Akerman Colin J, Tolhurst David J, Morgan James E, Baker Gary E, Thompson Ian D
University Laboratory of Physiology, Oxford OX1 3PT, United Kingdom.
J Comp Neurol. 2003 Jun 23;461(2):217-35. doi: 10.1002/cne.10684.
The abnormal organization of the central visual pathways in the albino ferret has been characterized anatomically and physiologically. Recordings in dorsal lateral geniculate nucleus of the albino ferret show that lamina A1, which receives an aberrant projection from the contralateral eye, contains an extensive representation of the ipsilateral visual hemifield with receptive fields located up to 35 degrees from the vertical meridian. This is not the case in pigmented ferrets, for which the vast majority of units, activated through either the contralateral or ipsilateral eye, have receptive fields confined to the contralateral hemifield. The few fields found in the ipsilateral hemifield are driven through the contralateral eye and none is more than 10 degrees from the midline. Cortical topography was studied by making closely spaced electrode penetrations across the area 17/18 border. In pigmented animals, the reversal of topography at the border is characterized by units with receptive fields centered a few degrees into the ipsilateral hemifield. In 22 of 25 albinos, the "Boston" aberrant topography was found: the representation of the vertical meridian is within area 17, rather than at the area 17/18 border. Instead, at the area 17/18 border, there is a reversal in the topographic progression at up to 30 degrees into the ipsilateral hemifield. This pattern was most pronounced in the upper visual field. In agreement with the "Boston" physiology, injections of retrograde tracer made in area 17 usually label neurons in either lamina A or the part of lamina A1 that is aberrantly innervated by the contralateral eye. A column of labeled cells extending through all geniculate layers is rarely seen in albinos, although this is commonly the pattern in pigmented ferrets.
白化雪貂中央视觉通路的异常组织已通过解剖学和生理学方法进行了表征。对白化雪貂背外侧膝状核的记录显示，接收对侧眼异常投射的A1层包含同侧视觉半视野的广泛表征，其感受野位于距垂直子午线35度以内。有色雪貂的情况并非如此，对于有色雪貂，通过对侧眼或同侧眼激活的绝大多数神经元，其感受野局限于对侧半视野。在同侧半视野中发现的少数感受野是由对侧眼驱动的，且没有一个距离中线超过10度。通过在17/18区边界进行紧密间隔的电极穿刺来研究皮质地形图。在有色动物中，边界处地形图的反转表现为感受野位于同侧半视野内几度处的神经元。在25只白化雪貂中有22只发现了“波士顿”异常地形图：垂直子午线的表征位于17区内，而不是在17/18区边界处。相反，在17/18区边界处，地形图的进展在同侧半视野内高达30度处发生反转。这种模式在上半视野中最为明显。与“波士顿”生理学一致，在17区注射逆行示踪剂通常会标记A层或被对侧眼异常支配的A1层部分中的神经元。在白化雪貂中很少见到穿过所有膝状层的一列标记细胞，尽管这在有色雪貂中是常见的模式。
