Characterization of visual percepts evoked by noninvasive stimulation of the human posterior parietal cortex

Phosphenes are commonly evoked by transcranial magnetic stimulation (TMS) to study the functional organization, connectivity, and excitability of the human visual brain. For years, phosphenes have been documented only from stimulating early visual areas (V1-V3) and a handful of specialized visual re...

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Bibliographic Details
Published in:PloS one 2011-11, Vol.6 (11), p.e27204-e27204
Main Authors: Fried, Peter J, Elkin-Frankston, Seth, Rushmore, Richard Jarrett, Hilgetag, Claus C, Valero-Cabre, Antoni
Format: Article
Language:English
Subjects:
Biology
Brain
Brain research
Clinical medicine
Cortex (occipital)
Cortex (parietal)
Deactivation
Dissociation
Electrodes
Excitability
Functional morphology
Humans
Information processing
Localization
Magnetic fields
Medicine
Neural networks
Neurobiology
Neurosciences
Occipital lobe
Parietal Lobe - physiology
Phosphene
Phosphenes
Photic Stimulation
Thresholds
Transcranial Magnetic Stimulation
Visual cortex
Visual Cortex - physiology
Visual Perception - physiology
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Summary:Phosphenes are commonly evoked by transcranial magnetic stimulation (TMS) to study the functional organization, connectivity, and excitability of the human visual brain. For years, phosphenes have been documented only from stimulating early visual areas (V1-V3) and a handful of specialized visual regions (V4, V5/MT+) in occipital cortex. Recently, phosphenes were reported after applying TMS to a region of posterior parietal cortex involved in the top-down modulation of visuo-spatial processing. In the present study, we systematically characterized parietal phosphenes to determine if they are generated directly by local mechanisms or emerge through indirect activation of other visual areas. Using technology developed in-house to record the subjective features of phosphenes, we found no systematic differences in the size, shape, location, or frame-of-reference of parietal phosphenes when compared to their occipital counterparts. In a second experiment, discrete deactivation by 1 Hz repetitive TMS yielded a double dissociation: phosphene thresholds increased at the deactivated site without producing a corresponding change at the non-deactivated location. Overall, the commonalities of parietal and occipital phosphenes, and our ability to independently modulate their excitability thresholds, lead us to conclude that they share a common neural basis that is separate from either of the stimulated regions.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0027204