Visual identification and memory in monkeys with circumscribed inferotemporal lesions.

Reports 2 experiments concerning the role of inferotemporal (IT) cortex in the processing of visual information, using a matching-to-sample procedure. Exp. I studied identification of visual stimuli at 3 levels of delay in 9 monkeys with anterior and posterior IT lesions and in normal controls. Exp. II examined proactive interference effects in the same groups. Results show that the 2 IT inferotemporal areas are involved in directing spatial and temporal attentional mechanisms in visual perception in complementary ways. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prestriate, inferotemporal, and superior temporal sulcus lesions on attention and gaze shifts in rhesus monkeys.

Studied the role of extrastriate cortical areas in selective attention in 12 rhesus monkeys. Ss learned a series of color–form pattern discrimination problems, with either color or form cues relevant. After each problem was mastered, correct behavior required a shift in attention (i.e., that responses be made to the previously irrelevant dimension). On some problems shifting attention required that the S maintain the same fixation; on other problems the color and form cues were separated in space, and the attention shift presumably required a shift in gaze. Matched groups of Ss with inferotemporal, prestriate, or superior temporal sulcus lesions, and normal controls, differed significantly in their ability to shift attention. Analyses of inferred stages in attention shift showed that different processes were disturbed in the 3 lesion groups. Results are discussed in terms of cortical substrates for "looking" and "seeing." (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of shape-discrimination training on the selectivity of inferotemporal cells in adult monkeys

Pretransplantation donor-specific transfusion (DST) can enhance allograft survival in man and animals. However, due to the lack of a specific marker to identify donor-reactive cells in vivo in man and normal (nontransgenic) animals, the underlying mechanism remains unknown. In this study, we use 2CF1 transgenic mice expressing a transgenic T-cell receptor (TCR) specifically recognizing Ld, a major histocompatibility complex (MHC) class I molecule, to delineate the role of DST in long-term skin allograft survival and its underlying mechanisms. Our main findings include: (1) in the absence of any other immunosuppressive treatment, a single dose pretransplantation infusion of viable splenocytes from an Ld+ donor is sufficient to induce permanent donor-specific skin allograft survival in 2CF1 anti-Ld TCR transgenic mice; (2) DST leads to a deletion of the majority (>60%) of donor-reactive T cells in the periphery of the recipient. However, deletion does not necessarily result in tolerance; (3) remaining donor-reactive T cells from DST-treated mice are fully responsive to Ld in vitro, and can suppress the antidonor response of naive T cells in vitro only when exogenous interleukin (IL)-4 is provided; and (4) the sera level of IL-4 in DST-treated tolerant mice is significantly increased. These results suggest that the generation of a subset of T cells with the potential to specifically inhibit antidonor responses, together with promotion of IL-4 production in recipients, may be important mechanisms for the induction and maintenance of antigen-specific tolerance.     

Effects of ventral putamen lesions on discrimination learning by monkeys.

Studied the effect of caudoventral putamen lesions on the postoperative retention of visual and auditory discriminations and on the postoperative acquisition of delayed alternation in 19 adolescent rhesus monkeys. Lesions in the caudoventral putamen and the adjacent white matter impaired performance of the visual but not the auditory and alternation tasks, indicating that this area is part of the neural circuitry underlying visual discrimination. However, the relative contribution to the deficit of the putamen damage and of the white matter damage could not be ascertained. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A decisional analysis of the effects of inferotemporal lesions in the rhesus monkey.

Modified signal detection procedures were used to analyze the effects of inferotemporal cortical resections in 2 experiments with a total of 14 adolescent rhesus monkeys. Results demonstrate (a) a severe difficulty in responding to differences in luminance; (b) a small but consistent change in sensitivity, which is attributed to an increased sensitivity to noise or a deficiency in the suppression of irrelevant aspects of the environment; and (c) an enhanced bias to respond to a nonrewarded stimulus (a lowering of criterion). This altered bias contrasts with the results obtained from limbic resections in a previous experiment, which produced a marked increase in bias to a rewarded contingency without influencing discrimination or detection. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual sensitivity following inferotemporal and foveal prestriate lesions in the rhesus monkey.

Performed ablations of inferotemporal (2 Ss) and of foveal prestriate cortex (2 Ss) in rhesus monkeys, impairing their visual learning. In order to determine if a sensory loss was associated with either lesion, the detectability of a light flash under scoptopic conditions was measured with a signal-detection procedure with the monkeys and with 2 male undergraduates. Neither lesion produced a decrease in sensitivity, although both produced the usual visual-learning deficit. Sensitivity of the human Ss was well within the limits of unoperated animals. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of septal and amygdaloid lesions on social behavior of the cat.

Tested 3 male and 43 female cats for social behavior and activity in an open field. Ss were then subjected to either septal or amygdaloid lesions and retested. Ss with septal lesions exhibited dramatic increases in social awareness as measured by the percentage of time they watched the Ss with which they were paired. Ss with amygdaloid lesions were twice as active postoperatively as they had been preoperatively. Both the enhanced social behavior of Ss with septal lesions and the enhanced activity with amygdalectomized Ss were independent of the locus of the lesion in the Ss with which they were paired. Results are discussed in terms of an alteration in disposition as opposed to an alteration of the response system after lesions of the septal region in the forebrain. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ventromedial hypothalamic lesions on hunger-motivated behavior in rats.

Previous studies show that lesions of the ventromedial hypothalamus (VMH) paradoxically increase food intake and decrease hunger motivation in the rat. In a series of experiments designed to examine this paradox, independent groups of VMH-lesioned, female hooded rats (N = 48) were tested on a VI schedule or were run in a straight alley to a food reward. Rate of food ingestion was also measured for all Ss. Performance of the VMH and control groups was compared at identical deprivation conditions defined in terms of preoperative base-line weights (80, 90, 100, and 110%). All test measures showed a significantly higher level of performance for VMH-lesioned Ss at the least severe deprivation conditions. Results suggest that the previously reported VMH paradox originated, in part, from inappropriate testing procedures and between-group comparisons. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective changes in foraging behavior following bilateral neurotoxic amygdala lesions in rhesus monkeys.

Across a variety of species, the amygdala appears to play a key role in the detection and avoidance of potential dangers (e.g., unfamiliar social partners, novel objects or contexts, potential predators, etc.). For many species, seeking out appropriate food sources and avoiding novel, distasteful or potentially tainted food is also a daily concern. Amygdala damage in nonhuman primates has been linked to increased willingness to select unfamiliar or unpalatable foods, as well as inedible items that intact animals typically reject. However, such findings have not always been consistent and have typically been observed in relatively restrictive, laboratory-based testing contexts. We evaluated the food choices of six adult male rhesus monkeys (Macaca mulatta) with bilateral, neurotoxic amygdala lesions and six age- and experienced-matched unoperated control animals. Each animal was able to forage freely in a large enclosure stocked with five preferred and five nonpreferred foods that changed locations each day. While both groups quickly selected palatable foods, monkeys with amygdala lesions consistently selected unpalatable foods that the unoperated control animals generally avoided. Even after repeated presentations of the unpalatable foods, the amygdala-lesioned monkeys failed to change their initial pattern of diminished avoidance. These results are consistent with a general role for the amygdala in danger detection and prevention of harm in the presence of novel or noxious stimuli, regardless of whether such stimuli are conspecifics, predators, objects or foods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lesions in the mesial frontal cortex on bimanual co-ordination in monkeys

The hypothesis was tested that the mesial frontal cortex, including the supplementary motor area, is engaged in bimanual co-ordination. Three monkeys, trained in a well-co-ordinated bimanual pull-and-grasp task, were subjected to unilateral or bilateral lesions of the mesial frontal cortex. With unilateral lesions, the deficit consisted in a delay in movement initiation of the contralateral arm. With a bilateral lesion, the deficit was more pronounced with marked bilateral delays in movement onset and slowing in reaching. However, in the three monkeys bimanual co-ordination at the moment of goal achievement remained intact with an excellent temporal co-variation of the two limbs. In the two unilateral cases, an adaptive strategy developed after a few sessions, either by catching up during reaching with the limb contralateral to the lesion (monkey M1) or by delaying movement initiation of the limb ipsilateral to the lesion (monkey M2). This outcome is discussed in terms of Lashley's principle of motor equivalence, i.e. invariant goal achievement with variable means. Bilateral lesions led to a transient and near-total impairment in movement self-initiation when all external cues were absent. It is concluded that in monkeys the mesial frontal cortex does not play a crucial role in bimanual co-ordination but rather in movement initiation, especially when sensory cues are absent.     

Effects of selective neonatal temporal lobe lesions on socioemotional behavior in infant rhesus monkeys (Macaca mulatta).

Normal infant monkeys and infant monkeys with neonatal damage to either the medial temporal lobe or the inferior temporal visual area were assessed in dyadic social interactions at 2 and 6 months of age. Unlike the normal infant monkeys, which developed strong affiliative bonds and little or no behavioral disturbances, the lesioned monkeys (each of which was observed with an unoperated control) exhibited socioemotional abnormalities and aberrant behaviors. The socioemotional changes predominated at 6 months of age and were particularly severe in monkeys with medial temporal lesions. In both the pattern and time course, the socioemotional deficits produced by the neonatal medial temporal lesions bear a striking resemblance to the behavioral syndrome in children with autism. Further analysis of these lesion-induced abnormalities in nonhuman primates may therefore provide insight into this debilitating human developmental disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of sequential preoptic and mammillary lesions on male rat sexual behavior.

Observed the sexual behavior of 52 male Sprague-Dawley rats prior to and following bilateral medial preoptic, unilateral medial preoptic, bilateral posterior preoptic, bilateral mammillary, and sham lesions. Bilateral medial preoptic lesions and mammillary lesions were made either simultaneously or sequentially within the same Ss in separate groups. Mammillary lesions had no effect on sexual behavior. Complete destruction of the medial preoptic area made prior to, simultaneous with, and following mammillary lesions completely abolished mating behavior. Partial destruction of the medial preoptic area increased mount and intromission latencies and slightly increased ejaculation latency. Results suggest that since there was no change in the postejaculatory-refractory interval, the medial preoptic area mediates sexual arousal but apparently is not involved in a copulatory-ejaculatory mechanism. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of posterior hypothalamic lesions on voluntary behavior and hippocampal electroencephalograms in the rat.

Postoperatively rated 126 male hooded rats with posterior hypothalamic lesions for somnolence. Ss were later subjected to formal testing. Ss showed deficits in initiating voluntary movements (walking, swimming) but more automatic movements seemed less impaired (grooming, scratching, tail rattling). Somnolent Ss swam in but could not escape cold water, but they could not swim in warm water. Initial somnolence was related to deficits in shock avoidance and the initiation of walking and swimming. Ss could learn a T maze to escape shock and an E maze to escape cold but not warm water. Hippocampal rhythmical slow activity frequency was reduced postoperatively; amplitude was normal. Results support the idea that the posterior hypothalamus is part of a trigger mechanism for the initiation and maintenance of voluntary movement. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of selective neonatal hippocampal lesions on tests of object and spatial recognition memory in monkeys.

Earlier studies in monkeys have reported mild impairment in recognition memory after nonselective neonatal hippocampal lesions. To assess whether the memory impairment could have resulted from damage to cortical areas adjacent to the hippocampus, we tested adult monkeys with neonatal focal hippocampal lesions and sham-operated controls in three recognition tasks: delayed nonmatching-to-sample, object memory span, and spatial memory span. Further, to rule out that normal performance on these tasks may relate to functional sparing following neonatal hippocampal lesions, we tested adult monkeys that had received the same focal hippocampal lesions in adulthood and their controls in the same three memory tasks. Both early and late onset focal hippocampal damage did not alter performance on any of the three tasks, suggesting that damage to cortical areas adjacent to the hippocampus was likely responsible for the recognition impairment reported by the earlier studies. In addition, given that animals with early and late onset hippocampal lesions showed object and spatial recognition impairment when tested in a visual paired comparison task, the data suggest that not all object and spatial recognition tasks are solved by hippocampal-dependent memory processes. The current data may not only help explain the neural substrate for the partial recognition memory impairment reported in cases of developmental amnesia, but they are also clinically relevant given that the object and spatial memory tasks used in monkeys are often translated to investigate memory functions in several populations of human infants and children in which dysfunction of the hippocampus is suspected. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Decisional analysis of the effects of limbic lesions on learning in monkeys.

Examined the hypothesis that behavior during discrimination learning and reversal is under control of 2 competing variables: the patterned cues to be discriminated and the noncontingent schedule of reinforcement. An experiment was conducted with 8 adolescent rhesus monkeys using a modified decision theoretic procedure. Results show that the 2 variables were operative and that noncontingent reinforcement produced a strong position bias against discriminating. This bias was quantitatively more easily overcome by normal Ss than by Ss with hippocampal-amygdala lesions though the strategy and tactics used were the same for both groups. It is concluded that the hippocampus and amygdala influence attention through mechanisms that regulate motivational bias. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of simultaneous and successive septal and amygdaloid lesions on social behavior of the rat.

Tested the social cohesiveness in an open field of 96 male hooded Long-Evans rats which had been subjected to either simultaneous or successive septal and amygdaloid lesions. Both the increased cohesiveness of Ss with septal lesions and the decreased cohesiveness of Ss with amygdaloid lesions were attenuated by the addition of the 2nd lesion. Ss with simultaneous lesions did not differ from controls. The 2 structures also were demonstrated to be reciprocally involved in mediating activity levels. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective hippocampal lesions and behavior: Effects of kainic acid lesions on performance of place and cue tasks.

Used kainic acid (KA; 1 and 2 μg/μl) lesions to study the effects of damage to the CA3 cell field and subiculum on performance of complex place and cue tasks by 54 male albino rats. In Exp I, neuroanatomical techniques determined the selectivity of the lesions. In a within-Ss design, Ss in Exp II were trained before the operations to run on an 8-arm radial maze with procedures that involved 2 kinds of learning (place and cue) and 2 memory functions (reference memory and working memory). Interrupting the intrahippocampal circuit by damaging the CA3 cell field with KA had minimal effects on performance; injections into subiculum and complete aspiration lesions of hippocampus resulted in impairments on the place but not the cue task. Only intraventricular injections of KA affected performance on both tasks. Results fail to support either the cognitive map or the working memory theory of hippocampal function. It is suggested that distant damage beyond the immediate area of injection complicates interpretation of the results and may limit the usefulness of KA as a neurotoxin in behavioral investigations. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abnormal social behavior in phenylketonuric monkeys.

Compared 4 rhesus monkeys, given a diet high in phenylalanine early in life, with 2 control groups in learning and social behavior when all Ss were on a normal diet. In comparison with the controls, the phenylketonuric (PKU) Ss were slow in learning a conditioned shock-avoidance task and showed extreme subnormal and inadequate social behavior. This gross incompetence in social interaction was reflected in the inconsistence of dominance rankings in a competitive food stituation and in the excessive hostility, excessive fear, and deficient play responses, both in the relatively unfamiliar playroom situation with familiar peers and in the home cage with unfamiliar stimulus monkeys. These PKU Ss were normal in more primitive, more reflexive behaviors, e.g., behaviors reflecting activity, simple social, environmental, and self-stimulating behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maternal behavior of socially deprived Rhesus monkeys.

The maternal behavior of 4 monkeys separated from their mothers at birth and denied opportunity to interact with other monkeys during the first 18 mo. of life is described and compared with the maternal behavior of 4 normal feral monkeys. The 4 socially deprived monkeys were grossly inadequate mothers, but the social development of the infants of these inadequate mothers was apparently normal. The maternal behavior of 5 additional mother-deprived monkeys is also described; 3 of these animals were inadequate and 2 adequate mothers. The 2 adequate mother-deprived mothers had early social experience; the 7 inadequate mothers did not. 3 inadequate mothers gave birth to a 2nd infant and exhibited normal maternal care. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ibotenic acid lesions of the nucleus accumbens on paced mating behavior in the female rat.

The present study investigated the role of the nucleus accumbens (NAcc) in paced mating behavior in female rats. A sexually receptive female rat will approach and withdraw from a sexually active male, thereby controlling the timing of the receipt of sexual stimulation (e.g., mounts, intromissions, ejaculations). In this study, ibotenic acid lesions in the NAcc core increased the likelihood that a female rat would withdraw from a male rat after a mount but did not affect contact return latency or sexual receptivity. lbotenic acid lesions in the NAcc shell did not affect paced mating behavior or sexual receptivity. The results suggest that the NAcc core plays a role in suppressing withdrawal behavior in response to less intense mating stimulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)