Recent Research Results
Development of synchronous activity in the primary visual cortex
September 5, 2018
Visual ability for animals including human is initially poor in the early postnatal period and improves under the strong influence of visual experience. So, early visual experience is essential for the maturation of visual functions in which the primary visual cortex plays crucial roles. Synchronized firing in the visual cortex plays an important role in visual information processing. However, it was an open question whether visual experience is required for the establishment of synchronized firing of visual cortical neurons.
Japan’s researchers find that synchronous firing occurs selectively in adjacent neurons sharing similar visual response preferences in layers 2-4 (upper layer) of rat visual cortex. This feature-selective synchrony is rudimentary when the eyes opened and becomes prominent after eye opening only in the presence of pattern vision. Synchronous firing in layers 5-6 (lower layer) is weakly dependent on visual preference, which is strengthened during development after eye opening independently of visual experience as a whole (Figure 1). Therefore, we speculate that feature-selective synchronization in the upper layer may convey detailed visual information to the higher-order cortex, whereas weakly feature-selective synchronization in the lower layer may covey rather rough visual information to the subcortical areas or higher-order cortex. Since the upper layer neurons outputs to the higher vision area, the maturation of synchronous activity in the upper layer might promotes information transmission between cortical areas and improves visual ability.
Brief summary:
1. Synchronous activity occurs more remarkably depending on the similarity of preferred visual stimuli in upper than lower layer neurons in the primary visual cortex.
2. Synchrony is strengthened after eye opening in both upper and lower layers
3. Pattern vision during development is required for the establishment of synchronous activity in the upper but not the lower layer.
4. The establishment of synchronous activity in the upper layer might contribute to the improvement of visual ability after eye-opening.
Figure 1:
Experience dependent establishment of feature-selective synchronization in the upper layer but not lower layer in rat primary visual cortex.
(A) Synchronous activity occurs selectively in neurons sharing similar visual response preference in layers 2-4 (upper layer) but not layers 5-6 (lower layer). Filled triangles show neurons with synchronous activity. The same color shows neurons with similar visual response preference. (B) The feature-selective synchronization is absent just after eye opening in both upper and lower layers. (C) Visual experience is required for establishment of the synchronization in the upper but not the lower layer.