From the late 1800s until approximately the middle of the 20th century, neurosurgeons made discrete motor cortex lesions in humans in attempts to reduce or eliminate a variety of involuntary movements, resulting mainly from epilepsy. In some cases, the neurosurgeons tested and recorded their patients' ability to perform various movements and to perceive various types of sensory stimuli after the operation. Although these studies have been largely forgotten, they have an immense advantage over primate lesion studies for understanding the function of the motor cortex because the patients were able to attempt to perform complex movements upon request, and to describe their perceptions of cutaneous stimuli, including integrated sensations (e.g., recognition of objects by palpation alone). We provide here a table containing the results of these studies pertaining to sensory deficits. The most consistent and persistent sensory deficits reported relate to object recognition and position sense. This finding is in keeping with recent electrophysiological studies in primates. Our analysis suggests that the “motor” cortex serves important sensory functions; hence, the term sensorimotor cortex, remains appropriate for the primate precentral (and postcentral) cortex.
Joel A. Vilensky and Sid Gilman
Katherine G. Holste, Alia L. Yasen, Matthew J. Hill and Anita D. Christie
The purpose of this study was to assess the effect of a cognitive task on motor cortex excitability and inhibition. Transcranial magnetic stimulation of the motor cortex was performed on 20 healthy individuals (18–24 years; 9 females) to measure motor evoked potentials (MEPs) and cortical silent periods at baseline, during, and following a secondary cognitive task. The MEP amplitude increased from 0.50 ± 0.09–0.87 ± 0.50 mV during a secondary cognitive task (p = .04), and returned to baseline (0.48 ± 0.31 mV; p = .90) posttask. The CSP duration also increased from 93.48 ± 28.76–113.6 ± 33.68 ms (p = .001) during the cognitive task, and returned to baseline posttask (89.0 ± 6.9 ms; p = .88). In the presence of a cognitive task, motor cortex excitability and inhibition were both increased relative to baseline. The increase in inhibition may help to explain the motor deficits experienced while performing a secondary cognitive task.
James Faulkner, Danielle Lambrick, Sebastian Kaufmann and Lee Stoner
The purpose of this study was to assess the acute effects of posture (upright vs recumbent) during moderate-intensity cycle exercise on executive function and prefrontal cortex oxygenation in young healthy adults.
Seventeen physically active men (24.6 ± 4.3 years) completed 2 30-minute submaximal exercise tests (conditions: upright and recumbent cycle ergometry). Executive function was assessed using the “color” and “word” Stroop task, preexercise (resting) and postexercise. Regional oxygen saturation (rSO2) to the prefrontal cortex was continuously monitored using near-infrared spectroscopy.
Significant improvements in executive function (Stroop color and word tasks) were observed after 30 minutes of exercise for both upright and recumbent cycling (P < .05). However, there were no differences in executive function between cycling conditions (P > .05). A significant increase in rSO2 was recorded immediately postexercise compared with preexercise for both conditions (P < .05), with a trend (P = .06) for higher peak rSO2 following recumbent cycling compared with upright cycling (81.9% ± 6.5% cf 79.7% ± 9.3%, respectively).
Although submaximal cycling exercise acutely improves cognitive performance and prefrontal oxygenation, changes in cognition are not perceived to be dependent on body posture in young, healthy men.
Nick J. Davey, Steve R. Rawlinson, David W. Maskill and Peter H. Ellaway
Transcranial magnetic stimulation (TMS) of the motor cortex was used to produce compound motor evoked potentials (cMEPs) in the first dorsal interosseus (FDI) muscle. The size of cMEPs was measured as an index of corticospinal excitability before and after initiation of a simple reaction task (SRT). The SRT, consisting of an abduction of the right index finger against a vertical support in response to a 1 kHz cueing tone, was performed in 6 healthy male subjects. cMEPs were facilitated when timed to occur just before the fastest simple reaction time (fSRT). When the cMEP was placed 15.5 ± 1.5 ms before the fSRT, its amplitude increased to 176 ± 36% of the control response seen in the relaxed state (no SRTs). Facilitation of the cMEP increased to 382 ± 43% of the control when it was placed 11.9 ± 1.5 ms after the fSRT. The facilitation of cMEP responses prior to the SRT is discussed with particular reference to the premovement potential that may be recorded over the cortex prior to a voluntary movement.
Y.L. Lo, H.H. Zhang, C.C. Wang, Z.Y. Chin, S. Fook-Chong, C. Gabriel and C.T. Guan
In overt reading and singing tasks, actual vocalization of words in a rhythmic fashion is performed. During execution of these tasks, the role of underlying vascular processes in relation to cortical excitability changes in a spatial manner is uncertain. Our objective was to investigate cortical excitability changes during reading and singing with transcranial magnetic stimulation (TMS), as well as vascular changes with nearinfrared spectroscopy (NIRS). Findings with TMS and NIRS were correlated. TMS and NIRS recordings were performed in 5 normal subjects while they performed reading and singing tasks separately. TMS was applied over the left motor cortex at 9 positions 2.5 cm apart. NIRS recordings were made over these identical positions. Although both TMS and NIRS showed significant mean cortical excitability and hemodynamic changes from baseline during vocalization tasks, there was no significant spatial correlation of these changes evaluated with the 2 techniques over the left motor cortex. Our findings suggest that increased left-sided cortical excitability from overt vocalization tasks in the corresponding “hand area” were the result of “functional connectivity,” rather than an underlying “vascular overflow mechanism” from the adjacent speech processing or face/mouth areas. Our findings also imply that functional neurophysiological and vascular methods may evaluate separate underlying processes, although subjects performed identical vocalization tasks. Future research combining similar methodologies should embrace this aspect and harness their separate capabilities.
Carsten Eggers, Ulrike Grüner, Mitra Ameli, Anna-Sophia Sarfeld and Dennis A. Nowak
This study investigated whether a period of low frequency rTMS preconditioned by tDCS over the primary motor cortex modulates control of grip force in Parkinson’s disease. The presented results are from the same patient cohort tested in an earlier study (Gruner et al. J Neural Transm 2010: 117: 207–216). 15 patients with Parkinson’s disease (mean age: 69 ±8 years; average disease duration: 5 ±3 years) on dopaminergic drugs performed a grasp-lift task with either hand before (baseline) and after a period of 1Hz rTMS (90% of the resting motor threshold; 900 pulses) preconditioned by sham, anodal or cathodal tDCS (1mA, 10 min) over the primary motor cortex. We found that compared with baseline, none of the grip force parameters was significantly influenced by either stimulation session and concluded that grasping is a higher order motor skill, which cannot be modulated by tDCS preconditioned 1Hz rTMS in PD.
Yu-Ting Tseng, Sanaz Khosravani, Arash Mahnan and Jürgen Konczak
This review addresses the role of exercise as an intervention for treating neurological disease. It focuses on three major neurological diseases that either present in acute or neurodegenerative forms—Parkinson’s disease, cerebellar ataxia, and cortical stroke. Each of the diseases affects primarily different brain structures, namely the basal ganglia, the cerebellum, and the cerebrum. These structures are all known to be involved in motor control, and the dysfunction of each structure leads to distinct movement deficits. The review summarizes current knowledge on how exercise can aid rehabilitation or therapeutic efforts. In addition, it addresses the role of robotic devices in enhancing available therapies by reviewing how robot-aided therapies may promote the recovery for stroke survivors. It highlights recent scientific evidence in support of exercise as a treatment for brain dysfunction, but also outlines the still open challenges for unequivocally demonstrating the benefits of exercise.
Masato Hirano, Shinji Kubota, Takuya Morishita, Kazumasa Uehara, Shusaku Fujimoto and Kozo Funase
The aim of this study was to investigate the plasticity of M1 innervating the tibialis anterior muscle (TA) induced by the long-term practice of football juggling using a transcranial magnetic stimulation (TMS) technique. Ten football juggling experts and ten novices participated in this study. Motor evoked potentials (MEP) and the H-reflex were recorded from the right TA during isometric dorsiflexion at 10% of maximum voluntary contraction. The MEP input-output curve of the experts was steeper than that of the novices, and reduced short-interval intracortical inhibition and long-interval intracortical inhibition were observed in the experts. In contrast, the ratio of Hmax to Mmax did not differ between the groups. Our results show that football juggling experts displayed enhanced excitability in the M1 innervating the TA, which was induced by the long-term practice of the ankle movements required to perform football juggling well.
Dong-Sung Choi, Hwang-Jae Lee, Yong-II Shin, Ahee Lee, Hee-Goo Kim and Yun-Hee Kim
showed relative changes in the primary motor cortex (M1), premotor cortex (PM), supplementary motor area (SMA), and prefrontal and somatosensory cortices. WBVe Protocol Whole-body vibration exercise was performed using a vibrating platform (Galileo® Advanced Plus, Novotec Medical, Pforzheim, Germany
Louisa D. Raisbeck, Jed A. Diekfuss, Dustin R. Grooms and Randy Schmitz
in the primary motor cortex, somatosensory cortex, and insular region of the left hemisphere. The authors surmised from these regions that are associated with sensory function, that an external focus promoted task-adequate brain activity for movement execution by shifting focus toward exteroceptive