Highlights• Motor activation can inhibit the visual system even during continuous visual stimulation.• Continual visual input produces sustained inhibitory influence on the motor system.• EEG can be reliably assessed during nystagmus.
AbstractObjectives: Inhibitory interactions between the visual and motor systems have been observed during transient stimulation of either system. However, it is unknown how inhibition operates during simultaneous and continuous engagement of both systems. Methods: We presented right-handed participants (n = 14) with optokinetic stimulation (OKS), with and without a simultaneous dynamic handgrip exercise. We assessed the EEG upper-alpha band (10-12 Hz) to investigate inhibitory interactions, and explored their effect on optokinetic nystagmus (OKN). Results: OKS + handgrip simultaneously produced motor activation and visual inhibition, compared to OKS alone. Meanwhile, the velocity of OKN increased, selectively during left handgrips. OKS without handgrip produced simultaneous visual activation and motor inhibition compared to an open-eyes baseline. The open-eyes baseline itself increased motor peak-frequency towards the inhibitory upper-alpha range compared to closed eyes. Conclusions: Motor activation inhibited the visual system even during visual stimulation. This inhibition likely disrupted visual processing, triggering an OKN speed-up to relocate the OKS. Increasing visual input produces increasing motor inhibition. Significance: These observations extend previous results in standard settings and confirm the reliability of EEG in conditions involving nystagmus, important in clinical vestibular research. Visual inhibition through handgrip could be a candidate for developing rehabilitation from visually induced dizziness.