Fig. 6.
Neurons responded selectively to the samples; the pattern of selectivity was consistent across delay periods; but selective activity elicited by each sample did not persist beyond the immediately ensuing delay period. A: spatial task. B: color task. The height of each bar indicates the strength of correlation between sample selectivity measured on odd trials under one testing condition and on even trials under another testing condition. The 2 testing conditions are identified under each bar according to the convention SxDy, where x indicates the ordinal number of the sample and y indicates the ordinal number of the delay period during which firing was measured. “Selectivity”: encoding of SnDn on odd trials was well correlated with encoding of SnDn on even trials. “Consistency”: encoding of SmDm on odd trials was well correlated with encoding of SnDn on even trials. “Persistence”: encoding of SmDm on odd trials was poorly correlated with encoding of SmDn on even trials. All positive correlations reflecting selectivity (black bars) and consistency (gray bars) were statistically significant (P < 0.0001) whereas those associated with persistence (white bars) were not. Quantification and breakdown by monkey are in Table 2.