期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：47
页码：13492-13497
DOI：10.1073/pnas.1606479113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceA central question in systems neuroscience is how cognitive functions can arise from the interplay of many different brain areas. For example the cognitive act of forming a decision requires a concerted computation involving sensory, mnemonic, and executive information residing in neural circuits that have different anatomical locations, that operate on different temporal scales, and that extend over different spatial dimensions. We find that in a central cortical hub--the posterior parietal cortex--firing rate information about upcoming decisions is pulsed according to intrinsic temporal structure in the beta- and gamma-frequency ranges. The brain may use temporal structure at several time scales to support distributed computations that underlie reward-guided decisions. Making a decision involves computations across distributed cortical and subcortical networks. How such distributed processing is performed remains unclear. We test how the encoding of choice in a key decision-making node, the posterior parietal cortex (PPC), depends on the temporal structure of the surrounding population activity. We recorded spiking and local field potential (LFP) activity in the PPC while two rhesus macaques performed a decision-making task. We quantified the mutual information that neurons carried about an upcoming choice and its dependence on LFP activity. The spiking of PPC neurons was correlated with LFP phases at three distinct time scales in the theta, beta, and gamma frequency bands. Importantly, activity at these time scales encoded upcoming decisions differently. Choice information contained in neural firing varied with the phase of beta and gamma activity. For gamma activity, maximum choice information occurred at the same phase as the maximum spike count. However, for beta activity, choice information and spike count were greatest at different phases. In contrast, theta activity did not modulate the encoding properties of PPC units directly but was correlated with beta and gamma activity through cross-frequency coupling. We propose that the relative timing of local spiking and choice information reveals temporal reference frames for computations in either local or large-scale decision networks. Differences between the timing of task information and activity patterns may be a general signature of distributed processing across large-scale networks.
