A Biologically Inspired Computational Model of Basal Ganglia in Action Selection

Figure 9

Temporal activity of the winning action channel in each structure of the whole network with different tonic dopamine levels, red dotted line low level, blue solid line normal level and black dashed line high level. No training was performed before. The tonic level of dopamine has effects on each structure of the network. In the cortex , the higher the tonic dopamine level, the faster the response, caused by a prompter feedback by the thalamus. Moreover, a higher tonic dopamine level promotes the direct pathway with respect to the indirect pathway: this is particularly noticeable in the activity of the Go and NoGo neurons of the winner, being the activity of the first higher and that of the second lower than normal. In case of low tonic dopamine level, the opposite effects are evident, promoting the indirect with respect to the direct pathway. Different levels of tonic dopamine exert differential effect also on the tonic activity of the cholinergic unit ChI: a lower dopamine level increases its activation, whereas higher dopamine levels tend to inhibit it.