ABSTRACT
An infrequent change to an otherwise repetitive sequence of stimuli leads to the generation of mismatch negativity (MMN), even in the absence of attention. This evoked negative response occurs in the scalp-recorded electroencephalogram (EEG) over the temporal and frontal cortices, 100-250 ms after onset of the deviant stimulus. The MMN is used to detect sensory information processing. The aim of our study was to investigate whether MMN can be recorded in the subthalamic nuclei (STN) as evidence of auditory information processing on an unconscious level within this structure. To our knowledge, MMN has never been recorded in the human STN. We recorded intracerebral EEG using a MMN paradigm in five patients with Parkinson's disease (PD) who were implanted with depth electrodes in the subthalamic nuclei (STN). We found far-field MMN when intracerebral contacts were connected to an extracranial reference electrode. In all five PD patients (and nine of ten intracerebral electrodes), we also found near-field MMN-like potentials when intracerebral contacts were referenced to one another, and in some electrodes, we observed phase reversals in these potentials. The mean time-to-peak latency of the intracerebral MMN-like potentials was 214 ± 38 ms (median 219 ms). We reveal MMN-like potentials in bilateral STN. This finding provides evidence that STN receives sensory (auditory) information from other structures. The question for further research is whether STN receives such signals through a previously described hyperdirect pathway between STN and frontal cortex (a known generator of the MMN potential) and if the STN contributes to sensorimotor integration.
Subject(s)
Contingent Negative Variation/physiology , Evoked Potentials, Auditory/physiology , Parkinson Disease/pathology , Subthalamic Nucleus/physiopathology , Acoustic Stimulation , Aged , Electroencephalography , Female , Functional Laterality , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Neuropsychological Tests , Parkinson Disease/complications , Reaction Time/physiology , Severity of Illness Index , Tomography Scanners, X-Ray ComputedABSTRACT
The aim of this study was to find whether 1-Hz cerebellar repetitive transcranial magnetic stimulation (rTMS) could affect upper limb movement in early-stage Parkinson's disease (PD). Twenty patients with PD underwent one session with real and one with sham rTMS. rTMS (1 Hz, 600 pulses) was targeted at the right lateral cerebellum. Before and after rTMS, patients performed two motor tests with their fingers and hands (ball test, nine-hole peg test). The duration of these tests was measured. There were statistically significant differences (p < 0.05) in the results of the tests after real stimulation and sham stimulation. We excluded the impact of learning. After real rTMS, we observed a significantly faster response in the ball test and a slower response in the nine-hole peg test, both on the right upper limb. This study indicates the influence of 1-Hz cerebellar rTMS in modifying the voluntary movements of the upper limb in PD. This influence is differentiated: the improvement of gross motor skills and the worsening of fine motor skills.
Subject(s)
Arm/physiology , Cerebellum/physiology , Motor Skills/physiology , Parkinson Disease/physiopathology , Parkinson Disease/therapy , Psychomotor Performance/physiology , Transcranial Magnetic Stimulation/methods , Aged , Female , Humans , Male , Middle Aged , Reaction Time/physiology , Single-Blind MethodABSTRACT
INTRODUCTION: The cerebellum is a very complex structure with many motor/non-motor functions and direct and indirect connections with almost the entire central nervous system. Transcranial magnetic stimulation (TMS) is a non-invasive electrophysiological method for studying, diagnosing, and treating disorders of the nervous system. The aim of the present review is to summarise the research and potential clinical uses of cerebellar TMS. METHODS: PubMed literature search using the key words "cerebellum TMS". RESULTS: TMS of the cerebellum is used in two types of protocols. The first type involves the separate stimulation of the cerebellum while tracking its clinical or electrophysiological influence on motor and non-motor functions. The second involves stimulation of the cerebellum as a conditioning stimulus before stimulating the motor cortex, to monitor the electrophysiological impact of cerebellar stimulation on the motor cortex. Most studies are performed on small groups of healthy volunteers; isolated studies are performed on patients with neurological disorders (spinocerebellar ataxia, migraine, dystonia, Miller Fisher syndrome). It has been shown that cerebellar TMS is able to influence motor systems, memory, and perception of time, and there is evidence of its electrophysiological effects in the frontal cortex. CONCLUSION: Published studies suggest that cerebellar TMS is currently only important in research. There is not yet any clear or reliable evidence of the therapeutic effects of cerebellar TMS. However, its use as a treatment method can be anticipated.
