ABSTRACT
OBJECTIVE: To investigate the subjective phenomenon and the neural underpinnings of tics compared with voluntary movements in patients with tic disorders. METHODS: We recorded electroencephalographic and electromyographic data while subjects completed a Libet clock paradigm. Patients and healthy volunteers reported the times of W (willing to move) and M (movement occurrence) while performing voluntary movements. This was repeated only for the patients for the tics. RESULTS: In the patients, W and M times preceding voluntary movements and tics did not significantly differ from voluntary movements of healthy volunteers. The Bereitschaftspotentials in the patients were similar to healthy volunteers. Tics were only assessable for 7 patients due to artifacts. Two subjects did not show Bereitschaftspotentials, and they reported the lowest levels of tic voluntariness. 5 subjects did not show beta band event-related desynchronization before tics. CONCLUSIONS: For patients, the sense of volition for tics is similar to that of their voluntary movements which is similar to normal. Patients showed dissociations between the Bereitschaftspotential and beta desynchronization for tics, with 5/7 showing normal Bereitschaftspotentials and 2/7 showing desynchronization. The absence of desynchronization may suggest attempts to suppress tics. SIGNIFICANCE: This physiology shows a difference for most tics compared with normal movements.
Subject(s)
Tic Disorders , Tics , Tourette Syndrome , Humans , Adult , Tic Disorders/diagnosis , Movement/physiology , Electroencephalography , Contingent Negative VariationABSTRACT
The spinal cord is able to express use-dependent plasticity, as demonstrated in spinalized cats following treadmill training. In humans, spinal use-dependent plasticity is inferred from modifications in the size of H reflex, which are often more prominent after skilled motor training. Plasticity can develop at synaptic connections between afferent fibres and/or descending tracts and motoneurones or interneurones interposed in the spinal pathways. Here we explore whether skilled training induces a change in synaptic efficacy at the synapse between Ia afferents and soleus (Sol) motoneurones. Synaptic efficacy can be modulated presynaptically through changes of the probability of transmitter release (homosynaptic depression, HD). The frequency-related depression of the Sol H reflex, thought to reflect HD, was tested at rest, before and after one single skilled (14 subjects) or non-skilled (9 subjects) cycling training session. Performance improved in both groups but to a larger extent with skilled training, while HD increased immediately after and the day following skilled training in the absence of changes with non-skilled training. These results support the view that spinal cord function is able to encode a local motor memory.
Subject(s)
H-Reflex/physiology , Neuronal Plasticity/physiology , Spinal Cord/physiology , Synaptic Transmission/physiology , Adult , Exercise Test , Female , Humans , Long-Term Synaptic Depression/physiology , Male , Motor Neurons/physiology , Neurons, Afferent/physiology , Physical Fitness/physiology , Psychomotor Performance/physiologyABSTRACT
OBJECTIVE: To test a possible strategy to alleviate somatosensory deficits after stroke. METHODS: Here, we applied ischemic nerve block to the intact hand of patients with chronic stroke, which in healthy subjects elicits improvements in sensibility of the other hand. RESULTS: We found that sensibility in the affected hand improved with intact hand anesthesia, but not with intact foot anesthesia or no anesthesia. INTERPRETATION: We conclude that reduction of sensory input from the intact hand leads to site-specific improvements in tactile discriminative skills in the affected hand after the period of anesthesia, a potentially relevant finding in designing neurorehabilitative interventions.
Subject(s)
Anesthesia/methods , Hand/innervation , Hand/physiopathology , Sensation Disorders/therapy , Adult , Aged , Analysis of Variance , Double-Blind Method , Female , Functional Laterality/physiology , Hand Strength , Humans , Male , Middle Aged , Psychomotor Performance , Reaction Time , Sensation Disorders/etiology , Sensory Thresholds , Stroke/complications , Time FactorsABSTRACT
In healthy volunteers, reduction of somatosensory input from one hand leads to rapid performance improvements in the other hand. Thus, it is possible that reduction of somatosensory input from the healthy hand can influence motor function in the paretic hand of chronic stroke patients with unilateral hand weakness. To test this hypothesis, we had 13 chronic stroke patients perform motor tasks with the paretic hand and arm during cutaneous anesthesia of the healthy hand and healthy foot in separate sessions. Performance of a finger tapping task, but not a wrist flexion task, improved significantly with anesthesia of the hand, but not the foot. This effect progressed with the duration of anesthesia and correlated with baseline motor function. We conclude that cutaneous anesthesia of the healthy hand elicits transient site-specific improvements in motor performance of the moderately paretic hand in patients with chronic stroke, consistent with interhemispheric competition models of sensorimotor processing.
