The gap effect for eye and hand movements in double-step pointing

Area of Science:

• Neuroscience
• Motor Control
• Human Factors

Background:

• A temporal gap between fixation target offset and peripheral target onset typically reduces reaction times.
• This phenomenon, known as the gap effect, is well-documented for saccadic eye movements.
• Its influence on corrective reaching movements remains less understood.

Purpose of the Study:

• To investigate the effect of a temporal gap on corrective saccades and reaching movements.
• To determine if a gap influences the timing of eye and arm corrections in a double-step paradigm.

Main Methods:

• A double-step paradigm was employed, introducing a temporal gap between the offset of an initial target and the onset of a new, unexpected goal target.
• Participants performed reaching movements towards the targets.
• Saccadic and manual reaction times, as well as arm trajectory corrections, were measured.

Main Results:

• The gap effect was replicated for corrective saccades, showing faster eye movement initiation.
• Conversely, arm trajectory corrections were initiated later in the Gap condition compared to the No-Gap condition.
• This indicates a dissociation between eye and arm movement corrections in the presence of a temporal gap.

Conclusions:

• The temporal gap differentially affects corrective eye and arm movements.
• In No-Gap conditions, reaching corrections likely rely on retinal error signals between targets.
• In Gap conditions, corrections may be guided by saccade-related signals to the second target, influencing arm movement timing.