Date of Award
Summer 9-15-2024
Document Type
Thesis (Ph.D.)
Department or Program
Psychological & Brain Sciences
First Advisor
Dr. Peter U. Tse
Abstract
Visual hallucinations are visual experiences that are spontaneously generated by the brain, in the absence of appropriate external stimuli. Understanding the neural processes that give rise to these experiences is a complex challenge that spans the domains of psychology, neuroscience, and clinical practice. Model hallucinations can serve as a valuable tool in this context. They allow researchers to study hallucinatory experiences under controlled conditions, thus providing insights into their behavioral and neural underpinnings, which can facilitate the development of effective treatments. By creating models that emulate different aspects of hallucinatory experience, whether through pharmacological means, sensory manipulation, or cognitive tasks, scientists can isolate specific variables and observe their effects on hallucination-like phenomena. This thesis evaluates the merits of three model paradigms for advancing our understanding of visual hallucinations. Chapter 1 validates a novel visual signal detection task, the Signal Detection Pareidolia Task (SDPT). We demonstrate that the SDPT can be used to investigate the ‘continuum hypothesis’ for visual hallucinations in a specific patient population: individuals with Lewy body diseases. Chapter 2 investigates the neuromodulatory effects of the serotonergic psychedelic psilocybin on the EEG power spectrum, with a specific focus on suppression in the alpha-power bandwidth (8-13Hz). While this effect is widely assumed to be a correlate of psychedelic-induced hallucinations, our results show that this assumption may not be warranted. Chapter 3 examines whether established neural correlates of psychedelics, including alpha-power suppression, are also correlates of strobe-induced geometric hallucinations. We find that both strobe stimulation and psychedelic administration induce a similar brain state, but that signatures of this state do not sufficiently distinguish between hallucinatory and non-hallucinatory perception. Altogether, this thesis argues for the need to clarify fundamental questions about the neural basis of visual hallucination and supports using these model paradigms to achieve that aim.
Original Citation
Heller, N. H. (2024). Psychophysical and Pharmacological Models of Visual Hallucination (Doctoral dissertation). Guarini School of Graduate and Advanced Studies, Dartmouth College, Hanover, New Hampshire.
Recommended Citation
Heller, Nathan H., "Psychophysical and Pharmacological Models of Visual Hallucination" (2024). Dartmouth College Ph.D Dissertations. 305.
https://digitalcommons.dartmouth.edu/dissertations/305
Included in
Biological Psychology Commons, Cognition and Perception Commons, Cognitive Psychology Commons
