Some further observations on the effects of unilateral cortical ablation on sound localization in the cat

Abstract

It has previously been shown that unilateral ablation of the whole auditory cortex in the cat disrupts the precedence effect, and also interferes with the ability of the normal animal to discriminate in the Y-maze between a single sound on one side and a double sound consisting of a signal on both left and right sides. The present work has confirmed these effects and has shown that both can be obtained with lesions confined to AI and AII. The "one-versus-two" deficit has invariably been seen in all the animals studied, but a proportion of animals do not show the precedence effect deficit. It has been confirmed that the apparent sucess of some animals can be due to the training effect of the one-versus-two paradigm, as was proposed in the earlier paper; however it has also been shown that this cannot be explanation in all cases. It has been demonstrated that cats are able to localize sound behind them with some success; turning around in the start box to reverse right and left space is therefore a possible strategy for overcoming a unilateral deficit. However, even with the head "fixed" in the forward-facing position, one animal was still able to run well above chance. The size of the lesion does not appear to be a correlate of the performance level.

Development of auditory localization in dogs: Single source and precedence effect sounds

“…This interpretation is supported by neuroanatomical work on the role of the auditory cortex in the precedence effect, mostly with adult cats (e.g., Whitfield et al, 1972Whitfield et al, , 1978. This work suggests that the auditory cortex plays a critical role in mediating localization under precedence effect conditions, although the specific binaural processes involved have not been unequivocally demonstrated (Cranford & Oberholtzer, 1976).…”

“…But for precedence-effect sounds, the system must compare the arrival times of the leading and lagging sounds and then suppress perception of the lagging sound. Evidence from adult cats suggests that precedence-effect and single-source sound localization involve different CNS structures (Whitfield, Cranford, Ravizza, & Diamond, 1972;Whitfield, Diamond, Chiveralls, & Williamson, 1978). Localization of precedence effect sounds appears to depend on an intact auditory cortex contralateral to the side of the leading sound.…”

Hearing suppression induced by electrical stimulation of human auditory cortex

“…It is possible that disruption of local cortical activity alone could suppress hearing, although it is generally agreed that in humans (Tramo et al, 2002;Kaga et al, 2000;Hausler and Levine, 2000;Penfield and Perot, 1963) and in laboratory animals (Heffner and Heffner, 1986;Heffner, 1997;Colombo et al,1996;Whitfield et al, 1978) that unilateral destruction of auditory cortex of the STG does not result in deafness. More likely, hearing suppression is the result of activating corticofugal efferent pathways that project to auditory thalamic, midbrain and brainstem structures, and possibly the cochlea (Hazama et al, 2004;He, 2003;Jacomme et al, 2003, Suga andPandya et al, 1994;Weedman and Ryugo, 1996a,b).…”

Neural Correlates of the Precedence Effect in the Inferior Colliculus of Behaving Cats

“…Based on animal lesion studies (Jenkins and Masterton 1982;Kelly and Kavanagh 1994), we propose that single-source localization and localization dominance is governed primarily, but not exclusively, by the IC contralateral to the single source or the leading source. Although there have been no behavioral studies of the PE after ablation of the IC in animals, behavioral deficits, such as reduced echo thresholds, do occur when the auditory cortex is lesioned unilaterally (Cranford et al 1971;Kalmykova 1995;Whitfield et al 1978).…”