Université Toulouse, CerCo, Université Paul Sabatier, Toulouse, France.
PLoS One. 2013 Apr 12;8(4):e60093. doi: 10.1371/journal.pone.0060093. Print 2013.
Psychophysics and brain imaging studies in deaf patients have revealed a functional crossmodal reorganization that affects the remaining sensory modalities. Similarly, the congenital deaf cat (CDC) shows supra-normal visual skills that are supported by specific auditory fields (DZ-dorsal zone and P-posterior auditory cortex) but not the primary auditory cortex (A1). To assess the functional reorganization observed in deafness we analyzed the connectivity pattern of the auditory cortex by means of injections of anatomical tracers in DZ and A1 in both congenital deaf and normally hearing cats. A quantitative analysis of the distribution of the projecting neurons revealed the presence of non-auditory inputs to both A1 and DZ of the CDC which were not observed in the hearing cats. Firstly, some visual (areas 19/20) and somatosensory (SIV) areas were projecting toward DZ of the CDC but not in the control. Secondly, A1 of the deaf cat received a weak projection from the visual lateral posterior nuclei (LP). Most of these abnormal projections to A1 and DZ represent only a small fraction of the normal inputs to these areas. In addition, most of the afferents to DZ and A1 appeared normal in terms of areal specificity and strength of projection, with preserved but smeared nucleotopic gradient of A1 in CDCs. In conclusion, while the abnormal projections revealed in the CDC can participate in the crossmodal compensatory mechanisms, the observation of a limited reorganization of the connectivity pattern of the CDC implies that functional reorganization in congenital deafness is further supported also by normal cortico-cortical connectivity.
失聪患者的心理物理学和脑成像研究揭示了一种功能上的跨模态重组，这种重组会影响到剩余的感觉模态。同样，先天性失聪的猫（CDC）表现出超常的视觉技能，这些技能得到了特定的听觉区域（DZ-背侧区和 P-听觉皮质后区）的支持，但不是初级听觉皮质（A1）。为了评估耳聋中观察到的功能重组，我们通过在先天性失聪和正常听力的猫的 DZ 和 A1 中注射解剖示踪剂，分析了听觉皮质的连接模式。对投射神经元分布的定量分析揭示了非听觉输入的存在，这些输入存在于 CDC 的 A1 和 DZ，但不存在于听力正常的猫中。首先，一些视觉（19/20 区）和躯体感觉（SIV）区域向 CDC 的 DZ 投射，但在对照组中没有观察到。其次，听觉猫的 A1 接收到来自视觉外侧后核（LP）的微弱投射。这些异常投射到 A1 和 DZ 的大多数仅代表这些区域正常输入的一小部分。此外，DZ 和 A1 的大多数传入纤维在区域特异性和投射强度方面看起来是正常的，在 CDC 中，A1 的核团定位梯度虽然受到了干扰，但仍然存在。总之，虽然在 CDC 中发现的异常投射可以参与跨模态补偿机制，但观察到 CDC 的连接模式的重组有限，这意味着先天性耳聋中的功能重组也得到了正常皮质-皮质连接的支持。
