Pup and object carrying by maternally and nonmaternally behaving female albino rats (Rattus norvegicus).

Pups and toys (rubber dropper-bulbs) were presented to 48 nulliparous and 10 lactating female albino Sprague-Dawley rats either together (choice test) or in separate tests. Regardless of their reproductive state, Ss fell into 3 categories according to their behavior: (a) Postpartum Ss as well as virgins that behaved maternally picked up pups much faster than toys, carried more pups than toys, gathered young into the nest, but scattered toys outside the nest site. (b) Virgins that carried young spontaneously but did not show any other elements of maternal behavior picked up pups and toys after equal latencies, carried pups and toys in equal numbers, and scattered both the pups and the toys about the floor of the cage. (c) Virgins that ignored pups did not carry young, but they did show high levels of toy carrying and dispersed the toys about the cage. It is proposed that the term retrieving should be limited, by its definition, to those cases in which the objects are carried to a specific location. Thus, pup retrieval was seen exclusively in Ss that showed maternal behavior (i.e., crouching, pup licking), because only these Ss carried pups consistently to the nest. On the other hand, pup carrying shown by nonmaternally behaving Ss and toy carrying shown by all Ss are both cases of scattered, nondirected object carrying, rather than retrieving. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activation of Fos-like immunoreactivity in the medial preoptic area and limbic structures of maternal and social interactions in rats.

Examined the number of cells showing Fos-like immunoreactivity (Fos-lir) in the brains of hormonally primed parturient rat dams immediately following their 1st behavioral interactions with pups. Groups were exposed to newborn pups (pup), adult conspecifics (social), or a new food (food), or they were left alone in cages (control/isolate) for a 1-hr period. Rats were then killed, and their brains were prepared for immunohistochemical detection of Fos-lir. Rats in the pup group had higher numbers of cells showing Fos-lir within the medial preoptic area (MPOA) nuclei than did the social, control/isolate, and, marginally, food groups and higher levels of Fos-lir in a number of amygdaloid nuclei (medial and cortical) and in cingulate and somatosensory cortices than did control/isolate or food groups. Fos-lir in amygdala did not differ between pup and social groups. There were also group differences in Fos-labeling in the olfactory bulbs, with the pup group showing the highest densities. These results show elevated expression of Fos-lir in brain structures that were activated during the expression of maternal behavior, including the olfactory structures, amygdala, and MPOA. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hormonal influences during the ontogeny of maternal behavior in female rats.

Two experiments involving a total of 223 female and 46 male CD rats examined the influence of ovarian hormones on sensitization latencies at different periods in ontogeny and on the olfactory inhibition of maternal behavior, maternal nest building, and pup retrievals from a T-maze extension of the home cage. Ss ovariectomized before puberty failed to show a decline in sensitization latencies when tested 3.5 wks postoperatively; Ss ovariectomized during and after puberty had significantly longer latencies than sham operates when tested 8 or more weeks later. Interrupting olfaction by intranasal ZnSO? reduced latencies. Ovariectomized Ss built less compact maternal nests, and fewer retrieved pups from a –T maze than did sham operates. Estradiol benzoate prior to pup exposure significantly reduced sensitization latencies of ovariectomized Ss, increased the proportion retrieving pups from the maze, and tended to increase maternal nest ratings. Findings indicate that ovarian hormones, primarily estrogen, exert a tonic facilitatory influence on maternal responsiveness, beginning at puberty. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of basolateral amygdala lesions on neophobia, learned taste aversions, and sodium appetite in rats.

Reports results of 8 experiments with a total of 327 male Sprague-Dawley rats. Lesions to the basolateral amygdala produced permanent impairment in Ss' ability to learn a taste aversion. When lesions were administered after Ss had already learned an aversion, there was complete loss of the aversion. Ss with amygdala lesions also had a diminished neophobic response when presented with a novel solution and showed a more generalized aversion to water after a sucrose-sickness trial. Whether a solution was novel or familiar affected the learning of an aversion for controls more than it did for Ss with amygdala lesions. Ss with amygdala damage also showed less sodium appetite than normals in response to desoxycorticosterone acetate injections. These results indicate that rats with amygdala lesions have deficits in recognizing the significance of stimuli. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective retrieving by maternal and nonmaternal female rats.

Conducted an investigation to learn whether nonpregnant female rats made maternal by exposure to pups would act more like nonmaternal females than lactating mothers. Ss were 32 nulliparous females of the Charles River CD strain and an additional number of females that provided pups for inducing maternal behavior in virgins and in testing all Ss in pup vs toy tests. The behavior toward a pup and a toy was studied in 1 group of nonmaternal virgins, 2 groups of maternal virgins, and 1 group of lactating mothers, during 7 daily 5-min tests. Measures of the frequency and duration of retrieving-related behavior and analysis of behavioral sequences in relation to the pup or toy showed that pup-induced maternal virgins more closely resemble the lactating mothers than nonmaternal virgins. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sparing of function after infant lesions of selected limbic structures in the rat.

The effects, in adult Ss, of limbic lesions produced in infancy were studied in 273 male Wistar rats using weight gain and conditioned emotional response (CER) and condtitioned avodiance response (CAR) acquisition as the critical measures. Ss received bilateral lesions of the amygdala, septum, postventral hippocampus (PH) anterodorsal hippocampus (AH), or frontal cortex either as infants (at 10 days of age) or as adults (at 60 days). Normal and anesthetized control groups were also used. Frontal cortical lesions, AH lesions, and anesthetization had no effect on weights or on CER and CAR acquisition. Both infant and adult amygdala and septal lesions significantly disrupted normal weight gain. Adult-accrued amygdala and PH lesions significantly retarded CER acquisition, and adult septal and PH lesions significantly facilitated CAR acquisition. Infant-accrued amygdala lesions significantly facilitated CAR acquisition, and infant PH lesions had no effect on either task. Results are interpreted to mean that the observed task-specific recovery in early-operated Ss may have been due to some form of functional reorganization. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of the frustration effect and the partial reinforcement extinction effect after limbic lesions in rats.

20 male albino Wistar rats with control operations, 20 with lesions in the amygdala, and 20 with lesions in the septal area were tested in a double runway. Results show that after omission of reward in the 1st goal box on 50% of the trials, control and septal Ss showed a frustration effect. Lesions in the amygdala eliminated this effect. Subsequent tests of extinction behavior indicated that Ss with control operations and Ss with damage in the amygdala showed a partial reinforcement extinction effect whereas Ss with septal lesions did not. It is concluded that frustration effects and extinction effects have independent neural substrates. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in urinary odors produced by young laboratory rats (Rattus norvegicus).

Examined the responses of 75 primiparous Long-Evans rat dams and 20 nonmaternal Long-Evans females to male and female pup urine in 3 experiments. Investigatory sniffing of male and female pup urine deposits by maternal Ss was compared in a series of simultaneous choice tests given at 3-day intervals between Day 2 and Day 17 postpartum. Male urine was consistently preferred. Introduction of male but not female pup urine to the nest was found to significantly elevate maternal licking of anogenital regions of pups. Thus, urine from pups of various ages contains sex-identifying odors that differentially elicit spontaneous maternal interest. The odor of male urine may provide a sufficient stimulus to account for the greater anogenital licking that males of this species normally receive. Nonmaternal, naive, adult Ss behaved like maternal Ss, preferring male urine in the choice test, which indicates that the maternal condition of a dam is not necessary either for the olfactory discrimination or for the male odor preference. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decline of maternal behavior in the virgin and lactating rat.

Gave to sensitized virgins and postpartum lactating mothers, both exhibiting maternal behavior, donor litters that increased in age by 1 day, for 28 days, starting at the onset of maternal behavior. Ss were 18 Charles River rats. Each day Ss were tested for maternal behavior with 4-8 day old pups. Maternal care (i.e., nursing-crouching, retrieving, nest building, and licking and maternal withdrawal, rejection, and prevention of nursing were recorded. After the 9th day, Ss were also tested with the progressively older pups 10-28 days of age with which they were living. Virgins and lactating mothers showed generally similar patterns of maternal care although some differences were found, and they declined in maternal behavior toward the older pups in a similar manner. Maternal behavior did not decline in tests with younger pups. Results are interpreted as supporting the hypothesis that the decline as well as the maintenance of maternal behavior postpartum is nonhormonally mediated. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hormonal dissociation of limbic lesion effects on shuttle box avoidance in rats.

In a study with a total of 57 male albino Holtzman-derived rats, Ss with septal or hippocampal lesions showed facilitated acquisition of a shuttle box avoidance response compared to normal controls. Ss with septal lesions were also highly resistant to extinction compared with normal Ss. When the same lesion effects were examined in hypophysectomized Ss, the Ss with septal lesions continued to show facilitated performance, and Ss with hippocampal lesions performed no differently than nonoperated controls. These findings are consistent with the hypothesis that the facilitated avoidance performance found in rats with hippocampal lesions is attributable to lesion-induced changes in hypophyseal activity, but similar changes induced by septal lesions are not. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural correlates of species-typical behavior in the Syrian golden hamster.

The behavior of a total of 84 Syrian golden hamsters with lesions to the medial frontal cortex (MF), orbital frontal cortex (OF), cingulate cortex (CING), posterior cortex (POST), hippocampus (HPC), septum (SEPT), or amygdala (AMYG) was compared with that of 12 control hamsters in a variety of situations, including weight regulation, food hoarding, nest building, neophobia, bait shyness, sex preference, territorial aggression, and shock-induced aggression. The behavior of Ss with OF or AMYG lesions was doubly dissociable from the behavior of Ss with MF, HPC, or SEPT lesions. The OF and AMYG lesions produced severe weight losses, and all OF Ss were aphagic and adipsic and subsequently died. The HPC, MF, and SEPT lesions severely disrupted hoarding and nest building, whereas the other lesions affected neither. None of the lesions impaired the development of bait shyness when a sucrose solution was paired with sickness, but both AMYG and SEPT lesions may have produced a mild impairment when an NaCl solution was paired with sickness. Only amygdala lesions produced consistent behavioral changes on the social tests. Neither cingulate nor posterior cortical lesions significantly altered behavior on any of the tests. Results support the idea that different forebrain regions can be functionally dissociated by using behavioral tests that are biologically significant. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual experience, unilateral cortical lesions, and lateralization of function in rats.

Measured the effects of early visual experience and later unilateral neocortical lesions on the behavior of 30 male hooded Long-Evans rats in an open-field, 17-arm spatial maze and on a visual field or perimetry test. 30 Ss were formed into 6 groups—3 light-reared (LR) and 3 dark-reared (DR)—of 5 Ss each in order to receive right-, left-hemisphere, or sham neocortical lesions. The comparison of behavior observed in the open field revealed that LR Ss with right-hemispheric lesions were more active and reared more than any of the other Ss. On the radial-maze task, in which 8 of 17 arms were baited, all Ss with lesions performed less effectively than did sham-operated Ss. The effect of the lesions was significantly greater for LR than for DR Ss. Perimetry testing revealed that, although the lesioned Ss did react to stimuli throughout their visual field, some contralateral neglect was evident in both LR and DR Ss; the lesions had a greater impact on orientation behavior of LR Ss, however. No evidence emerged of any functional asymmetry following the unilateral cortical lesions. Findings are discussed in terms of V. H. Denenberg's (1981) hypothesis about cerebral and functional asymmetry in the rat. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of the functions of coprophagy in juvenile rats.

Five experiments examined possible functions of the ingestion of maternal anal excreta by juvenile rats. Ss were 24 recently parturient Long-Evans rats and their 440 pups. No strong support was found for hypotheses suggesting that (a) maternal excreta serves as a major transition diet from mother's milk to solid food, (b) ingestion of maternal excreta influences pup diet selection at weaning, or (c) ingestion of maternal excreta is a necessary condition for inoculation of pups with enteric bacteria. Some support was found for the hypothesis that maternal excreta can serve as a short-term emergency food supply for rat pups after weaning. It is proposed that pup ingestion of maternal anal excreta may not be a functionally meaningful unit of behavior in preweaning rats. Allocoprophagy may be one facet of a broader pattern of oral exploration in which functional significance resides. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Limbic lesions and the energizing, aversive, and inhibitory effects of non-reward in rats.

Tested 30 male albino Wistar rats with bilateral lesions in the amygdala, septum, hippocampus, stria terminalis, and fornix on a multiple reinforcement schedule in which barpressing in one component was associated with VI reinforcement (S+) and the other with extinction (S–). Responses on a 2nd lever turned off S– for 5-sec periods during the extinction component. All groups, with the exception of Ss with amygdaloid lesions exhibited behavioral contrast. Ss with hippocampal or fornical lesions showed greater resistance to extinction. Response rates on the lever that turned off S– were higher after stria terminalis and septal lesions, whereas lower rates were obtained from Ss with amygdaloid lesions. It is concluded that amygdaloid lesions attenuate the energizing and aversive effects of nonreward, septal and stria terminalis lesions increase the aversive effects, and hippocampal and fornical lesions interfere with the inhibitory effects of nonreward. (French summary) (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immediate effect of septal area damage on DRL performance in the rat.

Investigated the immediate and long-term effects of septal area lesions on performance on a differential reinforcement of low rates (DRL) 10-sec schedule. Ss were 43 male albino rats. Septal area lesions produced immediate disruption of DRL responding in unanesthetized Ss, but cingulate area lesions or sham treatments did not. The induction of septal seizures without lesions produced only minimal disruption. For the first few testing sessions, Ss tested 7 days after receiving septal area lesions were indistinguishable in DRL performance from those tested immediately; the former, however, showed poorer recovery. It is concluded that neural or other changes requiring time to develop postoperatively are not essential to the disruption of DRL performance, but they may impede behavioral recovery. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental aspects of recovery of function following septal lesions in the infant rat.

In an experiment with 4 litters of Long-Evans hooded rats (14 pups/litter), 1/2 of each litter received septal lesions at the age of 7 days, and the remaining 1/2 received control operations (incision). Septal lesions in infant Ss resulted in hyperemotionality and altered open-field behaviors at the ages of 21, 42, 63, and 90 days. When Ss reached 90 days of age, their behavior was compared with that of normal adult rats and rats that had received septal lesions in adulthood. Measures of active avoidance, fixed-ratio responding, and social facilitation were collected for all groups. Results show that septal lesions in infancy or adulthood enhanced avoidance responding, fixed-ratio responding, and social behavior when compared with infant or adult controls. Failure to observe recovery of function was interpreted in terms of phylogeny and hierarchical cerebral organization. (26 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in spatial discrimination reversal learning between two inbred mouse strains following specific amygdaloid lesions.

Tested reversal learning for 2 groups of 85 male C57BL/6J and BALB/cJ mice following a bilateral lesion in either the basolateral, central, lateral, medial, or cortical nucleus of the amygdala. On the 2nd reversal, C57BL/6J Ss with a lesion in the lateral nucleus performed less well than intact controls and operated controls. The BALB/cJ Ss with a lesion in the cortical nucleus performed less well on the 1st reversal than these 2 control groups. Data indicate that effects of specific amygdaloid lesions on learning are not necessarily the same for all strains or stocks within a species, and that lesions simultaneously involving many nuclei may be of limited usefulness in understanding the relationship of the amygdala to reversal learning. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of reinforcement omission on rats with lesions in the amygdala.

Trained 12 male Wistar rats with bilateral lesions in the amygdala to barpress on an FI schedule of reinforcement. During test trials, when reinforcement was occasionally omitted, response rates of 12 controls increased in the subsequent interval, whereas lesioned Ss showed no significant change. In Exp II Ss received fixed-ratio reinforcement on 1 lever, which was followed by a time-out period and fixed-ratio reinforcement on a 2nd lever. Results indicate that after reinforcement was withheld Ss with damage in the amygdala did not increase responding in the subsequent time-out period, whereas controls showed significantly higher rates. Differential latencies to initiation of response after nonreinforcement were also found. The deficits following brain damage are attributed to a reduction in nonreinforcement-induced frustration. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retention of maternal behavior in nulliparous and primiparous rats: Effects of duration of previous maternal experience.

Lactating primiparous and nonlactating pup-induced maternal nulliparous female CD rats were given 1, 4, or 9 days of maternal experience with rat pups before they were isolated from the young. 25 days later, Ss were reexposed to 3–8 day old foster pups, and latencies to show maternal behavior in the home cage and a T-maze test were scored. In the home cage, the latencies of all nulliparous groups were shorter upon reinduction. Comparisons of primiparous and nulliparous groups revealed that primiparous females (1, 4, and 9 days combined) carried a pup, crouched, retrieved, and grouped the pups and built a good nest faster than did nulliparous females (combined groups). The number of behavioral differences between specific primiparous and nulliparous groups decreased as the length of prior maternal experience increased. In the T-maze, latencies to retrieve a pup were shorter in primiparous females. Results indicate that the processes underlying establishment of the long-term retention of short-latency maternal behavior in these groups may be comparable. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the medial and lateral striatum in the rat produce differential deficits in attentional performance.

Excitotoxic lesions of the medial frontal cortex and anterior cingulate cortex in rats have been shown to produce dissociable impairments on a reaction time visual attention (5-choice) task. Because these cortical areas project to the medial striatal region, the authors predicted similar deficits after lesions of this striatal area compared with the lateral area. Compared with sham-operated controls, rats with quinolinic acid-induced medial striatal lesions showed all the behavioral changes associated with medial frontal cortex and anterior cingulate cortex lesions. In contrast, lateral striatal lesions produced profound disturbances in the performance of the task. Control tests showed little evidence of gross deficits in either group of rats in terms of motivation, locomotor function, or Pavlovian appetitive conditioning. These data suggest that the medial and lateral striatum have contrasting roles in the control of instrumental responding related to the primary sources of their cortical innervation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)