Dissecting errors made in response to externally- and internally-driven visual tasks in the common marmosets and humans

Abstract

Various saccadic tasks traditionally used in oculomotor research, including both exogenously-driven and endogenously-driven saccades, have been proposed as clinical diagnostic for human movement disorders. Recently, common marmosets have been proven to be a good primate model for these movement disorders. However, whether similar saccadic measurements can be used for marmosets was not tested. Here, we trained three marmosets on the gap task, an exogenously-driven saccadic task, and the oculomotor delayed response (ODR) task, an endogenously-driven saccadic task. We demonstrated that with long-term training, they were able to learn and switch between the two tasks. The marmosets showed undershooting tendency in the gap and both under- and overshooting tendency in the ODR task when they made saccades to the target. We also categorized the error trails into distractive, impulsive, and visuomotor errors, depending on when a false saccade happened in relation to the task progression and interpreted possible causes of errors based on the saccade response time and the task history. Each error category may indicate specific failures in a particular aspect of cognitive or sensory-motor processes. Finally, and critically, we found that saccades from successful trials exhibited the highest saccade peak velocity and the shortest saccade duration comparing to the same saccade amplitude from error trials. Taken together, we showed the potential of training the same marmosets on conflicting oculomotor tasks simultaneously. We documented the baseline performance and compared successful and error trials in both gap and ODR tasks from the same animals. We propose that analyzing the error trials in sync with successful trials could provide a further understanding of the cognitive and sensorimotor processes of the marmosets, in both healthy and disease conditions.

Delay-related activity in marmoset prefrontal cortex

“…Although marmosets can be trained to perform saccadic eye movement tasks, it has thus far proven difficult to train these monkeys on the ODR task. To date, there are only a few conference reports regarding training marmosets on the ODR task, and the consensus is the performance of marmosets is quite low and that delay length is limited to short periods under 400 ms (Amly et al 2021). Another group (Carney et al 2019) delivered reward throughout the sample and delay periods as a means to encourage marmosets to maintain fixation, which often presents a challenge for this primate species and detrimentally affects task performance.…”