack of theories for synthesizing the existing literature is
one of the field’s significant characteristics. Although some accounts and models have been
proposed to interpret behavioral findings [
11
,
18
,
119
], they have focused on certain aspects.
Neural models for synthesizing neural evidence (e.g., [
2
]) are largely unknown or require
further examination. One of the main reasons is that both behavioral and neural empiri-
cal studies are very limited in number and diversity (see above), resulting in insufficient
evidence to be integrated into a theory or model.
In addition to proposing new theories or models, we advocate for efforts to use exist-
ing theories or models of mental imagery [
7
,
8
,
11
,
109
] as a foundation to theoretically guide
future directions on researching aphantasia. Modifications to these models or theories will
be made as more evidence is collected. We believe these changes will either refine existing
theories or help foster new ones. For instance, theories that explain the mechanisms of
visual imagery can be adapted to account for the absence of such imagery in individuals
with aphantasia. By modifying these models to include the cognitive and neural under-
pinnings of aphantasia, researchers can create a more robust theoretical framework that
encompasses both the presence and absence of mental imagery.
Given that aphantasia may extend beyond visual imagery to include other modalities,
such as auditory or tactile imagery, theories should be developed to address these broader
aspects. This could involve creating a unified model that categorizes different types of
aphantasia (e.g., visual, auditory, multisensory) and explores how these modalities interact
within cognitive processes. Such a model would not only clarify the nature of aphantasia
but also facilitate comparisons with individuals who possess typical imagery capabilities.
Vision 2024,8, 56 14 of 20
8.5. Encourage Direct and Conceptual Replications
In recent years, concerns about replication in psychology have increased (e.g., [
161
,
162
]).
Replicability is a crucial indicator of the reliability and stability of research findings [
163
].
Conducting replicable experiments to demonstrate the replicability of the findings lays a
solid foundation for further investigations. There are two types of replications, each with
different requirements. Conceptual replication deliberately modifies key elements of the
original program to test the robustness of the phenomenon or the generalizability of the
theoretical claims, while direct replication involves recreating the original experiment, which
has been questioned regarding its impossibility of implementation [164].
The inconsistencies in research findings on aphantasia, which can undermine confi-
dence in the literature, call for the consideration of replicability in existing studies, requiring
numerous replication studies to confirm the reliability and stability of results. For example,
there are limited studies on the relationship between aphantasia and atemporal and future
imagination, as well as visual search. Although consistent conclusions have been reached,
different experimental designs are still needed to validate the accuracy and replicability of
the results (conceptual replications). Moreover, researchers have explored the relationships
between attentional templates [
19
], sensory sensitivity [
48
], verbal overshadowing [
120
],
mid-level characteristics of drawings [
165
], and aphantasia, but these are isolated studies
lacking cross-validation from other research, indicating the necessity of conducting direct
and conceptual replication studies.
To facilitate replication efforts, aphantasia researchers should adopt open science
practices, such as sharing data, materials, and protocols. By making these more transparent,
the scientific community of aphantasia can more easily conduct replications and build upon
existing work. Open access to the datasets of research published or to be published can also
encourage more collaboration and foster a collective effort to understand this phenomenon
more deeply.
9. Conclusions
In this study, we have provided a comprehensive review of aphantasia, encompassing
its definition, prevalence, measurement methods, empirical research, and relevant theories.
The existing literature has contributed to a good understanding of aphantasia. The absence
of visual imagery can have significant implications for an individual’s cognitive and emo-
tional processing and is also associated with certain psychological disorders. Studies on the
neural bases of aphantasia are gradually increasing, especially in recent years. Following
these endeavors, theories and neural models have been proposed to summarize existing
behavioral and neural evidence. The research of visual imagery deficits is continually
growing, although there are still areas of debate. However, a consensus regarding the
theoretical framework has not yet been achieved. The theories still lack sufficient empirical
support, leaving a significant gap. We have emphasized several points to which researchers
can make contributions, such as clarifying diagnoses, strengthening behavioral and neu-
roimaging research, constructing and refining theories, and encouraging replications. New
work on the different aspects of aphantasia is not only beneficial for expanding researchers’
understanding of cognitive and emotional processes and their relationships with other
disorders, but is also helpful for building theories or model.
Supplementary Materials: The following supporting information can be downloaded at: https://www.
mdpi.com/article/10.3390/vision8030056/s1, Table S1. Criteria for quality assessment of the studies;
Table S2. Scores and quality categories of the 65 studies evaluated; Table S3. Prevalence; Table S4.
Performance on computer tasks; Table S5. Acquired aphantasia; Table S6. Non-visual imagery ability;
Table S7. Memory; Table S8. Object and spatial imagery; Table S9. Atemporal and future imagination;
Table S10. Mental rotation task performance; Table S11. Visual search ability; Table S12. Emotion;
Table S13. Aphantasia and related disorders; Table S14. Neural Basis of Aphantasia; Table S15. Others.
Author Contributions: F.J., study design, investigation, methodology, visualization, writing—original
draft, writing—review and editing; S.-M.H., investigation, writing—review and editing. Y.L., study
Vision 2024,8, 56 15 of 20
design, funding acquisition, investigation, methodology, resources, supervision, writing—original
draft, writing—review and editing. All authors have read and agreed to the published version of
the manuscript.
Funding: This study was funded by BNU-HKBU United International College Research Grants
(R72021207, R202102, R202011), and in part by the Guangdong Provincial Key Laboratory IRADS
(2022B1212010006, R0400001-22).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflicts of interest.
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