Leonardo G Cohen

Intracortical inhibition and facilitation in different representations of the human motor cortex. J. Neurophysiol. 80: 2870-2881, 1998. Intracortical inhibition (ICI) and intracortical facilitation (ICF) of the human motor cortex can be studied with paired transcranial magnetic stimulation (TMS). Plastic changes and some neurological disorders in humans are associated with changes in ICI and ICF. Although well characterized in the hand representation, it is not known if ICI and ICF vary ...

Performance of a unimanual hand motor task results in functional changes in both primary motor cortices (M1(ipsilateral) and M1(contralateral)). The neuronal mechanisms controlling the corticospinal output originated in M1(ipsilateral) and the resting hand during a unimanual task remain unclear. Here, we assessed functional changes within M1(ipsilateral) and in interhemispheric inhibition (IHI) associated with parametric increases in unimanual force. We measured motor-evoked potential ...

Motor practice may lead to expansion of trained representations in the motor cortex, but it is unknown whether this practice-dependent plasticity can be purposefully enhanced or depressed. Evidence, mainly based on animal experiments, indicates that the activity of GABA-related cortical inhibition is important in controlling the extent to which plasticity may occur. We tested the role of GABA in modulating practice-dependent plasticity in the human motor cortex. A decrease in ...

Phantom limb pain (PLP) in amputees is associated with reorganizational changes in the somatosensory system. To investigate the relationship between somatosensory and motor reorganization and phantom limb pain, we used focal transcranial magnetic stimulation (TMS) of the motor cortex and neuroelectric source imaging of the somatosensory cortex (SI) in patients with and without phantom limb pain. For transcranial magnetic stimulation, recordings were made bilaterally from the biceps ...

Associative stimulation has been shown to enhance excitability in the human motor cortex (Stefan et al. 2000); however, little is known about the underlying mechanisms. An interventional paired associative stimulation (IPAS) was employed consisting of repetitive application of single afferent electric stimuli, delivered to the right median nerve, paired with single pulse transcranial magnetic stimulation (TMS) over the optimal site for activation of the abductor pollicis brevis muscle ...

BACKGROUND: Non-immersive virtual reality is an emerging strategy to enhance motor performance for stroke rehabilitation. There has been rapid adoption of non-immersive virtual reality as a rehabilitation strategy despite the limited evidence about its safety and effectiveness. Our aim was to compare the safety and efficacy of virtual reality with recreational therapy on motor recovery in patients after an acute ischaemic stroke.

METHODS: In this randomised, controlled, single-blind, ...

In patients with chronic stroke, the primary motor cortex of the intact hemisphere (M1(intact hemisphere)) may influence functional recovery, possibly through transcallosal effects exerted over M1 in the lesioned hemisphere (M1(lesioned hemisphere)). Here, we studied interhemispheric inhibition (IHI) between M1(intact hemisphere) and M1(lesioned hemisphere) in the process of generation of a voluntary movement by the paretic hand in patients with chronic subcortical stroke and in healthy ...

Clinical recovery after stroke can be significant and has been attributed to plastic reorganization and recruitment of novel areas previously not engaged in a given task. As equivocal results have been reported in studies using single imaging or electrophysiological methods, here we applied an integrative multimodal approach to a group of well-recovered chronic stroke patients (n = 11; aged 50-81 years) with left capsular lesions. Focal activation during recovered hand movements was ...

Deafferentation leads to cortical reorganization that may be functionally beneficial or maladaptive. Therefore, we were interested in learning whether it is possible to purposely modulate deafferentation-induced reorganization. Transient forearm deafferentation was induced by ischemic nerve block (INB) in healthy volunteers. The following five interventions were tested: INB alone; INB plus low-frequency (0.1 Hz) repetitive transcranial magnetic stimulation of the motor cortex ipsilateral ...

We used high-frequency repetitive transcranial magnetic stimulation (rTMS) to study the role of the mesial frontocentral cortex (including the supplementary motor area) in the organization of sequential finger movements of different complexity in humans. In 15 subjects, rTMS was randomly applied to the scalp overlying the region of the supplementary motor area and over other positions, including the contralateral primary motor cortex (hand area) during the performance of three ...

OBJECTIVE: Previous studies demonstrated that single-pulse transcranial magnetic stimulation (TMS) of one motor cortex (M1) exerts a brief inhibitory effect on the contralateral M1. The purpose of this study was to test the hypothesis that 30min of 1Hz TMS of M1 will result in a lasting increase in excitability in the contralateral M1.

METHODS: Healthy volunteers were tested on 2 separate days, before (baseline) and after one of two interventions: (a) stimulation of M1 with 1Hz TMS for ...

Deafferentation induces rapid plastic changes in the cerebral cortex, probably via unmasking of pre-existent connections. Several mechanisms may contribute, such as changes in neuronal membrane excitability, removal of local inhibition, or various forms of short- or long-term synaptic plasticity. To understand further the mechanisms involved in cortical plasticity, we tested the effects of CNS-active drugs in a plasticity model, in which forearm ischemic nerve block (INB) was combined ...

Synaptic plasticity is conspicuously dependent on the temporal order of the pre- and postsynaptic activity. Human motor cortical excitability can be increased by a paired associative stimulation (PAS) protocol. Here we show that it can also be decreased by minimally changing the interval between the two associative stimuli. Corticomotor excitability of the abductor pollicis brevis (APB) representation was tested before and after repetitively pairing of single right median nerve ...

Stroke is a leading cause of adult motor disability. Despite recent progress, recovery of motor function after stroke is usually incomplete. This double blind, Sham-controlled, crossover study was designed to test the hypothesis that non-invasive stimulation of the motor cortex could improve motor function in the paretic hand of patients with chronic stroke. Hand function was measured using the Jebsen-Taylor Hand Function Test (JTT), a widely used, well validated test for functional ...