Developmental changes in cortical inhibitory circuits of visual and temporal cortex

Abstract

The development of neural circuit during critical period is controlled by inhibitory neuronal circuits constituting 20% of the neurons in the cerebral cortex. This change occurs dramatically at 3weeks to 1 month after birth with experience-dependent manner in rodent. Visual cortex shows a good correlation between the progress of the critical period and the development of inhibitory neural circuits. This brain area receives input directly to the visual information from the eye, but in case of temporal cortex does not receive direct input from sensory organs. The critical period timing is controlled by sensory experience. So, the critical period of sensory cortex is well defined but the development of inhibitory circuits in temporal cortex is still unknown. In this experiment, I investigated inhibitory circuit development of temporal cortex. First, I stained parvalbumin - positive interneuron, one of the inhibitory interneuron, which is projecting to GABAA receptor on pyramidal neuron. The GABAA receptor has important role to control the critical period. I found that the number of parvalbumin – positive neurons in temporal cortex is less than visual cortex both 3weeks and 8weeks. Next, I stained perineuronal nets which are associated mostly with inhibitory interneurons and are thought to be responsible for maintaining the excitatory/inhibitory balance in the adult brain. It is also related to the critical period. The intensity of perineuronal net in temporal cortex at 3weeks and 8weeks is weaker than visual cortex. These findings suggest that the meaning of inhibitory circuit development in temporal cortex. But it is unclear whether cortical areas excluding sensory cortices association cortices including temporal cortex have critical period.