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Biomedical subjects

R E Passingham

Publications and source records attributed to R E Passingham.

At least 127 records · Page 7Linked to original sources
PubMed1985

Premotor cortex and the conditions for movement in monkeys (Macaca fascicularis).

Cortical association areas direct their influence on motor cortex via premotor and supplementary motor cortex. In the present experiment premotor cortex was removed bilaterally in monkeys. The monkeys were unable to relearn a visual conditional motor task on which the correct action is specified by visual cues. It was shown that the same monkeys were unable to learn a non motor visual conditional task on which the visual cues specified which object should be chosen. It is concluded that the monkeys are only impaired when they must recall a movement from memory on the basis of a visual cue.

Animals↗
PubMed1985

Memory of monkeys (Macaca mulatta) with lesions in prefrontal cortex.

It is controversial whether damage to prefrontal cortex causes an impairment of memory. In this experiment, the tissue in sulcus principalis was removed in rhesus monkeys, and they were given 25 spatial locations to remember. They were poor at the task from the first. The same animals were able to indicate which of two locations they had touched if there was no delay before they were allowed to make their report. One possibility is that frontal mechanisms operate on information in working memory.

Animals↗
PubMed1985

Rates of brain development in mammals including man.

The paper considers the absolute rates at which the brain grows in different mammals and the relative rates of growth for the various subareas. It concludes that the various mammals are much more similar in the rates of growth of the brain than of the body. The rate of growth of the human brain is within the range of variation expected. Indirect evidence is presented that the different mammalian orders may differ in the relative rates of growth of the neocortex and other brain areas.

Aging↗
PubMed1983

The long-term effects of removal of sensorimotor cortex in infant and adult rhesus monkeys.

A comparison is made between the long-term effects of the unilateral removal of sensorimotor cortex in infant and adult rhesus monkeys. Both infants and adults recovered to a remarkable extent. They walked, climbed and jumped with ease. However, neither infant nor adult monkeys could grip food by using thumb and forefinger independently of the other fingers. It was demonstrated in the adults that there was a permanent impairment in the use not only of the fingers but also the wrist and forearm. The results do not support the claim made by Kennard (1942) that infants recover more completely than adults from the effects of brain lesions. An analysis of the relevant evidence suggests that compensation occurs only when the animal is very immature at the time of operation. The brain is much more mature in a neonatal monkey than a rat or hamster. True compensation can probably only occur in monkeys if the lesion is made well before birth.

Animals↗
PubMed1982

An assessment of the reinforcing properties of foods after amygdaloid lesions in rhesus monkeys.

The reinforcing strengths of foods were assessed in rhesus monkeys before and after bilateral radio-frequency lesions of the lateral amygdala (n = 4), basolateral amygdala (n = 4), and total amygdala (n = 3). None of these lesions altered preoperative preferences between three highly palatable foods. Moreover, the lesions had no discernible effect on the animals' responses to different food rewards as measured by a progressive ratio schedule, although performance on this schedule proved sensitive to the size and type of food reward and to the degree of deprivation. The results suggest that amygdalectomy leaves a normal appreciation of at least this one class of rewards, foods. The dietary changes typically seen after amygdalectomy, such as meat eating, which were also observed in the same animals, probably reflect a loss of neophobia.

Amygdala↗
PubMed1981

Broca's area and the origins of human vocal skill.

Chimpanzees appear to be unable to learn to speak. It is usual to attribute their lack of vocal skill to limitations of their vocal tract, and to the absence in their neocortex of any area corresponding to Broca's area in the human brain. The first signs of Broca's area in hominid endocasts are therefore taken to represent an evolutionary development of great significance. There are two outstanding questions. First, what exactly does Broca's area do? Secondly, why does Broca's area in one hemisphere play a much greater role in controlling speech than does the corresponding area in the other hemisphere? The following answers are proposed. (1) Broca's area seems to be concerned not with the production of individual sounds but with the regulation of sequences of sounds. Chimpanzees have no need for such an area because their natural calls are not made up by varying the sequential order of elementary units. (2) Cerebral dominance for speech may result from the fact that the vocal cords are innervated in the same way as other central organs, such as the tongue. Each hemisphere sends a projection, and the two projections overlap extensively so that either hemisphere can assume full control. It is argued that it is most efficient for a single hemisphere to dominate where a complex sequence of movements must be programmed. This reorganization has occurred for the production of song in some songbirds and for the control of the vocal cords in human speech.

Animals↗
PubMed1981

Stereotaxic surgery under X-ray guidance in the rhesus monkey, with special reference to the amygdala.

The anterior/posterior (AP) positions of three subcortical regions; the amygdala, supra-optic nucleus of the hypothalamus and mammillary bodies, were estimated with respect to the skull in 35 rhesus monkeys (Macaca mulatta). The distances from the external auditory meatus, from which stereotaxic coordinates are typically derived, to these subcortical nuclei were found to be highly variable. In contrast the posterior tip of the sphenoid bone, which was visualized on lateral radiographs, provided a landmark at a remarkably constant AP distance from these nuclei. This landmark was used to guide a series of a amygdaloid lesions and injections. The accuracy of these operations strongly suggested that the posterior tip of the sphenoid bone could be used to predict not only the AP but also the height of the amygdala. It is proposed that this radiographic technique could be applied to other hypothalamic and basal forebrain regions.

Amygdala↗
PubMed1981

Syndrome produced by lesions of the amygdala in monkeys (Macaca mulatta).

Behavioral effects of subtotal amygdaloid lesions were investigated in an attempt to dissociate some of the abnormalities seen after total amygdalectomy. Twelve monkeys received bilateral stereotaxic lesions centered in the basolateral amygdala, lateral amygdala, dorsal amygdala, or the temporal white matter lying adjacent to the lateral amygdala. These monkeys were compared with others with control operations. The control monkeys then received total amygdaloid lesions (AMX). The AMX monkeys exhibited the typical amygdaloid syndrome of hypoemotionality, meat eating, coprophagia, and excessive exploration. In contrast, the monkeys with subtotal amygdaloid lesions would not eat meat or feces, though they were more willing than control monkeys to investigate inanimate objects. Although minor changes in affect were observed, the extreme emotional changes seen after total amygdalectomy were found only in the monkey with the largest subtotal lesion. Only those animals that were hypoemotional showed a deficit in learning successive reversals of an object discrimination. This close association suggests that both the hypoemotionality and the successive reversal deficit arise from the same underlying dysfunction.

Amygdala↗
PubMed1980

Cortical and subcortical afferents to the amygdala of the rhesus monkey (Macaca mulatta).

The afferent projections to the primate amygdala were studied using horseradish peroxidase. The potential advantages of this technique are discussed compared with those previously used to determine amygdaloid afferents. The findings indicate that certain agranular or dysgranular cortical regions may project directly to the amygdala: in particular, the orbital frontal cortex, anterior cingulate gyrus, subcallosal gyrus, temporal pole and anterior insula. These projections probably terminate predominantly in either the lateral or accessory basal nuclei. Other cortical projections from the inferotemporal and superior temporal gyri are described. Evidence was found for a heavy projection from the superior temporal sulcus to the lateral nucleus. Subcortical afferents were found from the hypothalamus, substantia innominata, diagonal band, thalamus, periaqueductal central gray, peripeduncular nucleus and from a band of cells extending medially from the peripeduncular nucleus to the midline, just ventral to the thalamus. In the thalamus, labelled cells were restricted to the non-specific nuclei, and were common in the rostral midline nuclei. No projection was observed from the dorsomedial nucleus of the thalamus. We discuss the implications of these results for interpreting the functions of the amygdala.

Afferent Pathways↗
PubMed1980

Connections of the mediodorsal nucleus of the thalamus in the tree shrew. II. Efferent connections.

[35S]Methionine was injected into the mediodorsal nucleus of the thalamus of 5 adult tree shrews (Tupaia belangeri) and into the medioventral thalamic nucleus in another tree shrew. Three animals survived for 44 h and three others for two weeks (including the animal with the injection in the medioventral nucleus). Contact autoradiograms were made on an X-ray film. The mediodorsal thalamic nucleus was found to project ipsilaterally to all surfaces of the frontal pole of the cerebral cortex. No other projections of this nucleus have been established. Also in this species, the medioventral nucleus projects to the first layer of the entire neocortex ipsilaterally and to the mesencephalic tegmentum.

Animals↗
PubMed1979

Brain size and intelligence in man.

The relationship between brain size and intelligence was investigated in two ways. Cranial capacity was measured in people with known IQs. A very small correlation was found between cranial capacity and intelligence; but this was shown to be the result of the confounding effects of height. A large series of brains was also investigated, data being obtained on occupation from the case notes. When the effects of body height and weight were controlled for, it was possible to demonstrate a statistically significant, but very slight, relation between brain size and occupational group.

Adolescent↗
PubMed1978

Converging projections from the mediodorsal thalamic nucleus and mesencephalic dopaminergic neurons to the neocortex in three species.

Previous studies in the rat have shown that the neocortical dopaminergic afferents, originating in the mesencephalon, terminate in those areas of the frontal lobe which receive projections from the mediodorsal thalamic nucleus i.e., the prefrontal cortex. In order to clarify whether this overlap is accidental for the rat or a consistent feature of several species we have compared the projection areas of the ventral tegmental area and the mediodorsal thalamic nucleus in three species, rat, opossum and tree shrew, using HRP injections in combination with glyoxylic acid histofluorescence method. The results have shown, first, that the area innervated by the mediodorsal nucleus of the thalamus is localized in a different part of the frontal lobe in each species: dorsolateral in the opossum, anteromedial, polar and suprarhinal in the rat and frontopolar in the tree shrew. Secondly, this area alone in each species receives projections from the ventral tegmental area. Thirdly, this area alone receives a dense innervation in the deep cortical layers by fluorescent fibres probably containing dopamine. The neighbouring neocortical areas receive afferents neither from the mediodorsal nucleus of the thalamus nor from the ventral mesencephalic tegmentum; their catecholamine innervation is mainly confined to the superficial layers and appears to be of noradrenergic nature. Although the techniques used did not allow a precise determination of the borders of the two projection areas and, therefore, the exact degree of overlap, it appears that mesencephalic dopaminergic innervation is a characteristic feature of the prefrontal cortex in the mammalian brain.

Animals↗
PubMed1975

The brain and intelligence.

A measure of brain development is proposed which might correlate with intelligence. The neocortex/medulla volume is given for many species of primate, and it is found that this measure correlates with a measure of responsiveness to novel objects, and with performance on visual discrimination learning set. It is shown that cranial capacity/foramen magnum area is closely related to brain/medulla volume, and may therefore be used as a related measure with fossil species.

Animals↗