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At least 19 recordsLinked to original sources
PubMed1979

Disorders in somesthesis following lesions of parietal lobe.

1. We determined the effects of lesions of the parietal lobe on the capacities of monkeys to detect and discriminate between mechanical sinusoids delivered to the hand. Tests of discrimination measured the capacity to discriminate between frequencies of flutter (24--36 Hz) and the capacity to make gross discriminations of frequency of flutter-vibration over the range of 10--50 Hz. 2. A unilateral removal of the parietal lobe impaired sensory capacities only on the contralateral hand; detection threshold was elevated, the capacity to discriminate between frequenceis of flutter was permanently lost, and the capacity to discriminate between and identify frequencies of 10--50 Hz was grossly impaired. No defects were found on the hand ipsilateral to the lesion. Detection thresholds, but not discrimination thresholds, decreased during postoperative testing, but in most cases did not recover to preoperative values. The impairments in frequency discrimination remained through the last day of postoperative testing. 3. A unilateral, subtotal parietal lesion that completely destroyed the primary and secondary somatic areas and Brodmann's area 5 resulted in the same sensory impairments as those produced by total removal of the parietal lobe. In most cases, detection threshold was elevated; flutter-frequency discrimination was lost, and the capacity to discriminate between frequencies of 10--50 Hz over the extended range of flutter and vibration was impaired. 4. The loss in discriminative capacity following lesions of the somatosensory cortex is interpreted as due to the absence of a cortical mechanism that determined differences in the temporal pattern of cyclically entrained activity in the somatic afferent pathway. This loss was dissociated from the remaining capacity, although impaired, to detect the presence of any neural activity in the afferent pathways or to determine gross differences in the frequency of mechanical sinusoids by a mechanism of coding by the labeled line.

Animals↗
PubMed1977

Visual input to the visuomotor mechanisms of the monkey's parietal lobe.

A newly identified class of neurons of the parietal cortex, studied in waking monkeys (Macaca mulatta), is activated by visual stimuli, perhaps via the retino-collicular visual pathway. This afferent input is thought to provide the visual cues activating the visuomotor mechanisms of the parietal lobe for the direction of visual attention.

Action Potentials↗
PubMed1976

Personality disorder and parietal lobe dysfunction.

An inability to relate transitionally is a major feature of personality disorder. The developmental independence of transitional relatedness from verbal-symbolic growth, its orienting function, and the nature of its visual and tactile components support the conclusion that it is a function of the nondominant parietal lobe. Therefore it can be hypothesized that dysfunction of this area is the cerebral analogue of personality disorder. The fact that unawareness of illness ("anosognosia") in conjunction with grossly intact intellectual function is common to both personality disorder and minor parietal lobe dysfunction further supports this hypothesis.

Adult↗
PubMed1977

Ictal tonic postural changes and automatisms of the upper limb during epileptic parietal lobe discharges.

Tonic postural changes of the upper limb accompanied by epileptic parietal lobe discharges are not well known. The authors report 3 such cases. In the 3 patients, a total of 18 spontaneous seizures were recorded, 12 by telemetry, from either scalp electrodes or stereotactically implanted electrodes. Of these 18 seizures, 14 included tonic postural changes of the upper limb accompanied by a contralateral parietal discharge. Combining these 3 cases with the 4 such cases in the literature, the authors found that the clinical pattern consisted of a tonic postural change in one upper limb associated with automatisms of the opposite upper limb. It was also found that the same patient might have automatisms involving the upper limb in some seizures and upper limb postural changes in other seizures, both accompanied by the same electrical discharge. It is concluded that tonic postural changes and automatisms in the upper limb may be interchangeable.

Adult↗
PubMed1976

[Digital agnosia and lesions of the parietal lobe].

130 patients with focal brain damage have been submitted to non-verbal finger identification tasks. The results of this research can be summarized as follows: -when bilateral finger agnosia is studied with non-verbal tasks, no difference can be shown between right and left parietal lesions; -in left brain damaged patients the bilateral form of finger agnosia is generally due to large lesions involving the parietal lobe; -in right brain damaged patients the unilateral form of finger agnosia is almost always due to lesions centered on the parietal region.

Agnosia↗
PubMed1978

Inaccurate reaching associated with a superior parietal lobe tumor.

A man with a tumor in the right superior parietal lobule had difficulty reaching for visualized objects. There were no significant deficits in visual sensation, visual attention, somatosensory function, elementary motility, praxis, or visuospatial performance. If allowed to visually fixate the target before reaching, he misreached only with his left arm and only when he was not allowed to observe the reaching limb. If he was required to maintain central visual fixation while reaching into his peripheral visual fields, his left arm misreached into both visual hemifields but his right arm misreached only into the left visual hemifield. These results demonstrate abnormalities, referable to both the contralateral arm and the contralateral visual field, that can neither be reduced to elementary disturbances of visual or somatosensory function nor to an elementary disturbance of motility. This pattern of misreaching has not been previously reported in human subjects or in experimental animals, but this may be attributable to differences of methodology. The misreaching observed in this patient may correspond to loss of posterior parietal neurons serving a supramodal integrative function.

Aged↗
PubMed1978

Mechanisms of neural integration in the parietal lobe for visual attention.

The impulse discharges of neurons in the inferior parietal association cortex (area 7) were studied in the alert, behaving rhesus monkey, trained to fixate and follow visual targets. Four classes of cells related to visual or visuomotor function were found. Cells of one of these are sensitive to visual stimuli and have large, contralateral receptive fields with maximal sensitivity in the far temporal quadrants. Cells of the other three classes are related to visuomotor functions: visual fixation, tracking, and saccades. They are neither sensory nor motor in the usual sense for they are activated only by interested fixation of gaze or tracking, or before visually evoked saccadic eye movements. They are not activated during the spontaneous saccades and fixations that the monkey makes while casually exploring his environment. It is hypothesized that the light-sensitive neurons provide the visual input to the visuomotor cells that, in turn, produce a command signal for the direction of visual attention and for shifting the focus of attention from one target to another.

Animals↗
PubMed1977

Parietal lobe mechanisms for directed visual attention.

1. Experiments were made on the cortex of the inferior parietal lobule in 10 hemispheres of six alert, behaving monkeys. The electrical signs of the impulse discharges of single cortical cells were recorded as the monkeys executed tasks requiring them to fixate stationary visual targets, track those which moved slowly, and to make saccadic movements to foveate those which suddenly jumped from one locus to another within the field of view. A total of 907 neurons of area 7 were identified in terms of their physiological properties, particularly the correlation of their activity with the oculomotor components of these behavioral acts of directed visual attention; 480 of these were located by cytoarchitectural layer. Most identifiable cells of area 7 are visuomotor neurons, in a special and conditional sense. Their discharge frequencies increase before and during those steady fixations and movements of the eyes which secure and maintain foveation of objects, but only if the visual targets engaged are linked by a strong motivational drive; in our experiments, one between thirst and the light whose dimming the animal has learned to detect for liquid reward. We have identified and studied three major classes of neurons in area 7. 2. The visual fixation neurons (57%) accelerate discharge synchronously with fixation of a visual object the animal desires. The incremented discharge continues until reward, but then declines abruptly even when there is no immediate shift of the line of gaze. Fixation neurons are relatively inactive during those casual fixations by which the animal insepcts the surrounding environment. Mist fixation neurons subtend gaze fields limited to one quadrant or half of the total gaze field. The sum of the gaze fields of the fixation neurons in one hemisphere is weighted moderately toward the contralateral side. Fixation cells also discharge during slow pursuit movements in any direction so long as the movement stays within the gaze field of the neuron under study. About 40% of fixation cells are suppressed before and during saccadic movements of the eyes to a new target within the gaze field of the fixation cell. Those suppressed are located preferentially in layer V of the cortex. Suppression is maximal for saccades directed contralaterally to the hemisphere under study. 3. Visual tracking neurons are active during oculomotor pursuit of slowly moving visual objects, not during steady fixations. They show a marked directional but no laterality relation, and are suppressed before and during a visually evoked saccade superimposed on the smooth pursuit movement. The rate of discharge is a flat function of tracking speed so that these cells do not appear to emit signals which specify the speed of smooth pursuit movements. 4. The saccade neurons are active before and during visually evoked saccadic movements of the eyes but not before spontaneous saccades, no matter whether made in light or near darkness. The discharge of saccade neurons leads the eye movement by as much as 150 ms (mean, 73 ms)...

Action Potentials↗
PubMed1978

Modification of visual functions of the parietal lobe at early age in the monkey.

In addition to the visual pathway ending in the visual cortex, visual information is also processed in the associative areas of the cortex. We have studied the posterior parietal association area (Brodmann's area 7), and in our sample about 40% of the neurons were influenced by visual stimulation or ocular movements. The visually activated neurons in this region in normal adult monkeys have large, binocular receptive fields and they respond well to all moving visual stimuli near the animal. They do not differentiate between different patterns of visual stimuli but respond well to objects of interest, such as food, drinks, new objects, etc. Many visual neurons also respond to somatic stimulation. Preliminary experiments on two young monkeys suggest that the visual input into area 7 is strongly modified by early visual deprivation. In one monkey monocular deprivation lead to total absence of any influence from the deprived eye to area 7. No deprivation effect was observed in the lateral geniculate nucleus of the thalamus and the effect in area 7 was stronger than in the visual cortex (area 17). One monkey raised with bilateral eye closure was behaviourally blind after the opening of the eyes and remained so for the observation period of one month. In area 7 of this monkey the proportion of recording sites responsive to visual stimulation was sharply reduced. In kittens binocular deprivation is known to effect the function of the visual cortex much less than monocular deprivation. It seems possible that at early age inputs representing different sensory systems compete for influence in the associative cortical areas in the same way as there is competition between inputs from the two eyes to the visual cortex.

Age Factors↗