Similarity in the qualities of individual odors among kin and species in Turkish (Mesocricetus brandti) and golden (Mesocricetus auratus) hamsters.

In this investigation, the authors used habituation techniques to explore similarities and differences in the qualities of individual odors from hamsters. In Experiment 1, male Turkish hamsters (Mesocricetus brandti) treated flank-gland odors of 2 males from 1 litter as similar compared with the odor of a male from another litter, whether the odor donors were familiar or unfamiliar. At the same time, the Turkish hamsters discriminated between the subtle differences in the individual odors of their familiar brothers. In Experiment 2, male Turkish and golden hamsters (Mesocricetus auratus) treated the flank-gland odors of 2 unfamiliar, unrelated conspecifics as similar compared with the flank odor of a heterospecific individual. The results suggest that similarities in individual odors are related to genetic similarity of the odor donors. These similarities could provide a basis for different types of social recognition, including kin and species recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scent counter-marks: Specialized mechanisms of perception and response to individual odors in golden hamsters (Mesocricetus auaratus).

Scent counter-marking is a widespread phenomenon among mammals that is not well understood. Using a habituation paradigm, it was found that male golden hamsters (Mesocricetus auratus) exposed to partially overlapping scents of 2 females behaved on test trials as if they remembered the top scent but not the bottom scent. If the 2 females' scents did not overlap during exposure trials, males remembered both of them. Thus, if 2 individual scents partially overlap, hamsters (1) perceive which of the 2 scents was deposited most recently and (2) either remember the top scent and forget the bottom scent or attach greater significance to the top scent. These results indicate the existence of specialized perceptual and cognitive or motivational mechanisms that are used for interpretation and response to complex arrays of social odors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How golden hamsters (Mesocricetus auratus) discriminate top from bottom flank scents in over-marks.

Using a habituation-discrimination paradigm, the authors investigated what cues male golden hamsters (Mesocricetus auratus) use to determine the top and bottom positions in flank gland over-marks. A difference in the ages of 2 hamsters' marks did not, by itself, produce differential memory or evaluation of the 2 scents. A spatial configuration of marks suggestive of an overlap was sufficient for the apparently overlapping scent to be remembered or valued more than the apparently underlying scent. Cues from the overlap of 2 hamsters' marks were also sufficient. These results, consistent with those previously found for responses to hamster vaginal scent over-marks, suggest that hamsters use similar cues to analyze scent over-marks that are different in chemical composition and in social functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Causes of scent marking in female golden hamsters (Mesocricetus auratus): Specific signals or classes of information?

Odor-elicited scent marking is common among mammals, but the proximate causes of marking are not well understood. Scent marking by female hamsters in response to 8 different male odors was investigated. Two odors (flank, mouth) increased flank marking and 2 (flank, rump) increased vaginal marking; in the latter case the effects of flank and rump odors were additive. Two odors (feces, urine) decreased flank marking but did not affect vaginal marking; other odors (foot, ear, ano-genital) had no influence on either scent-marking behavior. Results show that scent marking by females is influenced by a limited number of male odors, suggesting specific effects of particular odors. Classes of information (such as sexual identity) were not relevant causes of scent marking, as some odors containing such information were effective but others were not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The teleradiology system and changes in work practices

Five minutes of global ischemia in gerbil results in delayed hippocampal CA1 neuronal degeneration, which is accompanied by working memory impairments and hyperactivity in novel environments. In this study, postischemic activity was characterized in familiar and in novel environments to determine whether hyperactivity was due to impaired spatial habituation or another form of motor hyperactivity. This study also determined whether 6-h delayed hypothermia, which reduces CA1 neuronal injury, would attenuate functional impairments. Gerbils were subjected to 5 min of normothermic ischemia or sham operation 2 days following implantation of brain temperature probes. One of two ischemic groups was cooled (>48 h) starting at 6-h postischemia. Locomotor activity in a familiar cage was measured for 6 days while activity in three novel environments was intermittently measured on days 4, 5 and 6. Open field behavior and working memory in a T-maze were also assessed. Untreated ischemia caused marked hyperactivity in the familiar cage on day 1, which reverted to near-normal by day 2. Nonetheless, these gerbils showed hyperactivity during novel environment sessions on days 4-6. This maze behavior, which predicted hippocampal CA1 injury, was not due to different habituation rates nor baseline hyperactivity. Conversely, open field sessions on day 8 revealed ischemic habituation rate deficits. Ischemia also impaired working memory in the T-maze. Delayed hypothermia, which reduced neuronal loss in the CA1 sector to 12% from 81%, reduced all functional impairments. Ischemic gerbils quickly developed spontaneous locomotion hyperactivity that returned to near-normal after 1 day. This motor hyperactivity did not explain the elevated activity found with delayed testing in novel environments. Regardless, only the open field test on day 8 revealed a habituation-like deficit.     

Perception of scent over-marks by golden hamsters (Mesocricetus auratus): novel mechanisms for determining which individual's mark is on top

Hamsters preferentially remember or value the top scent of a scent over-mark. What cues do they use to do this? Using habituation-discrimination techniques, we exposed male golden hamsters (Mesocricetus auratus) on 3 to 4 trials to genital over-marks from 2 females and then tested subjects for their familiarity with these 2 scents compared with that of a novel female's secretion. Preferential memory for 1 of the 2 individuals' scents did not occur if the 2 marks did not overlap or did not overlap but differed in age, but it did occur if a region of overlap existed or 1 mark apparently occluded another (but did not overlap it). Thus, hamsters use regions of overlap and the spatial configuration of scents to evaluate over-marks. These phenomena constitute evidence for previously unsuspected perceptual abilities, including olfactory scene analysis, which is analogous to visual and auditory scene analysis.     

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)     

Female voles discriminate males' over-marks and prefer top-scent males

Scent over-marking is a common form of competitive advertisement among many species of mammals. Recent observations in golden hamsters, Mesocricetus auratushave suggested that individuals have specialized mechanisms for interpretation of and response to such over-marks. In this study, we examined whether meadow voles, Microtus pennsylvanicushave similar abilities. Female voles were first exposed to anogenital scent marks of two males and were then tested in a Y-maze for their preferences for whole-body odours of these two males. Experiments were run using a variety of configurations of scent marks during the exposure phase, but all experiments yielded consistent results. If the scent marks of the two males overlapped, females later preferred the whole-body odours of the male whose scent was on top; if the two scent marks did not overlap, females showed no preference. Females also preferred odours of familiar males over novel males, and preferred both top-scent and bottom-scent males over novel males. The results suggest that female voles can tell which individual's scent is on top in an over-mark and that they prefer this top-scent male, even though they know that both males' scents were present during the exposure phase. We suggest that these odour preferences reflect mate preferences and discuss possible reasons why females might prefer top-scent males.1997The Association for the Study of Animal Behaviour     

Supersmart mice: Surprising or surprised? Theoretical comment on Singer, Boison, M?hler, Feldon, and Yee (2007).

The glycine transporter (GlyT1) regulates levels of the neurotransmitter glycine, a coagonist of the N-methyl-D-aspartate receptor (NMDAR), and as such may represent a novel site for developing cognition-enhancing drugs. Genetically modified mice with reduced levels of GlyT1 have been generated to test this hypothesis. P. Singer, D. Boison, H. M?hler, J. Feldon, and B. K. Yee (see record 2007-13974-001) now show, through a spontaneous exploration task, that mice in which GlyT1 has been deleted, specifically in neurons in the forebrain, demonstrate enhanced object recognition memory. Whereas both control and mutant mice show a preference for a novel object over a familiar object 2 min after the initial presentation of 1 of the objects, only the mutant mice show a preference for the novel object when tested after a 2-hr delay. The longer-lasting habituation displayed by the GlyT1 mice is consistent with a role for glycine/NMDAR-dependent synaptic plasticity in supporting a nonassociative, short-term memory trace of a recently experienced stimulus. This short-term habituation process may be independent of associative learning mechanisms and may be best described by A. R. Wagner's (1981) sometimes opponent process model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory for individuals: Hamsters (Mesocricetus auratus) require contact to develop multicomponent representations (concepts) of others.

In humans, individuals recognize other individuals by numerous types of independent information, such as the quality of the voice, appearance of the face, smell, gait, and posture. Humans also have integrated memories of others--that is, in response to a face or a voice the individual is recognized by name and other information about that individual is remembered. In many nonhuman species, individual recognition also occurs. Although observational studies suggest that individuals of some nonhuman species may be able to use several different cues for individual recognition, little experimental proof for this is available. Golden hamsters have at least 5 individually distinctive odors and they develop integrated, multi-odor memories (concepts) of familiar individuals, as shown by across-odor habituation experiments. Little is known, however, about the conditions that are necessary to develop such integrated memories. In these experiments we investigated what kinds of experiences were necessary for male hamsters to develop multiodor memories of females. The results show that exposure to all of the odors of another individual was not sufficient to develop such multiodor memories but that physical contact between the subjects and stimulus animals was necessary. Multiodor representations were developed after interactions with anesthetized individuals, confirming the finding that physical contact was important but also showing that interaction with an awake, behaving individual was not necessary to form multiodor representations of other individuals. We are not aware of experimental proof for integrated, multicomponant memories in any other nonhuman species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preferences for familiar or novel toys: Effect of familiarization time in 1-year-olds.

32 Ss were tested in 2 familiarization procedures: Ss in one group were habituated to a stringent criterion on an array of 5 toys, whereas Ss in another group were familiarized but interrupted before habituation could be completed. In a subsequent 10-min test trial, the familiar array and a comparable novel array were available for both groups. In general, habituated Ss spent more time exploring the novel array, and the interrupted Ss, the familiar array. It is concluded that preference for novel and familiar stimuli is not an age-dependent phenomenon but instead depends on when stimuli are introduced during the habituation process. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative learning and recognition memory in alcoholic Korsakoff patients.

Association learning and recognition memory were examined in 8 male alcoholic Korsakoff patients (mean age 58 yrs), and in the following 4 groups of 10 men: non-Korsakoff alcoholics (mean age 59 yrs), nonalcoholic controls (mean age 64 yrs), younger alcoholics (mean age 36 yrs), and nonalcoholic controls (mean age 37 yrs). The tasks were modeled after those used for testing memory functioning in nonhuman primates. Association learning, defined as the ability to distinguish rewarded from equally familiar nonrewarded visual stimuli, was impaired in Korsakoff patients. Korsakoff patients also were impaired on recognition memory—the ability to discriminate familiar from novel items. Results support the view of loss of multiple memory functions in alcoholic amnesia. An effect of aging was indicated by differences in performance levels between younger and older groups of non-Korsakoff participants, although the latter were superior to the Korsakoff patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of frontal cortex in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Orbital/agranular insular (ORB/AI) cortex has been implicated in traditional olfactory learning tasks and social behavior but its precise role in discriminating-learning social odors is not known. Female golden hamsters received aspiration lesions of ORB/AI or dorsomedial (DM) frontal cortex 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, and (c) scent-mark in response to male odors. Lesioned females readily discriminated between scents of individual males. Neither lesion altered female preferences for male odors. Females with DM lesions showed increased levels of scent marking to male odors, but those with ORB/AI cortex lesions did not differ from controls. Thus, ORB/AI cortex does not appear to be critical for discrimination of odors of individuals or sex or for scent-marking responses based on these discriminations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competitive short-term and long-term memory processes in spatial habituation.

Exposure to a spatial location leads to habituation of exploration such that, in a novelty preference test, rodents subsequently prefer exploring a novel location to the familiar location. According to Wagner's (1981) theory of memory, short-term and long-term habituation are caused by separate and sometimes opponent processes. In the present study, this dual-process account of memory was tested. Mice received a series of exposure training trials to a location before receiving a novelty preference test. The novelty preference was greater when tested after a short, rather than a long, interval. In contrast, the novelty preference was weaker when exposure training trials were separated by a short, rather than a long interval. Furthermore, it was found that long-term habituation was determined by the independent effects of the amount of exposure training and the number of exposure training trials when factors such as the intertrial interval and the cumulative intertrial interval were controlled. A final experiment demonstrated that a long-term reduction of exploration could be caused by a negative priming effect due to associations formed during exploration. These results provide evidence against a single-process account of habituation and suggest that spatial habituation is determined by both short-term, recency-based memory and long-term, incrementally strengthened memory. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Long gradient of retrograde amnesia in mice: Continuity with the findings in humans.

560 male albino mice were given a single training trial and then received either sham treatment or 4 ECS treatments at hourly intervals at 1 of 7 times (1–70 days) after training. Retention was always tested 2 wks after treatment. Controls exhibited gradual forgetting with increasing retention intervals. Ss given ECS exhibited severe retrograde amnesia, which diminished as the interval between training and ECS increased from 1 to 21 days. ECS given 21–70 days after training had no effect on memory. The finding of long, temporally graded retrograde amnesia in mice establishes continuity between the results for laboratory animals and those for humans and indicates that the neural changes involved in the consolidation of memory can continue for a significant portion of the lifetime of a memory. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Environmental influences on flank marking and urine marking by female and male rats (Rattus norvegicus).

Sprague-Dawley rats (Rattus norvegicus) were observed in a familiar environment. In Experiment 1, a leader entered a clean chamber, and an opposite-sex follower entered the chamber next. Both sexes began to flank mark after several sessions. Males flank marked more, and females locomoted more, but both sexes urine marked and investigated objects equally often. Leaders and followers did not differ on any measure. In Experiment 2, we measured floor marks more precisely and manipulated the number of objects and the presence of scent marks. Flank marking was more frequent in the presence of conspecific urine but did not vary with the number of objects or the sex of the rats. More objects elicited more investigating and urine marking and produced fewer floor marks but increased the number of marks in the central area in relation to the periphery. The results indicate that rats' flank marking is behaviorally distinct from urine marking and differentially affected by environmental variables. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the hippocampal system in social odor discrimination and scent-marking in female golden hamsters (Mesocricetus auratus).

Female golden hamsters (Mesocricetus auratus) received aspiration lesions of the parahippocampal region (PARA) or electrolytic lesions of the fimbria-fornix (FNX) and were tested for their (a) discrimination between odors of individual males in a habituation-discrimination task, (b) preference for male over female odors, and (c) scent-marking in response to conspecific odors. Both lesion groups habituated to repeated presentations of a male's odor. However, only FNX females discriminated between scents of individual males, whereas PARA females did not. Neither lesion eliminated female preferences for male odors. Females with FNX lesions showed decreased levels of scent marking, but those with PARA lesions had more subtle deficits. Thus, the PARA, but not the subcortical connections of the hippocampus, is critical for discrimination of the odors of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal acetylcholine and habituation learning

Acetylcholine neurotransmission is considered to play a critical role in processes underlying behavioural activity, arousal, attention, learning, and memory. These functional attributions have largely been based on pharmacological findings. or data from brain damaged animals, and humans with neurodegenerative diseases, such as Alzheimer's disease. With the introduction of the in vivo microdialysis method it has recently become possible to monitor acetylcholine in the brain of the behaving animal, which allows to investigate its activity in specific behavioural tasks. With respect to learning and memory, one of the most elementary experimental paradigms is that of behavioural habituation, where the decrease of exploratory activity as a function of repeated exposure to the same environment is taken as an index of memory. We have used this paradigm to monitor hippocampal acetylcholine levels by means of in vivo microdialysis in rats, which were exposed to a novel open field and which were re-exposed to it on the following day (10 min each). The results show that exposure of rats to the novel environment led to increased extracellular levels of hippocampal acetylcholine which were positively correlated with exploratory behaviour. These cholinergic activations were larger than those of control animals which were handled like the experimental animals but which were not exposed to the open field. When re-exposing the experimental animals to the same environment, exploratory behaviour, but not cholinergic activation, was decreased. indicating habituation. In the subsequent 10 min, that is, when the animals where back in their home cages, cholinergic activity was still increased. The magnitude of increase was larger after re-exposure than after exposure to the novel open field. Finally, we differentiated the animals into "superior" vs "inferior" learners and found that the "superior" learners showed higher behavioural activation in the novel environment and stronger neurochemical responses, both. in the novel and familiar environment. Our data show that extracellular levels of hippocampal acetylcholine are not only elevated in relation to novelty and behavioural activation. but also during behavioural habituation. Furthermore, an inter-individual variability of cholinergic activation seems to exist which is related to individual differences in behavioural responsiveness to novelty. Such differences in cholinergic activity may be related to other known differences in hippocampal structure and function and may be important for previously reported inter-individual variabilities in sensation-seeking and related mnestic functions.     

Dishabituating long-term memory for gustatory habituation in the cabbage looper, Trichoplusia ni.

The gustatory rejection response of the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae), habituates to antifeedant compounds, allowing for the consumption of deterrent yet nontoxic plant materials. In the present study, we demonstrate that habituation to an antifeedant compound (quinine) persists through the moult between larval instars. As an indirect test of whether the memory was protein synthesis-dependent, we tested whether disrupting protein synthesis would block memory reconsolidation after a reminder. The results indicated that disrupting protein synthesis in habituated larvae following a reminder treatment (reexposure to quinine) eliminated the memory for habituation and restored the antifeedant properties of the quinine. We then examined whether the learned memory could be dishabituated and whether this would disrupt or eliminate long-term memory. We show that 6 hr after exposure to a novel/noxious stimulus (a second antifeedent, xanthotoxin) habituated larvae showed a transient dishabituation-like effect in which the quinine deterred feeding again. However, this effect did not permanently eliminate the habituation produced by the extended exposure as larvae tested 72 hr after xanthotoxin exposure again showed a willingness to consume the quinine treated leaves, indicating that the earlier habituation was still present. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning to form a spatial category of tight-fit relations: How experience with a label can give a boost.

Two experiments explored the ability of 18-month-old infants to form an abstract categorical representation of tight-fit spatial relations in a visual habituation task. In Experiment 1, infants formed an abstract spatial category when hearing a familiar word (tight) during habituation but not when viewing the events in silence or when hearing a novel word. In Experiment 2, infants were given experience viewing and producing tight-fit relations while an experimenter labeled them with a novel word. Following this experience, infants formed the tight-fit spatial category in the visual habituation task, particularly when hearing the novel word again during habituation. Results suggest that even brief experience with a label and tight-fit relations can aid infants in forming an abstract categorical representation of tight-fit relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)