Saccades and reaches, behaving differently

Area of Science:

• Cognitive psychology
• Neuroscience
• Human motor control

Background:

• Previous research demonstrated an "anti-Hick's" effect in saccade generation, where latencies decrease as response alternatives increase.
• Conversely, reach latencies typically increase with more response alternatives.
• Interactions between saccade and reach systems are known, prompting investigation into their combined response patterns.

Purpose of the Study:

• To investigate if the anti-Hick's effect in saccade latencies is altered when saccades and reaches are executed concurrently.
• To determine the localization of the anti-Hick's effect within the motor control system.

Main Methods:

• A visually guided saccade and reach task was employed.
• Participants executed both saccades and reaches simultaneously under varying numbers of response alternatives.
• Saccade and reach latencies were measured and analyzed.

Main Results:

• The anti-Hick's effect persisted, with saccade latencies decreasing as response alternatives increased, even during concomitant reach execution.
• Reach latencies followed the expected pattern of increasing with response alternatives.
• The distinct patterns suggest independent processing within the saccade and reach systems.

Conclusions:

• The anti-Hick's effect is localized within the saccade system.
• This effect appears to be independent of reach system processing, occurring at a neural level where saccade and reach signals do not interact.