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The gap effect for eye and hand movements in double-step pointing
P Boulinguez1, J Blouin, V Nougier
1Laboratoire d'Analyse de la Performance Motrice Humaine, MSHS, 99 avenue du Recteur Pineau, BP 632, 86022 Poitiers, France. philippe.boulinguez@mshs.univ-poitiers.fr
Abstract:
The existence of a temporal gap between the offset of a fixation target and the onset of a peripheral target generally reduces the saccadic and manual reaction time in response to the peripheral target. Using a double-step paradigm, the present experiment investigated whether a temporal gap between the extinction of the first target and the presentation of the second target can help in reducing the time to trigger the corrective eye movements and to correct the arm trajectory towards the final target position. A gap was introduced between the presentation of the initial target and a new unexpected goal-target during the movement. The results replicated the gap effect for the corrective saccade to the second target, but revealed an opposite effect for the correction of the reaching movements as the arm correction occurred later in the Gap than in the No-Gap conditions. These results suggest that the information available for the arm motor system to correct the trajectory in relation to the second target was different in the Gap and No-Gap conditions. In the No-Gap condition, the correction of reaching movements would be based on retinal errors between the first and the second targets whereas, in the Gap condition, the correction would be based on information derived from the corrective saccade-related signals to the second target.
Insights
A temporal gap between targets speeds up corrective eye movements but delays arm trajectory corrections. This suggests different sensory information guides arm adjustments depending on the gap.
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.
