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Loss of place specificity in hippocampal complex spike cells of senescent rat.

Firing characteristics of "place" cells in dorsal CA1 of hippocampus were recorded from 5 young (10-14 months) and 5 old (25-29 months) Fischer-344 rats. Animals were trained to obtain food reward on a radial 8-arm maze. Entry to the arms was controlled by the experimenter so that all 8-arm were visited in random sequence from trial to trial. For each cell, 8 such trials were given (64 arm choices) in order that statistical reliability could be obtained for firing rates over the maze surface. Single unit activity and the animal's position on the maze were continuously monitored by digital computer. Twenty-seven cells from each age group were studied in this way. No statistically significant differences were found between age groups in unit spike height, width or firing rates. A large, statistically significant difference, however, was found in both spatial specificity and reliability of firing patterns from trial to trial. These results are discussed in terms of a possible deficit in spatial information processing in the older animals.

Action Potentials↗

Preservation of accurate spatial memory in aged rats.

Male rats were tested in an 8 arm radial maze from 6-26 months of age with 5 hr delay imposed between choices 4 and 5. At 26 months their spatial memory was more accurate than when they were first tested at 6 months and also more accurate than that exhibited by another 5 month old group tested concurrently. However, these old rats acquired a noval spatial habit more slowly than the younger animals. In a subsequent study, we compared the acquisition of accurate spatial memory by rats that were 3 or 21.5 months old at the start of training. Older rats adapted to the maze more slowly and required more sessions to achieve criterion with no delay imposed during the test. There was no reliable difference in acquisition when a 1 hr delay was imposed between choices 4 and 5, but the old rats learned more slowly with a 5 hr delay. On memory tests after criterion performance had been achieved, the older rats performed as well as the younger animals at all delay intervals. Aged rats are deficient in acquiring the skills required for accurate spatial memory, but once acquired these skills do not deteriorate. The possibility that other "memory" deficits associated with aging might be alleviated by overtraining is discussed.

Adaptation, Psychological↗

Effects of long-term restricted feeding on radial maze performance by aged rats.

Rats were fed every other day (EOD) from 3-21 months of age prior to training in an 8-arm radial maze with retention intervals of 0, 1 or 5 hr imposed between the fourth and fifth choices. Their performance was compared to that of another aged group fed ad lib throughout life prior to radial maze training and to 3 month old controls. Rats fed ad lib until training adapted to the maze more slowly than young controls and were impaired in acquiring accurate spatial memory. EOD feeding eliminated age-related differences in the initial rate of adaptation to the radial maze but had no effect on the development of accurate spatial memory at any of the retention intervals. These results indicate that differences in deprivation history are probably not responsible for previous findings that radial maze training early in life prevents the appearance of age-related deficits in accurate spatial memory.

Aging↗

The effects of life-long food restriction on spatial memory in young and aged Fischer 344 rats measured in the eight-arm radial and the Morris water mazes.

The effect of life-long 60% ad lib food restriction on performance in two tasks involving spatial memory, the eight-arm radial maze and the Morris water maze, was studied in young and aged Fischer 344 rats. Restricted (R) and ad lib (AL) feeding groups were compared at 8, 16, and 24 months of age on both tasks. A 30-month-old R group was also tested in the Morris water maze. In the eight-arm maze, although 24-month-old animals performed more poorly than 8- and 16-month-old animals during the first week of testing, overall accuracy of performance did not vary significantly as a function of age. Twenty-four-month-old animals took longer to make 10 choices than did younger animals, and there was a significant interaction between feeding regimen and age, reflecting the fact that at the two younger ages, R groups performed more quickly than the AL groups. In the Morris water maze, both distance swum and time to find the platform increased with age. Life-long food restriction led to small but significant improvements in performance in the water maze in aged rats. R groups showed evidence for better retention over 24-hour intervals than did AL groups. By 30 months of age, however, R animals showed impaired performance relative to younger R groups. These differential findings on the two tasks, as they were used here, suggest that there was greater impairment with age on the spatial memory task requiring retention of information over long intervals than there was on the task primarily involving working memory within a trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

Executive system dysfunction in the aged monkey: spatial and object reversal learning.

As part of the effort to characterize age-related cognitive changes in executive system function in a nonhuman primate model of human aging, the performance of seven rhesus monkeys, 20 to 28 years of age, was compared to that of five young adult monkeys, 6 to 11 years of age, on spatial and object reversal tasks. No differences in performance were found between the two groups in the initial learning of either task. On spatial reversals, aged monkeys were impaired relative to young adults, but there was no difference in overall performance between the groups on object reversals. Central to this article, a perseverative tendency was noted in the aged group on both spatial and object reversal tasks. Changes in executive system dysfunction may represent an important aspect of age-related cognitive decline.

Age Factors↗

The basis of privacy and autonomy in medical practice. A model.

Most of the medical literature concerned with privacy seems to be based on the implicit assumptions that there is such a thing as right-to-privacy and that privacy is a worthwhile end unto itself. This paper develops a model which should permit a better and more pragmatic understanding of the moral, ethical and psychosocial bases of these assumptions. Arguments are offered that privacy is, indeed, not mainly an intrinsic value but is more of an instrumental value. It is suggested that privacy, per se, is not an end but is, rather, a means to another end, autonomy. It is important to differentiate autonomy as used here from narcissism; the former is viewed as an advanced stage of cognitive development whereas the latter is a social deviance. The model is developed which states: the analogy of a person is as a unit consisting of a matrix which is unique and autonomous because of its separation from other units by means of a wall-of-privacy; the relationship between persons is measured by their social distance. Derived from this is the 'equation', A approximately equal to (P)(D). Intimacy, substitutive judgement, confidentiality and patient-physician relationship are conceptualized within this model.

Confidentiality↗

Evoked potential and visual half-field evidence for task-dependent cerebral asymmetries in congenitally deaf adults.

Twelve congenitally deaf subjects participated in a visual half-field experiment under two conditions, lexical decision and line orientation discrimination. Reaction time, accuracy, and evoked potentials from left and right temporo-parietal sites were simultaneously obtained. The evoked potential data were analyzed using a principal components analysis followed by analysis of variance and multiple regression. Both the visual half-field and the evoked potential data produced evidence of task-dependent cerebral asymmetries. Individual differences in visual half-field asymmetries in accuracy and individual scores on three cognitive paper and pencil tests were strongly predicted by linear combinations of several independent hemispheric asymmetry variables derived from evoked potential component scores. The results suggest that cerebral specialization in congenitally deaf people is a complex, multidimensional phenomenon, and provide the first evidence for a direct relationship between cerebral asymmetry and cognitive performance in this population.

Adult↗

EEG correlates of eye contact and interpersonal distance.

The EEG of 18 male subjects was monitored while the subject gazed at the eyes of a male experimenter located 2, 4, 8, 16 or 32 ft from the subject. The experimenter either gazed directly at the subject or averted his eyes. EEG arousal was highest when the experimenter was at 2 ft and gazing into the subject's eyes. EEG arousal diminished as a function of distance, while arousal for direct gaze was always higher than for averted gaze, whatever the distance.

Adolescent↗

Neuro-informatics and the neurology of perception.

In the preceding pages a description was given of spatial behaviour and spatial perception. Orientation in space develops under the guidance of a directional frame of reference. The formative power of this spatial organisation is gravity and anti-gravity by which throughout evolution the architecture of the body and its axial layout are shaped. There are no local signs at the surface of the body enabling us to read from them directions and orientations. Locomotion requires equilibrium. It is carried out by articulated limbs. The nervous system modulates the motor patterns dictated by physical forces. Peripheral control loops keep the limbs manageable. Higher levels of control organize control loops among each other. Their activity has the status of operations. As soon as animals are capable of locomotion orientation is based on relationships with objects, with a stable background in particular. As motor organisation develops spatial relationships become more complex. In the case of active touch the shape of an object is determined by manipulation, which is a form of scanning. Tactile scanning combines the features of sampling, tracking and measuring: f.e. solidity, weight, curvature, size. Manipulation is guided by the spatial frame of reference. The innumerable tactile impulses, many of them not perceived separately, are not the primary material of information. Only by ordering the impressions, by discriminating between noise and relevant events is the tactile experience guided by expectations transformed into information. The organism stops manipulating as soon as the scanning procedure has enabled it to match the shape under investigation with the spatial patterns it has at its disposal.(ABSTRACT TRUNCATED AT 250 WORDS)

Electronic Data Processing↗

Anosodiaphoria for dressing apraxia: contributory factor to dressing apraxia.

We report 2 patients with bilateral dressing apraxia. One patient had prominent bilateral dressing apraxia without severe constructional apraxia together with anosodiaphoria for dressing apraxia. The other patient had mild dressing apraxia with severe constructional apraxia and was aware of her disabilities. This dissociation implies that anosodiaphoria for dressing apraxia is an important factor in the severity of bilateral dressing apraxia. This also explains why automatic acts in dressing are more severely affected than when patients are asked to put clothing on in dressing examination.

Adult↗

Post-trial flicker stimulation interferes with spatial memory in the Morris water maze.

Rats (n = 20) trained under monocular viewing conditions in the working memory version of Morris water maze task received daily a single acquisition trial with a new location of the invisible escape platform followed after 15 min by a single retrieval trial. Escape latency decreased by 50% during retrieval. Flash stimulation (20 Hz, 0.6 J) during the entire 15-min delay disrupted retention, but this effect was not observed when the flashes started 3 or 5 min after acquisition. It is concluded that successful place learning requires a brief interference-free post-acquisition interval.

Animals↗

Event-related brain potentials (P300) and neuropsychological deficit in patients with focal brain lesions.

Sixteen patients with chronic focal brain lesions were investigated with an acoustic P300 test and psychological tests of spatial abilities (Maze Tracing Speed Test, Form Board Test), cognitive speed (Sequential Number Connection Test), categorization (Figure Sorting Test), verbal fluency and vigilance. Neither the psychological battery nor P300 analysis discriminated frontal from retrorolandic brain lesions. Abnormalities of P300 significantly correlated with impairments in those psychological tests which had a spinal component in common. We suggest that abnormality of the P300 with focal brain damage rather indicates higher mental function impairment than direct effects of the lesion.

Adult↗

Galanin impairs acquisition but not retrieval of spatial memory in rats studied in the Morris swim maze.

The effect of intraventricular administration of the neuropeptide galanin on acquisition and retrieval in a modified Morris swim maze was studied in rats. Galanin induced a significant deficit in the acquisition of the task while no effects on the retrieval were observed. No deficits were seen 24 h after the last treatment. Galanin did not increase the number of failures to reach the platform. It is suggested that endogenous galanin modulates learning possibly via the galanin-containing cholinergic neurons in the septum-basal forebrain area projecting to the hippocampus and cortex.

Animals↗

Thalamocortical connections of rat posterior parietal cortex.

The neuronal connections of rat posterior parietal cortex (PPC) have been examined using retrograde fluorescent axonal tracers. We have found that PPC receives thalamic input predominantly from the lateral posterior and lateral dorsal nuclei, and not from the ventrobasal nucleus, which projects to the rostrally adjacent hindlimb cortex, or from the dorsal lateral geniculate nucleus, which projects to the caudally adjacent visual association area. PPC has reciprocal corticocortical connections with medial agranular cortex and orbital cortex; together, these three cortical areas may function as a network for directed attention in rats.

Afferent Pathways↗

Enriched environment primes forebrain choline acetyltransferase activity to respond to learning experience.

Weanling rats were raised in an enriched or an impoverished environment. The enriched rats subsequently learned the Morris water maze faster than their impoverished counterparts. The enriched rats, both maze-trained and untrained, showed higher choline acetyltransferase (ChAT) activity in the caudate than did the impoverished, untrained rats. Maze training increased caudate ChAT in impoverished rats. Enriched but not impoverished rats showed increased hippocampal and anterior cortical ChAT activity after maze training. Thus, enrichment causes a long-lasting increase in caudate acetylcholine (Ach) synthesis and it also primes cortex and hippocampus to respond to a training experience with increased Ach synthesis.

Animals↗

Nerve growth factor (NGF) in rat brain following long-term barbital treatment: relation to convulsions and cognitive function.

Nerve growth factor (NGF) protein has been implicated in alterations of cognitive function either following brain damage, selective lesions or aging. Groups of rats were given long-term (48 weeks) oral barbital treatment or tap water and following an extended period of abstinence (14 weeks) were tested for spatial learning ability in the Morris swim maze. Following the maze test, they were sacrificed and the NGF content of hippocampal and cortical brain regions were analyzed. Barbital treated rats were divided into convulsing and non-convulsing groups. It was found that there was a slight, significant increase (12%) in NGF content of the hippocampus in convulsing rats. Correlations between maze learning performance, brain weight and NGF in the cortex indicated a significant negative relationship between (a) performance and brain weight on day 1 of testing and (b) NGF content and performance on day 2. These data indicate some involvement of NGF in functions derived from a considerably different animal model to those applied previously.

Animals↗