Amygdala lesions do not impair shock-probe avoidance retention performance.

The present experiment used the shock-probe paradigm, a procedure usually used to assess anxiolytic processes, to assess memory in amygdala-lesioned rats. Rats were placed in a chamber that contained a probe protruding from 1 of 4 walls and were kept there for 15 min after they contacted the probe. For half the rats, the probe was electrified (2 mA). Four days later, sham or neurotoxic amygdala lesions were induced. Retention performance was assessed 8 days later by measuring the latency to contact the probe and the number of contact-induced shocks. The results indicated that, although shock-naive amygdala-lesioned rats were impaired on the 2nd shock-probe test, shock-experienced amygdala-lesioned rats were not. These data indicate that the memory of a shock experience, as indexed with a shock-probe avoidance response, is spared in rats with large amygdala lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perirhinal cortex lesions impair simultaneous but not serial feature-positive discrimination learning.

The role of the perirhinal cortex in discriminative eyeblink conditioning was examined by means of feature-positive discrimination procedures with simultaneous (A-/XA+) and serial (A-/X→A+) stimulus compounds. Lesions of the perirhinal cortex severely impaired acquisition of simultaneous feature-positive discrimination but produced no impairment in serial feature-positive discrimination. The results suggest that the perirhinal cortex plays a role in discriminative eyeblink conditioning by resolving ambiguity in discriminations with overlapping stimulus elements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial temporal lesions in monkeys impair memory on a variety of tasks sensitive to human amnesia.

Relative to 3 unoperated controls, 4 cynomolgus monkeys with conjoint bilateral lesions of the hippocampus and amygdala were impaired on 4 tests of memory—delayed retention of object discriminations, concurrent discrimination, delayed response, and delayed nonmatching to sample. In 3 of the tasks, relatively long-delay intervals between training and test trials were used, and in 2 tasks, distraction was introduced during the delay intervals. The severity of the impairment increased with the length of the delay, and distraction markedly increased the memory impairment. For 1 task given on 2 occasions (delayed nonmatching to sample), the severity of the impairment was unchanged over 1.5 yrs. It is concluded that monkeys with medial temporal lesions constitute an animal model of human amnesia and that the 4 tasks used in the present study appear to constitute a sensitive and appropriate battery that could be used in other studies of the neuroanatomy of memory functions in the monkey. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal lesions do not impair negative patterning: A challenge to configural association theory.

According to configural association (CAS) theory (R. J. Sutherland and J. W. Rudy; see record 1989-38933-001), an intact hippocampus is required for rats to solve learning problems that are based on "configural" processes. This theory identifies the negative patterning discrimination as a critical example of this type of problem. Rudy and Sutherland (see record 1990-03930-001) reported disruption of negative patterning following hippocampal formation damage produced by intracranial infusion of a mixture of kainic acid?+?colchicine (KA?+?COL). Acquisition of negative patterning was assessed in rats with hippocampal damage produced by KA?+?COL compared with rats with more selective ibotenate lesions of hippocampus. Neither group showed impaired negative patterning relative to controls. A transfer test provided evidence that all groups used configural processes to solve the problem. Thus contrary to CAS theory, the hippocampus is not an important substrate for the operation of configural processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhinal cortex lesions impair simultaneous olfactory discrimination learning in rats.

Previous studies have found that combined lesions of the perirhinal and entorhinal (PRER) cortical areas do not impair, and in fact may facilitate, acquisition of successive olfactory discriminations. The present study sought to determine the effect of PRER lesions on the acquisition of simultaneous olfactory discriminations. Rats (N?=?24; 9 PRER-lesioned, 15 sham-operated controls) were trained on a single simultaneous olfactory discrimination; PRER-lesioned animals were dramatically and persistently impaired in acquisition of the discrimination relative to sham-operated subjects. These data are consistent with the view that, in concert with the hippocampus, these cortical regions participate in the encoding of relations among multiple extant stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus equivalence after inferior temporal lesions in monkeys.

Trained 4 monkeys with inferior temporal (IT) lesions and 4 unoperated monkeys to discriminate pairs of objects and then tested for transfer (i.e., stimulus equivalence) after the original discriminanda were made larger or smaller, rotated, or presented as 2-dimensional projections. Both groups of Ss transferred equally well to the discriminanda altered in size or orientation, but only unoperated Ss transferred to the 2-dimensional representation. Findings fail to support the possibility that IT lessions may impair shape constancy. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cynomolgus monkeys do not develop tolerance to opioids.

Trained 8 cynomolgus and 2 rhesus monkeys to press a lever for food reinforcement. Ss were then catheterized so that drugs or saline could be infused. Three doses of hydromorphone and 6 interdose intervals were studied. Hydromorphone infusions initially suppressed leverpressing for food in both species. The rhesus monkeys acquired tolerance to these sedative effects after 14 exposures to the opioid. However, the cynomolgus monkeys failed to acquire tolerance after more than 100 exposures. Naloxone challenge elicited withdrawal symptoms from the rhesus monkeys but not from the cynomolgus monkeys. This differential response to sustained opioid administration in these closely related species suggests that a genetic mechanism may underlie tolerance to and physical dependence on opioids. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Fimbria-Fornix lesions impair spatial working memory but not cognitive mapping.

Evaluated the relative merits of 2 theories of hippocampal function, the cognitive mapping theory, and the working memory theory. 49 albino male rats were tested in a series of maze tasks that varied in memory requirements. In Exps I and III, which required cognitive mapping but not working memory, Ss with fimbria–fornix lesions reached stable levels of performance that were as accurate as those of controls, and they also performed accurately during transfer tests, demonstrating that they used a cognitive mapping strategy to solve the discrimination. In Exp II, which required working memory, Ss with fimbria–fornix lesions performed at chance levels during all of postoperative testing, and they distributed their choices randomly between the correct and the incorrect goals. Results are consistent with the predictions of the working memory but not the cognitive mapping theory. Additional analyses examined the nature of a transitory impairment exhibited by Ss with fimbria–fornix lesions in 2 tasks that did not require working memory. Postoperatively, the performance of the Ss with lesions was initially impaired but recovered to normal levels with a time course similar to that seen during preoperative acquisition. Results require an extension of the working memory theory of hippocampal function, and discussion is focused on the possibility of a temporary retrograde amnesia following fimbria–fornix lesions and the distinctions between different types of memory abilities. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

P3-like brain waves in normal monkeys and in monkeys with medial temporal lesions.

The human brain produces a characteristic electrical response to relevant events that occur unexpectedly. Recent reports have suggested that a prominent part of this event-related brain potential—the P3 wave—may be related to memory functions and may arise from activity within the medial temporal lobe, especially the hippocampus. The latter idea was tested by means of epidural recordings of brain waves in monkeys. Responses to deviant auditory stimuli bore a close resemblance to P3 waves recorded from human subjects under comparable conditions. Monkeys with bilateral lesions of the medial temporal lobe still produced P3-like brain waves, which indicates that medial temporal brain structures are not critical for their generation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of spatial discrimination deficits following frontal and parietal lesions in monkeys.

Gave 40 rhesus monkeys dorsolateral prefrontal, posterior parietal, or inferotemporal lesions. 4 additional Ss served as unoperated controls. Ss then received 2 forms of spatial discrimination training, based on body position ("egocentric" cues) and on the position of an external referent ("allocentric" cues), respectively. On the former, a place discrimination reversal, frontal Ss were impaired but not parietals. On the latter, a landmark discrimination reversal, parietal Ss were impaired but not frontals; this result was also obtained on a test involving distance discrimination without reversal. Finally, the inferotemporals but not the frontals or parietals were impaired on a nonspatial object discrimination reversal. Results suggest that the 2 modes of spatial orientation, egocentric and allocentric, are related to frontal and parietal mechanisms, respectively. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal lesions impair memory for location but not color in passerine birds.

The effects of hippocampal complex lesions on memory for location and color were assessed in black-capped chickadees (Parus atricapillus) and dark-eyed juncos (Junco hyemalis) in operant tests of matching to sample. Before surgery, most birds were more accurate on tests of memory for location than on tests of memory for color. Damage to the hippocampal complex caused a decline in memory for location, whereas memory for color was not affected in the same birds. This dissociation indicates that the avian hippocampus plays an important role in spatial cognition and suggests that this brain structure may play no role in working memory generally. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning in monkeys after combined lesions in frontal and anterior temporal lobes.

Assigned 19 rhesus monkeys to 2 unoperated control groups, a group sustaining prefrontal lobectomy, and a group with prefrontal lobectomy plus removal of the anterior temporal neocortex. Ss were compared on delayed response ability, as well as on the ability to make object discriminations and to form learning sets. The combined frontal-temporal lesion did not increase the delayed response deficit produced by frontal damage alone, but it significantly increased difficulty in making 2-object discriminations and apparently also depressed oddity discrimination performance. Ability to form learning sets was not impaired in either lesioned group. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ventromedial hypothalamic lesions produced by gold thioglucose do not impair induction of NPY mRNA in the arcuate nucleus by fasting

The motorneuron degeneration (mnd) mutation causes one of the few late-onset progressive neurodegenerations in mice; therefore, the mnd mouse is a valuable paradigm for studying neurodegenerative biology. The mnd mutation may also model human neuronal ceroid lipofuscinosis (NCL) or Batten disease. mnd maps to the centromeric region of mouse chromosome 8, which likely corresponds to portions of human chromosomes 13,8, or 19; we note that the chromosome 13 portion maps close to a region thought to contain the human Type V NCL locus. We have identified candidate genes for the mnd locus from human chromosomes 13,8, and 19, and we are mapping these genes in the mouse to determine their proximity to the mutated locus and to refine the comparative human-mouse map in this area. A candidate gene from human chromosome 13 is LAMP1, which encodes lysosomal membrane protein 1. We found that LAMP1 in the mouse lies within the region of the mnd mutation. Therefore, we sequenced LAMP1 cDNAs from homozygous mnd mice and unrelated wildtype C57BL/6 mice. We find no differences between the two cDNA species in the regions examined, and expression analysis shows a similar LAMP1 protein distribution in wildtype and mutant mice, suggesting that an abnormal accumulation of material within normal lysosome structures is unlikely to be the pathogenetic mechanism in the mnd mouse.     

Area postrema lesions impair flavor-toxin aversion learning but not flavor-nutrient preference learning.

Rats with lesions of the area postrema. (APX) or sham lesions were trained to associate flavored solutions with positive or negative postingestive consequences. The APX rats were similar to controls in learning preferences for flavors paired with concurrent intragastric infusions of maltodextrin or corn oil and for a flavor paired with delayed maltodextrin infusions. In contrast, the APX rats displayed impaired aversion learning for flavors paired with toxic drug treatments (lithium chloride infusion or methylscopolamine injection). The aversion learning deficit ranged from mild to total, depending on training procedures. These findings confirm the important role of the area postrema in flavor-toxin learning but provide no evidence for its involvement in flavor-nutrient conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the perirhinal cortex do not impair integration of visual and geometric information in rats.

Rats with lesions of the perirhinal cortex and a control group were required to find a platform in 1 corner of a white rectangle and in the reflection of this corner in a black rectangle. Test trials revealed that these groups were able to integrate information regarding the shape of the pool and the color of its walls (black or white) to identify the correct location of the platform. A clear effect of the perirhinal cortex lesions was, however, revealed using an object recognition task that involved the spontaneous exploration of novel objects. The results challenge the view that the perirhinal cortex enables rats to solve discriminations involving feature ambiguity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term effects of selective neonatal temporal lobe lesions on learning and memory in monkeys.

Rhesus monkeys with neonatal damage to either the medial temporal lobe or the inferior temporal cortical area TE, and their normal controls, were reassessed in visual habit formation (24-hour intertrial interval task) and visual recognition (delayed nonmatching to sample [DNMS]) at 4–5 years of age and then tested on tactile and spatial DNMS. Results on the two visual tasks were the same as those obtained when the monkeys were under 1 year of age. Specifically, early medial temporal lesions, like late lesions, left habit formation intact but severely impaired recognition memory. Furthermore, the memory deficit extended to the tactile and spatial modalities. By contrast, early damage to TE, unlike late damage to it, yielded only mild deficits on both visual tasks and had no effect on tactile or spatial DNMS. Compensatory mechanisms that promote substantial and permanent recovery thus appear to be available after neonatal TE lesions but not after neonatal medial temporal lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Angiographic patterns of splenic lesions following blunt trauma. An experimental study in monkeys

Splenic angiography was performed before and after graded blunt trauma to the spleen in 15 monkeys. In 9 of these, followup angiography could be performed in week or more later. Pronounced spasm of the splenic artery and leakage of contrast medium into the peritoneal cavity were found to imply a serious prognosis. Local reversible spasm of arterial branches can cause transient defects in parenchymal filling. Larger defects corresponding to hematoma, extravasation of contrast medium, and displacement of vessels may be compatible with good primary prognosis. If, however, these signs indicate that the lesion is of sufficient magnitude and has a peripheral location there is a risk that extensive bleeding will occur. So-called delayed ruptures never occurred in this study.     

Visual discrimination impairments in rhesus monkeys with combined lesions of superior colliculus and striate cortex.

To test the hypothesis that posterior inferotemporal cortex and the adjoining foveal prestriate cortex contribute to vision by combining inputs from striate cortex and superior colliculus, a total of 18 rhesus monkeys with combined collicular and partial striate lesions, foveal prestriate-posterior inferotemporal lesions, or subcortical lesions (controls) were tested in a series of visual discrimination tasks. Prestriate-inferotemporal lesions, unlike striate-collicular lesions, consistently impaired retention of a pattern discrimination and produced partial impairments in a size discrimination test. However, prestriate-inferotemporal and striate-collicular lesions produced similar deficits in pattern discrimination learning and no deficits in brightness discrimination learning. The deficits of the striate-collicular monkeys are discussed with regard to the "input-combining" hypothesis and alternative views. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dorsal hippocampal lesions impair blocking but not latent inhibition of taste aversion learning in rats.

The aim of the present experiments was to study the effect of nonselective electrolytic lesions of the rat dorsal hippocampus on 2 learning phenomena: the L. J. Kamin (1969) blocking effect and latent inhibition of taste aversion learning. Bilateral dorsal hippocampal lesions selectively impaired blocking induced by 1 saccharin-lithium chloride pairing previous to 1 serial compound (saccharin–cider vinegar)–lithium pairing, but lesions had no effect on latent inhibition of a saline aversion, induced by 6 saline preexposures, in the same group of animals. Moreover, dorsal hippocampal lesions did not affect latent inhibition of saccharin-conditioned aversion induced by 1 or 6 preexposures. It is argued that blocking and latent inhibition of taste aversion learning do not share a common neural mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)