What Is the Difference between an Impulsive and a Timed Anticipatory Movement?

Area of Science:

• Neuroscience
• Cognitive Psychology
• Human Motor Control

Background:

• Behavioral responses can occur before a predictable event.
• These early responses may stem from distinct neural mechanisms, such as impulsivity versus anticipation.

Purpose of the Study:

• To investigate whether early responses before a predictable visual stimulus involve one or two independent neural processes.
• To differentiate between impulsive and anticipatory early motor responses.

Main Methods:

• An oculomotor task was employed with predictable delays between warning and "go" stimuli.
• Spatial uncertainty of the "go" signal was manipulated.
• Early saccades (responses before the "go" signal) were analyzed based on their latency and characteristics.

Main Results:

• Early saccades exhibited a bimodal latency distribution, suggesting two distinct response modes.
• The first mode (1st mode saccades) decreased with longer delays, while the second mode (2nd mode saccades) remained constant.
• Second mode saccades showed increased latency, variance, and amplitude, with decreased maximum velocity.

Conclusions:

• The findings suggest two independent neural processes precede expected events.
• A 1st mode saccade reflects an impulsive, unintentional release of inhibition.
• A 2nd mode saccade is indicative of a temporally guided anticipatory process.