Search PubMed⌕ Search

Biomedical subjects

M Petrides

Publications and source records attributed to M Petrides.

At least 91 records · Page 5Linked to original sources
PubMed1990

Nonspatial conditional learning impaired in patients with unilateral frontal but not unilateral temporal lobe excisions.

The present study examined the effect of unilateral frontal- or temporal-lobe excisions on the acquisition of a conditional task requiring that the subjects respond to each one of six different coloured stimuli by selecting, from a set of six abstract designs, the correct design for each stimulus. Patients with excisions from the left or right frontal cortex were impaired in learning this task, whereas patients with left or right temporal-lobe excisions, with or without radical involvement of the hippocampal region, were not impaired. These findings demonstrate that the major role played by the frontal cortex in the acquisition of conditional responses is a general one and not restricted to situations involving different movements.

Adolescent↗
PubMed1989

Mental rotation of the neuronal population vector.

A rhesus monkey was trained to move its arm in a direction that was perpendicular to and counterclockwise from the direction of a target light that changed in position from trial to trial. Solution of this problem was hypothesized to involve the creation and mental rotation of an imagined movement vector from the direction of the light to the direction of the movement. This hypothesis was tested directly by recording the activity of cells in the motor cortex during performance of the task and computing the neuronal population vector in successive time intervals during the reaction time. The population vector rotated gradually counterclockwise from the direction of the light to the direction of the movement at an average rate of 732 degrees per second. These results provide direct, neural evidence for the mental rotation hypothesis and indicate that the neuronal population vector is a useful tool for "reading out" and identifying cognitive operations of neuronal ensembles.

Animals↗
PubMed1988

Association fiber pathways to the frontal cortex from the superior temporal region in the rhesus monkey.

The projections to the frontal cortex that originate from the various areas of the superior temporal region of the rhesus monkey were investigated with the autoradiographic technique. The results demonstrated that the rostral part of the superior temporal gyrus (areas Pro, Ts1, and Ts2) projects to the proisocortical areas of the orbital and medial frontal cortex, as well as to the nearby orbital areas 13, 12, and 11, and to medial areas 9, 10, and 14. These fibers travel to the frontal lobe as part of the uncinate fascicle. The middle part of the superior temporal gyrus (areas Ts3 and paAlt) projects predominantly to the lateral frontal cortex (areas 12, upper 46, and 9) and to the dorsal aspect of the medial frontal lobe (areas 9 and 10). Only a small number of these fibers terminated within the orbitofrontal cortex. The temporofrontal fibers originating from the middle part of the superior temporal gyrus occupy the lower portion of the extreme capsule and lie just dorsal to the fibers of the uncinate fascicle. The posterior part of the superior temporal gyrus projects to the lateral frontal cortex (area 46, dorsal area 8, and the rostralmost part of dorsal area 6). Some of the fibers from the posterior superior temporal gyrus run initially through the extreme capsule and then cross the claustrum as they ascend to enter the external capsule before continuing their course to the frontal lobe. A larger group of fibers curves round the caudalmost Sylvian fissure and travels to the frontal cortex occupying a position just above and medial to the upper branch of the circular sulcus. This latter pathway constitutes a part of the classically described arcuate fasciculus.

Afferent Pathways↗
PubMed1986

The effect of periarcuate lesions in the monkey on the performance of symmetrically and asymmetrically reinforced visual and auditory go, no-go tasks.

Monkeys with lesions restricted to the periarcuate region of the frontal cortex were impaired on go, no-go tasks in which, depending on the stimulus present on any given trial, they were rewarded either for pushing a manipulandum or for withholding this response for a given period of time. By contrast, these animals were able to learn at a normal rate go, no-go tasks in which they were rewarded if they responded in the presence of a "positive" stimulus, but not in the presence of a "negative" stimulus. In the latter situation, responding in the presence of the "negative" stimulus was extinguished through non-reward, whereas the tasks on which impairments were demonstrated required solution on the basis of a conditional rule: If stimulus A, respond, and if stimulus B, withhold responding, to receive reward. Because the 2 experimental situations were identical in every respect except for the one critical difference in the testing procedure, the present set of experiments provides a powerful demonstration of the involvement of the periarcuate cortex in conditional learning with exteroceptive stimuli.

Animals↗
PubMed1985

Deficits on conditional associative-learning tasks after frontal- and temporal-lobe lesions in man.

Patients with unilateral frontal- or temporal-lobe excisions were tested on a spatial and a nonspatial conditional associative task. These tasks required the learning of arbitrary associations between a set of stimuli and a set of responses. Patients with excisions from the left or right frontal cortex were severely impaired in learning both tasks. Patients with left or right temporal-lobe excisions that did not involve extensive damage to the hippocampal region were not impaired, whilst those with more radical involvement of the hippocampal region exhibited deficits that were material-specific and varied with the side of the lesion.

Adolescent↗
PubMed1985

Deficits in non-spatial conditional associative learning after periarcuate lesions in the monkey.

Monkeys with lesions of the periarcuate region of the frontal cortex were severely impaired in learning a nonspatial conditional associative task. In this task, either one of two non-spatial responses (open the lit or the unlit box) was correct if emitted in the presence of the appropriate stimulus. In contrast, the periarcuate monkeys were able to learn, at a normal rate, the control tasks in which only one of the two responses was correct (e.g., go to the lit box), the animal's task being to emit this response when the cue to do so was given. These findings support the hypothesis that the periarcuate cortex is critically involved in conditional associative learning.

Animals↗
PubMed1985

Frontal lobes and the temporal organization of memory.

Evidence for a major involvement of the frontal cortex in various aspects of the temporal organization of memory has emerged from the study of patients who had sustained a unilateral frontal- or temporal-lobe excision for the control of cerebral seizures. It has now been established that the frontal cortex participates in judgements of the temporal order of recent events and of their frequency of occurrence, as well as in the planning and monitoring of the execution of self-determined sequences of responses. Some differential effects related to the side of the lesion were observed, these depending both on the nature of the stimulus material used and on the special demands of the task.

Discrimination, Psychological↗
PubMed1984

Projections to the frontal cortex from the posterior parietal region in the rhesus monkey.

The projections to the frontal cortex from the various subdivisions of the posterior parietal region in the rhesus monkey were studied by means of autoradiographic technique. The rostral superior parietal lobule (area PE) projects to the dorsal areas 4 and 6 on the lateral surface of the frontal lobe as well as to the supplementary motor area (MII) on its medial surface. The caudal area PE sends its connections to dorsal area 6 and MII. The projections from the medial parietal cortex (areas PEc and PGm) are similar to those of the superior parietal lobule but they tend to concentrate in the more rostral part of dorsal area 6, MII, and in the cingulate gyrus (area 24). The most caudal part of the medial parietal cortex also projects to area 8. The anteriormost part of the inferior parietal lobule (area PF) projects to the ventral area 6, including the caudal bank of the lower branch of the arcuate sulcus, to the ventral area 46 below the sulcus principalis, and to the frontal and pericentral opercular cortex. The middle inferior parietal lobule (areas PFG and PG) projects to the ventral part of area 46 and area 8, whilst the posteriormost inferior parietal lobule (caudal PG and area Opt) is connected with both dorsal and ventral area 46, dorsal area 8, as well as the anteriormost dorsal area 6, and the cingulate gyrus (area 24).

Animals↗
PubMed1982

Deficits on subject-ordered tasks after frontal- and temporal-lobe lesions in man.

Seventy-nine patients with unilateral frontal- or temporal-lobe excisions and 18 normal control subjects were tested on four self-ordered tasks requiring the organization of a sequence of pointing responses. There were two verbal and two nonverbal tasks. Patients wih excisions from the left frontal lobe exhibited significant impairments on all four tasks, whilst patients with excisions from the right frontal lobe showed deficits only on the two nonverbal tasks. Patients with temporal-love lesions not extending posteriorly, on the medial side, beyond the pes of the hippocampus were unimpaired on all tasks, whereas those with more radical hippocampal excisions exhibited material-specific deficits that varied with the side of the lesion.

Adolescent↗
PubMed1980

Adaptation to prismatic displacement by schizophrenics and normals.

A sample of schizophrenic inpatients and a control sample of normal volunteers, matched for age and sex were tested on two tasks before and after an exposure condition in which they pointed repeatedly to a target while viewing their hands and the target through prisms. Both groups showed significant changes in both tasks--judging the straight-ahead, and pointing to a single target without sight of the hands. The groups did not differ from each other in the amount of changes in straight-ahead judgments, but normals showed greater adaptive change in the pointing task. These results contradict earlier reports that schizophrenics fail to adapt to altered visual-proprioceptive inputs; but they also help distinguish between modes of proprioceptive utilization that do and do not differentiate schizophrenics from normals.

Adaptation, Physiological↗
PubMed1979

Restricted posterior parietal lesions in the rhesus monkey and performance on visuospatial tasks.

Monkeys with lesions restricted to the inferior parietal lobule or the banks and depths of the superior temporal sulcus were tested on a route-following task. These areas are considered on neuroanatomical grounds to be homologous to parts of the human posterior parietal cortex, where lesions produce profound spatial disorientation. The operated monkeys were impaired on the route task, thus confirming at the behavioural level the anatomical predictions of comparability between parietal cortex in monkey and that in man. The monkeys were not impaired, however, on a visual pattern discrimination or on a visual-spatial task with cue and response separation, a task that was considered on the basis of previous investigations with extensive posterior lesions in the monkey to be sensitive to parietal lesions.

Animals↗
PubMed1979

Giant cell arteritis of the female genital tract.

In a patient who had a hysterectomy and bilateral salpingo-oophorectomy for endometrial adenocarcinoma, a giant cell arteritis was found in many of the myometrial and tubal vessels and in a few of the small arteries of the cervix and ovaries. On subsequent questioning, a history of treatment for polymyalgia rheumatica during the preceding 12 months was elicited. Of the three previously reported patients with giant cell arteritis of the uterus, two were suffering from polymyalgia rheumatica whilst one possibly had disseminated visceral giant cell arteritis.

Female↗
PubMed1979

Visual-field asymmetries in letter recognition: evidence for asymmetry in early visual registration.

Two experiments on visual-field differences in tachistoscopic letter recognition are described. In the first, a bright pre-exposure field with a black fixation point was used, and the conventionally expected dominance of the right visual field was found. However, a large number of "blank" trials were observed, in which subjects completely failed to detect the presence of the flashed target. These "blanks" were themselves significantly asymmetric between visual fields, suggesting that asymmetry in early stimulus registration may play an unsuspected role in typical measures of cerebral asymmetry in recognition accuracy. This was confirmed in a second experiment in which use of dark pre-exposure fields eliminated "blanks" and led to higher over-all accuracy, with no visual-field differences. Implications for interpretation of laterality data with normal subjects are discussed.

Adult↗
PubMed1976

Cross-modal matching and the primate frontal cortex.

Rhesus monkeys with selective lesions of the prefrontal system were tested on a tactile-visual cross-modal matching task. Monkeys with lesions in the banks and depths of the arcuate sulcus were impaired, while normal controls and monkeys with lesions in the banks and depths of the sulcus principalis and in the anterodorsal part of the head of the caudate nucleus were not.

Animals↗