Hemispheric asymmetries for kinematic and positional aspects of reaching

Abstract

Kinematic analyses of reaching have suggested that the left hemisphere is dominant for controlling the open loop component of the movement, which is more dependent on motor programmes; and the right hemisphere is dominant for controlling the closed loop component, which is more dependent on sensory feedback. This open and closed loop hypothesis of hemispheric asymmetry would also predict that advance planning should be dependent on the left hemisphere, and on-line response modification, which defines closed loop processes, should be dependent on the right hemisphere. Using kinematic analyses of reaching in patients with left or right hemisphere damage (LHD or RHD), we examined the ability: (i) to plan reaching movements in advance by examining changes in reaction time (RT) when response amplitude and visual feedback were cued prior to the response; and (ii) to modify the response during implementation when target location changed at the RT. Performance was compared between the stroke groups, using the ipsilesional arm, and age-matched control groups using their right (RNC) or left (LNC) arm. Aiming movements to a target that moved once or twice, with the second step occurring at the RT, were performed with or without visual feedback of hand position. There were no deficits in advance planning in either stroke group, as evidenced by comparable group changes in RT with changes in amplitude and visual feedback. Response modification deficits were seen for the LHD group in secondary velocity only. In addition, LHD produced slower initial peak velocity with prolongation of the deceleration phase and faster secondary peak velocities, and the RHD group produced deficits in final error only. These differences are more consistent with the dynamic dominance hypothesis, which links left hemisphere specialization to movement trajectory control and right hemisphere specialization to position control, rather than to global deficits in open and closed loop processing.

Does motor lateralization have implications for stroke rehabilitation?

“…In fact, Healey et al described similar distinctions in dominant and nondominant arm use for a wide range of tasks across a large number of subjects [2]. The dynamic dominance model has recently been supported in studies of righthanded stroke patients that reveal deficits in the ipsilesional arm, the quality of which tend to vary with the side of the lesion [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The ipsilesional arm of these patients tends to show deficits in trajectory control following lefthemisphere damage and positional control following righthemisphere damage.…”

“…In fact, both animal studies [18][19][20] and human studies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] have revealed that unilateral brain damage can produce significant ipsilesional motor deficits. Studies in chronic stroke patients have reported performance deficiencies on the Purdue Pegboard Test [21], the JebsenTaylor Hand Function Test [22], as well as other tests that simulate activities of daily living (ADL) [4,10,[13][14]. In addition, significant ipsilesional deficits in movement coordination and accuracy have been revealed with the use of motion capture systems [3,[10][11][12]15,17].…”

Estudo comparativo entre a relação do hemisfério acometido no acidente vascular encefálico e a evolução funcional em indivíduos destros

“…Besides severe language dysfunctions, patients with left hemispheric injuries tend to demonstrate a greater frequency of apraxias 4,5 . Motor activities that require planning are more related to the left hemisphere and are therefore more aff ected after left hemispheric injuries 4 .…”

“…Motor activities that require planning are more related to the left hemisphere and are therefore more aff ected after left hemispheric injuries 4 . As the majority of activities of daily living involve complex motor sequences, it is possible to suppose that performance of these activities will be more aff ected in patients with left hemispheric injuries, especially because of the alterations in motor responses observed after CVA (hemiparesis), therefore, part of the movement sequence would need to be reprogrammed for activities of daily living.…”

“…Because the left hemisphere plays a lager role in motor behavior 4,5,26 , it was hypothesized that patients with left hemispheric injuries would demonstrate greater initial defi cits and slower recovery of the motor functions of gait and functional independence after injury assessed in this study. On the other hand, because the right hemisphere plays a larger role on spatial orientation 17,19,27 and posture 21 , it was hypothesized that patients with right hemispheric injuries would demonstrate greater defi cits and slower recovery rates of the postural and spatial attention functions after injury.…”