Quantitative Analysis of Roles of Direct and Indirect Pathways for Action Selection in The Basal Ganglia
The basal ganglia (BG) show diverse functions for motor and cognition. Here, we are concerned about action selection performed by the BG. Particularly, we make quantitative analysis of roles of direct pathway (DP) and indirect pathway (IP) for action selection in a spiking neural network with 3 competing channels. For such quantitative work, in each channel, we get the competition degree Cd , given by the ratio of strength of DP ( SDP ) to strength of IP ( SIP ) (i.e., Cd = SDP / SIP ). Then, desired action is selected in the channel with the largest Cd . Desired action selection is made mainly due to strong focused inhibitory projection to the output nucleus, SNr (substantia nigra pars reticulata) via the “Go” DP in the corresponding channel. Unlike the case of DP, there are two types of IPs; intra-channel IP and inter-channel IP, due to widespread diffusive excitation from the STN (subthalamic nucleus). The intra-channel “No-Go” IP plays a role of brake to suppress the desired action