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Biomedical subjects

R T Watson

Publications and source records attributed to R T Watson.

At least 55 records · Page 3Linked to original sources
PubMed1986

Apraxia and the supplementary motor area.

Anatomical, electrophysiological, and cerebral blood flow studies suggest that the supplementary motor area (SMA) may be important for programming certain skilled motor acts of the limbs. However, to our knowledge, abnormalities of complex distal motor behavior following SMA lesions have not been reported. We have studied two patients with left mesial hemisphere infarctions that included the SMA. These patients had bilateral ideomotor apraxia for transitive limb movements without buccofacial apraxia. The observations suggest that the types of skilled motor acts programmed by the left SMA are learned transitive limb movements.

Aged↗
PubMed1986

Apomorphine has a therapeutic effect on neglect produced by unilateral dorsomedial prefrontal cortex lesions in rats.

Neglect is a disorder in which the response to stimulation is diminished or absent on the side of the body contralateral to the lesion in the absence of an elemental sensory or motor defect. Most cases of neglect in humans are induced by cortical damage, but there have been no investigations of the pharmacologic basis of neglect induced by cortical damage. We examined the role of the dopamine system in polymodal neglect caused by a unilateral lesion of the medial precentral prefrontal cortex of the rat. A dose-response examination of the effect of apomorphine on neglect revealed that apomorphine, at 0.5 mg/kg, the highest dose examined, significantly improved the orientation scores of subjects in all modalities tested and significantly decreased the total number of allesthetic responses. The therapeutic effect of apomorphine was mediated by dopamine receptors as the therapeutic effect of apomorphine was blocked by prior administration of spiroperidol. These results demonstrate the important role of disruption of dopamine mechanisms in neglect induced by a lesion of medial precentral cortex.

Animals↗
PubMed1986

Apraxia after a superior parietal lesion.

We studied a patient who had unilateral (left) limb apraxia associated with a lesion of her right superior (Brodmann areas 5 and 7) and inferior parietal lobes. In monkeys areas 5 and 7 contain "hand-manipulation neurons" that are thought to be important in proprioceptive guidance. Therefore, we tested our patient with her eyes open and closed. Her left hand performance with pantonime, imitation, and use of actual objects dramatically deteriorated in the absence of visual guidance. In addition, although the patient did not have optic ataxia and had normal proprioception, she had difficulty using her left forelimb in tasks that require transcoding from a visual to a somatesthetic spatial coordinate system. We propose that each superior parietal lobe is not only responsible for transcoding from a visual-spatial code into a somatesthetic-spatial code but is also critical for transcoding spatial-temporal representations of skilled movement into a somatesthetic-spatial code.

Adult↗
PubMed1986

Hypometria with hemispatial and limb motor neglect.

A patient with a haemorrhage in the right mesial frontal lobe exhibited hypokinesia, bradykinesia and a hypometric movement disorder of his contralateral limbs. This movement disorder was characterized by reduced amplitude of otherwise normally formed movements (hypometria). In addition, the left limb hypokinesia improved with placement of the left forelimb into right hemispace (hemispatial motor neglect). We postulate that the hypokinesia, bradykinesia and hypometria were induced by reduction in activation of forebrain dopaminergic and basal ganglion motor systems, which in conjunction with the supplementary motor area are critical for setting the activational level for motor output.

Analysis of Variance↗
PubMed1986

Normal tactile threshold in monkeys with neglect.

To learn whether animals with parietotemporal lesions have sensory inattention or defective intention, we trained monkeys to respond with the contralateral limb to a threshold tactile stimulus. After parietotemporal lesions that induced neglect, the monkeys continued to respond normally to threshold stimuli on the side opposite the lesion (the neglected side), but made errors when stimulated on the normal side (ipsilateral to the lesion), often failing to use the contralateral extremity. On this learned task, there was no abnormality of sensory input or sensory attention. The problem was attributed to an impaired preparation to respond (intention).

Animals↗
PubMed1986

From benign fasciculations and cramps to motor neuron disease.

Fasciculations and cramps may occur in motor neuron disease or as part of a more benign syndrome. A man with apparently benign fasciculations and cramps for 4 years developed progressive muscle weakness and wasting. Such a previously undocumented evolution of benign fasciculations and cramps to motor neuron disease may further implicate anterior horn cell dysfunction in the pathogenesis of muscle fasciculation-cramp syndromes.

Atrophy↗
PubMed1986

Resolution of gumma with steroid therapy.

Antibiotic usage has rendered neurosyphilis uncommon, and cerebral gummas are rare. Reduced awareness of cerebral gummas and abolition of serologic screening can delay diagnosis of this treatable disease. Diagnostic confusion between syphilitic and nonsyphilitic cerebral mass lesions can be increased by apparent resolution of a gumma during steroid therapy. Such an occurrence in a young woman emphasizes the need for serologic testing for syphilis in diagnosing cerebral mass lesions. A trial of conservative therapy using penicillin (with or without prednisone) should be considered for patients with intracerebral mass lesions and positive serologic findings.

Adult↗
PubMed1986

The right hemisphere: neuropsychological functions.

In the past two to three decades, clinicians and neuroscientists have been studying the functions of the right hemisphere. Neither hemisphere seems to be dominant in the absolute sense. Each appears to be specialized and is dominant for different functions. However, most functions require the cooperation of both hemispheres. When one is damaged, the other can often compensate for the damaged one. Lesions of the left hemisphere are associated with language (speech, reading, and writing) and praxic disorders, and lesions of the right hemisphere can result in visuospatial, attentional, and emotional disorders. The authors review some of the major behavior disorders associated with right hemisphere dysfunction and concentrate on three major types of disorders--visuospatial, attentional, and emotional. Although not all the behavioral defects associated with right hemisphere damage can be subgrouped under these three types, they are the ones most often associated with right hemisphere lesions.

Agnosia↗
PubMed1986

Autoimmune optic neuritis: a potentially treatable form of visual loss.

In most patients, idiopathic optic neuritis remits spontaneously. Among those in whom it does not are patients with systemic lupus erythematosus, who often respond to pulse methylprednisolone. This subset of patients may be expanded to patients with other autoimmune phenomena, as in the case of a young woman who had myasthenia gravis and other laboratory evidence of autoimmunity. She had permanently lost vision in the right eye without treatment of optic neuritis, but in a later similar episode the left eye responded to pulse methylprednisolone after failing to respond to orally administered prednisone.

Adult↗
PubMed1985

Pantomime comprehension and ideomotor apraxia.

In a prior study it was shown that apraxic patients with posterior infarctions that included the parietal lobe could not discriminate between gestures. In this study these observations were replicated using a nonverbal paradigm in which the subjects did not have to discriminate between gestures, but instead had to comprehend their meaning. Pantomimed acts on videotape were shown to six apraxic-aphasic patients, seven nonapraxic-aphasic patients, and six normal subjects. Four drawings were also shown, one of which matched the pantomime (for example, if the pantomime was of hammering, one drawing was of a nail and three were foils). Subjects responded by pushing a button corresponding to the desired picture. The apraxics made more errors than the aphasics or controls.

Adult↗
PubMed1985

Directional hypokinesia: prolonged reaction times for leftward movements in patients with right hemisphere lesions and neglect.

Patients with hemispatial neglect perform activities poorly in the hemispace contralateral to the lesion. We postulate that hemispatial neglect induced by right hemisphere lesions may be associated with a directional hypokinesia: initiation of movements toward the hemispace contralateral to the lesion is affected more than movements toward the lesion. We tested 6 patients with hemispatial neglect caused by right hemisphere damage, 7 with left hemisphere damage and no neglect, and 12 controls. Patients with left hemispatial neglect initiated responses to left hemispace more slowly than toward right hemispace.

Adult↗
PubMed1984

Afferent connections of medial precentral cortex in the rat.

The principal sources of input to rat medial precentral cortex (PCm), as revealed by iontophoretically applied horseradish peroxidase, are: the ventral lateral, mediodorsal, central lateral and ventromedial thalamic nuclei; contralateral PCm; ipsilateral cortical areas related to vision, somatic sensation and audition; retrosplenial and ventrolateral orbital cortex. These results are compared to findings in monkeys and discussed in relation to the phenomenon of polymodal neglect of hemispace.

Afferent Pathways↗
PubMed1984

Pseudoneglect in a patient with partial callosal disconnection.

Each hemisphere may not only be responsible for processing stimuli from the contralateral sensory systems and for programming movements of the contralateral hand, but may also be important for mediating attention-intention within the contralateral hemispace. If each hemisphere mediates attention-intention within contralateral hemispace, both hemispheres must work in concert especially when an arm is crossed and used in opposite hemispace. If both hemispheres did not work together, the directional bias of each hemisphere would become manifest and induce the contralateral extremity to err toward its own hemispace, inducing pseudoneglect . To test this hypothesis, we examined a patient who had a partial callosal disconnection. In trying visually and somaesthetically to bisect lines with her left hand in right hemispace, the patient made systematic errors to the left; in bisecting lines in left hemispace with her right hand, she made systematic errors to the right. The patient also made less dramatic systematic errors even when a hand was used in its own hemispace, which suggests that each hemisphere mediates attention-intention within and towards the contralateral hemispace.

Adolescent↗
PubMed1984

The effect of corpus callosum lesions on unilateral neglect in monkeys.

The cerebral hemispheres may be mutually inhibitory. An injured hemisphere may continue to be inhibited while the uninjured hemisphere is released from inhibition, inducing attentional bias. Patients with neglect might therefore benefit from transection of the corpus callosum. To test this hypothesis, we ablated the frontal arcuate gyrus alone or several months after corpus callosum transection in monkeys. Neglect was significantly worse in animals with a corpus callosum transection. Therefore, the hemispheres may be mutually excitatory or compensatory, and a callosal transection would not be therapeutic. Because the rate of recovery in the two groups was not different, recovery seemed to be an intrahemispheric phenomenon.

Animals↗
PubMed1983

Callosal apraxia.

A 43-year-old woman suffered a spontaneous corpus callosum disconnection, resulting in apraxia and apraxic agraphia confined to the left hand. She initially had a functionally total callosal disconnection. With time, the splenium of the corpus callosum became functional, and a computerized tomographic scan performed five months after the onset showed infarction of only the body of the corpus callosum. Concomitant with this improvement in callosal function, the apraxia changed from ideational (loss of the concept of skilled movements) to classic ideomotor apraxia. A temporal analysis of this case provided support for Liepmann's (Liepmann, 1900; Liepmann and Maas, 1970) hypothesis that there is a centre for visuokinaesthetic (space-time) engrams in the left hemisphere of right-handed patients that controls skilled motor acts in either hand. This patient's recovery also allowed us a better understanding of the mechanisms underlying various types of apraxia.

Adult↗
PubMed1983

Performance on hemispatial pointing task by patients with neglect syndrome.

Five patients with left hemispatial neglect and five aphasic control subjects were given a hemispatial pointing task. They were instructed to point to an imaginary point in space perpendicular to the midline of the chest. Right hemisphere-damaged subjects with neglect deviated more into the hemispace ipsilateral to the lesion than left hemisphere-damaged controls. This task did not require sensory input from left hemispace, and the defective performance cannot be attributed to sensory inattention or to impaired gaze or memory. The finding is compatible with hemispatial akinesia.

Adult↗