Biomedical subjects

J B Mattingley

Publications and source records attributed to J B Mattingley.

4 recordsLinked to original sources

PubMed1992

Initiation and execution of movement sequences in those suffering from and at-risk of developing Huntington's disease.

Recent research has shown that Huntington's disease (HD) causes problems in the initiation and execution of movement (akinesia, bradykinesia): information which is useful in documenting the functional progression of the disease. The present experiment used a sequential movement task to characterize such impairments. Eighteen patients diagnosed as suffering from HD, and a similar number of matched At-Risk (AR) and Normal control subjects, performed sequential button pressing tasks, under varying amounts of visual advance information. Specific dimensions of motor control were examined (hand, direction). Movement initiation and in particular movement duration were useful indicators of the functional progression of the disease, and also detected anomalies of performance in some AR individuals. Impaired motor programming was indicated by patients' difficulty in initiating movements in the absence of external visual cues, and their problems in utilizing advance information to control movement. Patients had specific deficits in initiating movements with the nonpreferred hand, and directional movement asymmetries were accentuated. The results suggest that HD causes difficulties at three discrete levels: in utilizing advance information, in the initiation and in the spatial representation of movement.

Adult↗

PubMed1992

Impairments of movement initiation and execution in unilateral neglect. Directional hypokinesia and bradykinesia.

Patients with unilateral neglect may exhibit slowness in the initiation of contralesionally directed movements in peripersonal space (directional hypokinesia). The present study used a sequential movement task to characterize any such impairment in a group of 24 patients with right hemisphere lesions, 18 of whom had left neglect. A further five patients with left hemisphere lesions, one of whom had right neglect, were also tested. We measured movement initiation and execution times for leftward and rightward movements in either hemispace and across the body midline. Most left neglect patients, particularly those with lesions involving posterior cortex, showed directional hypokinesia. Left neglect patients with anterior and/or subcortical lesions also showed directional bradykinesia, i.e. a slowing in the execution phase of contralesionally directed movements. This impairment occurred regardless of the spatial location of the apparatus and was exacerbated as patients moved closer to their neglected side. The patient with right neglect showed directional hypokinesia but not directional bradykinesia. Right hemisphere and left hemisphere lesion patients without neglect performed in a manner comparable to controls, who did not exhibit directional hypokinesia or directional bradykinesia. These results suggest that directional hypokinesia is associated with both left hemisphere and right hemisphere damage, but only in the context of unilateral neglect. Moreover, the site of hemispheric lesion may determine the temporal characteristics of movement impairments in neglect. Damage to posterior cortex produces deficits in detecting contralesional targets and initiating movements toward them, while damage to anterior or subcortical structures may disrupt the internal representation of an intended trajectory.

Adult↗

PubMed1991

Spatial maps.

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Attention↗

PubMed1991

The shift effect can be elicited with both foveal and peripheral masks.

Foveal target detection thresholds are elevated by presenting a counterphasing, vertical squarewave grating in the peripheral retina. This psychophysical "shift effect" has been considered to be an analogue of the neurophysiological "periphery effect" first described by McIlwain (1964; Journal of Neurophysiology, 27, 1154-1173). Physiological response properties of cells from the retina and lateral geniculate nucleus of cat and primate visual systems predict that sensitivity thresholds should also be elevated for peripheral targets in the presence of a foveal counterphasing mask. In these experiments, contrast sensitivities for human observers were obtained using a two-interval forced-choice procedure for peripheral target sinusoids in the presence of a foveal counterphasing mask. A suppressive shift effect was elicited by the foveal counterphasing squarewave mask, but only for counterphasing peripheral sinusoids. Masking was only obtained at the lowest spatial frequencies for both the peripheral and foveal shift effects.

Contrast Sensitivity↗