Some Views on the Neurophysiological and Neuropharmacological Mechanisms of Storage and Retrieval of Information
Electrophysiological and behavioral studies were carried out in the rabbit, the rat, and man in an attempt to clarify the qualitative nature, the underlying mechanisms, and the functional consequences of drug-induced arousal. Our data support the existence of two subcortical arousal systems, probably mutually inhibitory, which produce the same end product, namely cortical activation, but also which produce functionally different forms of arousal. One of the systems appears to be related to the reticular formation and the other, to the limbic system (particularly, the hippocampus). Direct electroencephalographic (EEG) measures in the rabbit showed that amphetamine can affect concurrently the inter-relationships between the reticular formation and cortex, and the hippocampus and cortex. However, our EEG data from human subjects indicate that the relative effect of acute doses on the two systems is controlled, at least partially, by the pre-existing states of these systems. The highly variable performance of rats tested on a continuous attention task after acute doses of amphetamine support indirectly the premise that the baseline state of the systems dictates their response to pharmacological manipulation.
EEG measures in rabbits supplied evidence that nicotine also affects the inter-relationships both between the reticular formation and cortex and the hippocampus and the cortex, but to different relative degrees depending on whether the administration is acute or chronic. Acute doses act primarily on the reticular-cortex relationships, while chronic treatment causes a gradual shift from predominant reticular formation control of arousal to hippocampal control. Behavioral testing of rats operating on the continuous attention task, revealed that initial doses of nicotine cause impairment of performance, but that chronic treatment causes rats to perform more efficiently on the task than they do under saline control conditions. Acquisition studies with rats on this same task indicate that unlike its effect on performance per se, nicotine disrupts the learning of the task.
The arousal system related to the reticular formation does appear to control the general reactivity of the organism and provide organization for response, while the second system (related to the limbic structures, particularly the hippocampus) provides control of responses through incentive-related stimuli. The functional consequences of the manipulation of the two arousal systems is discussed in relation to information storage (learning) and retrieval (performance).
KeywordsLimbic System Saline Treatment Commission Error Omission Error Chronic Nicotine
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