Letter

Nature 450, 425-429 (15 November 2007) | doi:10.1038/nature06289; Received 17 April 2007; Accepted 21 September 2007

A synaptic memory trace for cortical receptive field plasticity

Robert C. Froemke1, Michael M. Merzenich1 & Christoph E. Schreiner1

  1. Coleman Memorial Laboratory and W. M. Keck Foundation Center for Integrative Neuroscience, Department of Otolaryngology, University of California, San Francisco, California 94143, USA

Correspondence to: Robert C. Froemke1 Correspondence and requests for materials should be addressed to R.C.F. (Email: rfroemke@phy.ucsf.edu).

Receptive fields of sensory cortical neurons are plastic, changing in response to alterations of neural activity or sensory experience1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. In this way, cortical representations of the sensory environment can incorporate new information about the world, depending on the relevance or value of particular stimuli1, 6, 9. Neuromodulation is required for cortical plasticity, but it is uncertain how subcortical neuromodulatory systems, such as the cholinergic nucleus basalis, interact with and refine cortical circuits13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24. Here we determine the dynamics of synaptic receptive field plasticity in the adult primary auditory cortex (also known as AI) using in vivo whole-cell recording. Pairing sensory stimulation with nucleus basalis activation shifted the preferred stimuli of cortical neurons by inducing a rapid reduction of synaptic inhibition within seconds, which was followed by a large increase in excitation, both specific to the paired stimulus. Although nucleus basalis was stimulated only for a few minutes, reorganization of synaptic tuning curves progressed for hours thereafter: inhibition slowly increased in an activity-dependent manner to rebalance the persistent enhancement of excitation, leading to a retuned receptive field with new preference for the paired stimulus. This restricted period of disinhibition may be a fundamental mechanism for receptive field plasticity, and could serve as a memory trace9, 25 for stimuli or episodes that have acquired new behavioural significance.

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