Induction of long-term receptive field plasticity in the auditory cortex of the waking guinea pig by stimulation of the nucleus basalis.

Learning induces neuronal receptive field (RF) plasticity in primary auditory cortex. This plasticity constitutes physiological memory as it is associative, highly specific, discriminative, develops rapidly, and is retained indefinitely. This study examined whether pairing a tone with activation of the nucleus basalis could induce RF plasticity in the waking guinea pig and, if so, whether it could be retained for 24 hr. Subjects received 40 trials of a single frequency paired with electrical stimulation of the nucleus basalis (NB) at tone offset. The physiological effectiveness of NB stimulation was assessed later while subjects were anesthetized with urethane by noting whether stimulation produced cortical desynchronization. Subjects in which NB stimulation was effective did develop RF plasticity and this was retained for 24 hr. Thus, activation of the NB during normal learning may be sufficient to induce enduring physiological memory in auditory cortex.