Changes In Exploratory Behavior Research Articles

Kinematics of Goal-Directed Arm Movements in Neglect: Control of Hand Velocity

Do patients with unilateral neglect exhibit direction-specific deficits in the control of movement velocity when performing goal-directed arm movements? Five patients with left-sided neglect performed unrestrained three-dimensional pointing movements to visual targets presented at body midline, the left and right hemispace. A group of healthy adults and a group of patients with right-hemispheric brain damage but no neglect served as controls. Pointing was performed under normal room light or in darkness. Time-position data of the hand were recorded with an opto-electronic camera system. We found that compared to healthy controls, movement times were longer in both patient groups due to prolonged acceleration and deceleration phases. Tangential peak hand velocity was lower in both patient groups, but not significantly different from controls. Single peak, bell-shaped velocity profiles of the hand were preserved in all right hemispheric patients and in three out of five neglect patients. Most important, the velocity profiles of neglect patients to leftward targets did not differ significantly from those to targets in the right hemispace. In summary, we found evidence for general bradykinesia in neglect patients, but not for a direction-specific deficit in the control of hand velocity. We conclude that visual neglect induces characteristic changes in exploratory behavior, but not in the kinematics of goal-directed movements to objects in peripersonal space.

Axon-sparing lesions of the medial nucleus of the amygdala decrease affiliative behaviors in the prairie vole (Microtus ochrogaster): behavioral and anatomical specificity.

The neural basis of affiliative behavior was examined in the prairie vole, a rodent that exhibits high levels of social contact and paternal behavior. In the first study, the axon-sparing excitotoxin N-methyl-D,L-aspartic acid (NMA) produced lesions in the basolateral nucleus of the amygdala or the corticomedial amygdala. Males with corticomedial lesions showed significantly less contact with a familiar adult female and a pup when compared with males with lesions of the basolateral nucleus or controls. This behavioral change was not associated with changes in exploratory behavior, motor function, performance in an olfactory task, fearfulness, physical well-being, or body temperature. In a second study, NMA lesions restricted to the medial nucleus also decreased paternal behavior. Neurons in the medial nucleus of the amygdala appear to be essential for the normal expression of paternal care in this species.

Maternal Discrimination and the Development of Sex Differences in Exploratory Behaviour in Infant Spiny Mice (Acomys Cahirinus)

The present paper reports sex differences in exploratory behaviour by infant Spiny Mice, Acomys cahirinus, that may, in part, be related to differences in maternal behaviour towards pups; like some other rodents, mother Acomys differentiate behaviourally between male and female pups. In Experiment 1 infant Acomys were allowed to explore a novel arena. This experiment showed that even by Day 3 (the day of birth = Day 1) female Acomys explored a novel environment more than males; they entered the arena sooner than males and spent more time in contact with a novel object. Experiment 2 showed that infant females were more active than males when observed in the home cage in the presence of their parents and made more approaches to the mother. Mothers, on the other hand, directed more licking behaviour towards males. Experiment 3 focused on the exploratory behaviour of individual pups in the presence of the mother. Given access to a large, complex arena, female pups explored more than males. The results also showed that mothers direct more of their social interactions towards sons than daughters, particularly when pups are about a week old. Some mothers appear to "direct" the movement of their offspring, by blocking their forward movement; this was done more often to male than to female pups. The data suggest that the previously observed changes in exploratory behaviour at this time, and the emergence of sex differences in exploration, may in part depend upon the mothers' reactions to pups by sex.

Perinatal diazepam exposure: Alterations in exploratory behavior and mesolimbic dopamine turnover

Perinatal exposure to diazepam has been shown to lead to alterations in motor activity and exploratory behavior in neonatal animals. Exploratory and locomotor behavior have been associated with changes in mesotelencephalic dopamine function. We have therefore examined the effects of perinatal diazepam administration on both exploratory behavior and mesotelencephalic dopamine turnover in the adult rat. Animals exposed to the benzodiazepine during the perinatal period engaged in significantly less exploratory behavior than did control subjects. The diazepam-induced alterations in behavior were developmentally specific: decreased exploratory behavior was observed at 90, but not 60, days of age. At 90 days of age, specific changes in dopamine turnover in diazepam-treated animals were restricted to mesolimbic (nucleus accumbens and ventral tegmental area) sites; alterations in dopamine turnover were not seen in other mesotelencephalic sites examined. The findings indicate that perinatal exposure to benzodiazepines leads to behavioral changes that are present in adulthood. These changes in exploratory behavior may be associated with alterations in mesolimbic dopamine function.

Changes in exploratory behaviour of hamsters following treatment with 8-hydroxy-2-(di- n-propylamino)tetralin

The influence of the centrally active 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on the exploration of objects was studied in hamsters, using a radioactographic method. This spatial paradigm allows the study of the behavioural expression of underlying locomotor and cognitive (attentional, mnemonic, representative) mechanisms. The drug was found to enhance the cognitive components of the exploratory process, i.e. object-oriented exploration, habituation and, under certain temporal conditions, response-to-change, in a dose-dependent manner. Since drug-injected animals did not differ from controls when no object was present, 8-OH-DPAT probably has no role in non-oriented exploratory activity. The influence of time was further investigated by varying the duration of successive trials and intertrial intervals. In situations where the durations were extremely shortened (3-min trials/3-min intertrial intervals), drug-treated subjects, in contrast to control ones, exhibited a 'hypernormal' time course: they explored and habituated. 8-OH-DPAT appears to increase the efficiency of exploration possibly via a positive effect on arousal or attention. 8-OH-DPAT is assumed to act on 5-HT somatodendritic autoreceptors, lowering 5-HT utilization in the hippocampus, which is the main structure implicated in spatial memory. This exploration paradigm could be employed in the study of time components of environmental adaptation without the need to restrain subjects.

Restraint-stress-induced changes in exploratory behavior appear to be mediated by norepinephrine-stimulated release of CRF

Exploratory behavior, measured by the time an animal spends investigating objects in a novel environment, has been shown to be sensitive to prior exposure of the animal to stressors. Using this paradigm, it was demonstrated previously that both corticotropin-releasing factor (CRF) and the alpha 2-adrenoreceptor antagonist, idazoxan, elicited stress-like decreases in exploratory behavior. Because an activation of cerebral noradrenergic systems is observed during stress, following intracerebroventricular (i.c.v.) administration of CRF, or following peripheral administration of idazoxan, the involvement of noradrenergic systems in the behavioral effect of restraint and CRF was examined. Inhibition of norepinephrine (NE) release using the alpha 2-agonist clonidine (25 micrograms/kg, i.p.) or the noradrenergic-selective neurotoxin DSP-4 antagonized the restraint-induced decrease in exploratory behavior. The combination of these 2 treatments completely prevented this effect of restraint. The alpha 1-receptor antagonist prazosin (200 micrograms/kg) also prevented the behavioral effect of restraint, whereas the alpha 1-agonist phenylephrine (50 or 100 ng, i.c.v.) decreased exploratory behavior. None of these treatments consistently altered locomotor activity as measured by the number of entries into the different compartments or the number of rears. These results implicate noradrenergic systems in the stress-related changes in this behavior, consistent with our parallel measures on the production of NE catabolites. Thus, both CRF and noradrenergic systems appear to be involved in the effect of restraint on exploratory behavior in this task. Neither DSP-4 nor prazosin had any effect on the CRF-induced decrease in exploratory behavior. However, the CRF antagonist alpha-helical CRF (20 micrograms, i.c.v.) reversed the decrease in exploratory behavior induced by phenylephrine. The most likely explanation is that the 2 systems act in tandem such that noradrenergic systems regulate the release of brain CRF via an alpha 1-adrenoreceptor. This arrangement parallels that involved in the release of hypothalamic CRF to activate the pituitary-adrenal axis. The implications of these results for research on stress-related behaviors and for the etiology of depression are discussed.

Neuroanatomical sites of action of 5‐HT3 receptor agonist and antagonists for alteration of aversive behaviour in the mouse

1. The cerebral topography of the action of diazepam and the action of the 5-hydroxytryptamine 5-HT3 receptor antagonists GR38032F and ICS 205-930 in attenuating an aversive response was studied in the mouse. 2. Mice which had been cannulated to allow drug injection into the dorsal and median raphe nuclei, the amygdala, nucleus accumbens or caudate-putamen were placed in a two compartment black (dimly illuminated) and white (brightly illuminated) test box. Measurements were made of the time spent, rearing and line crossings in the two sections and the latency of initial movement from the white to the black area. 3. The injection of diazepam (0.1-10 ng), GR38032F (0.01-1.0 ng) and ICS 205-930 (1.0-10 ng) into the dorsal raphe nucleus and amygdala, and the injection of diazepam (0.1-10 ng) into the median raphe nucleus, reduced an aversive response to the brightly illuminated white area, delaying the initial movement into the black section and increasing the time spent, rearings and line crossings in the white area. Concomitantly such activities were decreased in the black section. 4. The injection of the 5-HT3 agonist 2-methyl-5-hydroxytryptamine (0.1-10 ng) into the dorsal raphe nucleus and amygdala caused the opposite response, decreasing the time taken to move into the black section and increasing the time spent, rearings and line crossings in the black section, decreasing such activities in the white area. 5. The 5-HT3 agonist and antagonists showed little or no effect following injection into the median raphe nucleus and there were no changes in exploratory behaviour following their injection, or injection of diazepam, into the nucleus accumbens or caudate-putamen. 6. It is concluded that in the mouse the cerebral topography of action of GR38032F and ICS 205-930 in attenuating an aversive response follows that of diazepam in the dorsal raphe nucleus and amygdala but that diazepam may have additional effects mediated via the median raphe nucleus.

A corticotropin-releasing factor antagonist reverses the stress-induced changes of exploratory behavior in mice

Corticotropin-releasing factor (CRF) administered intracerebroventricularly (ICV) to rats and mice has been shown to elicit a variety of behaviors resembling those that occur in stress. In a novel multicompartment chamber, ICV CRF altered the behaviors in a manner closely resembling that observed following a period of restraint. In particular, 75 ng CRF ICV or 30–40 min restraint markedly reduced the time mice spent in contact with novel stimuli. ICV injections of a peptide antagonist of CRF, α-helical CRF 9–41, (ahCRF), reversed the effects of restraint on this measure. This effect of ahCRF was dose dependent, with a minimal effective dose of 10 μg. Other behavioral measures appeared normal, and ahCRF did not significantly alter the stimulus-contact time in unrestrained mice. These results provide strong evidence to support the hypothesis that endogenous CRF may be a factor affecting stress-induced changes in exploratory behavior in mice.

Experience-dependent changes in exploratory behavior in the adult rat (Rattus norvegicus): Overall activity level and interactions with objects.

Experience-dependent changes in exploratory behavior in the adult rat (Rattus norvegicus): Overall activity level and interactions with objects.

Experience-dependent changes in exploratory behavior in the adult rat (Rattus norvegicus): Overall activity level and interactions with objects.

Experience-dependent changes in exploratory behavior in the adult rat (Rattus norvegicus): Overall activity level and interactions with objects.

Antagonistic effects of aldosterone on corticosterone-mediated changes in exploratory behavior of adrenalectomized rats

The effect of aldosterone administration on exploratory activity of chronic adrenalectomized (10 days) male rats was investigated. Aldosterone (30 μg/100 g body wt sc) administered 1 hr or 30 min prior to the behavioral test failed to normalize disturbed exploratory activity of adrenalectomized rats, in contrast to the restoration observed after corticosterone, the naturally occurring glucocorticoid of the rat. Administration of the mineralocorticoid 30 min prior to corticosterone prevented the normalization of the behavioral response by the latter steroid. Administration of the same dose of aldosterone 30 min prior to a tracer amount of [ 3H]corticosterone effectively blocked cell nuclear uptake of radioactive-labeled hormone in the hippocampus. The specific action of corticosterone on exploratory behavior corresponds with the stringent specificity of the neuronal hippocampal corticosterone receptor system. Mineralocorticoid receptors do not seem to be involved in effects on this behavior. The antagonistic action of aldosterone is probably exerted by competitive binding to the corticosterone receptor.

Behavioral changes in mice infected withtoxocara canis

The common roundworm of the dog, Toxocara canis, may also infect a number of other species including humans and mice. Previously, we found profound behavioral and neurological changes in mice infected with this parasite. The present investigation examined the relationship between dose of T. canis and changes in exploratory behavior in mice; issues raised in considering such relationships in a host‐parasite preparation are discussed.

Involvement of hippocampal serotonergic activity in age-related changes in exploratory behavior

The effect of aging on exploratory behavior was investigated in adult (5 month) and aged (28 month) CB6F 1 mice. During the first 10 minutes of the test session, aged mice made fewer head dip responses and spent less time exploring the novel stimuli. Because the aged mice were observed to subsequently increase their duration of exploration, it was suggested that the initial differences in exploration reflected a suppression of exploratory behavior by the aged mice. Immediately after behavioral testing, mice were sacrificed and hippocampal serotonin (5HT) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were determined. While 5HT concentrations were not found to be significantly altered with age, significant increases in 5-HIAA concentrations and in the ratio of 5-HIAA/5HT were observed in the aged mice. Further, the elevation in the 5-HIAA/5HT ratio was found to be significantly correlated with age-related differences in the duration, but not the frequency, of head dip responses. In view of this finding, it was suggested that alterations in serotonergic function with age may selectively affect specific aspects of an animal's response to novel stimuli.

Effects of lateral and medial septal lesions on exploratory behavior in the albino rat

The effects of selective medial and lateral septal lesions on exploratory behavior were studied in the rat. Three types of open-field test and two tests of object exploration were used. In the firts experiments, medial but not lateral septal lesions abolished exploration of an open-field accessible from the home-cage. No effects of either of the lesions were found in a standard open-field (Experiment 2). In the third experiment, rats with medial septal lesions were less active and showed a preference for the smaller compartments of the testing apparatus. These results suggest that a change in exploratory behavior following medial septal lesions may be primarily due to their effect on emotionality (increased fear). Two tests of object exploration (Experiments 4 and 5) showed that both types of selective septal lesions enhanced approaches to the novel object placed in the home-cage, but they did not affect object exploration and object preference in other conditions (Experiment 5). The same experiments revealed an increased level of activity (rearing and ambulation) in the rats with lateral septal lesions. It is concluded that the effect of medial septal lesions on exploration is due to increased fear of novel places (but not objects). Lateral septal lesions, on the other hand, increase activity in the rats but there is no evidence that this activity represents enhanced exploration.

Measurement of pharmacological depression of exploratory activity in mice: a contribution to the problem of time-economy and sensitivity.

Changes in exploratory behaviour in mice due to two variables, size of test enclosure and intensity of illumination, each at three levels were tested repeatedly over five exposures. The most suitable procedure for eliciting depressant effects of drugs on exploratory activity was to use a small enclosure (8×24 cm) with dim illumination (2 lx), and to partially habituate the animals to this environment before giving drugs. Under these conditions the amount of walking and rearing by untreated mice was about 70% of the maximal values obtained. It was also found that test sessions lasting for one minute provided sufficient information. In the selected “optimal” setting, the lowest effective depressant doses of chlorpromazine and barbitone were 0.3 mg/kg and 5.0 mg/kg, respectively, while under other conditions it was necessary to use higher doses of the drugs to obtain similar effects, and occasionally, increases in activity were also recorded. Since it took not more than 70 sec to test each mouse, up to 200 animals could be tested each day, which makes it possible to determine both dose- and time-response relationships quite rapidly. These results suggest ways in which experimental variables can be manipulated to “tune-up” exploratory behaviour and to make it more sensitive to specific types of psychotropic drugs.