Ascending Projections to the Medial Geniculate Body from Physiologically Identified Loci in the Inferior Colliculus

1997 ◽  
pp. 295-302 ◽  
Author(s):  
M. S. Malmierca ◽  
A. Rees ◽  
F. E. N. Le Beau
Keyword(s):  
Inferior Colliculus ◽  
Medial Geniculate Body ◽  
Medial Geniculate

scholarly journals Inhibitory Projections from the Inferior Colliculus to the Medial Geniculate body Originate from Four Subtypes of GABAergic Cells

eNeuro ◽  
2018 ◽  
Vol 5 (5) ◽  
pp. ENEURO.0406-18.2018 ◽  
Author(s):  
N. L. Beebe ◽  
J. G. Mellott ◽  
B. R. Schofield
Keyword(s):  
Inferior Colliculus ◽  
Medial Geniculate Body ◽  
Medial Geniculate

scholarly journals Antidromic Activation Reveals Tonotopically Organized Projections From Primary Auditory Cortex to the Central Nucleus of the Inferior Colliculus in Guinea Pig

2007 ◽  
Vol 97 (2) ◽  
pp. 1413-1427 ◽  
Author(s):  
Hubert H. Lim ◽  
David J. Anderson
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Spatial Organization ◽  
Medial Geniculate Body ◽  
Primary Auditory Cortex ◽  
Central Nucleus ◽  
Antidromic Activation ◽  
Antidromic Stimulation ◽  
Medial Geniculate ◽  
Layer V

The inferior colliculus (IC) is highly modulated by descending projections from higher auditory and nonauditory centers. Traditionally, corticofugal fibers were believed to project mainly to the extralemniscal IC regions. However, there is some anatomical evidence suggesting that a substantial number of fibers from the primary auditory cortex (A1) project into the IC central nucleus (ICC) and appear to be tonotopically organized. In this study, we used antidromic stimulation combined with other electrophysiological techniques to further investigate the spatial organization of descending fibers from A1 to the ICC in ketamine-anesthetized guinea pigs. Based on our findings, corticofugal fibers originate predominantly from layer V of A1, are amply scattered throughout the ICC and only project to ICC neurons with a similar best frequency (BF). This strict tonotopic pattern suggests that these corticofugal projections are involved with modulating spectral features of sound. Along the isofrequency dimension of the ICC, there appears to be some differences in projection patterns that depend on BF region and possibly isofrequency location within A1 and may be indicative of different descending coding strategies. Furthermore, the success of the antidromic stimulation method in our study demonstrates that it can be used to investigate some of the functional properties associated with corticofugal projections to the ICC as well as to other regions (e.g., medial geniculate body, cochlear nucleus). Such a method can address some of the limitations with current anatomical techniques for studying the auditory corticofugal system.

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