Publication DetailsJ Neuroscience Chronic Rat Inferior Colliculus Penetrating Electrode A1x16-5mm100-413|A1x32-6mm-50-177
StreamÂ segregationÂ enables a listener to disentangle multiple competing sequences of sounds. A recent study from our laboratory demonstrated that cortical neurons in anesthetized cats exhibit spatialÂ streamÂ segregationÂ (SSS) by synchronizing preferentially to one of two sequences of noise bursts that alternate between two source locations. Here, we examine theÂ emergenceÂ of SSS along theÂ ascendingÂ auditoryÂ pathway. Extracellular recordings were made in anesthetized rats from the inferior colliculus (IC), the nucleus of the brachium of the IC (BIN), the medial geniculate body (MGB), and the primaryÂ auditoryÂ cortex (A1). Stimuli consisted of interleaved sequences of broadband noise bursts that alternated between two source locations. At stimulus presentation rates of 5 and 10 bursts per second, at which human listeners report robust SSS, neural SSS is weak in the central nucleus of the IC (ICC), it appears in the nucleus of the brachium of the IC (BIN) and in approximately two-thirds of neurons in the ventral MGB (MGBv), and is prominent throughout A1. The enhancement of SSS at the cortical level reflects both increasedÂ spatial sensitivity and increased forward suppression. We demonstrate that forward suppression in A1 does not result from synaptic inhibition at the cortical level. Instead, forward suppression might reflect synaptic depression in the thalamocortical projection. Together, our findings indicate thatÂ auditory streams are increasingly segregated along theÂ ascendingÂ auditoryÂ pathwayÂ as distinct mutually synchronized neural populations.
J Neurosci.Â 2015 Dec 9;35(49):16199-212. doi: 10.1523/JNEUROSCI.3116-15.2015.http://www.jneurosci.org/content/35/49/16199.long December 9, 2015 University of California, Irvine