Projections of the inferior colliculus in cat

Abstract

Projections of the feline inferior colliculus were studied using the Nauta-Laidlaw method to demonstrate degenerating axons. A subtentorial stereotaxic approach was used to avoid corticofugal degeneration. Direct connections from the inferior colliculus to the anterior midline cerebellar cortex were observed. There is a topographical relationship of fibers of the brachium of the inferior colliculus and parabrachial region to the superior colliculus. A definite projection to the superior colliculi including a pathway through its commissure was found from the parabrachial region. A projection exists from the inferior colliculus to the dorsolateral portion of the central gray as far as the pretectum. There is a projection along the medial portion of the superior colliculus to the pretectum. Projections to the midbrain reticular formation, central gray and superior colliculi were substantial. Thalamic projections include a distribution of fibers to the magnocellular and rostral portion of the principal divisions of the medial geniculate body and to the lateral posterior thalamic nucleus. The rostral connections of the inferior colliculus with areas other than the medial geniculate body indicate that it may function in roles in addition to that of a mass somatomotor reflex center. Possible roles of the inferior colliculus in attention, habituation, and integration of corticovisual and auditory impulses are suggested.Neuroanatomical studies have been made which describe projections of the inferior colliculus. Ascending projections of the inferior colliculus have been reported by Woollard and Harpman ('40) as ending only in the principal division of the medial geniculate body via the ipsilateral brachium. Recently, workers have observed projections entering the magnocellular and rostral part of the principal divisions (Barnes, Magoun and Ranson, '43; Rasmussen, '61 ; Moore and Goldberg, '63). Whitfield ('67) states that comparatively little work seems to have been done on the details of the afferent fiber connections to the medial geniculate body from the inferior colliculus and other structures. Some projections to the medial geniculate body and inferior colliculus from limbic structures have been described (Powell and Hoelle, '67; Akagi and Powell, '68). Rasmussen ('61) and Moore and Goldberg ('63) in turn, found that the reticular formation of the midbrain receives terminal projections from the inferior colliculus through the parabrachial region. Some projections coursing mediad from the inferior colliculus to the midbrain central gray have been described in the cat by Woollard and Harpman ('40) and Moore and Gddberg ('63). Rose, Greenwood, Goldberg and J. COMP. NEUR., 136: 183-192.Hind ('63) have shown that the inferior colliculus is highly tonotopic. Hoelle ('67) placed lesions in the inferior colliculi bilaterally to study their role in frequency discrimination. He concluded that the observed effects were due to the interruption of fibers to midline thalamic nuclei. Such evidence implies that the inferior...

Projections of the Inferior Colliculus in Insectivores and Primates; pp. 314–327

“…The central nucleus also innervates most of the central and external nuclei of the contralateral colliculus, with the exception of a ventromedial part of the central nucleus. This pattern of innervation of the ipsilateral external nucleus and contralateral colliculus is similar in all species in this study and is consistent with what is seen in nonprimate mammals [rabbit: Tarlov and cat: Moore and Goldberg, 1966; van Noort, 1969;Powell and Hatton, 1969], Central Gray and Superior Colliculus Degenerating fibers and terminals are routinely observed in the peria queductal gray at the level of the lesion. A few additional fibers enter the periaqueductal gray from commissural fibers, either as they cross the mid line or as they curve medial to the opposite central nucleus.…”

“…No significant variation has been noted, in these or other in- vestigations, in species which are primitive or advanced, generalized or acoustically specialized, over a wide range of mammals [opossum: Mar tin, 1969; rabbit: T arlov and kangaroo rat: Carey and Webster, 1971;guinea pig: Woolard and Harpman, 1940;cat: Moore and Goldberg, 1963;van Noort, 1969;Powell and Hatton, 1969; macaque monkey: Moore and Goldberg, 1966], In all species studied to date, the ascending collicular projection has two components: first, short fibers to other areas of the tectum, including the central gray, superior colliculus, and opposite inferior colliculus; and secondly, long fibers which project through the inferior brachium bilaterally to distribute ter minals to the parabrachial and intrabrachial regions of the tegmentum, and to the principal and internal division of the medial geniculate nucleus in the thalamus. Disagreement in the literature as to whether or not brachial fibers terminate in the posterior nucleus is probably due to the difficulty in establishing a clear boundary between the posterior nucleus and the internal division of the medial geniculate.…”

Auditory brainstem projections to the ferret superior colliculus: Anatomical contribution to the neural coding of sound azimuth

“…Some of these studies did not identify which regions of the IC provide the SC afferents (Moore and Goldberg, 1966;Tarlov and Moore, 1966;Powell and Hatton, 1969;Cadusseau and Roger, 1985), whereas others reported SC inputs originating in the BIN (Edwards et al, 1979;van Buskirk, 1983;Kudo et al, 1984;Wallace and Fredens, 1989), ICX (Edwards et al, 1979;Kudo and Niimi, 1980;van Buskirk, 1983;Hashikawa and Kawamura, 1983;Druga and Syka, 1984;Covey et al, 1987;Zhang et al, 1987), ICP (Edwards et al, 1979;Hashikawa and Kawamura, 1983), and ICC (Druga and Syka, 1984;Covey et al, 1987;Zhang et al, 1987). The majority of these studies described inputs either predominantly or exclusively from regions of the ipsilateral IC.…”

“…Reports based on anterograde tracing techniques concur that the intermediate and deep layers of the SC are the primary target of auditory brainstem nuclei (Powell and Hatton, 1969;Kudo and Niimi, 1980;Henkel, 1983;Kudo et al, 1984;Covey et al, 1987;Wallace and Fredens, 1989). This is likely to be the case in the ferret too because recording studies in this species have only very rarely encountered acoustically responsive units in the superficial layers (King and Hutchings, 1987).…”

“…These authors did not distinguish different regions of the IC, but this pattern of labelling does correspond to what we observed in the ipsilateral BIN of the ferret. By using the Nauta-Laidlaw method in cats in which lesions had been made in the IC, Powell and Hatton (1969) described a topographic relationship between the position of degenerating axons within the BIC and their termination sites in the ipsilateral SC. Degenerating fibres in the lateral part of the SC originated from the lateral part of the brachium, whereas those terminating in medial SC came from the medial part of the brachium and from the more medially located parabrachial region.…”