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Previous neuroimaging evidence revealed an 'invasion' of 'hand' over 'lower limb' primary sensorimotor cortex in paraplegic subjects, with the exception of a rare patient who received a surgical motor reinnervation of hip-thigh muscles by the ulnar nerve. Here, the authors show that a functional reorganization of cortico-muscular and cortico-cortical oscillatory coupling was related to the recovery of t he rare patient, as a paradigmatic case of long-term plasticity in human sensorimotor cortex after motor reinnervation of paraplegic muscles. This conclusion was based on electroencephalographic and electromyographic data collected while the patient and normal control subjects performed isometric muscle contraction of the left hand or lower limb. Cortico-muscular and cortico-cortical coupling was estimated by electroencephalographic-electromyographic coherence and directed transfer function of a multivariate autoregressive model.

Reversed Robin Hood syndrome (RRHS) has recently been identified as one of the mechanisms of early neurologic deterioration in acute ischemic stroke (AIS) patients related to arterial blood flow steal from ischemic to nonaffected brain. We sought to investigate the association of RRHS with risk of stroke recurrence in a single-center cohort study.

The aim of the study was to investigate and follow up the tonotopic organization of the primary auditory cortex in otosclerotic patients before and after corrective surgery. The characteristics of primary auditory cortex activation were studied in ten otosclerotic patients (i.e., subjects suffering from a conductive hearing loss, prior to and following stapes substitution). Magnetoencephalographic recordings of auditory evoked fields by tone-burst stimulation at octave frequencies between 250 and 2000 Hz were performed during monaural stimulation. The brain topography of the main cortical response (N100m) generators at different tones was studied in patients and compared with ten healthy controls; pre- post-surgical changes were also correlated to their clinical outcome following corrective surgery. A significant decrease of the tonotopic extension in the cortical region responsive to the four explored frequencies was found in patients before surgery with respect to the control population. At the time of postsurgical follow-up, the tonotopic representation had enlarged and was approaching the dimensions seen in normal subjects, although with higher variability. The extent of the enlargement of the postoperative tonotopically organized area was directly correlated with the postsurgery period duration. Our findings indicate that auditory cortical areas of human adults undergo functional reorganization following peripheral alteration of the sensory input entering the CNS. The restriction of the cortical tonotopic region caused by the long-term reduction of acoustic input is followed by a reorganization within the usual boundaries following the recovery of auditory function; this process is taking place in a time scale of a few weeks. Hum. Brain Mapping 10:28–38, 2000. © 2000 Wiley-Liss, Inc.

Objective: Intracortical excitability was studied for 4 muscles in the upper extremity by paired transcranial magnetic stimulation on the motor cortex, using focal and non-focal coils.

Objectives: In the present study we investigated whether in advanced Parkinson's disease (PD) patients the frontal component of short somatosensory evoked potentials (SEPs) to median nerve stimulation may be modified by basal ganglia deep brain stimulation (DBS).

Aim of the study was to analyze the characteristics of motor action potentials recruitment during magnetic trans-cranial stimulation (TCS) of the brain. Coaxial needle recordings from hand and upper limb musculature, as well as surface electrodes were employed in 20 healthy controls during magnetic TCS with regular and figure-of-8 coil in different experimental protocols including: (a) simple reaction time paradigm during which TCS at subthreshold intensity for eliciting MEPs in relaxation was delivered at various intervals between the signal to move and the onset of the voluntary EMG burst; (b) suprathreshold TCS was randomly delivered while the subject was voluntarily firing at a regular rate one ‘low’ and/or ‘high threshold’ motor unit action potential (MUAP). The pre- and post-TCS MUAPs recruitment as well as their firing rates were compared; (c) recordings with two separate needles picking up individual MUAPs from the same or from two different muscles were obtained in order to test ‘synchrony’ of MUAP's discharge before and after TCS; (d) the influence of the time-interval separating the last discharged MUAP from ICS was evaluated. (e) differences between simultaneous surface and depth recordings were examined. The following results were obtained. (a) The same low-amplitude MUAP which is first voluntarily recruited at the onset of the EMG burst is the one initially fired by TCS in the pre-movement period. Latency shortenings and amplitude enlargement of surface MEPs were observed with faster reaction times. Such changes were coupled to the recruitment of high-threshold MUAPs being larger in amplitude and briefer in latency than the initial one. (b) When using suprathreshold TCS, MEPs followed by silent periods were found. The SP was followed by a rebound acceleration of the MUAPs firing rate compared with pre-TCS levels. Besides rebound acceleration, new MUAPs of larger amplitude than the original (=pre-stimulus) ones were recruited beyond the voluntary control. This phenomenon-together with longer SPs- was progressively more pronounced with stronger stimuli. (c) TCS was affecting the ‘synchrony’ of MUAPs. (d) If the latency difference between the last pre-stimulus spike and the TCS was exceeding the half-cycle of the MUAP ‘natural’ firing, the SP was longer in duration. (e) SPs not preceded by MEPs were clearly present in depth recordings. Surface recordings mainly reflected the behavior of high-threshold and large MUAPs.