Ankaoua D, Malach R
Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel.
Isr J Med Sci. 1993 Sep;29(9):555-69.
The potential for peripheral modification of intrinsic horizontal connections was studied in the primary visual cortex (area 17) of adult, hooded rats that underwent monocular enucleation (ME) or binocular enucleation (BE) at the day of birth. The intrinsic connections were labelled by localized tracer injections at various sites in area 17. The pattern of interhemispheric callosal connections was revealed in the same animals by extensive injections of a distinguishable tracer in the contralateral hemisphere. The results show marked and consistent changes in area 17 intrinsic connections as a result of the neonatal enucleations. Specifically, in contrast to normally reared rats in which intrinsic connections are short ranged and are organized fairly uniformly around the injection site, in ME cases intrinsic connections extend over half the width of area 17, usually targeting a second field within area 17. In BE cases, the injection sites result in the appearance of elongated tongues and patches of label that protrude in different directions from the injection site. The observed modifications of intrinsic connections are clearly related to the abnormalities induced by enucleations in the pattern of callosal connections, such that intrinsic connections tend to form either between callosally connected sites or between a-callosal sites but avoid intermixing the two. The results reveal a high level of plasticity in the developing intrinsic connections. A Hebbian rule of connectivity is proposed as the underlying process guiding the formation of horizontal intrinsic connections in area 17.
在出生当天接受单眼摘除（ME）或双眼摘除（BE）的成年带帽大鼠的初级视觉皮层（17区）中，研究了内在水平连接的外周修饰潜力。通过在17区的不同部位进行局部示踪剂注射来标记内在连接。通过在对侧半球广泛注射可区分的示踪剂，在同一动物中揭示了半球间胼胝体连接的模式。结果显示，由于新生儿摘除眼球，17区的内在连接发生了显著且一致的变化。具体而言，与正常饲养的大鼠不同，正常饲养的大鼠内在连接范围较短，且在注射部位周围组织相当均匀，而在ME组中，内在连接延伸超过17区宽度的一半，通常靶向17区内的第二个区域。在BE组中，注射部位导致出现从注射部位向不同方向突出的细长舌状和斑块状标记。观察到的内在连接修饰显然与胼胝体连接模式中摘除眼球引起的异常有关，使得内在连接倾向于在胼胝体连接部位之间或无胼胝体连接部位之间形成，但避免两者混合。结果揭示了发育中的内在连接具有高度可塑性。提出了一种赫布连接规则作为指导17区水平内在连接形成的潜在过程。
