Ascending projections of the inferior colliculus in the cat: An autoradiographic study

Abstract

The ascending projections of the inferior colliculus (IC) in the cat were traced by the autoradiographic method, with special reference in the differenial projections of each subnucleus of IC. The laminated ventrolateral part of the central nucleus of IC (CNv) projects to the ventral and medial divisions of the ipsilateral medial geniculate body (MGB). The projections to the ventral division are topographically organized in the mediolateral direction, the terminals being arranged in the form of lamina, while those to the medial division are diffuse. The unlaminated dorsomedial part of the central nucleus of IC (CNd) sends fibers to every division of the ipsilateral MGB, particularly to the dorsal division and the ventromedial portion of the ventral division. It is noteworthy that the external nucleus of IC (EN) projects to the superior colliculus, part of the pretectum, and the anterior extremity of MGB ipsilaterally, in addition to the ventral and medial divisions of MGB. The posterior cap of IC, regarded as the pericentral nucleus of IC (PC), projects ipsilaterally to the ventral part of the caudal tip of MGB and the posterior part of the suprapeduncular nucleus. In addition of these projections, the parabrachial region and interstitial nucleus of the brachium of IC (BIC) are identified as common targets of projections of each nucleus of IC on the ipsilateral side. Contralaterally, every subnucleus of IC except for PC projects via the commissure of IC to areas corresponding to the targets of the ipsilateral projections, such as the ventral and medial divisions of MGB and the parabrachial region and the interstitial nucleus of BIC, although these contraleral projections are in general much sparser than those ipsilateral. Intrinsic and commissural connections within IC are also revealed in this study, providing characteristic configurations of each subnucleus of IC. It is concluded that the ascending projections of IC in the cat are highly differentially organized according to its subnucleus.

Signaled two-way avoidance learning using electrical stimulation of the inferior colliculus as negative reinforcement: effects of visual and auditory cues as warning stimuli

“…Supporting this statement, an independent group of animals submitted to the same procedure, except for the pairing of tone with footshock, showed reliable learning rates comparable to those from typical avoidance-escape procedures that utilize an auditory stimulus paired with electric shock as the unconditioned stimulus (21,22). One possible explanation for these surprising results is that repeated electrical stimulation of tomical connections between the inferior colliculus and these structures (17,18). The present results show that rats quickly learn to make a shuttling response in order to avoid or escape from electrical stimulation of the inferior colliculus.…”

“…It is likely that the inferior colliculus may be responsible for the elaboration of aversion and fear-like responses, together with other structures of the brain aversion system, such as dorsal periaqueductal gray matter and amygdala. As a matter of fact, there are important connections between the inferior colliculus and the dorsal periaqueductal gray matter (17). Furthermore, recent findings from this laboratory have shown that lesion of the central nucleus of the amygdala attenuates, while lesion of the basolateral complex enhances the aversive consequences of the electrical stimulation of the inferior colliculus (18).…”

Systematic mapping of the monkey inferior colliculus reveals enhanced low frequency sound representation

“…DCIC and LN do project to the MGB, like the ICC does, but they mainly synapse on cells in the medial and dorsal regions (Calford and Aitkin 1983), along a purported modulatory pathway of the auditory system (Lee and Sherman 2010). These regions also send output to the SC (Kudo and Niimi 1980).…”

Activity-Dependent Synaptic Plasticity in the Central Nucleus of the Amygdala

“…Indeed, the PO receives auditory inputs from the external, pericentral, and brachial nuclei of the inferior colliculus (Kudo and Niimi, 1980;Kudo et al, 1984;Linke et al, 2000) as well as the dorsal nucleus of the lateral lemniscus (Kudo et al, 1983). In addition, PO receives visual and somatosensory inputs from the superior colliculus and spinal cord (for review, see Jones, 1985).…”