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R M Ridley

Publications and source records attributed to R M Ridley.

At least 145 records · Page 8Linked to original sources

Further evidence of impaired tactile learning after removals of the second somatic sensory projection cortex (SII) in the monkey.

Four rhesus monkeys with bilateral removals of SII and five unoperated monkeys were trained on tests of tactile equivalence, weight discrimination and generalization, tactile discrimination learning (including concurrent learning and serial reversal) and inter-manual transfer of tactile learning. Lesioned animals were impaired on almost all tactile learning tasks and on inter-manual transfer but not on the test of tactile equivalence nor on the propioceptive tasks. The results are considered in the context of previous studies of somatosensory and parietal cortex.

Animals↗

Disturbance of cage-finding in the monkey.

Qualitative and quantitative observations were made on two monkeys with unilateral or bilateral removals of areas 5 and 7 of Brodmann. The task was to return to the home cage in the light or in the dark. Both animals were slower in the dark, and also qualitatively abnormal in the light.

Animals↗

Stimulus- and response-dependent units from the occipital and temporal lobes of the unanaesthetized monkey performing learnt visual tasks.

43% of units recorded from the foveal prestriate cortex, inferotemporal cortex or amygdala of 15 rhesus monkeys performing visual discrimination or serial reversal tasks were responsive to all or some visual stimuli or other aspects of the task. Six units showed activity during movements required for performance of the task. It was not possible to determine whether unit activity could be related to the learnt association of the visual stimuli with reward.

Animals↗

Spatial disorientation in the monkey.

The incidence of misdirected movements of the hand during tactile discrimination performance in the dark has been tabulated for monkeys with bilateral removals of parieto-prestriate cortex. The observations support the existence of a spatial disorientation (in addition to their inaccuracies of reaching) in these animals.

Animals↗

Behavioral assessment of the ability of intracerebral embryonic neural tissue grafts to ameliorate the effects of brain damage in marmosets.

The transplantation of neuronal tissue into the brains of patients with Parkinson's disease is already being assessed as an experimental treatment for the symptoms of this disease, and the possibility of using similar graft tissue to ameliorate the symptoms of other neurodegenerative diseases is being considered. In this context, a small number of transplant experiments have been carried out in monkeys with lesions of the central dopamine and cholinergic systems. These experiments make it possible to determine the optimum methods of transplantation in an animal whose brain is structurally more closely related to the human than that of the rat and to assess the behavioral consequences of transplantation on symptoms that either resemble very closely the symptoms seen in patients, or are of a complex cognitive nature and are therefore more difficult to measure in the rat. It is intended that these experiments will contribute to the development of better treatments for the neurodegenerative diseases, either by the use of transplantation as a clinical treatment, or by contributing to a better understanding of the mechanisms that normally maintain neuronal function and that fail in these diseases.

Animals↗

A critical evaluation of monkey models of amnesia and dementia.

In this review we consider various models of amnesia and dementia in monkeys and examine the validity of such models. In Section 2 we describe the various types of memory tests (tasks) available for use with monkeys and discuss the extent to which these tasks assess different facets of memory according to present theories of human memory. We argue that the rules which govern correct task performance are best regarded as a form of semantic rather than procedural memory, and that when information about stimulus attributes or reward associations is stored long-term then that knowledge is semantic. The demonstration of episodic memory in monkeys is problematic and the term recognition memory has been used too loosely. In particular, it is difficult to dissociate episodic memory for stimulus events from the use of semantic memory for the rule of the task, since dysfunction of either can produce impairment on performance of the same task. Tasks can also be divided into those which assess memory for stimulus-reward associations (evaluative memory) and those which tax stimulus-response associations including spatial and conditional responding (non-evaluative memory). This dissociation cuts across the distinction between semantic and episodic memory. In Section 3 we examine the usefulness of the classification of tasks described in Section 2 in clarifying our understanding of the contribution of the temporal lobes and the cholinergic system to memory. We conclude that evaluative and non-evaluative memory are mediated by separate parallel systems involving the amygdala and hippocampus, respectively.

Amnesia↗