All procedures were approved by the IACUC of the Nathan Kline Institute. Recordings were made in six awake macaques. Binaural auditory stimuli of tones and BBN were delivered through directional free field speakers. Linear array multielectrodes, having 23 electrical contacts with either 100 or 200 μm inter-contact spacing were used. Electrodes were advanced downward from the surface of brain with steps of 2 or 4 mm for arrays of 100 or 200 μm spacing, respectively, until they reached the auditory cortex. At each step, responses to 50~100 repetitions of BBN were recorded. Reference electrodes were positioned above dura. See Supplemental Experimental Procedures for more details.
