title: Cortical Synaptic Inhibition Declines during Auditory Learning.
abstract: Auditory learning is associated with an enhanced representation of acoustic cues in primary auditory cortex, and modulation of inhibitory strength is causally involved in learning. If this inhibitory plasticity is associated with task learning and improvement, its expression should emerge and persist until task proficiency is achieved. We tested this idea by measuring changes to cortical inhibitory synaptic transmission as adult gerbils progressed through the process of associative learning and perceptual improvement. Using either of two procedures, aversive or appetitive conditioning, animals were trained to detect amplitude-modulated noise and then tested daily. Following each training session, a thalamocortical brain slice was generated, and inhibitory synaptic properties were recorded from layer 2/3 pyramidal neurons. Initial associative learning was accompanied by a profound reduction in the amplitude of spontaneous IPSCs (sIPSCs). However, sIPSC amplitude returned to control levels when animals reached asymptotic behavioral performance. In contrast, paired-pulse ratios decreased in trained animals as well as in control animals that experienced unpaired conditioned and unconditioned stimuli. This latter observation suggests that inhibitory release properties are modified during behavioral conditioning, even when an association between the sound and reinforcement cannot occur. These results suggest that associative learning is accompanied by a reduction of postsynaptic inhibitory strength that persists for several days during learning and perceptual improvement.
authors.affiliation: Center for Neural Science, New York University, New York, New York 10003 emma.sarro@nyumc.org.
authors.forename: Emma C
authors.initials: EC
authors.lastname: Sarro
authors.affiliation: Center for Neural Science, New York University, New York, New York 10003.
authors.forename: Gardiner
authors.initials: G
authors.lastname: von Trapp
authors.affiliation: Center for Neural Science, New York University, New York, New York 10003.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Mowery
authors.affiliation: Center for Neural Science, New York University, New York, New York 10003.
authors.forename: Vibhakar C
authors.initials: VC
authors.lastname: Kotak
authors.affiliation: Center for Neural Science, New York University, New York, New York 10003.
authors.forename: Dan H
authors.initials: DH
authors.lastname: Sanes
mesh_terms: D000818:Animals; D001245:Association Learning / Q000502:physiology*; D001303:Auditory Cortex / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology; D003214:Conditioning, Classical / Q000502:physiology; D005849:Gerbillinae; D053444:Inhibitory Postsynaptic Potentials / Q000502:physiology; D008297:Male; D009433:Neural Inhibition / Q000502:physiology*; D017966:Pyramidal Cells / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology
keywords: associative learning; auditory cortex; inhibition; synaptic plasticity