Nicotinic modulation of tone-evoked responses in auditory cortex reflects the strength of prior auditory learning.
Nicotinic acetylcholine receptors (nAChRs) contribute to sensory-cognitive function, as demonstrated by evidence that nAChR activation enhances, and nAChR blockade impairs, neural processing of sensory stimuli and sensory-cognitive behavior. To better understand the relationship between nAChR function and behavior, here we compare the strength of nAChR-mediated physiology in individual animals to their prior auditory behavioral performance. Adult rats were trained on an auditory-cued, active avoidance task over 4 days and classified as "good," "intermediate" or "poor" performers based on their initial rate of learning and eventual level of performance. Animals were then anesthetized, and tone-evoked local field potentials (LFPs) recorded in layer 4 of auditory cortex (ACx) before and after a test dose of nicotine (0.7mg/kg, s.c.) or saline. In "good" performers, nicotine enhanced LFP amplitude and decreased response threshold to characteristic frequency (CF) stimuli, yet had opposite effects (decreased amplitude, increased threshold) on responses to spectrally distant stimuli; i.e., cortical receptive fields became more selective for CF stimuli. In contrast, nicotine had little effect on LFP amplitude in "intermediate" or "poor" performing animals. Nicotine did, however, reduce LFP onset latency in all three groups, indicating that all received an effective dose of the drug. Our findings suggest that nicotinic regulation of cortical receptive fields may be a distinguishing feature of the best-performing animals, and may facilitate sensory-related learning by enhancing receptive field selectivity.
Liang
Kevin
K
Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, Center for Hearing Research, University of California, Irvine, CA 92697, USA.
Poytress
Bonnie Sue
BS
Weinberger
Norman M
NM
Metherate
Raju
R
D000109:Acetylcholine / Q000502:physiology; D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000187:drug effects / Q000502:physiology*; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000187:drug effects / Q000502:physiology; D008297:Male; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000502:physiology*
D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; D009538:Nicotine; D000109:Acetylcholine