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Biomedical subjects

W Overman

Publications and source records attributed to W Overman.

9 recordsLinked to original sources
PubMed1996

Children's performance on "animal tests" of oddity: implications for cognitive processes required for tests of oddity and delayed nonmatch to sample.

To investigate the ontogenesis of oddity learning, children (16 to 102 months of age) and adults were tested on two versions of the oddity task using non-verbal procedures originally developed for monkeys. On the standard, "one-part" or "simultaneous" oddity task (Experiment 1), young children (16 to 74 months of age) performed more poorly than older children (81-102 months of age) who were as proficient as adults. The delayed mastery of one-part oddity contrasts to mastery, at much younger ages (3 to 4 years of age) of a similar, but two-part task, delayed non-match to sample (DNMS) (Overman, 1990). In Experiment 2, those children from the first experiment who had difficulty in learning the one-part oddity task were tested on a two-part oddity task, and a subset of the subjects was retested on the one-part oddity task, and, finally, given verbal instructions for the one-part oddity task. The two-part oddity task was mastered significantly more rapidly than the previous one-part task; however, children's performance dropped significantly when tested on the one-part oddity task, and finally, children rapidly mastered the one-part oddity task when given verbal instructions. The data suggested that (a) children used different strategies to solve the different versions of the oddity task, (b) the solution for the two-part-task appeared earlier in life than the solution for the one-part task and did not involve the use of the concept of "oddity relations", and (c) in tasks in which stimuli are shown twice, behavior may come under control of the absolute properties of the exemplar stimulus via a simple "win-shift" pattern of behavior. In contrast, in tasks in which all stimuli are presented simultaneously, behavior may be controlled by stimulus relations, the analysis of which has a protracted ontogenetic development.

Adult↗
PubMed1992

Object recognition versus object discrimination: comparison between human infants and infant monkeys.

Human infants (12-32 months old) and adults learned a delayed nonmatching-to-sample (DNMS) task and single- and multiple-pair discrimination tasks using nonverbal procedures previously used with monkeys. Infants learned discriminations rapidly and at a young age (12 months), but they required prolonged training and maturation before learning the DNMS task. Adults learned all tasks rapidly. After learning the DNMS task to criterion, memory performance declined systematically in an inverse relation to age. The dissociation in ability of infants on the DNMS versus discrimination tasks closely resembles the dissociation previously reported with infant monkeys (Bachevalier & Mishkin, 1984). Results from both infant humans and monkeys support a neurocognitive maturational model.

Adolescent↗
PubMed1988

Guidelines for legal and financial counseling of Alzheimer's disease patients and their families.

As soon as there is reasonable evidence for the diagnosis of Alzheimer's disease (primary progressive degenerative dementia), the physician should urge legal and financial counseling of the patient and the family in planning for the patient's long-term care. The general purposes and the process of such counseling are described as a guide for physicians who care for these patients and their families. The issues of informed consent, competency, powers of attorney, guardianship, inter vivos trusts, wills, and living wills are discussed. Timely planning eases the burden on the family and assists the physician in the patient's care during the later stages of the disorder.

Alzheimer Disease↗
PubMed1981

Behavioral effects of early rearing conditions and neonatal lesions of the visual cortex in kittens.

Kittens with neonatal lesions of the marginal and posterolateral gyri, along with unoperated controls, were reared either in an enriched environment or in laboratory cages. Kittens with lesions were inferior to controls at learning mazes and at discriminating forms and gratings, whether they were raised in enriched or impoverished conditions. Enrichment did not facilitate form or grating discrimination by either normal or operated cats, although such experience facilitated maze learning by both groups. It is concluded that early enrichment of sensorimotor experience was probably not the cause of the complete sparing of pattern vision after neonatal damage of the visual cortex reported in earlier studies. Discussion centers on task variables and completeness of the lesions as reasons for sparing of vision.

Animals↗
PubMed1980

Subtotal lesions of the visual cortex impair discrimination of hidden figures by cats.

Cats with partial or nearly total ablation of areas 17, 18, and 19 were assessed on the discrimination of hidden figures and other visually guided behaviors to determine whether such insults produce deficits like those that follow lateral striate lesions in monkeys. Cats with destruction limited to the representation of central vision (Group M) were impaired at discriminating patterns complicated by extraneous cues, but they were less impaired than cats with more complete lesions (Group MS). The deficit was not a general one in visual learning since animals in both Groups M and MS learned simple pattern discriminations as rapidly as controls. It is suggested that the loss of geniculocortical functions representing central vision produces similar deficits in cats and monkeys but that to have this effect in cats, damage must extend beyond area 17.

Animals↗
PubMed1978

Extent of recovery from neonatal damage to the cortical visual system in cats.

Cats that received either marginal or marginal plus extramarginal lesions as 3-day-old kittens were assessed on a series of tests of visually guided behavior. These cats were not conspicuously different from normal controls in avoiding obstacles or in activity level. Yet these same operated cats were severely impaired in performance on the visual cliff and in visual discrimination learning, even when the lesions were limited to the geniculocortical portion of the visual system. However, maximum losses in pattern and form discrimination learning were observed only in cats with severe retrograde degeneration in both the lateral geniculate nucleus and the complex of the pulvinar and nucleus lateralis posterior. Photically evoked potentials were recorded in the lateral regions of the neocortex more reliably from operated cats that had made fewer errors in discrimination learning than from more severely debilitated cases; this relation was present even among cases with nearly equivalent amounts of retrograde degeneration in the visual thalamus. These findings suggest that in the cat (a) recovery of vision is incomplete after neonatal lesions of the visual cortex and (b) a cortical system lateral to the geniculocortical projections may be involved in pattern vision.

Animals↗
PubMed1976

Performance on the visual cliff by cats with marginal gyrus lesions.

Lesions in 12 cats that destroyed almost all of area 17 (Group MS) abolished differential responding on the visual cliff. Performance was not impaired in 9 cats in which regions of the striate cortex were spared in the depths of the splenial sulcus or in 23 cats with damage to extramarginal areas. There were 37 controls. Additional experiments indicated that the deficit in performance by MS cats was not reduced either by the administration of amphetamine or by increases in cues for motion parallax. Monocularly occluded normal cats preferred the shallow surface of the visual cliff, demonstrating that the deficit was not due solely to removal of neurons sensitive to binocular disparity. The findings were discussed in light of electrophysiological evidence that lesions of the visual cortex disrupt functions of the superior colliculus.

Amphetamine↗