Long-term, but not transient, threshold shifts alter the morphology and increase the excitability of cortical pyramidal neurons

Sungchil Yang, Wendy Su, Shaowen Bao

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Partial hearing loss often results in enlarged representations of the remaining hearing frequency range in primary auditory cortex (AI). Recent studies have implicated certain types of synaptic plasticity in AI map reorganization in response to transient and long-term hearing loss. How changes in neuronal excitability and morphology contribute to cortical map reorganization is less clear. In the present study, we exposed adult rats to a 4-kHz tone at 123 dB, which resulted in increased thresholds over their entire hearing range. The threshold shift gradually recovered in the lower-frequency, but not the higherfrequency, range. As reported previously, two distinct zones were observed 10 days after the noise exposure, an enlarged lower-characteristic frequency (CF) zone displaying normal threshold and enhanced cortical responses and a higher-CF zone showing higher threshold and a disorganized tonotopic map. Membrane excitability of layer II/III pyramidal neurons increased only in the higher-CF, but not the lower-CF, zone. In addition, dendritic morphology and spine density of the pyramidal neurons were altered in the higher-CF zone only. These results indicate that membrane excitability and neuronal morphology are altered by long-term, but not transient, threshold shift. They also suggest that these changes may contribute to tinnitus but are unlikely to be involved in map expansion in the lower-CF zone.

Original languageEnglish (US)
Pages (from-to)1567-1574
Number of pages8
JournalJournal of neurophysiology
Volume108
Issue number6
DOIs
StatePublished - Sep 15 2012
Externally publishedYes

Keywords

  • Hearing lesions
  • Homeostatic plasticity
  • Intrinsic property
  • Sensory map

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

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