Process in which the brain selectively removes weaker or less active synaptic connections, strengthening the efficiency and precision of neural networks. Synaptic pruning refines the wiring of the brain following periods of intense synaptogenesis during early development and adolescence. Synaptic pruning is a cornerstone of neural maturation, sculpting the [[Human Brain|brain's]] architecture by balancing connectivity and efficiency. It embodies the brain’s adaptive economy—retaining only what experience proves useful. ## Phases - **Early Development (Infancy)** Rapid synaptogenesis followed by large-scale pruning, especially in sensory and motor cortices. - **Adolescence** Secondary wave of pruning in association and prefrontal regions, shaping executive functions and emotional regulation. - **Experience-Dependent Refinement** Activity-based mechanisms ensure that frequently used neural pathways are preserved and optimized. ## Mechanisms - **Microglial Activity**: Microglia engulf and remove inactive synapses through phagocytosis. - **Complement System (C1q, C3)**: Marks synapses for elimination. - **Neural Activity Patterns**: Hebbian processes (“use it or lose it”) strengthen active connections and weaken silent ones. - **Neurotrophic Factors**: Levels of BDNF (Brain-Derived Neurotrophic Factor) modulate synaptic maintenance and survival. ## Key Brain Regions - [[Prefrontal Cortex]]: Pruning during adolescence enhances cognitive control and decision-making. - [[Visual Cortex]]: Early pruning critical for visual acuity and depth [[perception]]. - [[Hippocampus]]: Experience-driven refinement supports memory encoding and spatial navigation. ## Clinical Relevance - **Excessive Pruning**: Linked to neurodevelopmental disorders such as **[[schizophrenia]]** and **autism spectrum disorder (ASD)**. - **Insufficient Pruning**: May contribute to inefficient neural processing and overconnectivity. - **Aging**: Dysregulated pruning contributes to cognitive decline and synaptic loss in neurodegenerative diseases like **Alzheimer’s disease**.