Mechanisms of visual cortical development

描述(申请人提供)：从睁眼前开始，并在成熟的成人大脑中继续，视觉通路中的神经元活动发挥着突出但不断变化的作用。在睁眼前和早期视觉系统发育的关键时期，自发的和视觉驱动的活动在早期突触连接的建立和稳定中起着主要作用。在成熟的大脑中，神经元活动为感觉输入的检测和编码提供了底层底物。拟议的实验将集中于调查和操纵视觉通路内神经元活动在这段时间内的相关和统计特性。首先，多电极记录将被用来评估P24的LGN和视觉皮质内的自发和视觉驱动活动与正常饲养的成年清醒雪貂的相关结构。其次，我们将考察时空图案化活动在取向选择性成熟过程中的作用。已有研究表明，不同形式的早期视觉经验不同地改变了定向选择性和定向偏好图的发展。虽然人们认为这些变化是由视觉通路内活动的相关结构的变化驱动的，但这些变化的神经基础尚未得到直接研究。利用长期植入觉醒的行为雪貂的多电极记录阵列，将比较各种不同饲养条件下LGN和视皮层内神经元活动的相关结构，包括暗饲养和双眼眼睑缝合。改变视觉体验的时空关联结构的效果将通过饲养带有微型头盔LCD显示器的动物来直接评估。这些显示器将允许长期呈现动态的计算机生成的图案，其中包含不同的短期和远程空间和时间相关性。最后，我们将研究发育中的视皮层和LGN中单个细胞和细胞群对视觉刺激编码的变化。虽然基本的皮质调节特性，如定向选择性的发展已经被很好地研究了，但在成熟的大脑中出现更复杂的视觉皮质编码特性仍然不清楚。稀疏性、信息容量、互信息和冗余等编码属性将在后睁眼开发期间进行评估。这些实验应该会为大脑内感觉编码机制的发展提供新的信息。

DESCRIPTION (provided by applicant): Beginning before eye opening and continuing in the mature adult brain, neuronal activity within the visual pathway plays a prominent but changing role. Before eye opening and during the critical period of early visual system development, spontaneous and visually driven activity play a primary role in the establishment and stabilization of early synaptic connections. In the mature brain, neuronal activity provides the underlying substrate for the detection and coding of sensory input. The proposed experiments will focus on investigating and manipulating the correlational and statistical properties of neuronal activity within the visual pathway throughout this period of time. First, multielectrode recording will be utilized to assess the correlational structure of spontaneous and visually driven activity within the LGN and visual cortex of P24 to adult awake behaving normally reared ferrets. Second, the role of spatio-temporally patterned activity in the maturation of orientation selectivity will be examined. It has been shown that different forms of early visual experience differentially alter the development of orientation selectivity and orientation preference maps. While it is believed that these alterations are driven by changes in the correlational structure of activity within the visual pathway, the neural basis of these changes has not been directly examined. Utilizing chronically implanted multielectrode recording arrays in awake behaving ferrets, the correlational structure of neuronal activity within the LGN and visual cortex will be compared under a variety of different rearing conditions including dark rearing and binocular lid suture. The effect of altering the spatio-temporal correlational structure of visual experience will be directly assessed by raising animals with miniature head mounted LCD displays. These displays will allow the chronic presentation of dynamical computer generated patterns containing varying short and long-range spatial and temporal correlations. Finally, changes in the coding of visual stimuli by single cells and cell ensembles within the developing visual cortex and LGN will be investigated. While the development of basic cortical tuning properties such as orientation selectivity is well studied, the emergence of more complex properties of visual cortical coding in the mature brain remains unclear. Coding properties such as sparseness, information capacity, and mutual information and redundancy will be assessed during post eye-opening development. These experiments should provide new information about the development of mechanisms underlying sensory coding within the brain.