disruptive effect of atropine sulfate (2 mg/kg) on working memory in a six-arm radial maze but found reference memory unaffected or even slightly improved. Similar differential effects of scopolamine HBr (0.1-0.8 mg/kg) on reference and working memory in the eight-arm radial maze were also described by Wirsching, Beninger, Jhamandas, Boegman, and El-Defrawy(1984). Watts, Stevens, and Robinson (1981) reported slow acquisition of an 8-arm radial maze task in rats receiving 0.5 mg/ kg scopolamine HC1 before each of the 14 daily acquisition trials. In a similar study, rats receiving 0.3 mg/kg scopolamine

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Although there are many papers describing the electrophysiological correlates of conditioning (see the review by Mon]~Im 1961) most Of the observed changes are due to activation of extensive non-specific areas rather than to formation of new connections themselves. Since many drugs evoke well-defined eleetroeneephMographie changes in the central nervous system, another approach to the neurophysiology of learning becomes more and more important. Correlation of EEG pattern induced by these drugs, with the behavioral capacities of the animal may indicate the neural circuits subserving specific behavioral functions. Characteristic EEG changes due to atropine described by Wv, scoE et al. (1948), FvNI)]~BunY: and CAsv, (1951), WI~L]~R (1952), BnAI)L~Y and EL~:~s (1953), WI~IT]~ and Bou (1960) are very suitable for this purpose.Atropine induces in experimental animals a slow wave high voltage sleep-like EEG pattern, which is not accompanied by behavioral sleep, however, as pointed out by FV~DJZr~J3V~K and CAsh (1951) and WI~:Ls.~ (1952) In the present paper it has been attempted to establish to what degree the sleep-like EEG pattern, induced by atropine, is compatible with acquisition, retention, and retrieval of memory traces in rats. Technique Electrophysiologieal experiments. Wistar albino rats aged 3 mouthswere used throughout.In unanaesthetised freely moving animals with chronically implanted bipolar silver electrodes the EEG activity was recorded from the mesencephalic reticular formation, dorsal hippocampus, frontal neocortex and, in some pilot experiments, also from the eaudate nucleus.The peak to peak amplitude of the EEG activity was measured in regular five minutes intervals before and after intraperitoneal administra-Psychopharmacologia, Bd. 5 18