Subject: Inhibition in cortical vs. subcortical areas From: Mark Sanderson <Mark_Sanderson(at)BROWN.EDU> Date: Tue, 22 May 2001 08:14:36 -0400
Thanks to all who responded to my question last week regarding the relative strength of inhibition in cortex versus sub-cortical structures. A brief summary, and references follow: From a limited population, DCN Type II neurons received the highest number of votes as those neurons with the strongest sideband inhibition (1/1 votes cast). I was most interested in how cortex compared to the inferior colliculus, and Didier Depireux pointed out that only cortical units are selective for ripple frequency, whereas IC units tend to exhibit low-pass tuning. From this one would conclude that inhibition (at least as it is engaged by ripple stimuli) tends to be stronger in cortex than the IC. If non-monotonicity can serve as another indirect measure of inhibition, then several papers below support a similar conclusion in that the relative numbers of non-monotonic neurons increases as one ascends from IC to AC (Barone et al. 1996; Pfingst and Connor 1981;Ryan and Miller 1978). The degree of non-monotonicity increases from MGB to AC (Barone et al. 1996). (thanks to Didier for making the 1996 ARO poster available): http://www.isr.umd.edu/CAAR/posters/aro96.pdf and http://www.isr.umd.edu/CAAR/posters/aro97.pdf Barone, P., Clarey, J.C., Irons, W.A. and Imig, T.J. (1996) Cortical synthesis of azimuth-sensitive single-unit responses with nonmonotonic level tuning: A thalamocortical comparison. J. Neurophysiol., 75: 1206-1220. Pfingst, B.E. and Connor T. Characteristics of neurons in auditory cortex of monkeys performing a simple auditory task. J.Neurophysiol 45:16-34, 1981 Ryan, A and Miller J. Single unit responses in the inferior colliculus of the awake and performing rhesus monkey. Exp. Brain. Res. 32:389-407, 1978. Spirou, George A., Kevin A. Davis, Israel Nelken, and Eric D. Young. Spectral Integration by Type II Interneurons in Dorsal Cochlear Nucleus. J. Neurophysiol. 82: 648-663, 1999. Suga, N., Zhang, Y. and Yan, J. (1997) Sharpening of frequency tuning by inhibition in the thalamic auditory nucleus of the mustached bat. J. Neurophysiol., 77: 2098-2114. Suga, N. (1995) Sharpening tuning by inhibition in the central auditory system: tribute to Yasuji Katsuki. Neurosci. Res., 21: 287-299.