Mapping visual search errors to covert operations with frontal eye field neurophysiology and double factorial design

Behavior is the outcome of covert perceptual, cognitive, and motor operations that can be described by mathematical models and are produced by brain systems comprised of diverse neurons. Using the logic of selective influence, we previously distinguished the stages of processing supporting visual search (Lyu, Reppert, Schall, 2023). In that study, macaque monkeys searched for a color singleton among distractors. Two operations necessary for the task were independently manipulated. Singleton localizability was manipulated by varying the similarity between singleton and distractor colors. Stimulus-response mapping was manipulated by varying the discriminability of search array shape, signaling GO/NOGO response. The organization and termination rule of the two operations were determined using System Factorial Technology (SFT; Lowe et al, 2019). The necessary next step in this research is to account for performance errors in this difficult task, which influence the logic of the SFT diagnosis. Monkeys made two key errors: on GO trials, monkeys occasionally shifted gaze to a distractor due to unsuccessful localization (GO error). On NOGO trials, they failed to inhibit their saccade towards either the singleton or the distractors (NOGO errors). NOGO errors reflect failure in discrimination alone or both operations, respectively. We probed the neural sources of these error saccades using single-unit spiking in frontal eye field. Neurons representing stimulus salience were distinguished from neurons mediating saccade preparation. Our data suggest that GO errors occur when visual salience neurons misrepresenting the distractor as the singleton. NOGO errors to singleton arise from incorrect discrimination by saccade preparation neurons whereas NOGO errors to distractor arise from inaccurate response from both neuron types. The convergence of performance and neural results on error trials offer constraints to mathematical models and provide evidence so that distinct operations and their organization during visual search can be resolved.