Article

Synaptic Mechanisms for Plasticity in Neocortex

Department of Molecular and Cell Biology, and Helen Wills Neuroscience Institute, University of California, Berkeley, USA.
Annual Review of Neuroscience (Impact Factor: 19.32). 04/2009; 32(1):33-55. DOI: 10.1146/annurev.neuro.051508.135516
Source: PubMed

ABSTRACT

Sensory experience and learning alter sensory representations in cerebral cortex. The synaptic mechanisms underlying sensory cortical plasticity have long been sought. Recent work indicates that long-term cortical plasticity is a complex, multicomponent process involving multiple synaptic and cellular mechanisms. Sensory use, disuse, and training drive long-term potentiation and depression (LTP and LTD), homeostatic synaptic plasticity and plasticity of intrinsic excitability, and structural changes including formation, removal, and morphological remodeling of cortical synapses and dendritic spines. Both excitatory and inhibitory circuits are strongly regulated by experience. This review summarizes these findings and proposes that these mechanisms map onto specific functional components of plasticity, which occur in common across the primary somatosensory, visual, and auditory cortices.

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    • "For example, it is not clear which specific functional components of plasticity, if any, mediate which types or sites of rapid structural components of plasticity or whether chemical signaling is a proximal driver of structural plasticity (Feldman, 2009). Moreover, the relationship between functional changes and structural microscopic and then macroscopic changes – that is anatomical connectivity – is unknown (Feldman, 2009). Finally, the relationship between anatomical, functional, and effective connectivity in the cortex also represents a significant challenge (Tononi et al., 1994; Sporns et al., 2004 ). "
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    • "To determine how whisker deprivation affects development of L4 mIPSCs, we deprived the D-row whiskers by plucking beginning at P7. Deprivation was maintained continuously by re-plucking every 2–3 days until the date of recording (Fig 1D) . Whisker plucking reduces sensory-evoked activity in the corresponding S1 column [27] and drives robust plasticity of whisker-evoked spiking responses and synaptic properties in L2/3 of deprived columns282930. It has previously been shown that continuous whisker deprivation from P7 in GAD67-GFP mice causes weakened L4 inhibitory synapse efficacy measured at P28 [13]. "
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    • "The cerebral cortex shows a remarkable capacity for functional plasticity (Feldman, 2009; Fox et al., 2000; Fox and Wong, 2005). Broadly, plasticity can take one of two forms: input-specific plasticity, which involves weakening of inactive inputs and strengthening (or weakening) of active inputs, and an inputagnostic form of plasticity, which involves both deprived and spared inputs and acts to maintain neuronal activity at some set point in a homeostatic fashion. "
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