Kok Melanie A, Lomber Stephen G
Department of Physiology & Pharmacology, University of Western Ontario, London, N6A 5C2, Canada; Department of Psychology, University of Western Ontario, London, N6A 5C2, Canada; Cerebral Systems Laboratory, University of Western Ontario, London, N6A 5C2, Canada; Brain and Mind Institute, University of Western Ontario, London, N6A 5C2, Canada.
Department of Physiology & Pharmacology, University of Western Ontario, London, N6A 5C2, Canada; Department of Psychology, University of Western Ontario, London, N6A 5C2, Canada; Cerebral Systems Laboratory, University of Western Ontario, London, N6A 5C2, Canada; Brain and Mind Institute, University of Western Ontario, London, N6A 5C2, Canada; National Centre for Audiology, University of Western Ontario, London, N6A 5C2, Canada.
Hear Res. 2017 Jan;343:108-117. doi: 10.1016/j.heares.2016.05.013. Epub 2016 Jun 2.
While it is now well accepted that the brain reorganizes following sensory loss, the neural mechanisms that give rise to this plasticity are not well understood. Anatomical tract tracing studies have begun to shed light on the structural underpinnings of cross-modal reorganization by comparing cerebral connectivity in sensory-deprived animals to that of their non-deprived counterparts. However, so far, full documentation of connectional patterns within hearing, congenitally deaf, as well as animals deafened early versus later in life exist only for primary auditory cortex, a region not known to undergo cross-modal reorganization in the deaf. The purpose of the present investigation was to examine thalamo-cortical patterns of connectivity in hearing, late- and early-deafened cats to the dorsal zone (DZ), a region of auditory cortex that cross-modally reorganizes to mediate enhanced visual motion perception following deafness. In hearing cats, the largest projections to DZ arose from the dorsal division of the medial geniculate body (MGB) with lesser projections originating in the medial and ventral MGB and from the suprageniculate and the lateral posterior nuclei. In general, while some variations in the strength of specific thalamic projections were noted, the pattern of projections arising from the thalamus in early- and late-deafened animals remained consistent with that of hearing subjects. These results complement the existing thalamic connectivity data described for congenitally deaf animals, which together demonstrate that thalamo-cortical connectivity patterns to DZ are conserved following deafness, irrespective of the time of onset and etiology of deafness.
虽然现在人们已经普遍接受大脑在感觉丧失后会进行重组，但导致这种可塑性的神经机制仍未得到充分理解。解剖学上的束路追踪研究已开始通过比较感觉剥夺动物与未剥夺动物的大脑连通性，来揭示跨模态重组的结构基础。然而，到目前为止，仅针对初级听觉皮层（已知该区域在聋动物中不会发生跨模态重组），才有关于听力正常、先天性耳聋以及在生命早期或晚期致聋动物的听觉连接模式的完整记录。本研究的目的是检查听力正常、晚期和早期致聋猫到背侧区（DZ）的丘脑 - 皮层连通模式，DZ是听觉皮层的一个区域，在耳聋后会进行跨模态重组以介导增强的视觉运动感知。在听力正常的猫中，投射到DZ的最大纤维束来自内侧膝状体（MGB）的背侧部分，较小的纤维束起源于内侧和腹侧MGB以及上膝状体和外侧后核。总体而言，虽然特定丘脑投射的强度存在一些差异，但早期和晚期致聋动物丘脑产生的投射模式与听力正常的动物一致。这些结果补充了针对先天性耳聋动物描述的现有丘脑连通性数据，这些数据共同表明，无论耳聋的发病时间和病因如何，耳聋后丘脑与DZ的皮层连通模式都是保守的。
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