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D P Crowne

Publications and source records attributed to D P Crowne.

27 records · Page 2Linked to original sources
PubMed1983

Brief deprivation of vision after unilateral lesions of the frontal eye field prevents contralateral inattention.

Brief deprivation of vision after unilateral lesions of the frontal eye field prevents the appearance of contralateral inattention to visual, auditory, and somatosensory stimuli. The forced circling that accompanies inattention, however, is not affected. An equivalent preoperative period in the dark only partly reduces inattention symptoms. Visual deprivation does not reduce or prevent inattention resulting from lesions of the superior colliculus.

Animals↗
PubMed1982

Some attentional effects of unilateral frontal lesions in the rat.

Visual learning, sensory neglect and motor behaviour were studied in rats with unilateral lesions of anteromedial (AM) or dorsolateral (DL) frontal cortex. The purpose was to determine whether the principal features of the syndrome seen after unilateral frontal eye field lesions in primates appear in the rat. In the first two experiments, rats were trained on a visual discrimination using shock avoidance. AM lesions greatly prolonged choice latency but did not increase errors, and this held both for binocular performance and for monocular performance with the contralateral eye. One group of AM-lesion animals was postoperatively maintained in the dark, and their latencies, binocular and monocular, did not differ from the DL controls. Thus, deprivation of visual experience prevented the effects of the AM lesion. The second experiment used simple sensory stimuli to test for visual, auditory and tactile neglect. Ipsiversive circling was also investigated. All rats with AM lesions neglected contralaterally and circled in the first postoperative week. Recovery was underway by the second week and complete in three weeks. The animals were trained preoperatively on a conditioned avoidance problem in which shock was signalled from various points in the visual field. Tested postoperatively, the AM-lesion rats avoided normally. The findings of the two experiments strongly suggest that the functions of AM cortex in the rat are similar to those of the frontal eye field in primates. This cortical region appears to be part of a system which prominently includes the superior colliculus and serves attentional/orienting functions.

Animals↗
PubMed1981

The effects of unilateral frontal eye field lesions in the monkey: visual-motor guidance and avoidance behaviour.

Macaque monkeys were tested on a visual-motor guidance task and observations of avoidance behaviour were made following unilateral frontal eye field lesions. Visual-motor guidance was assessed by speed and accuracy of reaching to press recessed, illuminated buttons arrayed in a 90 degree arc in front of the monkey. Unilateral frontal eye field lesions produced a marked neglect of stimulus lights contralateral to the side of the lesions, as shown in greatly increased errors and response latencies. Responses to the most peripheral of the ipsilateral stimulus lights were also affected, although not to the same degree. Partial to complete recovery occurred, usually within a month. A unilateral lesion of the principal sulcus did not cause symptoms of neglect in the visual-motor guidance task. Section of the cerebral commissures partially restored the visual-motor guidance deficit in the frontal eye field-lesioned monkeys, with recovery again occurring. Commissurotomy and the unilateral frontal eye field lesion performed in a single-stage operation produced an initially more severe neglect than the two-stage operation, but recovery was no less rapid. The unilateral frontal eye field lesions resulted in a severe neglect of contralateral threat objects when the monkeys were threatened from both sides (avoidance-avoidance tests). Avoidance was normal when the threat was presented to one side. Commissurotomy fully restored the avoidance-avoidance deficit and made it permanent. These and other recent findings suggest that the contralateral visual field defect and the other symptoms resulting from frontal eye field lesions represent an impairment in directing and sustaining attention in regions of the visual field arising from disruption of a corticothalamotectal sensorimotor integration system.

Animals↗