Auditory brainstem responses after electrolytic lesions in bilateral subdivisions of the medial geniculate body of tree shrews

Abstract

This study aimed to establish a tree shrew model of bilateral electrolytic lesions in the medial geniculate body (MGB) to determine the advantages of using a tree shrew model and to assess the pattern of sound processing in tree shrews after bilateral electrolytic damage in different parts of the MGB. The auditory brainstem responses (ABRs) of a normal control group (n = 30) and an electrical damage group (n = 30) were tested at 0 h, 24 h, 48 h, 72 h, 7 days, 15 days, and 30 days after surgery. (1) The bilateral ablations group exhibited a significant increase in the ABR threshold of the electrolytic damage group between pre- and post-operation. (2) There were significant increases in the I-VI latencies at 0 h after MGBd and MGBm lesions and at 24 h after MGBv lesion. (3) The amplitudes of wave VI were significantly decreased at 24 h and 48 h after MGBd lesion, at 72 h and 7 days after MGBm lesion, and at 24 h, 48 h, 72 h, and 7 days after MGBv lesion. (1) The electrolytic damage group suffered hearing loss that did not recover and appeared to be difficult to fully repair after bilateral ablation. (2) The latencies and amplitudes of responses in the MGB following bilateral electrolytic lesion were restored to pre-operation levels after 15–30 days, suggesting that a portion of the central nuclei lesion was reversible. (3) The tree shrew auditory animal model has many advantages compared to other animal models, such as greater complexity of brain structure and auditory nuclei fiber connections, which make the results of this experiment more useful for clinical diagnoses compared with studies using rats and guinea pigs.

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