Document Detail

Induced visual illusions and gamma oscillations in human primary visual cortex.
MedLine Citation:
PMID:  15233769     Owner:  NLM     Status:  MEDLINE    
Using magnetoencephalography, we studied the spatiotemporal properties of cortical responses in terms of event-related synchronization and event-related desynchronization to a range of stripe patterns in subjects with no neurological disorders. These stripes are known for their tendency to induce a range of abnormal sensations, such as illusions, nausea, dizziness, headache and attacks of pattern-sensitive epilepsy. The optimal stimulus must have specific physical properties, and maximum abnormalities occur at specific spatial frequency and contrast. Despite individual differences in the severity of discomfort experienced, psychophysical studies have shown that most observers experience some degree of visual anomaly on viewing such patterns. In a separate experiment, subjects reported the incidence of illusions and discomfort to each pattern. We found maximal cortical power in the gamma range (30-60 Hz) confined to the region of the primary visual cortex in response to patterns of 2-4 cycles per degree, peaking at 3 cycles per degree. This coincides with the peak of mean illusions and discomfort, also maximal for patterns of 2-4 cycles per degree. We show that gamma band activity in V1 is a narrow band function of spatial frequency. We hypothesize that the intrinsic properties of gamma oscillations may underlie visual discomfort and play a role in the onset of seizures.
Peyman Adjamian; Ian E Holliday; Gareth R Barnes; Arjan Hillebrand; Avgis Hadjipapas; Krish D Singh
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The European journal of neuroscience     Volume:  20     ISSN:  0953-816X     ISO Abbreviation:  Eur. J. Neurosci.     Publication Date:  2004 Jul 
Date Detail:
Created Date:  2004-07-05     Completed Date:  2004-09-30     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8918110     Medline TA:  Eur J Neurosci     Country:  France    
Other Details:
Languages:  eng     Pagination:  587-92     Citation Subset:  IM    
The Wellcome Trust Laboratory for MEG Studies, Neurosciences Research Institute, Aston University, Birmingham, UK.
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MeSH Terms
Brain Mapping
Electroencephalography / methods
Evoked Potentials, Visual / physiology*
Illusions / physiology*
Magnetoencephalography / methods
Middle Aged
Photic Stimulation / methods
Visual Cortex / physiology*
Visual Perception / physiology*

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