Microstimulation of extrastriate area MST influences performance on a direction discrimination task

Area of Science:

• Neuroscience
• Visual Perception
• Computational Neuroscience

Background:

• Neurons in the medial superior temporal visual area (MST) are hypothesized to carry directional signals influencing motion perception.
• Understanding the causal role of MST neurons in psychophysical judgments is essential for mapping visual processing pathways.

Purpose of the Study:

• To test whether microstimulation of directionally selective MST neurons influences rhesus monkeys' psychophysical judgments of motion direction.
• To investigate the spatial scale and characteristics of MST neuron influence on behavior.

Main Methods:

• Performed 46 microstimulation experiments on two rhesus monkeys using dynamic random dot patterns.
• Monkeys performed a two-alternative, forced-choice direction discrimination task with microstimulation applied randomly on half the trials.
• Analyzed psychophysical data to determine the effect of MST stimulation on choice behavior and the spatial specificity of the effects.

Main Results:

• Microstimulation significantly influenced monkey choices in 67% of experiments, biasing choices toward the encoded motion direction.
• Stimulation effects were spatially specific to the multiunit receptive field, but with a coarser scale than in area MT.
• Stimulation resembled a pure motion signal rather than noise, with minimal impact on psychometric function slopes.

Conclusions:

• MST neurons, similar to MT neurons, exert a strong influence on direction discrimination performance.
• The findings support the role of MST in visual motion processing and decision-making.
• Further research is needed to determine if MT and MST contribute to decisions in parallel or series.