Ups and downs in catch-up saccades following single-pulse TMS-methodological considerations

Area of Science:

• Neuroscience
• Ophthalmology
• Motor Control

Background:

• Transcranial magnetic stimulation (TMS) is known to affect saccades and smooth pursuit.
• The impact of TMS on catch-up saccades, crucial for smooth pursuit, remains largely unexplored.

Purpose of the Study:

• To investigate the effect of TMS on catch-up saccades during visually guided eye movements.
• To explore TMS effects on catch-up saccades when their occurrence is reduced.

Main Methods:

• Participants performed visually guided eye movements with reduced catch-up saccade occurrence.
• Single-pulse TMS was applied over the vertex and M1 hand area.
• Saccadic activity and accuracy were analyzed across different post-stimulation time windows.

Main Results:

• TMS induced a transient modulation of saccadic activity, with initial decrease, subsequent resumption, and a later decrease.
• Despite temporal modulations, the accuracy of catch-up saccades was preserved.
• Overall saccadic activity over 300ms remained unchanged, suggesting functional compensation.

Conclusions:

• TMS over non-oculomotor regions can interfere with the initiation of catch-up saccades.
• Findings highlight the need for careful consideration of TMS timing and stimulation sites in eye movement research.
• This study provides methodological insights for future investigations into the neural circuitry of catch-up saccades.