Functional subregions in primary auditory cortex defined by thalamocortical terminal arbors: An electrophysiological and anterograde labeling study

David S. Velenovsky, Justin S. Cetas, Robin O. Price, Donal G. Sinex, Nathaniel T. McMullen

Research output: Contribution to journalArticle

48 Scopus citations

Abstract

Several functional maps have been described in primary auditory cortex, including those related to frequency, tuning, latency, binaurality, and intensity. Many of these maps are arranged in a discontinuous or patchy manner. Similarly, thalamocortical projections arising from the ventral division of the medial geniculate body to the primary auditory cortex are also patchy. We used anterograde labeling and electrophysiological methods to examine the relationship between thalamocortical patches and auditory cortical maps. Biotinylated dextran-amine was deposited into physiologically characterized sites in the ventral division of the medial geniculate body of New Zealand white rabbits. Approximately 7 d later, the animal was again anesthetized and the ipsilateral auditory cortex was mapped with tungsten microelectrodes. Multi-unit physiological data were obtained for the following characteristics: best frequency (BF), binaurality, response type, latency, sharpness of tuning, and threshold. Immunocytochemical methods were used to reveal the injection site in the ventral division of the medial geniculate body as well as the anterogradely labeled thalamocortical afferents in the auditory cortex. In 86% of the cases (12 of 14), entry into a thalamocortical patch was associated with a marked change in physiological responses. A consistent BF and binaural class were usually observed within a patch. The patches appear to innervate distinct functional regions coding frequency and binaurality. A model is presented showing how patchy thalamocortical projections participate in the formation of tonotopic and binaural maps in primary auditory cortex.

Original languageEnglish (US)
Pages (from-to)308-316
Number of pages9
JournalJournal of Neuroscience
Volume23
Issue number1
DOIs
StatePublished - Jan 1 2003

Keywords

  • Audition
  • Frequency map
  • Medial geniculate body
  • Neocortex
  • Patches
  • Thalamus

ASJC Scopus subject areas

  • Neuroscience(all)

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