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J Neurosci. 2015 Jun 17;35(24):9024-37. doi: 10.1523/JNEUROSCI.4583-14.2015.

Delayed and Temporally Imprecise Neurotransmission in Reorganizing Cortical Microcircuits.

Author information

  • 1MRC Centre Neurodegeneration Research, King's College London, De Crespigny Park, London SE5 8AF, United Kingdom, and.
  • 2Computer Vision Laboratory and.
  • 3Bio-EM facility, Centre of Interdisciplinary Electron Microscopy, EPFL, CH-1015 Lausanne, Switzerland.
  • 4MRC Centre Neurodegeneration Research, King's College London, De Crespigny Park, London SE5 8AF, United Kingdom, and gerald.finnerty@kcl.ac.uk.

Abstract

Synaptic neurotransmission is modified at cortical connections throughout life. Varying the amplitude of the postsynaptic response is one mechanism that generates flexible signaling in neural circuits. The timing of the synaptic response may also play a role. Here, we investigated whether weakening and loss of an entire connection between excitatory cortical neurons was foreshadowed in the timing of the postsynaptic response. We made electrophysiological recordings in rat primary somatosensory cortex that was undergoing experience-dependent loss of complete local excitatory connections. The synaptic latency of pyramid-pyramid connections, which typically comprise multiple synapses, was longer and more variable. Connection strength and latency were not correlated. Instead, prolonged latency was more closely related to progression of connection loss. The action potential waveform and axonal conduction velocity were unaffected, suggesting that the altered timing of neurotransmission was attributable to a synaptic mechanism. Modeling studies indicated that increasing the latency and jitter at a subset of synapses reduced the number of action potentials fired by a postsynaptic neuron. We propose that prolonged synaptic latency and diminished temporal precision of neurotransmission are hallmarks of impending loss of a cortical connection.

KEYWORDS:

latency; neural code; plasticity; presynaptic; rewiring; synapse

PMID:
26085628
PMCID:
PMC4469734
DOI:
10.1523/JNEUROSCI.4583-14.2015
[PubMed - indexed for MEDLINE]
Free PMC Article
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