Figure 8.

Summary of population-averaged neurophysiological activity in three cortical areas for matching and non-matching test sounds. (A) In PFC, firing rates on match trials became elevated relative to non-match trials during the early sound presentation period. Elevated firing rates were similarly observed on match trials in (B) primary auditory cortex and (C) dorsal temporal pole. However, these effects occurred later than in PFC, during the sound period or cue offset period, consistent with the notion that elevated firing in these areas may reflect top–down feedback originating in PFC. In contrast to these late match enhancement effects, significant suppression was observed on match trials in the early sound period in dorsal temporal pole. Early match suppression was also observed in auditory cortex in a portion of the individual units as well as in the single-unit subpopulation (Table 1, Figures 4, 6). The gray bars above the abscissae indicate the test stimulus presentation period (0–500 ms from cue onset). (A) Adapted from Plakke et al. (2013); (C) adapted from Ng et al. (2014). Each of the summarized experiments were conducted using the same subjects and auditory short-term memory task (see Methods for details).