Wednesday, June 6, 2007

Enhanced Category Tuning Revealed by Intracranial Electroencephalograms in High-Order Human Visual Areas

Eran Privman, Yuval Nir, Uri Kramer, Svetlana Kipervasser, Fani Andelman, Miri Y. Neufeld, Roy Mukamel, Yehezkel Yeshurun, Itzhak Fried, and Rafael Malach
The Journal of Neuroscience, June 6, 2007, 27(23):6234-6242;

The functional organization of human sensory cortex was studied by comparing intracranial EEG (iEEG) recordings of local field potentials in neurosurgical patients with functional magnetic resonance imaging (fMRI) obtained in healthy subjects. Using naturalistic movie stimuli, we found a tight correlation between these two measures throughout the human sensory cortex. Importantly, the correlation between the iEEG and fMRI signals was site-specific, exhibiting neuroanatomically specific coupling. In several cortical sites the iEEG activity was confined strictly to one object category. This site selectivity was not limited to faces but included other object categories such as houses and tools. The selectivity of the iEEG signals to images of different object categories was remarkably higher when compared with the selectivity of the corresponding fMRI signals. A plausible interpretation of the fMRI and iEEG results concerns cortical organization in which object categories are organized in a mosaic of narrowly tuned object-selective clusters.

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