The neural mechanisms underlying spontaneous tremor were investigated in monkeys. Tremor-producing ventromedial tegmental (VMT) lesions involve at least three major neural elements. (1) Parvocellular division of the red nucleus (RNpc); (2) cerebellothalamic fibers passing through the red nucleus, and, (3) nigrostriatal fibers. These three elements were destroyed stereotaxically in areas remote from the VMT area separately and/or in various combinations, and correlation between the site of lesions and tremor was made. Lesion-induced tremor appeared only when the three elements were destroyed. A possible, particular role of the RNpc in the production of the spontaneous tremor is discussed.

Animals↗

PubMedDate not supplied

Correlation between the neural noise in the thalamus after cerebrovascular disease and computerized tomography. A case report.

The case is presented of a 45-year-old man who suffered from a sudden attack of unconsciousness with right hemiplegia and later developed a spastic hemiparesis accompanied by involuntary movement of the right upper limb. CT scan revealed an old putaminal hemorrhage and almost intact thalamus, but neural noise recordings during the stereotactic thalamotomy of this case showed marked decrease of the neural activity in the thalamus suggesting some functional changes.

Cerebral Hemorrhage↗

PubMedDate not supplied

Connections from the basal ganglia to the thalamus.

Many data suggest that the basal gnaglia exerts an indirect influence onto the motor cortex through the thalamus which receives pallidal and nigral efferences. According to the anatomical data, the internal segment of globus pallidus projects to the VL-VA and CM of thalamus and the substantia nigra sends axons ending in the VL and VA with an intranuclear organization which did not overlap the pallidal terminations. The electrophysiological records in the VL-VA nucleus demonstrates that pallidal stimulation induces an inhibitory response, mainly on thalamic neurons, which does not receive cerebellar input. If spreading of excitation is avoided, nigral stimulation also induces an inhibition at the thalamic level. This inhibitory effect can be recorded on relay cells with cerebellar input and cortical output as well as on nonrelay cells. The electrophysiological results in the case of the striatopallidal and striatonigral projections are also briefly reported.

Animals↗

PubMedDate not supplied

Slight cerebellar signs in stereotactic thalamotomy and subthalamotomy for parkinsonism.

After the stereotactic treatment of patients with Parkinson's disease, a correlative study between the site of the deep subcortical lesions and subsequent cerebellar signs (dysmetria and hypotonia) was made. Cerebellar signs appeared in 27 cases (40.8%) of subthalamotomy and in 3 cases (8.6%) of VIM thalamotomy 2 weeks after an operation. The appearance of these signs after an operation was independent from the operative effect on tremor. Thus, we concluded that VIM thalamotomy might be better than subthalamotomy for the relief of tremor in Parkinson's disease.

Cerebellar Diseases↗

PubMedDate not supplied

Physiologically defined VIM nucleus. Its special reference to control of tremor.

In the course of stereotactic surgery for some 100 parkinsonian patients, correlative study of recording and stimulation has been done in and around the thalamic nucleus ventralis intermedius (VIM) under local anesthesia. The VIM nucleus is roughly identified either by the increase of neural noise level or radiological measurement. More accurately, in the thus identified VIM, sensory neurons related to kinesthetic sense of the contralateral extremity were found in about half of the cases. Electrical stimulation of this point at threshold intensity produced paresthesia on the contralateral area around its receptive field. With increased stimulus intensity, increment of grouping discharge in EMG of that part was pertinent in the majority of cases. A small localized lesion at such a thalamic point was shown to be quite effective for alleviation of tremor without any neurological, especially sensory, deficit.

Brain Mapping↗

PubMedDate not supplied

[Neuronal behavior of the striatum in man].

Units of the caudate and putamen were studied during stereotactic operations in 11 patients with movement disorders. Responses of these units to different visual stimuli were found for cells of the caudate nucleus head. These units were activated mainly during the presentation of nutritional stimuli. The responses appeared when a slide was shown presenting an image of drink or food or the corresponding word. Frequently the same unit was activated by slides of the image and the word presented in succession. Responses to similar stimulations were not observed in the putamen. Among the parkinsonian patients, only those with tremor had responsive cells while the rigid patients had not. This discrepancy was correlated with the lowering of cortical metabolism demonstrated by PET scan in the rigid group of patients. These results are in agreement with those obtained in monkeys during food presentation. They present, moreover, the advantage of showing that these responses could be provoked in man by more abstract stimuli, not only the image but the name of the object. These observations do not imply a long testing period; 2 or 3 cells only are studied in each patient. They have the advantage for the patient of ascertaining the position of the trajectory in the striate structure, in the same way as thalamic nuclei are delineated using other types of stimuli. Moreover, it is of interest to have a better knowledge of the behavioral role played by different striatal regions at a time when lesions or stimulations at this level are proposed to cure abnormal movements in human.

Behavior↗