Figure 7. Event related potentials recorded from auditory and visual cortex.

Evoked responses were calculated from differential LFPs recorded with bipolar electrodes. (a) Location of the two bipolar electrodes (circled) that yielded the examples of auditory and visual evoked potentials in (b) and (c), respectively. The ECoG array is the same as that shown in Fig. 2a. (b) Example of an evoked potential to an auditory stimulus (a 74-msec harmonic complex tone with a fundamental frequency of 500 Hz). Upper panel, the trial-averaged spectrogram of the evoked potential recorded from a bipolar electrode located in the primary auditory cortex on the STP of the lateral sulcus. The activity is normalized to the baseline activity recorded before the onset of the stimulus. Lower panel, the trial-averaged waveform of the evoked response (c) Examples of evoked potentials from 9 bipolar recording sites in the ECoG array implanted on the STP. The auditory stimulus used is the one in as (b). Upper panel, the 9 recording sites on STP. Recording site #1 is located in the most caudal part of this intrasulcal array. These 9 sites span more than 2cm in the caudorostral direction of the STP. Lower panel, the trial-averaged waveforms of the auditory evoked potentials recorded from the 9 sites. The magnitude of the evoked potential is normalized by calculating z-scores for each site. (d) Example of an evoked response to a visual stimulus (white square flashed for 1 second). Upper panel, the trial-averaged spectrogram of the evoked potential recorded from a bipolar electrode located in the primary visual cortex. This activity is normalized to the baseline activity recorded before the onset of the stimulus. Lower panel, the trial-averaged waveform of the evoked response.