Table 1.

Response to first or second flashes instructing movements

Movement InstructedPRRLIP
ResponsesNo. of cells > vs. < No. of significantly > No. of significantly <ResponsesNo. of cells > vs. < No. of significantly > No. of significantly <
Preferred vs. Null26.2 ± 2.31-160 16 vs. 130.8 ± 2.11-160 20 vs. 0
vs.15* vs.14*
16.1 ± 1.81* 18.2 ± 1.50
−/P vs. −/N 23.3 ± 3.41-160 15 vs. 231.2 ± 3.51-160 20 vs. 0
vs.11* vs.9*
12.9 ± 2.61* 20.8 ± 3.00
N/P vs. P/−30.4 ± 3.812 vs. 533.6 ± 3.813 vs. 7
vs.6* vs.4*
26.2 ± 2.3030.8 ± 2.11*
P/P vs. P/−16.1 ± 3.11-160 2 vs. 1528.9 ± 3.310 vs. 10
vs.1* vs.1*
26.1 ± 2.313* 30.8 ± 2.14*
N/P vs. P/P 30.4 ± 3.81-160 15 vs. 233.6 ± 3.81-160 13 vs. 7
vs.13* vs.1*
16.1 ± 3.11* 28.9 ± 3.30
P/N vs. N/N 12.3 ± 2.65 vs. 1222.6 ± 2.813 vs. 7
vs.1* vs.4*
13.4 ± 2.72* 19.0 ± 3.21*
  • Population firing rate (in spikes per second; columns 2 and 4) and cell counts (columns 3 and 5) from parietal reach region (PRR; n = 17) and lateral intraparietal area (LIP; n = 20) showing responses to first or second flashes instructing movements of a preferred (P) or nonpreferred type (N). In PRR, reaches were preferred, whereas in LIP, saccades were preferred. This held for responses to both first (row 1) and second (row 2) responses. The next two rows compare second vs. first flash responses, where each instructed the same preferred movement but the second flash either countermanded (row 3) or affirmed (row 4) the first flash. The final two rows compare the response to a countermanding vs. affirming second flash, instructing either a preferred (row 5) or nonpreferred (row 6) movement. Population data show means ± SE under each condition with

  • F1-160 P ≤ 0.01. First line of single cell data shows the number of cells in which first condition responses were greater than second condition responses vs. the number in which the second responses were greater than first. The next two lines show the number of cells for which these two inequalities were significant at P < 0.05 (*), respectively. See text for details.