Article
The impact of sequential bilateral auditory cortex lesions on discrimination performance of fast amplitude modulations in Mongolian gerbils – an update
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Published: | July 30, 2013 |
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Outline
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Fast periodic amplitude modulations (AM) are a characteristic of speech. It was shown in an earlier study that in Mongolian gerbils (Meriones unguiculatus) simultaneous bilateral ablation of the auditory cortex (AC) eliminates the ability to access learned discrimination of AM differing in modulation frequencies. Here we investigate the impact of sequential instead of simultaneous ablations of AC in both hemispheres. Additionally we examine possible neurophysiological correlates to the behavioral results after unilateral lesion.
Learning behavior during sound discrimination trainings was studied by an aversive shuttle box go/no go paradigm. Animals received sequential lesions of both AC, starting on the ipsilateral side after 3 weeks of initial discrimination training, followed by 3 weeks of additional training, lesion of the contralateral side, and 3 final weeks of training. At the same time we conducted 16-channel extracellular single cell recordings in the left AC.
In contrast to simultaneous ablation of both AC, sequential ablation did not lead to a comparable severe impairment of pre-learned discrimination performance. This result was independent of the order of ablation (left-right vs. right-left). Single cell recordings show neuroplastic changes of the tonotopic organization in the intact contralateral AC after ipsilateral lesion.
Our results show that one AC is sufficient for maintaining learned discrimination performance of fast AM. The consecutive ablation of the second AC in combination with our previous finding of impaired discrimination performance after simultaneous bilateral AC ablation points to a subcortical reorganization process that is triggered by the ablation of the first AC and requires an intact contralateral AC to preserve the ability to discriminate fast AM even after lesion of this contralateral AC.