Localization of Scopolamine Induced Electrocortical Brain Activity Changes, in Healthy Humans at Rest

Abstract

To prevent the participants of parabolic flights from nausea they are optionally treated with subcutaneously injected antiemetic scopolamine. The range of side effects of this substance include reductions of the α-2 frequency band. Previous studies, however, have given no information as to which generator centers are responsible for this effect. The objective of this study therefore, is to identify the cortex area that may be responsible for this effect. Six participants were subcutaneously administered 0.7 mg of scopolamine. EEG was recorded for 10 minutes before to 20 minutes after injection. Data preprocessing followed including filtering and artifact minimization. A statistical analysis was performed with sLORETA/eLORETA software for each subject over a time window from 3 minutes before to 17-20 minutes after scopolamine injection. Results show, that in the BA7, the precuneus, on both hemispheres suffered a α-2 activity decrease in absolute power. The identified brain cortex center is an important hub with high connectivity and centrality values within the neural network. It contributes to the control of movement and to space orientation. Therefore, an activity alteration in this area can possibly explain the antiemetic effect of scopolamine and open a window to understand the origin of motion sickness.

Scopolamine effects on functional brain connectivity: a pharmacological model of Alzheimer’s disease

“…Specific regions of the DMN, including the precuneus in the medial parietal cortex, are selectively vulnerable to early pathological changes in AD 33 . Besides, precuneus was identified as a critical anatomical area 9 34 35 , thus suggesting that this structure could be a “network hub” which is affecting other functional regions. Beyond the DMN, other cortical areas showed loss of FC.…”

“…Scopolamine, a muscarinic receptor antagonist, produces a blocking of the activity of the muscarinic acetylcholine receptor, and the concomitant appearance of transient cognitive amnesia and electrophysiological changes, which resemble those observed in Alzheimer’s Disease (AD) 8 9 . Indeed, to date, several studies have explored neurophysiological changes associated with scopolamine injection mirroring those observed in AD 10 .…”

“…Additionally, studies using coherence during resting-state have shown a decrease in this measure after scopolamine 12 15 . Further, an interesting recent study on reconstructed EEG sources using LORETA 9 , found changes in brain activity following scopolamine administration, mainly at the precuneus. Taken together, these neurophysiological and cognitive alterations suggest that the administration of scopolamine may be an adequate approximation to simulate the modifications in brain activity that take place in AD 13 .…”

The influence of scopolamine on motor control and attentional processes

“…Several studies ( Ellis et al, 2006 ; Ramos Reis et al, 2013 ; Simmons et al, 2010 ; Weerts et al, 2015b ; Wesnes & Warburton, 1984 ) have evaluated the effects of various doses of scopolamine on cognitive tasks, and partly contradictory results have been reported, likely related to methodological differences between studies. Despite the low number of subjects which could prevent from detecting subtle changes, we found that a 0.2 mg dose of scopolamine did not affect the reaction time and the movement duration ( Figs.…”

“…Neural mechanisms of motion sickness have been well described in the literature, and the sensory conflict theory ( Reason, 1975 ) seems to be a primary explanation for understanding this state. According to this theory, motion sickness results from a discrepancy between the information provided by the visual and the vestibular systems ( Ramos Reis et al, 2013 ; Schmal, 2013 ). The motion signals transmitted by the eyes and the vestibular system conflict with each other and with what is expected on the basis of previous interactions with the environment ( Reason, 1978 ).…”