Posted on behalf of Jaime Martinez:
The authors of the present work studied the extent to which visual brain regions participate in non-sensory cognitive processes of visual representation. To this end, they evaluated the role of ventral visual pathway areas in visual imagery and working memory by analyzing intracerebral EEG recordings from the left inferior temporal lobe of an epileptic patient. Using a set up that allowed real time measurement and visualization of gamma band activity they found a systematic activity increase in the inferior temporal gyrus (ITG) when the patient was visualizing a letter (visual imagery) or during visuo-spatial working memory, but not during perception of letters neither during verbal working memory. In contrast, in the fusiform gyrus (located 7 mm more medially than the ITG), gamma band activity increased during verbal working memory retention and letter presentation, but not during visual imagery or visuo-spatial working memory. From these results the authors conclude that neural networks supporting imagination of visual elements are not necessarily the same as those underlying perception of the element. They also present evidence that gamma band activity in the inferior temporal lobe can be used as direct measure of the efficiency of top down attentional control over visual areas. Finally, the results indicate that only by reading gamma band activity in the ITG and the fusiform gyrus is possible to decode the type of material being maintained in working memory (verbal vs. visuo-spatial) on a single trial basis.
Hamamé, C., Vidal, J., Ossandón, T., Jerbi, K., Dalal, S., Minotti, L., Bertrand, O., Kahane, P., & Lachaux, J. (2012). Reading the mind’s eye: Online detection of visuo-spatial working memory and visual imagery in the inferior temporal lobe NeuroImage, 59 (1), 872-879 DOI: 10.1016/j.neuroimage.2011.07.087
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