Abstract
Oculomotor circuits generate eye movements based on the physical salience of objects and current behavioral goals, exogenous and endogenous influences, respectively. However, the interactions between exogenous and endogenous mechanisms and their dynamic contributions to target selection have been difficult to resolve because they evolve extremely rapidly. In a recent study (Salinas et al., 2019), we achieved the necessary temporal precision using an urgent variant of the antisaccade task wherein motor plans are initiated early and choice accuracy depends sharply on when exactly the visual cue information becomes available. Empirical and modeling results indicated that the exogenous signal arrives ∼80 ms after cue onset and rapidly accelerates the (incorrect) plan toward the cue, whereas the informed endogenous signal arrives ∼25 ms later to favor the (correct) plan away from the cue. Here, we scrutinize a key mechanistic hypothesis about this dynamic, that the exogenous and endogenous signals act at different times and independently of each other. We test quantitative model predictions by comparing the performance of human participants instructed to look toward a visual cue versus away from it under high urgency. We find that, indeed, the exogenous response is largely impervious to task instructions; it simply flips its sign relative to the correct choice, and this largely explains the drastic differences in psychometric performance between the two tasks. Thus, saccadic choices are strongly dictated by the alignment between salience and behavioral goals.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Grants: Research was supported by the NIH through grant R21MH120784 from the NIMH, grant R01EY025172 from the NEI, and training grant T32NS073553-01 from the NINDS.
Disclosures: The authors declare no conflicts of interest, financial or otherwise.
Abbreviations
- CAS
- compelled antisaccade
- CPS
- compelled prosaccade
- CI
- confidence interval
- ERI
- exogenous response interval
- FEF
- frontal eye field
- rPT
- raw processing time
- RT
- reaction time
- SC
- superior colliculus
- SD
- standard deviation
- SE
- standard error