?
Mouse tracking reveals new dimensions for the analysis of response-related potentials
A response action consists of at least two stages: initiation and execution. Recording keystrokes and button presses is the method most commonly used in the field of cognitive psychophysiology; this method provides data on response accuracy and response time, which seem to be mostly related to the initiation stage. On the contrary, mouse tracking provides continuous data on response dynamics. Particularly, we assume that mouse movement duration is an important response parameter that is related to the execution stage of the response. Here, we applied this method to probe the functional significance of the response-related event-related potential (ERP) components such as correct-related negativity (CRN) and a Pe-like positivity.
We used the condensation task, which involves complex stimulus-to-response mapping: participants had to make responses to four auditory stimuli relying on the combination of two independent stimulus features. During each trial, participants had to respond to auditory stimuli by moving a computer mouse either to the top-left or to the top-right mousepad corner. EEG was recorded during the experiment. The following parameters of mouse movement were assessed: movement initialization time and movement duration. Within each subject, we divided the trials with correct responses into four quartiles for each of the mouse movement parameters separately. We compared ERP waveforms for trials within each pair of marginal quartiles.
Both movement initialization time and movement duration were higher for errors compared to correct responses. These mouse movement parameters were uncorrelated. We found that CRN amplitude within 10-110 ms time window was higher for early correct responses compared to late ones (p=0.004). In addition, we found a significant effect of mouse movement duration on ERP in early Pe time window (120-265 ms): amplitude of the Pe-like positivity was significantly higher for long correct responses compared with short correct responses (p<0.001).
We suggest that the early Pe-like component is not specifically related to errors; rather, both CRN and Pe-like component seem to be related to response uncertainty. Particularly, uncertainty during response execution stage seems to result in increased Pe-like component and prolonged mouse movement. We also assume that early correct responses are mostly premature responses, and increased CRN may indicate stronger performance monitoring arising after response initiation.
The study was implemented in the framework of the Basic Research Program at the National Research University Higher School of Economics (HSE) in 2018.