Food wresting and dodging: Strategies used by rats (Rattus norvegicus) for obtaining and protecting food from conspecifics.

We describe two previously undocumented stereotyped behaviors used by group-housed laboratory rats to obtain and protect food. Rats in social groups with limited access to food will attempt to obtain food by wresting it away from each other. To gain food, a rat will approach a feeding rat from behind, walk along its side, and then attempt to seize the food that it holds. To protect the food, the victim dodges laterally away from the approaching rat. The dodge effectively positions the robber to the rear and gives the victim time to continue eating. Contralaterally directed dodges take two general forms: One type involves a body turn and rear leg step that carries the rat about 19 cm in an arc of about 175° contralateral to the robber; the food is held in the forepaws. The second type involves a body turn and rear leg step that carries the rat in a longer arc; the food is transferred to the mouth and then back to the forepaws. Wresting attempts and dodges made by male and female rats are not different. The wrester–dodge relation can be used as a laboratory paradigm for the study of features of social dominance, for the investigation of the neural substrate of orienting behavior, and for investigating other aspects of social behavior or parasitic behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compensatory changes in striatal dopamine neurons following recovery from injury induced by 6-OHDA or methamphetamine: A review of evidence from microdialysis studies.

Reviews microdialysis experiments by E. Casta?eda et al (1989, in press), T. E. Robinson and I. Q. Whishaw (1987, 1988), and Robinson et al (1990) involving the association between recovery from dopamine (DA) depletion and normalization of extracellular DA. Data suggest that the 3 behavioral outcomes (sparing, recovery, and loss of function) associated with DA depletion may be related to differences in the ability of the residual population of DA neurons to maintain extracellular concentrations of DA; this effect may vary with lesion size. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats with fimbria-fornix lesions can acquire and retain a visual-tactile transwitching (configural) task.

The idea that the hippocampus is essential for acquisition and retention of a transwitching (configural) problem is evaluated with a visual-tactile task. The task requires the rats to pull up a string of one of two sizes for food, as signalled by room lighting conditions. Rats received cathodal fimbria-fornix lesions either prior to or after learning the task. Rats with fimbria-fornix lesions were unimpaired in acquisition or retention. The results do not support the position that the hippocampal formation is essential for the acquisition and retention of a transwitching configural problem. The result is discussed in relation to the configural theory of hippocampal function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the reduction of dodging in mice: A comparison of food wrenching and dodging in rats (Rattus norvegicus) and mice (Mus musculus).

Rats attempt to steal food from conspecifics by approaching them from the side to wrench the food from the victims' paws, but victims dodge laterally away to protect their food. Given the pervasive necessity of obtaining food, it might be expected that the behaviors of food wrenching and dodging would be common to many animals, but this idea has not been examined. In the present study, food wrenching and dodging were compared in Long-Evans and Sprague-Dawley rats (Rattus norvegicus) and out-crossed CDF1 and inbred C57b mice (Mus musculus). Mice stole food using a strategy very similar to that of rats, but they did not dodge in an open field test and dodged less in a home cage test and ran away or fought more than rats. There were no strain differences in rats, but C57b mice dodged less than CDF1 mice. Given that dodging is a component not only of food defensive behavior but also of play, sexual, and aggressive behavior, the species and strain difference may be a marker (or a key element) of changes in social behaviors that have occurred since the evolutionary separation of rats and mice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Can male decorticate rats copulate?

28 hooded sexually experienced or naive male rats, subjected to neocortex removal or neocortex plus hippocampus removal, were paired with female rats for up to 180 days and compared with 14 control rats with respect to success and latency to impregnate the female. All of the controls and half of the brain-damaged Ss successfully impregnated females at least once. Success was not correlated with lesion type or presurgical experience. The brain-damaged Ss took longer to impregnate the females than did controls. Since the ablations were extensive, more than 95% of the neocortex in many Ss, results show that decorticate rats can copulate. Presumably the intact subcortical structures are sufficient for male copulation, but cortical structures in some way facilitate rapid female impregnation. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Progressive atrophy of pyramidal neuron dendrites in autoimmune MRL-lpr mice

The autoimmune-prone MRL-lpr substrain of mice develop an autoimmunity-associated behavioral syndrome (AABS) which resembles in many respects the behavior of animals exposed to chronic stress. The present study examined whether these mice show changes in the morphology of neuronal dendrites, as found in animals exposed to chronic stress. A modified Golgi-Cox procedure was used to visualize the dendrites of pyramidal neurons in the parietal cortex and in the CA1 hippocampal field of 5-week and 14-week old MRL-lpr mice and MRL + / + controls. Reduced dendritic branching and length, and an up to 20% loss of dendritic spines were observed in parietal and hippocampal pyramidal neurons of MRL-lpr mice at both ages. In the parietal cortex, there was an age-dependent potentiation in the reduction of basilar, but not apical, dendrite branching and length, as well as in the loss of spines on basilar segments. Loss of spines in the hippocampus followed an age-related course for apical but not basilar dendrites. Moreover, compared to age-matched controls, brain weight was smaller in MRL-lpr mice at 14 but not 5 weeks of age. Considering that dendritic atrophy becomes more extensive when autoimmune disease is florid in MRL-lpr mice, it is proposed that immune/inflammatory factor(s) produce dendritic loss. Reduced dendritic complexity may represent, at least in part, a structural basis for the altered behavioral profile of MRL-lpr mice.     

Bilateral cutaneous stimulation of the somatosensory system in hemidecorticate rats.

In Exp I with 12 male Long-Evans hooded rats, small adhesive stimuli were attached to the forelimbs of hemidecorticate Ss, and the latencies to contact and to remove each stimulus were recorded. Neglect of the contralateral (C) stimulus lasted 2–3 days. Thereafter, the ipsilateral (I) stimulus was removed first, followed immediately by the C stimulus. This I sensorimotor bias lasted several months. Further analysis with unremovable tactile stimuli provided evidence for true extinction. During the 1st 2 postoperative weeks, Ss ignored the stimulus on the C limb and persisted in their attempts to remove the I stimulus. A key feature of the extinction was its complete reversibility. Simply by adjusting the sensory fields occupied by the C and I stimuli (specifically, by increasing the C/I ratio), the sensorimotor bias was totally shifted to C. During recovery, the size of the C/I ratio necessary to reverse sensorimotor asymmetry gradually decreased. In Exp II, asymmetrical sensorimotor behavior and amphetamine-induced circling were examined in 3 additional groups of 6 hemidecorticate rats (and 6 anesthetized controls), which were given their initial behavioral tests at 2, 12, or 52 postoperative weeks. This confirmed Exp-I findings and controlled for practice. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An analysis of feeding and sensorimotor abilities of rats after decortication.

Within 24 hrs after surgery, decorticate adult male Long-Evans and Sprague-Dawley rats ate mash, unfamiliar foods, dry chow, and tap and sugar water from a spatula (Exp I). They sampled nonnutritive substances but rejected noxious substances. Although initially anorectic, given mash, they arrested weight loss as early as 2–4 days. Throughout survival they had oral manipulatory difficulties with chewing food, lapping water, and trimming toenails. They showed sensorimotor neglect (Exp II) to objects touched to the body, but did orient when touched on the head. When lifted from a surface, decorticate Ss showed limb and postural abnormalities; when dropped, righting responses were impaired. Ss showed stereotyped reflexive responses to surfaces and became trapped on platforms and in alleys. The range of abnormalities, from simple acts of chewing to more complex behaviors of orienting and escaping traps, showed that Ss were impaired to such an extent that they would not survive in any but the simplest environment. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal activity, behavior, self-stimulation, and heart rate during electrical stimulation of the lateral hypothalamus.

Observed hippocampal electrical activity in relation to behavior elicited by stimulation of the lateral hypothalamus in 30 male hooded rats. Rhythmical slow activity (RSA) was always present during walking, rearing, digging, bar pressing, and other presumably "voluntary" movements, but at low stimulation intensities it was often absent during licking, chewing, face washing, and other presumably "automatic" movements. At higher stimulation intensities, Ss became hyperactive and RSA was almost continually present. No relation was found between RSA and heart rate or licking movements. An ascending hypothalamic system may require hippocampal participation in the control of voluntary movements, but hippocampal participation may not be required for the control of more automatic movements. (30 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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

Successive tests reexamined the grooming, swimming, and eating behaviors of 20 decorticate male Long-Evans rats by evoking the behaviors in various circumstances (stimulus conditions). Ss showed normal-length grooming sequences during spontaneous home cage grooming; when grooming was elicited by removing them from their home cage and soaking their fur by a brief swim, grooming sequences were shorter. In cold water (18°C), Ss swam well and with exaggerated vigor and frequently inhibited forelimb movements; in warm water (37°C), they swam poorly and paddled with all 4 limbs. To eat small pieces of food, Ss sat up and used 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 ones. They also improve with practice in some tasks but not in others. In order to elucidate the role of the cortex in control of motor behavior, it is considered necessary to obtain "behavior profiles" of each behavior by testing the animals repeatedly and under widely varying test conditions. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)