Impact of interhemispheric inhibition on bimanual movement control in young and old

Abstract

Interhemispheric interactions demonstrate a crucial role for directing bimanual movement control. In humans, a well-established paired-pulse transcranial magnetic stimulation paradigm enables to assess these interactions by means of interhemispheric inhibition (IHI). Previous studies have examined changes in IHI from the active to the resting primary motor cortex during unilateral muscle contractions; however, behavioral relevance of such changes is still inconclusive. In the present study, we evaluated two bimanual tasks, i.e., mirror activity and bimanual anti-phase tapping, to examine behavioral relevance of IHI for bimanual movement control within this behavioral framework. Two age groups (young and older) were evaluated as bimanual movement control demonstrates evident behavioral decline in older adults. Two types of IHI with differential underlying mechanisms were measured; IHI was tested at rest and during a motor task from the active to the resting primary motor cortex. Results demonstrate an association between behavior and short-latency IHI in the young group: larger short-latency IHI correlated with better bimanual movement control (i.e., less mirror activity and better bimanual anti-phase tapping). These results support the view that short-latency IHI represents a neurophysiological marker for the ability to suppress activity of the contralateral side, likely contributing to efficient bimanual movement control. This association was not observed in the older group, suggesting age-related functional changes of IHI. To determine underlying mechanisms of impaired bimanual movement control due to neurological disorders, it is crucial to have an in-depth understanding of age-related mechanisms to disentangle disorder-related mechanisms of impaired bimanual movement control from age-related ones.

Assessment of Brain Inhibitory Function in Physical Therapy

“…Similarly, motor overflow observed during finger movement tasks has been reported to be caused by the increased activation of bilateral cerebral hemispheres with advancing age [34,35]. Recently, Morisita et al reported a relationship between interhemispheric inhibition and motor overflow using TMS [11]. In this study, 22 individuals were included in a group of young individuals with a mean age of 26.1 years and a group of elderly individuals with a mean age of 65.0 years.…”

“…However, recent studies have demonstrated a link between age-related alterations and interhemispheric inhibition [9]. Therefore, in the context of an increasingly elderly population worldwide, interhemispheric inhibition may serve as a predictive indicator of motor and cognitive decline in the elderly [9][10][11]. In this chapter, we review the latest assessment indices for interhemispheric inhibition and assessment methods for potential application in the clinical physiotherapy setting.…”

Age-related Facilitation of Bimanual Finger Behaviors by Haptic Augmentation

“…The interactions are complex enough that bimanual cortical activations are not necessarily stronger than unimanual [26, 14]. The interhemispheric inhibition plays an important role in the control of bimanual movements [32, 21] Increasing evidence on participation of both cortical hemispheres in unilateral motion has led some researchers to speculate that unimanual motions are specific case of bimanual motions, where the opposing arm is inhibited [11, 6].…”