Abstract
Recent neural ensemble recordings have established a link between goal-directed spatial decision making and internally generated neural sequences in the hippocampus of rats. To elucidate the synaptic mechanisms of these sequences underlying spatial decision making processes, we develop and investigate a spiking neural circuit model endowed with a combination of two synaptic plasticity mechanisms including spike-timing dependent plasticity (STDP) and synaptic scaling. In this model, the interplay of the combined synaptic plasticity mechanisms and network dynamics gives rise to neural sequences which propagate ahead of the animals’ decision point to reach goal locations. The dynamical properties of these forward-sweeping sequences and the rates of correct binary choices executed by these sequences are quantitatively consistent with experimental observations; this consistency, however, is lost in our model when only one of STDP or synaptic scaling is included. We further demonstrate that such sequence-based decision making in our network model can adaptively respond to time-varying and probabilistic associations of cues and goal locations, and that our model performs as well as an optimal Kalman filter model. Our results thus suggest that the combination of plasticity phenomena on different timescales provides a candidate mechanism for forming internally generated neural sequences and for implementing adaptive spatial decision making.
Highlights
Neural sequences have been widely observed in many brain areas including the cortex [1, 2, 3, 4], and the hippocampus [5, 6, 7, 8, 9, 10, 11]
Adaptive goal-directed decision making is critical for animals, robots and humans to navigate through space
We show that in a spiking neural circuit model, the interplay of network dynamics and a combination of two synaptic plasticity rules, spike-timing dependent plasticity (STDP) and synaptic scaling, gives rise to neural sequences
Summary
Neural sequences have been widely observed in many brain areas including the cortex [1, 2, 3, 4], and the hippocampus [5, 6, 7, 8, 9, 10, 11]. Recent experimental studies with multi-electrode array recordings have revealed that when the animals rest between goal-directed spatial navigation episodes, neural ensemble activity propagates forward towards potential goal locations [15]. Such recordings of rodents trained on spatial decision tasks have found that when rodents paused around the decision point, forward sweeping IGS were formed [6]. Despite the importance of IGS for goal-directed behaviours such as spatial decision making, the neural mechanism underlying the formation of these IGS and their general computational roles remain unclear
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