1. Brain Plasticity and 2. development

Short-Term vs. Long-Term Synaptic Changes

• Short-term: temporary strengthening of synapses through increased neurotransmitter release or receptor sensitivity. • Long-term: structural changes such as growth of new synapses or dendritic spines (basis of learning and memory).

Synaptic Plasticity

• The ability of synapses to strengthen or weaken over time in response to increases or decreases in activity.

Structural Plasticity

• Physical changes in the brain's structure, such as new connections forming or old ones being pruned.

Hebb’s Rule

• “Neurons that fire together, wire together.” Repeated activation strengthens synaptic connections.

LTP (Long-Term Potentiation)

• Persistent strengthening of synapses based on recent patterns of activity. • Occurs mainly in the hippocampus; associated with learning and memory.

Adult Neurogenesis

• Formation of new neurons in adults, mainly in the hippocampus and olfactory bulb. • Supports learning, memory, and adaptation.

Ischemic Stroke

• Caused by blockage of a blood vessel leading to loss of oxygen to brain tissue. • Results in neuron death; early intervention is critical.

Kennard Principle

• Younger brains show greater plasticity and recovery potential after injury than adult brains.

Peripheral vs. Central Damage

• Peripheral Nervous System (PNS): axons can regrow (1–2 mm/day) if myelin sheath intact. • Central Nervous System (CNS): regeneration limited due to scar tissue and inhibitory molecules.

Focal Hand Dystonia

• Condition caused by cortical reorganization after repetitive hand movements (common in musicians); leads to loss of fine motor control and involuntary contractions.

Phantom Limb

• Sensation of an amputated limb caused by cortical reorganization; neighboring brain areas take over the missing region.

Proliferation

• Production of new cells, mostly stem cells, early in development.

Migration

• Movement of newly formed neurons to their destined locations in the brain.

Differentiation

• Neurons develop specific structures and functions based on their location.

Apoptosis

• Programmed cell death that eliminates unnecessary neurons to refine neural circuits.

Myelination

• Formation of myelin sheath by glial cells; improves speed of neural transmission.

Synaptogenesis

• Formation of new synapses between neurons; continues throughout life.

BDNF (Brain-Derived Neurotrophic Factor)

• Promotes survival, growth, and differentiation of neurons.

Inside-Out Organization

• Newer neurons migrate past older ones, forming the brain’s layers from inside to outside.

Axon Pathfinding & Sperry’s Experiment

• Axons follow chemical gradients to reach targets (chemoaffinity hypothesis). • Sperry showed axons regrow to original targets even if positions are altered (frog-eye experiment).

Pruning

• Removal of weak or unused synapses; strengthens neural efficiency.

Nerve Growth Factor (NGF)

• Protein promoting survival and growth of axons and dendrites.

Synesthesia

• Cross-wiring of sensory areas; stimulation of one sense evokes another (e.g., seeing colors when hearing sounds).