Document Detail

Stimuli of varying spatial scale induce gamma activity with distinct temporal characteristics in human visual cortex.
MedLine Citation:
PMID:  17306988     Owner:  NLM     Status:  MEDLINE    
Gamma activity to stationary grating stimuli was studied non-invasively using MEG recordings in humans. Using a spatial filtering technique, we localized gamma activity to primary visual cortex. We tested the hypothesis that spatial frequency properties of visual stimuli may be related to the temporal frequency characteristics of the associated cortical responses. We devised a method to assess temporal frequency differences between stimulus-related responses that typically exhibit complex spectral shapes. We applied this methodology to either single-trial (induced) or time-averaged (evoked) responses in four frequency ranges (0-40, 20-60, 40-80 and 60-100 Hz) and two time windows (either the entire duration of stimulus presentation or the first second following stimulus onset). Our results suggest that stimuli of varying spatial frequency induce responses that exhibit significantly different temporal frequency characteristics. These effects were particularly accentuated for induced responses in the classical gamma frequency band (20-60 Hz) analyzed over the entire duration of stimulus presentation. Strikingly, examining the first second of the responses following stimulus onset resulted in significant loss in stimulus specificity, suggesting that late signal components contain functionally relevant information. These findings advocate a functional role of gamma activity in sensory representation. We suggest that stimulus specific frequency characteristics of MEG signals can be mapped to processes of neuronal synchronization within the framework of coupled dynamical systems.
Avgis Hadjipapas; Peyman Adjamian; Jennifer B Swettenham; Ian E Holliday; Gareth R Barnes
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-01-19
Journal Detail:
Title:  NeuroImage     Volume:  35     ISSN:  1053-8119     ISO Abbreviation:  Neuroimage     Publication Date:  2007 Apr 
Date Detail:
Created Date:  2007-03-19     Completed Date:  2007-06-04     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9215515     Medline TA:  Neuroimage     Country:  United States    
Other Details:
Languages:  eng     Pagination:  518-30     Citation Subset:  IM    
The Wellcome Trust Laboratory for MEG Studies, Neurosciences, School of Life and Health Sciences, Aston University, Birmingham B4 7ET, UK.
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MeSH Terms
Photic Stimulation / methods*
Time Factors
Visual Cortex / physiology*

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