RT Journal Article SR Electronic T1 Functional Subregions in Primary Auditory Cortex Defined by Thalamocortical Terminal Arbors: An Electrophysiological and Anterograde Labeling Study JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 308 OP 316 DO 10.1523/JNEUROSCI.23-01-00308.2003 VO 23 IS 1 A1 David S. Velenovsky A1 Justin S. Cetas A1 Robin O. Price A1 Donal G. Sinex A1 Nathaniel T. McMullen YR 2003 UL http://www.jneurosci.org/content/23/1/308.abstract AB 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.