Microglia are the resident immune cells of the brain. Increasingly, they are recognized as important mediators of normal neurophysiology, particularly during early development. Here we demonstrate that microglia are critical for ocular dominance plasticity. During the visual critical period, closure of one eye elicits changes in the structure and function of connections underlying binocular responses of neurons in the visual cortex. We find that microglia respond to monocular deprivation during the critical period, altering their morphology, motility and phagocytic behaviour as well as interactions with synapses. To explore the underlying mechanism, we focused on the P2Y12 purinergic receptor, which is selectively expressed in non-activated microglia and mediates process motility during early injury responses. We find that disrupting this receptor alters the microglial response to monocular deprivation and abrogates ocular dominance plasticity. These results suggest that microglia actively contribute to experience-dependent plasticity in the adolescent brain.
Synaptic pruning refers to the process by which extra neurons and synaptic connections are eliminated in order to increase the efficiency of neuronal transmissions.
Synaptic prunning or axon prunning is the process of synapse elimination that occurs notably between early childhood and the onset of puberty in many mammals, including humans.Prunning starts near the time of birth and alot is completed by the time of sexual maturation in humans. This may be a reason why smoking pot is not the best idea during that time, as cannabinoids can alter synaptogenesis and the brain doesn’t completely develop until your early twenties. At birth, the human brain consists of approximately 86 (± 8) billion neurons. The infant brain will increase in size by a factor of up to 5 by adulthood. Two factors contribute to this growth: the growth of synaptic connections between neurons, and the myelination of nerve fibres; the total number of neurons, however, remains the same. Prunning is influenced by environmental factors and is widely thought to represent learningand so you need to prune throughout life. What this study indicates is that microglia are involved in that pruning ad they probably ingest the underused synapses.