The influence of scopolamine on motor control and attentional processes

Abstract

Background: Motion sickness may be caused by a sensory conflict between the visual and the vestibular systems. Scopolamine, known to be the most effective therapy to control the vegetative symptoms of motion sickness, acts on the vestibular nucleus and potentially the vestibulospinal pathway, which may affect balance and motor tasks requiring both attentional process and motor balance. The aim of this study was to explore the effect of scopolamine on motor control and attentional processes.Methods: Seven subjects were evaluated on four different tasks before and after a subcutaneous injection of scopolamine (0.2 mg): a one-minute balance test, a subjective visual vertical test, a pointing task and a galvanic vestibular stimulation with EMG recordings.Results: The results showed that the reaction time and the movement duration were not modified after the injection of scopolamine. However, there was an increase in the center of pressure displacement during the balance test, a decrease in EMG muscle response after galvanic vestibular stimulation and an alteration in the perception of verticality.Discussion: These results confirm that low doses of scopolamine such as those prescribed to avoid motion sickness have no effect on attentional processes, but that it is essential to consider the responsiveness of each subject. However, scopolamine did affect postural control and the perception of verticality. In conclusion, the use of scopolamine to prevent motion sickness must be considered carefully because it could increase imbalances in situations when individuals are already at risk of falling (e.g., sailing, parabolic flight).

Impaired Attentional Processing During Parabolic Flight

“…Similarly, Bestaven and colleagues reported no effect on reaction time in a scoring task up to 30 min after the injection of scopolamine at a dose of 0.2 mg (Bestaven et al, 2016). However, these authors reported an effect on posture and on vestibulomotor control of the lower limbs (Bestaven et al, 2016), which could be related to the effect of scopolamine on the brainstem reported in animals (Gall et al, 2007). We found slower RT in CPT and PVT, whereas only the latter reached the level of statistical significance.…”

“…Lower doses of 0.22 mg induced only peripheral signs, but did not impair cognitive functions ( Flicker et al, 1990 ). Similarly, Bestaven and colleagues reported no effect on reaction time in a scoring task up to 30 min after the injection of scopolamine at a dose of 0.2 mg ( Bestaven et al, 2016 ). However, these authors reported an effect on posture and on vestibulomotor control of the lower limbs ( Bestaven et al, 2016 ), which could be related to the effect of scopolamine on the brainstem reported in animals ( Gall et al, 2007 ).…”

“…Further, participants may also experience severe motion sickness that is typically attenuated by an antiemetic drug administered before the flight. A lack of sleep and poor sleep quality, antiemetic drugs, mood, and stress, each of which can confound cognitive and motor performance ( Wesnes and Warburton, 1983 ; Lim and Dinges, 2008 ; Bestaven et al, 2016 ), functions that are known to be dependent on the level of attention and selective attention abilities ( Carrasco, 2018 ; Ruff and Cohen, 2019 ; Song, 2019 ).…”

No Gain No Pain: Relations Between Vestibulo-Ocular Reflexes and Motion Sickness in Mice

“…On the other hand, Tal et al ( 65 ) reported a significant decrease in cVEMP p13 latency following scopolamine administration. Bestaven et al ( 16 ) demonstrated a significant reduction of ~30% of the vestibulo-spinal reflexes following galvanic vestibular stimulation associated with a decrease in balance test and vertical perception. In cat, no direct effect of scopolamine on the VOR was found at low doses, while at high doses the effects were confounded by sedation ( 66 ).…”

“…To date, one of the most efficient drugs to prevent in particular space motion sickness ( 10 , 11 ) is scopolamine ( 12 – 14 ), a muscarinic antagonist commonly administered through transdermal patches. While its molecular effects are well characterized, its putative action on the peripheral and/or central vestibular system, at the neuronal ( 15 ) and behavioral levels ( 14 , 16 ) have still to be specified. Several studies have also tried non-pharmacological approaches to help prevent motion sickness by habituating the system to vestibular stimulation ( 17 – 20 ).…”