BEHAVIORAL HABITUATION TO SPATIAL NOVELTY - INTERFERENCE AND NONINTERFERENCE STUDIES

Long-term behavioral habituation (LTH), that is activity decrement upo n repeated exposures to spatial novelty, is a relatively simple and ub iquitous form of behavioral plasticity in the animal kingdom, that can be used as a model of nonassociative learning in the freely behaving organism. Several strategies can be followed to tackle upon it. (a) In terference studies pertain to manipulation of the between-exposure int erval by a variety of agents of different nature, that are known to in terfere with hypothesized ''consolidation process(es)'' in associative learning paradigms. This approach indicates that LTH is modulated by NMDA receptors, requires polysome aggregation and protein synthesis, a functioning neocortex and both slow wave and paradoxical sleep. Furth er, it is modulated by endogenously released or exogenously given vaso pressin and is not affected by blockade of endogenous opioids, at leas t through the ''mu'' receptor type. Moreover, LTH is disrupted by bila teral, electrolytic lesion of the locus coeruleus, but it is only impa ired by 6-OH-DA bilateral lesion of the dorsal noradrenergic bundle, a nd it is facilitated by electrolytic lesion of the medial septal nucle i. (b) Noninterference correlative studies: Individual differences in behavioral variables can be correlated to some components of the archi tecture of the hippocampus to reveal structure-function relationships. (c) Noninterference maturation studies pertain to the study of the ma turation of LTH during postnatal development in a scaled-down Lat-maze in normally reared rats and in rats with deranged rate of body and br ain growth by litter size technique, differential stimulation or by pe rinatal propylthiouracil-induced hypothyroidism. (d) Noninterference d evelopment studies pertain to the formation of LTH varying the between -exposure interval. It was studied in albino rats of a Sprague-Dawley, random-bred stock (NRB) and of the Naples High (NHE) and Low-Excitabi lity (NLE) lines. The study was carried out during the light or the da rk phase of a 12:12LD cycle, by retesting at different inter-exposure intervals. Multivariate analysis of variance showed significant effect s of strain, inter-exposure interval and of postexposure sleep or wake fulness. Furthermore, analysis of the temporal pattern showed the form ation of LTH to follow a non linear complex function. Further, behavio ral habituation consists of emotional and cognitive components that ca n be separated across different approaches. In conclusion, long-term