The Neuroscience of Visual Hallucinations
The brain combines sensory signals, processes it in the context of what it knows from the past, and guesses what is happening in real time. For example, we might see an object through the visual cortex, but what helps us identify said object is the past compendium of information we have accumulated until that point.
Which is why he says our conscious reality is so similar to hallucination—the only difference is that we collectively agree on these particular hallucinations and deem them reality. Seth, who grew up in Oxfordshire, England, became fascinated by consciousness around the age of 19 through the lens of math and physics.
At Cambridge University, he started to absorb books on the topic while studying natural sciences. In Consciousness Explained , cognitive scientist Daniel Dennett described consciousness as a cluster of brain activity, rather than a centralized entity. Seth continued to study the brain after university. He received a Masters of Science in Knowledge-Based Systems at the University of Sussex in and said academia provided the resources and professors to help him explore different avenues of addressing consciousness and how it determines what we perceive, from psychology to brain imaging data.
His role in San Diego was multifaceted. Seth spent his time building robots with brain architecture that mimicked the human brain.
The robots were tasked with solving visual perception problems , or mazes. Afterward, Seth needed to find a way to continue his exploration of consciousness.
In , Seth moved back to England and arrived at the University of Sussex. A related intriguing bit of evidence is provided by David and Rapoport Chapter 12 , who, in describing their childhood onset schizophrenia COS studies, highlight results showing how IQ is related to the breadth of hallucinatory experiences. Specifically, highest IQ was found in COS patients who had only visual hallucinations, lower IQ was found in those who also had either somatic or olfactory hallucinations, and lowest IQ was found in those who had hallucinations spanning all three modalities.
Other contributions further highlight the importance of viewing hallucinatory experiences as phenomena that span many syndromes, and that may parallel generalized brain dysfunction, rather than being a characteristic of any particular diagnostic group. Clinicians may particularly enjoy learning more about the assessment of hallucinations.
Widespread clinical practice often reduces assessment of hallucinatory experiences to a few broad categorical judgments. Stephane Chapter 5 details more than 30 qualities, and summarizes findings suggesting that three dimensions may characterize hallucinations: inner—outer spatial location; self-other attribution; and linguistic complexity. Instrumentation reviews offer a cogent perspective and should enable the neuropsychologist to determine what tools may be most useful for either clinical or selected research applications.
The cognitive models all tend to emphasize a role for speech and language mechanisms as these intersect with other central or higher order monitoring systems that lead to misattribution of source. Several models emphasize further the critical roles played by exogenous and endogenous emotional stressors, helping to explain the unusual and unique content of hallucinatory experiences.
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Most familiar to neuropsychologist readers are likely to be the functional anatomic, genetic, and neurochemical models, and particularly those which emphasize monitoring failures and the speech-language systems. These reviews may be particularly valuable in highlighting for neuropsychologists the mechanisms that must be operating when they do observe hallucinatory phenomena in their patients.click here
Neuroscience of Hallucinations | Archives of Clinical Neuropsychology | Oxford Academic
There is sometimes still a tendency in clinical neuropsychology to view hallucinations as attributable to a psychiatric syndrome, rather than to specific patterns of brain dysfunction. The models illustrated in this book help to put hallucinations and their likely causes in a clearer perspective.
The second half of the book Parts III—V provide solid coverage of modern neural network models that have led to some strong hypotheses about the plausible mechanisms underlying hallucinations in the brain. These models are juxtaposed with evidence from a broad range of experimental approaches spanning electrophysiological recordings and structural and functional brain imaging methods.
Taking the long view
These models are helping tie together diverse theoretical elements advanced in the cognitive models, and increasingly generating a more unified view of hallucinatory experiences spanning molecular, cellular, systems, and cognitive levels of explanation. Overall, The Neuroscience of Hallucinations provides a welcome and valuable collection of works on hallucinatory experience that is unprecedented in its scope. It must be acknowledged that the works come from a renowned international group of scientists and the English is occasionally uneven; it is a credit to the authors and editors that all contributions are sufficiently lucid for those of us who speak only English.
The substantive contents of the book are of high value to neuropsychologists, however, by providing a deeper insight into the relatively common but poorly understood phenomena of hallucinations. Another year in the books A special order item has limited availability and the seller may source this title from another supplier. In this event, there may be a slight delay in shipping and possible variation in description. Our Day return guarantee still applies.
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