scholarly journals The Ferret Auditory Cortex: Descending Projections to the Inferior Colliculus

2006 ◽  
Vol 17 (2) ◽  
pp. 475-491 ◽  
Author(s):  
V. M. Bajo ◽  
F. R. Nodal ◽  
J. K. Bizley ◽  
D. R. Moore ◽  
A. J. King
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Descending Projections

Descending Projections From Auditory Cortex Modulate Sensitivity in the Midbrain to Cues for Spatial Position

2008 ◽  
Vol 99 (5) ◽  
pp. 2347-2356 ◽  
Author(s):  
Kyle T. Nakamoto ◽  
Simon J. Jones ◽  
Alan R. Palmer
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Frequency Tuning ◽  
Large Change ◽  
Spike Count ◽  
Neural Population ◽  
Tuning Curves ◽  
Interaural Level Differences ◽  
Descending Projections ◽  
Stimulation Of

The function of the profuse descending innervation from the auditory cortex is largely unknown; however, recent studies have demonstrated that focal stimulation of auditory cortex effects frequency tuning curves, duration tuning, and other auditory parameters in the inferior colliculus. Here we demonstrate that, in an anesthetized guinea pig, nonfocal deactivation of the auditory cortex alters the sensitivity of populations of neurons in the inferior colliculus (IC) to one of the major cues for the localization of sound in space, interaural level differences (ILDs). Primary and secondary auditory cortical areas were inactivated by cooling. The ILD functions of 46% of IC cells changed when the cortex was inactivated. In extreme cases, the ILD functions changed from monotonic to nonmonotonic during cooling and vice versa. Eight percent of the cells became unresponsive after deactivation of the auditory cortex. Deactivation of the cortex has previously been shown to alter the maximum spike count of cells in the IC; the change in normalized ILD functions is shown to be separate from this effect. In some cases, the ILD function changed shape when there was no change in the maximum spike count and in other cases there was no change in the shape of the ILD function even though there was a large change in the maximum spike count. Overall, the sensitivity of the IC neural population to ILD is radically altered by the corticofugal pathway.

Descending projections to the inferior colliculus from the posterior thalamus and the auditory cortex in rat, cat, and monkey

2002 ◽  
Vol 168 (1-2) ◽  
pp. 181-195 ◽  
Author(s):  
Jeffery A Winer ◽  
Michelle L Chernock ◽  
David T Larue ◽  
Steven W Cheung
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Posterior Thalamus ◽  
Descending Projections

scholarly journals Disparity in interaural time difference improves the accuracy of neural representations of individual concurrent narrowband sounds in rat inferior colliculus and auditory cortex

2020 ◽  
Vol 123 (2) ◽  
pp. 695-706
Author(s):  
Lu Luo ◽  
Na Xu ◽  
Qian Wang ◽  
Liang Li
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Interaural Time Difference ◽  
Critical Role ◽  
Low Frequency ◽  
Time Difference ◽  
Neural Representation ◽  
Frequency Bands ◽  
Neural Segregation ◽  
Peripheral Auditory System

The central mechanisms underlying binaural unmasking for spectrally overlapping concurrent sounds, which are unresolved in the peripheral auditory system, remain largely unknown. In this study, frequency-following responses (FFRs) to two binaurally presented independent narrowband noises (NBNs) with overlapping spectra were recorded simultaneously in the inferior colliculus (IC) and auditory cortex (AC) in anesthetized rats. The results showed that for both IC FFRs and AC FFRs, introducing an interaural time difference (ITD) disparity between the two concurrent NBNs enhanced the representation fidelity, reflected by the increased coherence between the responses evoked by double-NBN stimulation and the responses evoked by single NBNs. The ITD disparity effect varied across frequency bands, being more marked for higher frequency bands in the IC and lower frequency bands in the AC. Moreover, the coherence between IC responses and AC responses was also enhanced by the ITD disparity, and the enhancement was most prominent for low-frequency bands and the IC and the AC on the same side. These results suggest a critical role of the ITD cue in the neural segregation of spectrotemporally overlapping sounds. NEW & NOTEWORTHY When two spectrally overlapped narrowband noises are presented at the same time with the same sound-pressure level, they mask each other. Introducing a disparity in interaural time difference between these two narrowband noises improves the accuracy of the neural representation of individual sounds in both the inferior colliculus and the auditory cortex. The lower frequency signal transformation from the inferior colliculus to the auditory cortex on the same side is also enhanced, showing the effect of binaural unmasking.

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