Rodents have a topographic map in primary somatosensory cortex of the contralateral facial whiskers. A brief period of whisker trimming causes the representation of the nontrimmed whiskers (spared) to expand into the cortex that has lost its principal sensory input (deprived). It has been hypothesized that this is mediated by a period of persistent disinhibition in deprived cortex that enables the expansion of spared whisker representations. Alternatively, it has been proposed that inhibition undergoes a biphasic change with an initial, brief period of disinhibition to promote plasticity in excitatory circuits followed by a more prolonged increase in inhibition to re-establish the excitatory – inhibitory balance. These hypotheses make different predictions about how inhibition changes during cortical map plasticity, which I have tested in this thesis. I focused on fast-spiking (FS) interneurons, which are thought to play an important role in adult cortical plasticity. I made electrophysiological recordings in layer 2/3 to determine how inhibitory circuitry in deprived cortex is affected by whisker deprivation. The amplitude of miniature excitatory postsynaptic potentials (mEPSPs) in deprived FS interneurons was increased with no change in mEPSP frequency suggesting that the global excitatory drive onto FS interneurons was potentiated. In contrast, the amplitude of miniature inhibitory postsynaptic currents (mIPSCs) in layer 2/3 pyramidal neurons was unchanged, but there was a small but significant increase in mIPSC frequency. I investigated feedback inhibitory circuits in more detail by recording from pairs of pyramidal cells and FS interneurons that were synaptically-connected. Surprisingly, I found that the strength of local excitation onto FS interneurons and the strength of FS – mediated inhibition on deprived pyramidal neurons were unchanged. I concluded that, contrary to two popular hypotheses, a brief period of sensory deprivation did not alter the feedback inhibition in layer 2/3 of deprived cortex.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:628411 |
| Date | January 2013 |
| Creators | Albieri, Giorgia |
| Publisher | King's College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://kclpure.kcl.ac.uk/portal/en/theses/the-role-of-fastspiking-interneurons-in-cortical-map-plasticity(3d7b76ff-1833-4147-addd-6f24accbd6cc).html |
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