Cerebral Hemodynamics during Maximal Muscle Contraction with Visual Feedback-A Near-infrared Spectroscopy Study-

Abstract

It is well known that visual feedback of exerted force enhances muscle force during maximal voluntary contraction (MVC). Based on the previous reports on the force exertion tasks and the other tasks using the visual feedback paradigm, we hypothesized that the prefrontal cortex (PFC) is related to the enhancement of voluntary contraction force. The purpose of this study was to test the hypothesis and to identify the detail active regions in the PFC that correlates with the muscle force enhancement with visual feedback of exerted force, using near-infrared spectroscopy (NIRS). The cerebral blood flow of 11 male subjects was measured by NIRS during the MVC tasks with visual feedback of exerted torque (VFB) and without visual feedback (nVFB). As a result, both the elbow flexion torque during MVC and cerebral blood flow of the right PFC significantly increased under the VFB condition ( pϽ Ͻ0.05). In addition, the increased cerebral blood flow of the right PFC was correlated with the torque enhancement (pϽ Ͻ0.05). The present results suggest that the right PFC is related to the increase of torque under the VFB condition. Since the PFC has a significant role in motivation, the enhancement of torque with visual feedback may be associated with such a function.Keywords: maximal voluntary contraction, prefrontal cortex, cerebral blood flow, visual feedback, near-infrared spectroscopy . Since the muscle force exerted during MVC is enhanced by presenting feedback information to subjects, MVC is considered to be greatly affected by cortical activation regions related to process that information.There is a considerable research on cortical activation regions related to force exertion tasks. In addition to known movement-related cortical regions, the primary motor cortex, premotor cortex, and supplementary motor area, the prefrontal cortex (PFC) has been reported to show extensive cortical activity during force exertion tasks. For example, according to previous studies that measured PFC activity during voluntary contraction by using functional magnetic resonance imaging (fMRI), the activation has been observed over extensive cortical regions in the PFC on the cerebral hemisphere during 80% MVC and 100% MVC of handgrip task (Dai et al., 2001;Liu et al., 2005). Liu et al. (2005) reported that the PFC during 100% MVC was activated more extensively than any other movement-related cortical regions. Further, PFC is also known to be activated by giving feedback information about task performance to subjects. Kawashima et al. (2000) reported that when subjects received appropriate feedback information and those that did not after line drawing tasks were measured for cerebral activity by positron emission tomography (PET), the latter subjects exhibited activated PFC along with improved accuracy of the line drawing task. Brunia et al. (2000) reported that subjects who were presented feedback information improved accuracy of button press timing, simultaneously PFC was activated compared with control subjects.From the findings of these pre...