Estradiol induces hypothalamic progesterone receptors but does not activate mating behavior in male hamsters (Mesocricetus auratus) before puberty.

This study investigated pubertal changes in neural and behavioral responses to estradiol. Gonadectomized pre- and postpubertal male hamsters (Mesochcetus auratus) were treated with 0.00, 0.05, 0. 10, or 0.2 mg estradiol and tested 1 week later for sexual behavior with a receptive female. Estradiol activated behavior in postpubertal, but not prepubertal, males. In contrast, estrogen receptor α (ERα) and progesterone receptor (PR) immunoreactivity in forebrain nuclei that mediate mating behavior was similar in pre- and postpubertal males. Thus, absence of a behavioral response before puberty is not associated with reduced levels of steroid receptors. Because estradiol induced PR in prepubertal males these data also suggest that ERα is functional before puberty. Therefore, gonadal steroids facilitate male reproductive behavior only after as-yet-unidentified developmental processes occur during puberty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial preoptic lesions disrupt parental behavior in both male and female California mice (Peromyscus californicus).

California mice (Peromyscus californicus) are monogamous and naturally biparental, making them an ideal species in which to study the neural basis of paternal behavior. A male or female from each male-female pair was given an electrolytic or sham lesion in the medial preoptic area (MPOA), an area known to be critical for the expression of maternal behavior in rats, and retested for parental responsiveness. MPOA-lesioned males and females showed significantly longer latencies to show parental behavior and spent significantly less time near pups, sniffing pups, and licking pups than sham-lesioned mice. However, MPOA lesions did not reduce time spent hovering over pups. The results suggest that the neural mechanisms mediating paternal behavior are similar to those mediating maternal behavior in this species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contributions of endothermy to huddling behavior in infant Norway rats ( Rattus norvegicus) and Syrian golden hamsters ( Mesocricetus auratus).

Infant Syrian golden hamsters (Mesocricefus auratus) do not exhibit endogenous heat production before 3 weeks of age and do not huddle effectively during cold exposure, gaining little thermoregulatory benefit from the presence of multiple littermates. In contrast, infant Norway rats (Rattus norvegicus) produce heat endogenously and are effective at maintaining elevated body temperatures by huddling. Therefore, the ineffective huddling of infant hamsters may be due to the absence of endogenous heat production. The huddling behavior of infants in mixed huddles of 8-day-old hamsters and weight-matched 4-5-day-old rats was observed to explore this possibility. The results indicate that hamsters, even when cold, effectively gain access to heat-producing rats, supporting the idea that endothermy contributes to the behavior of huddling by providing heat to each individual and thermal stimuli to other infants to support aggregation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of Fos-like immunoreactivity in the brains of parent ring doves (Streptopelia risoria) given tactile and nontactile exposure to their young.

Neuronal activation was examined by fos immunohistochemistry in ring doves (Streptopelia risoria) reunited with their young after overnight separation. In an initial study, squab-exposed parents showed more fos immunoreactivity (ir) in the preoptic area (POA) and lateral hypothalamus (LH) than squab-deprived parents. In a 2nd study, parents allowed free access to young and those separated from young by a wire mesh partition showed more fos-ir in the POA, LH, and lateral septum than box-exposed controls. Contact with young also increased fos-ir in the medial preoptic nucleus and bed nucleus of the stria terminalis, but noncontact exposure did not. Conversely, nontactile squab exposure stimulated more fos-ir in the POA than did free access to young, which suggests POA involvement in appetitive aspects of parenting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Short-term contact elicits heterospecific behavior discrimination of individual odors in mound-building mice (Mus spicilegus).

The authors used a habituation-dishabituation procedure to test the ability of male mound-building mice (Mus spicilegus) to discriminate individual odors from males of another species of mouse. Male mound-building mice failed to spontaneously discriminate individual odors from Mus musculus musculus males, a natural competitor. After 24-hr contact with a male of one of the M. musculus subspecies (M. m. musculus or M. m. domesticus), experienced M. spicilegus males discriminated the individual odors of unfamiliar males of the same subspecies. These results confirm that discrimination of individual chemosignals is not confined to olfactory cues of a single species and provide new information about the effect of short-term contact on discrimination of individual odors across species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bilateral neurotoxic amygdala lesions in rhesus monkeys (Macaca mulatta): Consistent pattern of behavior across different social contexts.

[Correction Notice: An erratum for this article was reported in Vol 122(4) of Behavioral Neuroscience (see record 2008-09788-025). In the aforementioned article, Table 1 on page 256 was incorrect. The correct table is printed in the erratum.] Although the amygdala has been repeatedly implicated in normal primate social behavior, great variability exists in the specific social and nonsocial behavioral changes observed in nonhuman primates with bilateral amygdala lesions. One plausible explanation pertains to differences in social context. This study measured the social behavior of amygdala-lesioned and unoperated rhesus monkeys (Macaca mulatta) in 2 contexts. Monkeys interacted in 4-member social groups over 32 test days. They were previously assessed in pairs (N. J. Emery et al., 2001) and were therefore familiar with each other at the beginning of this study. Across the 2 contexts, amygdala lesions produced a highly consistent pattern of social behavior. Operated monkeys engaged in more affiliative social interactions with control partners than did controls. In the course of their interactions, amygdala-lesioned monkeys also displayed an earlier decrease in nervous and fearful personality qualities than did controls. The increased exploration and sexual behavior recorded for amygdala-lesioned monkeys in pairs was not found in the 4-member groups. The authors concluded that the amygdala contributes to social inhibition and that this function transcends various social contexts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual discrimination by heifers (Bos taurus) of their own species.

Species discrimination has been described in several taxa but rarely in domestic animals. In contrast to wild species, domestic species present a great phenotypic variety. This study investigated whether 10 Prim'Holstein heifers (Bos taurus) could discriminate images of cows from images of other domestic animals. The experiment was based on simultaneous discrimination. Responses were obtained through instrumental conditioning using a food reward. In Experiment 1, the reward was associated with a cow face and, in the reversal learning task, with faces of other domestic species. The results showed that in both tasks, cows were able to reach the criterion in few sessions. Therefore, despite great phenotypic variety (a cognitive challenge) cows were able to visually discriminate their own species from other domestic species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Bilateral neurotoxic amygdala lesions in rhesus monkeys (Macaca mulatta): Consistent pattern of behavior across different social contexts": Correction.

Reports an error in "Bilateral neurotoxic amygdala lesions in rhesus monkeys (Macaca mulatta): Consistent pattern of behavior across different social contexts" by Christopher J. Machado, Nathan J. Emery, John P. Capitanio, William A. Mason, Sally P. Mendoza and David G. Amaral (Behavioral Neuroscience, 2008[Apr], Vol 122[2], 251-266). In the aforementioned article, Table 1 on page 256 was incorrect. The correct table is printed in the erratum. (The following abstract of the original article appeared in record 2008-03769-001.) Although the amygdala has been repeatedly implicated in normal primate social behavior, great variability exists in the specific social and nonsocial behavioral changes observed in nonhuman primates with bilateral amygdala lesions. One plausible explanation pertains to differences in social context. This study measured the social behavior of amygdala-lesioned and unoperated rhesus monkeys (Macaca mulatta) in 2 contexts. Monkeys interacted in 4-member social groups over 32 test days. They were previously assessed in pairs (N. J. Emery et al., 2001) and were therefore familiar with each other at the beginning of this study. Across the 2 contexts, amygdala lesions produced a highly consistent pattern of social behavior. Operated monkeys engaged in more affiliative social interactions with control partners than did controls. In the course of their interactions, amygdala-lesioned monkeys also displayed an earlier decrease in nervous and fearful personality qualities than did controls. The increased exploration and sexual behavior recorded for amygdala-lesioned monkeys in pairs was not found in the 4-member groups. The authors concluded that the amygdala contributes to social inhibition and that this function transcends various social contexts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of lesions of the vomeronasal and olfactory nerves on garter snake (Thamnophis sirtalis) responses to airborne chemical stimuli.

The roles of the main (MOS) and accessory (AOS) olfactory systems of garter snakes in response to airborne chemicals were investigated. Preoperatively, all snakes responded to airborne odors with increased tongue-flick rate and duration. Postoperatively, sham-operated snakes responded to airborne odors with increased tongue-flick rates, but snakes with main olfactory nerve cuts failed to respond to the odors, and snakes with vomeronasal nerve cuts responded to nonprey odors only. Preoperatively, exposure to earthworm odor produced more frequent and shorter duration tongue-flicks during locomotion compared with exposure to water. Postoperatively, only sham-lesioned snakes exhibited differential responding to earthworm odors. This study demonstrates that the MOS is critical for the initiation of tongue-flick behavior in response to airborne odors and that discrimination of odors with biological significance requires a functional AOS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions centered on the medial amygdala impair scent-marking and sex-odor recognition but spare discrimination of individual odors in female golden hamsters.

The medial amygdala (Me) has been implicated in various social behaviors that depend on chemosensory cues, but its precise role in discriminating and learning social odors is not known. Female golden hamsters (Mesocricetus auratus) received electrolytic lesions of the Me or sham surgery and were tested for their ability to (a) discriminate between odors of individual males in a habituation–discrimination task, (b) show preferences for male over female odors in a Y maze, and (c) scent-mark in response to male and female odors. All females discriminated between scents of individual males. In contrast, Me lesions eliminated female preferences for male odors in a Y maze. Females with Me lesions also showed a substantial reduction in vaginal marking and virtually no flank marking in response to odors. Thus, the Me in female hamsters is critical for differential investigation of opposite-sex odors and for scent-marking behavior but is not involved in discrimination between odors of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrasting object-based and texture-based accounts of same/different discrimination learning with trial-unique stimuli.

Same/different discrimination is a classic task for investigating relational learning in animals. Recent research suggests that pigeons can learn a trial-unique same/different discrimination, which eliminates the opportunity to memorize the training items (Brooks & Wasserman, 2008). The authors conducted three tests to elucidate the role that item-based comparison plays in this trial-unique discrimination. In the first, the authors tested the possibility that pigeons’ same/different discrimination was based on textural features of the displays by creating a single, unitary texture from same and different displays; pigeons failed to discriminate these unitary textural displays. In the second, the authors varied the number of items (mosaics) in the display and the authors reproduced the characteristic decline in performance associated with fewer items. In the third, the authors systematically increased the area of two mosaics to closely match the area occupied by increasing numbers of mosaics; the results obtained with two small items persisted even when the size of the mosaics was increased. These results clearly show that pigeons’ same/different discrimination was based on object-level variability and not on other properties of the displays. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory discrimination of aliphatic odorants in South African fur seals (arctocephalus pusillus).

Using a food-rewarded, two-choice, instrumental conditioning paradigm we assessed the ability of South African fur seals, Arctocephalus pusillus, to discriminate between members of five chemical classes of aliphatic odorants presumed to differ in their abundance in the marine chemical environment. We found that the fur seals were able to distinguish between 24 of the 25 odor pairs presented and thus have a well-developed ability to discriminate between structurally related odorants, that aliphatic n-acetic esters were significantly more poorly discriminated by the fur seals than aliphatic n-aldehydes and n-carboxylic acids, and a lack of correlations between discrimination performance and structural similarity of odorants in terms of differences in carbon chain length. These results suggest that the sense of smell may play an important and hitherto underestimated role in regulating the behavior of fur seals. Further, they support the notion that regular connections between the perceived quality of odorants and their molecular structural properties are not a general phenomenon but appear to be odorant class- and species-specific. Our data support the hypothesis that a species' chemical environment may affect its olfactory capabilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparative analysis of the categorization of multidimensional stimuli: I. Unidimensional classification does not necessarily imply analytic processing; evidence from pigeons (Columba livia), squirrels (Sciurus carolinensis), and humans (Homo sapiens).

Pigeons (Columba livia), gray squirrels (Sciurus carolinensis), and undergraduates (Homo sapiens) learned discrimination tasks involving multiple mutually redundant dimensions. First, pigeons and undergraduates learned conditional discriminations between stimuli composed of three spatially separated dimensions, after first learning to discriminate the individual elements of the stimuli. When subsequently tested with stimuli in which one of the dimensions took an anomalous value, the majority of both species categorized test stimuli by their overall similarity to training stimuli. However some individuals of both species categorized them according to a single dimension. In a second set of experiments, squirrels, pigeons, and undergraduates learned go/no-go discriminations using multiple simultaneous presentations of stimuli composed of three spatially integrated, highly salient dimensions. The tendency to categorize test stimuli including anomalous dimension values unidimensionally was higher than in the first set of experiments and did not differ significantly between species. The authors conclude that unidimensional categorization of multidimensional stimuli is not diagnostic for analytic cognitive processing, and that any differences between human’s and pigeons’ behavior in such tasks are not due to special features of avian visual cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Conditioning During Amygdalar Inactivation on Training-Induced Neuronal Plasticity in the Medial Geniculate Nucleus and Cingulate Cortex in Rabbits (Oryctolagus cuniculus).

This study addressed the amygdala's role in avoidance conditioning in rabbits (Oryctolagus cuniculus). Intra-amygdalar muscimol infusion before 60 or 120 conditioning trials blocked training-induced neuronal activity (TIA) in the medial geniculate (MG) nucleus. One hundred twenty trials with muscimol blocked TIA permanently, during conditioning with muscimol and then later without muscimol; 60 trials with muscimol blocked TIA only when muscimol was present. Cingulate cortical TIA was blocked only when muscimol was present. Behavioral learning did not occur with muscimol, but later learning was facilitated (i.e., savings occurred) in rabbits initially given muscimol plus training. These results define the time period wherein amygdalar processes initiate TIA in the MG nucleus and suggest that distinct forms of amygdalar processes induce TIA in the MG nucleus and cingulate cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decreased density of amygdaloid parvalbumin-positive interneurons and behavioral changes in dystonic hamsters (Mesocricetus auratus).

The dtsz hamster represents a model of primary paroxysmal nonkinesiogenic dyskinesia in which dystonic episodes can be induced by stress and anxious stimuli. This disease is regarded as a basal ganglia disorder. In fact, a deficit of striatal interneurons could play a key role in the pathophysiology in dystonic hamsters. Because the involvement of limbic structures cannot be excluded so far, the density of parvalbumin-immunoreactive (PV+) interneurons was determined in the basolateral amygdala in the present study. Compared with nondystonic hamsters, the density of PV+ interneurons was moderately decreased in the dtsz mutant. The functional consequence of this finding was examined by behavioral analyses. Examinations in the elevated plus maze and in a modified open field failed to disclose an enhanced anxiety-related behavior in dtsz hamsters (Mesocricetus auratus). A lower acoustic startle response and a stronger habituation in mutant hamsters than in controls correlated with a decreased body weight. Interestingly, prepulse inhibition was absent in mutant hamsters. The latter finding suggests a disturbed sensorimotor gating that can be related to alterations in both the basal ganglia nuclei and in limbic structures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of discrimination and reversal learning for olfactory and visual stimuli in aged rats.

The present study investigated age-related differences in discrimination and reversal learning for olfactory and visual stimuli in 6-month and 24-month-old rats. Rats were trained to discriminate between two pseudo-randomly selected odors or objects. Once each animal reached a criterion on discrimination trials, the reward contingencies were reversed. Young and aged rats acquired the olfactory and visual discrimination tasks at similar rates. However, on reversal trials, aged rats required significantly more trials to reach the learning criterion on both the olfactory and visual reversal tasks than young rats. The deficit in reversal learning was comparable for odors and objects. Furthermore, the results showed that rats acquired the olfactory task more readily than the visual task. The present study represents the first examination of age-related differences in reversal learning using the same paradigm for odors and objects to facilitate cross-modal comparisons. The results may have important implications for the selection of memory paradigms for future research studies on aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of humidity on reproductive behavior in male and female zebra finches (Taeniopygia guttata).

Zebra finches (Taeniopygia guttata) are regarded as opportunistic breeders with reproductive behaviors mediated by short-term proximal environmental conditions. This article provides experimental evidence for the role of humidity in reproductive behaviors. Zebra finches were subjected to experimentally manipulated high levels of relative humidity. Males gathered more nest material and sang more. Females showed no relationship between humidity and gathering nest materials, egg laying, or changes in rates of vocalization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emergence of stereotypies in juvenile monkeys (Macaca mulatta) with neonatal amygdala or hippocampus lesions.

The emergence of stereotypies was examined in juvenile rhesus monkeys (Macaca mulatta) who, at 2 weeks of postnatal age, received selective bilateral ibotenic acid lesions of the amygdala (N = 8) or hippocampus (N = 8). The lesion groups were compared to age-matched control subjects that received a sham surgical procedure (N = 8). All subjects were maternally reared for the first 6 months and provided access to social groups throughout development. Pronounced stereotypies were not observed in any of the experimental groups during the first year of life. However, between 1 to 2 years of age, both amygdala- and hippocampus-lesioned subjects began to exhibit stereotypies. When observed as juveniles, both amygdala- and hippocampus-lesioned subjects consistently produced more stereotypies than the control subjects in a variety of contexts. More interesting, neonatal lesions of either the amygdala or hippocampus resulted in unique repertoires of repetitive behaviors. Amygdala-lesioned subjects exhibited more self-directed stereotypies and the hippocampus-lesioned subjects displayed more head-twisting. We discuss these results in relation to the neurobiological basis of repetitive stereotypies in neurodevelopmental disorders, such as autism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intracerebroventricular Self-Administration of Commonly Abused Anabolic-Androgenic Steroids in Male Hamsters (Mesocricetus auratus): Nandrolone, Drostanolone, Oxymetholone, and Stanozolol.

Previous studies by the authors have shown voluntary intracerebroventricular (icv) testosterone self-administration in hamsters (Mesocricetus auratus). Here, the authors compared icv self-administration of 4 anabolic steroids (drostanolone, nandrolone, oxymetholone, and stanozolol) at 0.1, 1.0, and 2.0 μg/μl, each for 8 days. Males (n=8/group) showed the highest levels of operant behavior for injectable steroids (drostanolone, nandrolone) compared with orally active androgens (oxymetholone, stanozolol). For nandrolone, responses on the active and inactive nose-pokes averaged 22.3 ± 4.6/4 hr and 10.7 ± 2.0/4 hr, respectively. Responding for drostanolone was similar. Males self-administering oxymetholone or stanozolol did not prefer the active nose-poke. These data demonstrate that injectable androgens are more reinforcing than oral steroids. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transfer Effects and Conditional Learning in Rats With Selective Lesions of Medial Septal/Diagonal Band Cholinergic Neurons.

The authors examined visual-spatial conditional learning with automated touchscreen tasks in male Long-Evans rats with selective lesions of medial septal/vertical limb of diagonal band (MS/VDB) cholinergic neurons produced by 192 IgG-saporin. Performance on a conditional task, in which 1 of 2 centrally displayed stimuli directed the rat to respond to an illuminated panel on the left or right, depended on training history: Control rats with experience on other visual tasks performed better than MS/VDB-lesioned rats with similar training histories, whereas this effect was reversed in naive rats. This difference appears to reflect transfer effects present in the control rats that are absent in the MS/VDB-lesioned rats. These findings may suggest that MS/VDB cholinergic neurons play a particular role in the transfer of behavioral experience and flexibility of application of behavioral rules in memory, rather than a role in conditional learning per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)