Cortical gamma-oscillations modulated by visuomotor tasks: Intracranial recording in patients with epilepsy

Abstract

We determined how visuomotor tasks modulated gamma-oscillations on electrocorticography in epileptic patients who underwent epilepsy surgery. Each visual-cue consisted of either a sentence or hand gesture instructing the subject to press or not to press the button. Regardless of the recorded hemisphere, viewing sentence and gesture cues elicited gamma-augmentation sequentially in the lateral-polar occipital and inferior occipital-temporal areas; subsequently, button-press movement elicited gamma-augmentation in the Rolandic area. The magnitudes of gamma-augmentation in the Rolandic and inferior occipital-temporal areas were larger when the hand contralateral to the recorded hemisphere was used for motor responses. A double dissociation was found in the left inferior occipital-temporal cortex in one subject; the lateral portion had greater gamma-augmentation elicited by a sentence-cue, whereas the medial portion had greater gamma-augmentation elicited by a gesture-cue. The present study has increased our understanding of the physiology of the human visuomotor system.

Figure 1. Differential gamma-augmentation elicited by sentence- and gesture-cues in patient 10

Time-frequency ECoG matrixes relative to the onset of visual-cues revealed a functional double dissociation in patient 10. The sentence-cue visuomotor task resulted in gamma-augmentation in the lateral portion but not in the medial portion of the inferior occipital-temporal area (upper row). The gesture-cue visuomotor task resulted in gamma-augmentation in the medial and lateral portions of the inferior occipital-temporal area with greater intensity in the medial portion (middle row). Comparison of amplitudes between sentence- and gesture-cues revealed that the relatively lateral portion of inferior occipital-temporal area had significantly greater gamma-augmentation elicited by a sentence-cue (denoted by red areas in the bottom row), whereas the relatively medial portion had significantly greater gamma-augmentation elicited by a gesture-cue (denoted by blue areas in the bottom row). Please also see Videos S1 and S2 on the website.

Figure 2. Differential gamma-augmentation elicited by sentence- and gesture-cues at the group level

Red circles represent electrode sites showing gamma-augmentation elicited by sentence-cues significantly more than gesture-cues. Blue circles represent electrode sites showing gamma-augmentation elicited by gesture-cues significantly more than sentence-cues. The number in each circle indicates the patient number (Table 1).