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Induced visual illusions and gamma oscillations in human primary visual cortex

Adjamian, Peyman, Holliday, Ian E., Barnes, Gareth R., Hillebrand, Arjan, Hadjipapas, Avgis and Singh, Krish Devi 2004. Induced visual illusions and gamma oscillations in human primary visual cortex. European Journal of Neuroscience 20 (2) , pp. 587-592. 10.1111/j.1460-9568.2004.03495.x

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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.

Item Type: Article
Status: Published
Schools: Psychology
Neuroscience and Mental Health Research Institute (NMHRI)
Subjects: R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Uncontrolled Keywords: event-related synchronization and desynchronization; gamma oscillations; magnetoencephalography; visual discomfort; visual stress
Publisher: Wiley-Blackwell
ISSN: 0953-816X
Last Modified: 04 Jun 2017 04:10

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