Perseveration of attention to conspecific odors and novel objects in castrated gerbils

The Pleasures of Uncertainty: Prolonging Positive Moods in Ways People Do Not Anticipate

The authors hypothesized that uncertainty following a positive event prolongs the pleasure it causes and that people are generally unaware of this effect of uncertainty. In 3 experimental settings, people experienced a positive event (e.g., received an unexpected gift of a dollar coin attached to an index card) under conditions of certainty or uncertainty (e.g., it was easy or difficult to make sense of the text on the card). As predicted, people's positive moods lasted longer in the uncertain conditions. The results were consistent with a pleasure paradox, whereby the cognitive processes used to make sense of positive events reduce the pleasure people obtain from them. Forecasters seemed unaware of this paradox; they overwhelmingly preferred to be in the certain conditions and tended to predict that they would be in better moods in these conditions.

Adult development: plasticity of stable behavior

Gerbils in a longitudinal study demonstrated very stable behavior over more than a third of their median lifespan. There was highly significant individual stability of such behaviors as locomotor activity, rearing on the hind legs, latency to jump down from a platform, and marking with the ventral gland for thirteen months of adult life, from six to eighteen months of age. In some of these behaviors, general changes were observed over time, such as increased latency to jump down from a platform. Additionally, brief, outdoor enrichment (one hour a month) resulted in more scent marking than was found in control gerbils. In gerbils tested monthly there was less locomotor activity and rearing on the hind legs than in gerbils tested only once. It was observed that gerbils with a strong tendency to have seizures had more locomotor activity, more rearing, fewer markings, and shorter latency to jump down from a platform than those who rarely seized. Further, when gerbils had a seizure prior to testing, their activity scores and number of rearings were greater than on days when they did not have a seizure. Sex differences are discussed. These normative data provide important knowledge of adult development for comparison with studies of aging changes in gerbils.

Attention and habituation: separation of specific components in development

In four experiments using habituation procedures, it was shown that selective investigation of stimuli that are novel gradually developed between 13 and 28 days of age in gerbil pups. The youngest pups investigated the stimuli, but were highly variable in their responses to an object or to odors of conspecifics. Habituation could, but did not reliably, occur. By 21 days of age, investigation of a cup attenuated in a series of 5 one-minute trials and responses increased after the cup was moved to a new location. By 28 days of age, reliable habituation was shown 24 hours after a one-minute exposure to a cup. The data were used to infer how an immature process of selective attention may be responsible for variability in expression of habituation during development.

The gerbil: a unique model for research on aging

The Mongolian gerbil (Meriones unguicultatus) is suggested as a model for aging research because of its unique physiological attributes, ease of handling, and because of data previously collected. Factors that demonstrate the gerbils' suitability in fulfulling practical and scientific considerations important in determining a model for aging research are listed. Additionally, several unique physiological attributes of gerbils are described. Based on these attributes and on review of research in gerbils, it is suggested that gerbils can serve as animal models for behavioral and biological processes, and for normative and pathological aspects for aging.

Differential effects of haloperidol and clozapine on attention

Haloperidol (0, 0.1, 0.3, or 1.0 mg/kg), the typical butyrophenone neuroleptic, decreased investigation of novel objects by gerbils following systemic injections. When given prior to apomorphine (1 or 3 mg/kg), haloperidol blocked apomorphine-induced disruption of selective attention in a dose-dependent manner. Thus, haloperidol acts like pimozide in this paradigm. In contrast, clozapine (0, 0.03, 0.1, 0.3, 1.0, or 3.0 mg/kg), the atypical dibenzodiazepine neuroleptic, increased frequency of investigation both soon after injection and 24h later, suggesting interference with maintenance of attention. When given with apomorphine (1.0 mg/kg), clozapine did not block apomorphine effects on selective attention. The results are related to differential effects of these neuroleptics on other behaviors and to their individual pharmacological profiles.