Distinct sources of decision-related signals in visual cortex are represented in different local field potential bands

by Yueyue Sapphire Hou, Pooya Laamerad, Liu D. Liu, Christopher C. Pack

Fluctuations in single-neuron activity in the sensory cortex often correlate with perceptual decisions. This kind of correlation is often hypothesized to reflect a causal influence of sensory signals on decisions, but it can be attributed to various noncausal factors as well. To disentangle these different possibilities, we have examined local field potentials (LFPs) recorded from the middle temporal (MT) area and area V4 of nonhuman primates (Macaca mulatta) while they performed two different perceptual decision-making tasks. Compared to single-neuron spiking, LFPs have the advantage of being decomposable into frequency bands that are associated with different anatomical sources of input. More importantly, they persist when spiking activity is inactivated, which precludes a causal influence of the corresponding neural activity on behavior. We found that high-gamma frequency (70, 150 Hz) LFP power was correlated with perceptual decisions and that this correlation disappeared when spikes were inactivated, consistent with a causal role for this frequency band in decision-making. These signals overlapped in time with decision signals in the lower gamma band (30, 70 Hz), which persisted after spiking inactivation, suggesting a noncausal input. Interestingly, lower-frequency LFP signals (5, 30 Hz) reflected both impending perceptual decisions and the outcome of preceding trials, suggesting a modulatory influence of recent experience on neural dynamics. Our results, therefore, reveal that neural activity multiplexes different sources of information about perceptual decisions and that these types of information can be estimated reliably from different LFP frequencies.