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Neuron Nov 2005Synesthesia is a condition in which stimulation of one sensory modality causes unusual experiences in a second, unstimulated modality. Although long treated as a... (Review)
Review
Synesthesia is a condition in which stimulation of one sensory modality causes unusual experiences in a second, unstimulated modality. Although long treated as a curiosity, recent research with a combination of phenomenological, behavioral, and neuroimaging methods has begun to identify the cognitive and neural basis of synesthesia. Here, we review this literature with an emphasis on grapheme-color synesthesia, in which viewing letters and numbers induces the perception of colors. We discuss both the substantial progress that has been made in the past fifteen years and some open questions. In particular, we focus on debates in the field relating to the neural basis of synesthesia, including the relationship between synesthesia and attention and the role of meaning in synesthetic colors. We propose that some, but probably not all, of these differences can be accounted for by differences in the synesthetes studied and discuss some methodological implications of these individual differences.
Topics: Attention; Brain; Cognition; Color Perception; Feedback; Humans; Models, Neurological; Perceptual Disorders; Photic Stimulation
PubMed: 16269367
DOI: 10.1016/j.neuron.2005.10.012 -
Annual Review of Psychology 2013Although synesthesia has been known about for 200 years, it is only in the past decade or so that substantial progress has been made in studying it empirically and in... (Review)
Review
Although synesthesia has been known about for 200 years, it is only in the past decade or so that substantial progress has been made in studying it empirically and in understanding the mechanisms that give rise to it. The first part of the review considers the characteristics of synesthesia: its elicited nature, automaticity, prevalence, and consistency, and its perceptual and spatial phenomenology. The second part considers the causes of synesthesia both in terms of candidate neural mechanisms and the distal influences that shape this: genetic differences in developmental synesthesia and plasticity following sensory loss in acquired synesthesia. The final part considers developmental synesthesia as an individual difference in cognition and summarizes evidence of its influence on perception, imagery, memory, art/creativity, and numeracy.
Topics: Humans; Perceptual Disorders; Synesthesia
PubMed: 22747246
DOI: 10.1146/annurev-psych-113011-143840 -
Frontiers in Bioscience (Landmark... Jan 2021Synesthesia literally means a "union of the senses" whereby two or more of the five senses that are normally experienced separately are involuntarily and automatically... (Review)
Review
Synesthesia literally means a "union of the senses" whereby two or more of the five senses that are normally experienced separately are involuntarily and automatically joined together in experience (1, 2, 3). For example, some synesthetes experience a color when they hear a sound, although many instances of synesthesia also occur entirely within the visual sense. In this paper, I first mainly engage critically with Sollberger's view that there is reason to think that at least some synesthetic experiences can be viewed as truly veridical perceptions, and not as illusions or hallucinations (4). Among other things, I explore the possibility that many forms of synesthesia can be understood as experiencing what I will call "second-order secondary properties," that is, experiences of properties of objects induced by the secondary qualities of those objects. In doing so, I shed some light on why synesthesia is typically one-directional and its relation to some psychopathologies such as autism.
Topics: Autistic Disorder; Hallucinations; Humans; Synesthesia
PubMed: 33049694
DOI: 10.2741/4918 -
Dementia & Neuropsychologia 2015The present review examined the cross-modal association of sensations and their relationship to musical perception. Initially, the study focuses on synesthesia, its... (Review)
Review
The present review examined the cross-modal association of sensations and their relationship to musical perception. Initially, the study focuses on synesthesia, its definition, incidence, forms, and genetic and developmental factors. The theories of the neural basis of synesthesia were also addressed by comparing theories emphasizing the anatomical aspect against others reinforcing the importance of physiological processes. Secondly, cross-modal sensory associations, their role in perception, and relationship to synesthesia were analyzed. We propose the existence of a lower, unconscious degree of synesthesia in non-synesthetes. This latent synesthesia (without explicit sensory manifestations) would be functional, aiding the construction of abstract associations between different perceptual fields. Musical meaning might be constructed largely by synesthetic processes, where the sensory associations from sound activate memories, images, and emotions.
PubMed: 29213937
DOI: 10.1590/S1980-57642015DN91000004 -
Current Psychiatry Reports Jun 2007Synesthesia is an experience in which stimulation in one sensory or cognitive stream leads to associated experiences in a second, unstimulated stream. Although... (Review)
Review
Synesthesia is an experience in which stimulation in one sensory or cognitive stream leads to associated experiences in a second, unstimulated stream. Although synesthesia is often referred to as a "neurological condition," it is not listed in the DSM IV or the ICD classifications, as it generally does not interfere with normal daily functioning. However, its high prevalence rate (one in 23) means that synesthesia may be reported by patients who present with other psychiatric symptoms. In this review, I focus on recent research examining the neural basis of the two most intensively studied forms of synesthesia, grapheme --> color synesthesia and tone --> color synesthesia. These data suggest that these forms of synesthesia are elicited through anomalous activation of color-selective areas, perhaps in concert with hyperbinding mediated by the parietal cortex. I then turn to questions for future research and the implications of these models for other forms of synesthesia.
Topics: Association; Cerebral Cortex; Color Perception; Electroencephalography; Humans; Magnetic Resonance Imaging; Magnetoencephalography; Models, Neurological; Parietal Lobe; Pattern Recognition, Visual; Perceptual Disorders; Pitch Perception; Positron-Emission Tomography; Reading; Semantics; Visual Cortex; Visual Perception
PubMed: 17521514
DOI: 10.1007/s11920-007-0018-6 -
The Neuroscientist : a Review Journal... Apr 2017Since mirror neurons were introduced to the neuroscientific community more than 20 years ago, they have become an elegant and intuitive account for different cognitive... (Review)
Review
Since mirror neurons were introduced to the neuroscientific community more than 20 years ago, they have become an elegant and intuitive account for different cognitive mechanisms (e.g., empathy, goal understanding) and conditions (e.g., autism spectrum disorders). Recently, mirror neurons were suggested to be the mechanism underlying a specific type of synesthesia. Mirror-touch synesthesia is a phenomenon in which individuals experience somatosensory sensations when seeing someone else being touched. Appealing as it is, careful delineation is required when applying this mechanism. Using the mirror-touch synesthesia case, we put forward theoretical and methodological issues that should be addressed before relying on the mirror-neurons account.
Topics: Animals; Cerebral Cortex; Humans; Mirror Neurons; Perceptual Disorders; Synesthesia; Touch Perception; Visual Perception
PubMed: 27242280
DOI: 10.1177/1073858416652079 -
Frontiers in Psychology 2015Synesthesia is a phenomenon in which additional perceptual experiences are elicited by sensory stimuli or cognitive concepts. Synesthetes possess a unique type of... (Review)
Review
Synesthesia is a phenomenon in which additional perceptual experiences are elicited by sensory stimuli or cognitive concepts. Synesthetes possess a unique type of phenomenal experiences not directly triggered by sensory stimulation. Therefore, for better understanding of consciousness it is relevant to identify the mental and physiological processes that subserve synesthetic experience. In the present work we suggest several reasons why synesthesia has merit for research on consciousness. We first review the research on the dynamic and rapidly growing field of the studies of synesthesia. We particularly draw attention to the role of semantics in synesthesia, which is important for establishing synesthetic associations in the brain. We then propose that the interplay between semantics and sensory input in synesthesia can be helpful for the study of the neural correlates of consciousness, especially when making use of ambiguous stimuli for inducing synesthesia. Finally, synesthesia-related alterations of brain networks and functional connectivity can be of merit for the study of consciousness.
PubMed: 26696921
DOI: 10.3389/fpsyg.2015.01850 -
Multisensory Research Jun 2020It has been repeatedly suggested that synesthesia is intricately connected with unusual ways of exercising one's mental imagery, although it is not always entirely clear...
It has been repeatedly suggested that synesthesia is intricately connected with unusual ways of exercising one's mental imagery, although it is not always entirely clear what the exact connection is. My aim is to show that all forms of synesthesia are forms of (often very different kinds of) mental imagery and, further, if we consider synesthesia to be a form of mental imagery, we get significant explanatory benefits, especially concerning less central cases of synesthesia where the inducer is not sensory stimulation.
Topics: Exercise; Humans; Imagery, Psychotherapy; Synesthesia
PubMed: 33706281
DOI: 10.1163/22134808-bja10027 -
Neuropsychologia Jun 2022Synesthesia represents an atypical merging of percepts, in which a given sensory experience (e.g., words, letters, music) triggers sensations in a different perceptual...
Synesthesia represents an atypical merging of percepts, in which a given sensory experience (e.g., words, letters, music) triggers sensations in a different perceptual domain (e.g., color). According to recent estimates, the vast majority of the reported cases of synesthesia involve a visual experience. Purely non-visual synesthesia is extremely rare and to date there is no reported case of a congenitally blind synesthete. Moreover, it has been suggested that congenital blindness impairs the emergence of synesthesia-related phenomena such as multisensory integration and cross-modal correspondences between non-visual senses (e.g., sound-touch). Is visual experience necessary to develop synesthesia? Here we describe the case of a congenital blind man (CB) reporting a complex synesthetic experience, involving numbers, letters, months and days of the week. Each item is associated with a precise position in mental space and with a precise tactile texture. In one experiment we empirically verified the presence of number-texture and letter-texture synesthesia in CB, compared to non-synesthete controls, probing the consistency of item-texture associations across time and demonstrating that synesthesia can develop without vision. Our data fill an important void in the current knowledge on synesthesia and shed light on the mechanisms behind sensory crosstalk in the human mind.
Topics: Blindness; Color Perception; Humans; Male; Music; Perceptual Disorders; Synesthesia; Touch; Touch Perception
PubMed: 35358538
DOI: 10.1016/j.neuropsychologia.2022.108226 -
Frontiers in Psychology Oct 2013Synesthesia is a fairly common condition in which individuals experience atypical responses (such as color experiences) in association with certain types of stimuli... (Review)
Review
Synesthesia is a fairly common condition in which individuals experience atypical responses (such as color experiences) in association with certain types of stimuli (such as non-colored letters). Although synesthesia has been described for centuries, only very recently has there been an explosive growth of systematic scientific examinations of this condition. In this article, we review and critically evaluate current methods for both assessing synesthesia and examining its psychological basis, including the "test-retest" procedure, online battery assessments, and behavioral experiments. We highlight the limitations of these methods for understanding the nature of this complex condition and propose potential solutions to address some of these limitations. We also provide a set of markers that aid in distinguishing synesthesia from other closely related psychological phenomena.
PubMed: 24155733
DOI: 10.3389/fpsyg.2013.00763