Summary
A ramp to threshold activity of frontal Eye Field (FEF) movement-related neurons best explains the reaction time of single saccades. How such activity is modulated by a concurrent saccade plan is not known. Borrowing from psychological theories of capacity sharing that are designed to explain the concurrent planning of two decisions, we show that processing bottlenecks are brought about by decreasing the growth rate and increasing the threshold of saccade-related activity. Further, rate perturbation affects both saccade plans, indicating a capacity-sharing mechanism of processing bottlenecks, where both the saccade plans compete for processing capacity. To understand how capacity sharing was neurally instantiated, we designed a model in which movement fields that instantiate two saccade plans, mutually inhibit each other. In addition to predicting the greater reaction times for both saccades and changes in growth rate and threshold activity observed experimentally, we observed a greater separation of the two neural trajectories in neural state space, which was verified experimentally. Finally, we show that in contrast to movement related neurons, visual activity in FEF neurons are not affected by the presence of multiple saccade targets, indicating that inhibition amongst movement-related neurons instantiates capacity sharing. Taken together, we show how psychology-inspired models of capacity sharing can be mapped onto neural responses to understand the control of rapid saccade sequences.
Competing Interest Statement
The authors have declared no competing interest.
