Table 1.

Modulation Indices of Attention-Related Neuronal Changes.

Modulation Index	Criterion sessions (Δc)		Sensitivity sessions (Δd′)		Criterion sessions vs. sensitivity sessions
	Monkey F (n = 22)	Monkey L (n = 10)	Monkey F (n = 22)	Monkey L (n = 25)	Monkey F	Monkey L
Firing rate (Sample stimulus)	0.006 ± 0.005 p < 0.31	0.002 ± 0.007 p < 0.78	0.060 ± 0.004 p < 10−11	0.028 ± 0.003 p < 10−8	p < 10−8	p < 10−3
Firing rate (Delay period)	0.009 ± 0.005 p < 0.09	0.004 ± 0.012 p < 0.75	0.109 ± 0.006 p < 10−13	0.078 ± 0.005 p < 10−13	p < 10−14	p < 10−7
Noise correlation	0.040 ± 0.026 p < 0.13	0.057 ± 0.056 p < 0.34	−0.295 ± 0.020 p < 10−11	−0.198 ± 0.030 p < 10−6	p < 10−12	p < 10−3
Fano factor	0.002 ± 0.004 p < 0.68	0.007 ± 0.014 p < 0.62	−0.043 ± 0.010 p < 10−3	−0.019 ± 0.004 p < 10−4	p < 10−3	p < 0.02

Each of the four columns to the left reports the mean ± SEM aross sessions and the probability that the indices have a mean 0 (t-test). The remaining two columns indicate the probability that the modulation indices from the two types of sessions have the same mean (paired t-test). A single modulation index was computed for each session. A positive index for a sensitivity session indicates a higher measure (e.g. firing rates) in the high d′ task condition, and a positive index for a criterion session reflects a higher measure in the low c condition. Indices were computed using both correct and error trials, but results are highly similar if only correct trials were used.