Figure 1.

Basic electrode and behavioral task layout. (A) The craniotomy and recording chamber were placed over the left central sulcus. Electrodes placed within regions marked as Area 3b exhibited small receptive fields with defined edges, while larger receptive fields with gradual borders were observed in the region marked Area 1. (B) A change-detection task was used to probe the discriminability of ICMS of somatosensory cortex. Blocks of different types of stimuli (pictures, sounds, single-channel ICMS, or multichannel ICMS) were presented. During multichannel ICMS trials, a 1-s train of multichannel stimulation, corresponding to the movement of a sensor in one of four or eight directions, was delivered across three microelectrodes after a holdpad (HP) was depressed. If the stimulus was different from that delivered during the previous trial, the animal was required to release the holdpad and press a button (PB); if the stimulus was the same as the previous trial, the holdpad had to remain continually depressed until the end of the trial. A juice reward was delivered for some subset of correct trials (50–100% probability of reward) during the intertrial interval.