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W A Mackay

Publications and source records attributed to W A Mackay.

6 recordsLinked to original sources
PubMed1982

Participation of precentral neurons in somatically and visually triggered movements in primates.

Monkeys were trained to perform somatically and visually triggered wrist flexion-extension (F-E) movements. Extracellular unit recordings were made in the contralateral precentral forelimb area. These neurons were identified as being best related to particular single forelimb joints by their responses to passive somatosensory stimulation and to the determining effects of local intracortical microstimulation. It was found that almost 60% of single-joint related cells participated in both somatically and visually triggered movements. All wrist (F-E) neurons responded reciprocally while non-wrist (F-E) neurons had reciprocal as well as bidirectional responses to the oppositely directed visual and somatic perturbations. Somatically related responses and visually related responses were both uniformly distributed throughout the vertical layers of precentral cortex. With respect to horizontal spatial arrangements, multiple clusters of reciprocally and bidirectionally responsive neurons were intermingled. This latter finding supports the concept of a context-sensitive organization for motor control within precentral cortex.

Animals↗
PubMed1978

An intracortical microstimulation study of output organization in precentral cortex of awake primates.

We investigated the output organization of the forelimb control area in primate precentral cortex by using low-current (less than 30 microamperemeter) intracortical microstimulation (ICMS). Movement about a joint was selected as the index of response. Penetrations perpendicular to the cortical surface and deep into the rostral bank of the central sulcus were made in two awake unanesthetized monkeys (Macaca arctoides). Cortical areas were designated by the joint about which movements occurred. 1. ICMS loci which produced movements about finger joints were found to tightly cluster in a central zone, and were surrounded by loci controlling movement about the wrist. This wrist zone was in turn approximately encircled by an elbow zone, which itself was enclosed by a shoulder zone. 2. Appreciable overlap between these zones controlling movements about contiguous joints was observed. 3. The observations indicate a nested-ring organization of the forelimb output zones of precentral cortex, such that a cortical zone controlling movement of a more distal joint is partly encircled by the zone controlling a more proximal joint.

Animals↗
PubMed1977

Simple probe for localized cryogenic blockade in the brain.

The construction of a simple probe utilizing an air-space thermal insulation and circulating coolant for localized cooling of brain tissue is described. Results of isotherm studies in the cerebellum and electrophysiological observations in the motor cortex are presented indicating the effectiveness of localized cooling by the probe.

Animals↗