Countermanding saccades in humans.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Human Motor Control

Background:

• Human saccades are rapid eye movements crucial for visual processing.
• Controlling saccades involves complex neural mechanisms, including inhibition.
• Understanding saccade control aids in diagnosing and treating neurological disorders affecting motor function.

Purpose of the Study:

• To investigate the relationship between conflicting cues and human saccade control using a countermanding paradigm.
• To estimate the stop-signal reaction time (SSRT) required for saccade inhibition.
• To test a race model's ability to predict saccade inhibition performance.

Main Methods:

• Employed a countermanding paradigm where subjects initiated saccades to targets but sometimes received stop-signals to inhibit them.
• Measured saccadic latency and the probability of successful inhibition across varying stop-signal delays.
• Utilized Monte Carlo simulations to test a race model against empirical data.

Main Results:

• Stop-signal reaction times (SSRTs) were consistent across participants, ranging from 125 to 145 ms.
• SSRTs did not significantly vary with changes in target luminance.
• The race model accurately predicted successful saccade inhibition probabilities and saccadic latency distributions.

Conclusions:

• A simple race model with linear signal rise to a threshold may underlie behavioral performance in saccade control tasks.
• Findings provide a comparative basis with previous studies in non-human primates.
• The study enhances understanding of the neural mechanisms governing voluntary motor inhibition.