PubMed Health⌕ Search

Biomedical subjects

A J Nonneman

Publications and source records attributed to A J Nonneman.

At least 37 records · Page 2Linked to original sources
PubMed1982

Role of residual anterior neocortex in recovery from neonatal prefrontal lesions in the rat.

Lesions of mediofrontal cortex in adult rats produce behavioral impairments on spatial alternation tasks as well as retrograde degeneration in the mediodorsal thalamic nucleus. The severity of the behavioral deficits and of the thalamic degeneration correlates positively with lesion size. In contrast, similar lesions in neonatal rats (10 days or younger) produce neither spatial alternation deficits nor thalamic degeneration, even after extensive lesions removing all of the mediofrontal cortex. This study examined the possibility that residual anterior cortex remaining intact after early mediofrontal lesions might be involved in the observed anatomical and behavioral sparing. The results show that the sparing of spatial alternation after neonatal frontal cortex lesions does not depend on functional substitution by intact regions of anterior cortex. Neonatal rats receiving extensive lesions including both the medial and orbital frontal cortex or the entire anterior neocortex remained unimpaired on this task. However, these same animals suffered severe retrograde degeneration in the mediodorsal thalamus. Therefore, although some form of neural plasticity cannot be entirely dismissed as the basis for the behavioral results, it seems more likely that behavioral rather than neural plasticity is involved. We suggest that rats deprived of frontal cortex from infancy are able to perform the spatial alternation task in a manner that differs from that used by most intact rats.

Animals↗
PubMed1982

Morphologic and behavioral effects of perinatal glucocorticoid administration.

Male rats were infused with one of two doses of dexamethasone or saline on day 4 of life. Body, whole brain, hippocampal, and cerebellar weights were obtained at 10, 20 and 150 days of age, and the ability of the rats to acquire and reverse a spatial discrimination task was assessed at 90 days of age. Body weights and brain weights were severely and permanently suppressed in the high dose group (100 mg/kg), resulting in a 20% decrement from saline-injected controls in adulthood. Low dose (1 mg/kg) animals were transiently slowed in body and brain growth, but differences from controls were no longer detectable at 60 days of age. Both high dose and low dose animals were significantly impaired in acquisition and reversal of a spatial learning task in an open field water maze, and exhibited deficits characteristically seen in animals with hippocampal damage. The animals' swimming performance per se was unimpaired. It appears that even transient interruption of normal interactive sequences of brain development by the alteration of post-natal neurogenesis or gliogenesis by glucocorticoids results in a permanent behavioral deficit.

Animals↗
PubMed1982

Serial lesion effect in rat medial frontal cortex as a function of age.

This experiment examined the potential for behavioral recovery in juvenile, adult, and senescent rats following serial lesions of medial frontal cortex. The subjects were trained on spatial delayed alternation in a T-maze under conditions designed to enhance the probability of a serial lesion effect. All subjects were given extensive handling and adaptation to the maze, interoperative training, and long interoperative and postoperative intervals. There were several major behavioral findings: (a) the aged intact subjects were not impaired in their ability to learn spatial delayed alternation, (b) one-stage bilateral lesions of frontal cortex produced equivalent deficits on spatial delayed alternation at all ages, (c) subjects in all of the age categories demonstrated a serial lesion effect, but (d) the 150 day and 570 day serial lesions groups demonstrated significantly better performances than the 35 day serial lesions group on several measures of performance.

Aging↗
PubMed1981

Differential effects of prefrontal cortex ablation in neonatal, juvenile, and young adult rats.

Rats sustaining lesions restricted to the medial (MF) or the orbital (OF) pre-frontal cortex at various ages (10, 25, 40, or 60 days postnatally) were tested as adults on a series of behavioral tasks that are known to be sensitive to such lesions in adults. On spatial alternation learning, both the 40- and 60-day MF operates were seriously impaired, whereas neither the 10- nor the 25-day MF operates differed from control. On a hoarding task, 25- and 60-day MF operates hoarded less food than either controls or 10-day MF operates. Lesions of OF cortex in males at 40 or 60 days of age produced a significant increase in running-wheel activity; OF lesions in both sexes at 25 days of age or later produced a decrease in the rate of continuous reinforcement reacquisition (following experience with differential reinforcement of low rates of responding and bar-press extinction) relative to controls, whereas 10-day OF operates did not differ from controls on either task. Thus, rats with lesions of either frontal area at 10 days of age showed complete behavioral sparing on all measures. The effects of lesions at later ages varied with the behavioral tasks employed and with lesion locus. Although the 10-day operates received a somewhat longer postoperative recovery interval than most of the later operates, these results cannot be explained on the basis of recovery time alone. A control group of 60-day operates with the same recovery interval as the 10-day operates did not differ on any measure from the 60-day operates with shorter recovery intervals.

Aging↗
PubMed1981

Environmental constraints on motor abilities used in grooming, swimming, and eating by decorticate rats.

In a number of successive tests, grooming, swimming, and eating behaviors of decorticate rats were reexamined by evoking the behaviors in various circumstances (stimulus conditions). The rats showed normal-length grooming sequences during spontaneous home cage grooming; when grooming was elicited by removing the rats from their home cage and soaking their fur by a brief swim, grooming-sequence length was abbreviated. In cold (18 degrees C) water, they swam well and with exaggerated vigor and frequently inhibited forelimb movements; in warm (37 degrees C) water, they swam poorly and paddled with all four limbs. To eat small pieces of food, they sat up and used their forepaws as do normal rats, but they frequently dropped the food; they did not use their forepaws to eat large pieces of food. When given powdered food, they first tried to grasp it in their mouth while they scratched at the floor surface with their front limbs; thereafter, they became increasingly proficient in licking it up. Thus, in a narrow range of stimulus conditions, decorticate rats can make movements resembling those of normal rats. They also improve with practice in some (eating powdered food) but not other (forepaw immobility, eating large food pellets) tasks. The study shows that in order to elucidate the role of the cortex in control of motor behavior, it is necessary to obtain "behavior profiles" of each behavior by testing the animals repeatedly and under widely varying test conditions.

Animals↗
PubMed1978

Sparing of function in rats with early prefrontal cortex lesions.

Previous work has shown that medial frontal lesions in adult rats produce deficits on spatial reversals, delayed responses, and active avoidance, whereas more ventrolateral (orbital) lesions have little effect on these tasks. These findings were confirmed. However, when lesions were made at 2, 5 or 9 days of age, rats tested as adults showed dramatic sparing of function on all these tasks, whereas similar lesions inflicted at 35 or 40 days of age produced deficits on delayed responses and spatial reversals. Orbital frontal lesions failed to significantly alter behavior on any task at any age. The effects of the neonatal lesions are in striking contrast to the effects of juvenile or adult lesions, even though the infant lesions were considerably larger. Histological analysis revealed no retrograde degeneration in the dorsomedial thalamic nucleus of the rats operated in infancy unless the lesions were so large that the adjacent caudate-putamen was also damaged. The contrast between these results, and results obtained after similar lesions in adults may indicate the growth of sustaining collaterals after the infant lesions which might be involved in the observed behavioral sparing.

Age Factors↗
PubMed1976

Functional development of prefrontal cortex in rats continues into adolescence.

Bilateral removal of the sulcal prefrontal cortex in rats at 60 days of age and older results in aphagia and adipsia, but removal of this area before 60 days of age does not affect food or water regulation. Apparently the development of the role of this neocortical region in feeding and drinking continues well beyond the time of weaning in the rat.

Age Factors↗
PubMed1976

Marginal and extramarginal cortical lesions and visual discrimination by cats.

Seventy-five cats learned a shape discrimination with zero, one, or two irrelevant cues. They were then subjected to sham operations (n = 34), ablation of the marginal and splenial gyri (n = 9), or lesions in the extramarginal (EM) cortex. The 32 EM cats comprised four groups, three with small (EM1, n = 9), intermediate (EM2, n = 10), and large (EM3, n = 9) decortications, and a fourth group with both EM lesions and heavy degeneration in the lateral geniculate nucleus (LGN, n = 4). The cats with marginal or extensive extramarginal lesions were severely impaired in shape and size discrimination. Two lines of evidence indicate that their behavioral defects resulted from different neural dysfunctions. (a) The errors made by marginal gyrus cases increased sharply as a function of the number of irrelevant cues present in shape discrimination training; no other group, including Group EM3, was affected by this variable. (b) Cats with extramarginal ablations and strong LGN degeneration were no more severely impaired than were subjects with comparable extramarginal damage and little or no LGN degeneration. While the nature of the two kinds of deficits remains unclear, they seem parallel to those following posterior cortical lesions in monkeys.

Animals↗
PubMed1976

The search for cerebral dominance in monkeys.

Twelve monkeys with statistically significant and consistent manual preferences on three handedness tests were subjected to unilateral ablations in the association cortex. Eight received lesions in the foveal prestriate cortex, and four lesions in the dorsolateral frontal cortex; half the subjects in each group were operated on the dominant, and half on the nondominant hemisphere for handedness. The unilateral posterior preparations were significantly inferior to the control group of four unilateral frontals and five sham operated monkeys on three series of visual pattern discrimination problems. No evidence was obtained that lesions in the nondominant hemisphere. The results of this and four other experiments indicate that there is no cerebral dominance for problem-solving in monkeys. Recent research indicates that handedness in rhesus monkeys is only superficially similar to handedness in humans; thus, monkeys appear to lack cerebral dominance for handedness as well as for cognitive behavior.

Animals↗
PubMed1975

Prefrontal cortex and the regulation of food intake in the rat.

The postoperative regulation of food and water intake was studied in rats with aspiration lesions to either the medial frontal or orbital frontal projection fields of thalamic nucleus medialis dorsalis (prefrontal cortex). These projection fields proved functionally dissociable in that orbital frontal lesions impaired immediate postoperative regulation of food and water intake for up to 2 wk., while medial frontal lesions produced finickiness. Neither lesion affected response to cellular dehydration or recovery from extended deprivation. These data are consistent with data from rhesus monkeys with prefrontal lesions and differ from animals with lateral hypothalamic lesions.

Animals↗