The effects of isolation rearing on exploration in the rat

Abstract

The hypothesis that isolation rearing enhances exploration was tested in two settings which varied the extent to which exploratory behavior would be affected by competing hyperactivity. Experiment 1 measured exploration as contact of a discrete novel stimulus, in terms of bout frequency and duration. Locomotor activity was measured by photocell beam interruption. Isolation-reared rats were hyperactive, showed an increased incidence of exploratory bouts but no differences in duration of exploratory behavior, compared with group-reared controls. Experiment 2 measured, independently, locomotor activity and the preference for a novel environment over a familiar one. Isolation-reared rats, whether male or female, showed enhanced novelty preference compared with controls. No significant differences were found in locomotor activity. The results are discussed in terms of the hyperactivity of isolates interfering with investigative behavior by response incompatibility.

Activity differences of individually and group-housed male and female rats

“…In contrast, reports of open-field hyperactivity in individually housed rats have usually used handled, well-habituated animals (Morgan, 1973), have repeatedly tested the animals (Einon, Morgan, & Sahakian, 1975), or have exposed them to long durations of open-field presentation (Sahakian et al, 1977). In the light of these comparisons, it appeared that the conditions and duration of the activity test and the prior experimental history might be especially important in determining the relative activity levels of individually and group-housed 1.e.…”

“…This finding does not necessarily mean, however, that isolation has a similar effect on exploration directed towards discrete novel stimuli ("inspective exploration," Berlyne, 1960). The hyperactivity of isolates is associated with the former type of exploration but is found to interfere with the latter type (Sahakian et al, 1977). It is therefore not surprising that isolates are inferior to group-housed animals on measures of manipulatory, but not nonmanipulatory, cont~cts with objects (Einon & Morgan, 1976) and that Isolates spend less time investigating objects in a hole-board (File, 1978).…”

Social Isolation in the Rat Produces Developmentally Specific Deficits in Prepulse Inhibition of the Acoustic Startle Response Without Disrupting Latent Inhibition

“…The data are discussed with respect to the involvement of ventral striatal DA mechanisms in the expression of PPI and LI, differences in the impact of social isolation in young and adult animals, and the utility of social isolation model as a nonlesion, nonpharmacologic means of perturbing ventral striatal DA function. [Neuropsychopharmacology 10:61-72, 1994J conditioned locomotor activity (Gentsch et al 1981;Sa hakian et al, 1982;Jones et al, 1990), altered responses to environmental novelty (Sahakian et al 1977;Gentsch et al 1982aGentsch et al , 1982bGentsch et al , 1983, impairments in discrimina tion learning (Jones et al 1991), and resistance to ex tinction (Einon et al 1975;Morgan et al 1977). Rats iso lated in this way also show an increased sensitivity to psychomotor stimulant drugs such as d-amphetamine and cocaine, both in terms of the locomotor enhancing properties of these agents and their ability to induce stereotyped behaviors Jones et al 1990Jones et al , 1992, responses that depend on the meso lim bic and mesostriatal dopamine (DA) projections, respec tively (Kelly et al 1975).…”

Isolation rearing impairs novel object recognition and attentional set shifting performance in female rats

“…It represents a rat analogue of the human Wisconsin Card Sorting Task (WCST, Berg, 1948) and CANTAB ID/ED task (Downes et al, 1989) in which schizophrenic patients exhibit impaired set-shifting (Kolb and Wishaw, 1983;Haut et al, 1996;Pantelis et al, 1999;Tyson et al, 2004). Effects of isolation rearing on cognition in rats Early observations of behaviour in rats reared in isolation led to the portrayal of the "isolation syndrome" (Hatch et al, 1965;Sahakian et al, 1977). Rats reared in isolation from weaning until adulthood show several behavioural changes, consistently including increased locomotor activity, anxiogenesis, (Puglisi-Allegra and Oliverio, 1983), enhanced sensitivity to psychoactive drugs such as amphetamine and cocaine (Jones et al, 1990;Smith et al, 1997) and sensorimotor gating deficits as measured by reduced pre-pulse inhibition (PPI) of a startle response (Geyer et al, 1993;Cilia et al, 2001;.…”