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At least 793 records · Page 44Linked to original sources
PubMed1999

Extrapyramidal involvement in amyotrophic lateral sclerosis: backward falls and retropulsion.

Three patients with sporadic amyotrophic lateral sclerosis (ALS) presented with a history of backward falls. Impaired postural reflexes and retropulsion accompanied clinical features of ALS. Hypokinesia, decreased arm swing, and a positive glabellar tap were noted in two of these three patients. Cognitive impairment, tremor, axial rigidity, sphincter dysfunction, nuchal dystonia, dysautonomia, and oculomotor dysfunction were absent. Brain MRI disclosed bilateral T2 weighted hyperintensities in the internal capsule and globus pallidus in one patient. Necropsy studies performed late in the course of ALS have shown degeneration in extrapyramidal sites-for example, the globus pallidus, thalamus, and substantia nigra. Clinically, backward falls and retropulsion may occur early in ALS. This may reflect extrapyramidal involvement.

Aged↗
PubMed1984

Phase-dependent responses evoked in limb muscles by stimulation of medullary reticular formation during locomotion in thalamic cats.

Electromyographic and kinematic responses of all four limbs were studied when loci within the medullary reticular formation (MRF) were stimulated (30-ms train of 0.2-ms pulses at 300 Hz, strength 35 microA) during treadmill locomotion in spontaneously walking thalamic cats. Responses could be evoked in flexor or extensor muscles of any given limb by such stimulation, depending on the time during the step cycle at which the stimulus was delivered. Stimulation normally excited flexor muscles but could either excite or inhibit extensor muscles depending on the exact position of the electrode. Excitatory responses in extensor muscles were often followed by a short period of inhibition of activity. The responses in muscles of the opposing limbs of the same girdle were, in general, reciprocally organized. For instance, a stimulus delivered during the swing phase of the ipsilateral limb normally evoked excitatory responses both in flexor muscles of that limb and in extensor muscles of the contralateral limb. The same stimulus delivered during the stance phase of the ipsilateral limb evoked excitatory responses in ipsilateral extensor muscles and in contralateral flexor muscles. Responses were also observed at the same time in fore- and hindlimbs that were well organized with respect to the locomotor cycle. Seventy-five percent of all responses occurred within 8-20 ms of the onset of the stimulus train. Responses evoked in muscles of the opposing limbs of one girdle (e.g., a flexor of one limb and an extensor of the other) had similar latencies, suggesting that the responses were synchronously organized on both sides of the body rather than one being a consequence of the other. Although the majority of responses in a given muscle were elicited during its period of activity, responses could occasionally be evoked when there was no activity in that muscle or could be absent despite activity in the muscle. The short trains of stimuli were normally potent enough to affect the limb trajectory, which reflected changes in the onset or the offset of the activity of most muscles. Thus the stimuli effectively changed both the duration of the period of activity in these muscles and the overall step cycle. Longer trains of stimuli (200 ms) markedly amplified these changes to the point of completely resetting the locomotor rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

PAD and PAH response patterns of group Ia- and Ib-fibers to cutaneous and descending inputs in the cat spinal cord.

The characteristics of the primary afferent depolarization (PAD) of Ia- and Ib-fibers generated by segmental and descending inputs have been analyzed in the spinal cord of anesthetized cats. The PAD was inferred from the changes produced by conditioning inputs on the intraspinal stimulus current required to produce a constant antidromic firing of single group I afferent fibers from the gastrocnemius (GS) or posterior biceps and semitendinosus (PBSt) nerves. Group I GS and PBSt fibers ending in the intermediate nucleus could be classified in three different types according to their PAD patterns in response to stimulation of cutaneous nerves and of descending fibers. In one set of group I fibers stimulation of cutaneous nerves and of the ipsilateral brain stem reticular formation, or the contralateral red nucleus, produced no PAD, but was able to inhibit the PAD generated by stimulation of group I fibers from flexors (type A PAD pattern). PBSt nerve fibers with this PAD pattern had peripheral thresholds and conduction velocities between 1.01 and 1.56 times threshold and 76.3 to 118 m/s, respectively. A second set of group I fibers was found to be depolarized by cutaneous nerves as well as by stimulation of rubrospinal and reticulospinal fibers (type B PAD pattern). The peripheral thresholds and conduction velocities of PBSt afferent fibers with a type B PAD pattern were of 1.66-2.03 times threshold and 71-83 m/s, respectively. We found a third set of group I fibers that were also depolarized by reticulospinal and rubrospinal inputs, but not by cutaneous nerves that instead inhibited the PAD elicited by group I volleys in flexor nerves (type C PAD pattern). All PBSt afferent fibers with a type C PAD pattern, with the exception of two, had peripheral thresholds and velocities between 1.46 and 2.16 times threshold and between 72 and 89 m/s, respectively. Stimulation of the Deiter's nucleus was found to depolarize the intraspinal terminals of a small fraction of group I GS fibers with a type A PAD pattern and of all group I GS and PBSt fibers with type B and C PAD patterns. The PAD produced by vestibulospinal stimulation in fibers with type A and C PAD patterns could be inhibited by conditioning volleys applied to cutaneous nerves. It is suggested that group I afferent fibers from flexors and extensors with a type A PAD pattern are group Ia, and that most fibers with type B and type C PAD patterns are group Ib.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed2001

Reduced regional [14C]2-deoxyglucose uptake in response to long-term clozapine administration in rats.

Clozapine has superior effects in treating negative symptoms of schizophrenia and causes less extrapyramidal side effects than traditional antipsychotics. In this study, we investigated the effects of acute and long-term clozapine administration on [14C]2-deoxyglucose uptake (2-DG uptake) in rats, as measured using the [14C]2-deoxy-D-glucose method. The 2-DG uptake was reduced in fewer regions after chronic clozapine (46%) than after acute clozapine (97%). After chronic clozapine treatment, the 2-DG uptake was reduced in the shell, but not the core, of the nucleus accumbens. In addition, long-term clozapine treatment remained affecting 2-DG uptake in several regions of the extrapyramidal system and the thalamus. The pattern of 2-DG uptake changes after long-term clozapine administration may provide information for the regions related to the therapeutic effect of clozapine.

Animals↗
PubMedDate not supplied

Sensory organization of the human thalamus.

A computerized program has been developed for on-line display and tape-library storage of stimulation-mapping data collected during stereotactic procedures. Using computer-generated displays of pooled clinical physiological data it has been possible to map through the upper midbrain and thalamus the lemniscal, spinoquintothalamic, auditory, vestibular, visual, extrapyramidal, and motor pathways, as well as the location of the pia. Each system is recognizable by a stereotyped, artificial, somatotopically organized stimulation-induced response that is devoid of modality information and independent of the site and parameters of stimulation.

Auditory Pathways↗