Chapter 23: Wiring the Brain: Development and Synaptic Plasticity

Neurons

85 billion cells interconnecting in the brain.

Neurogenesis

Formation of new neurons during development.

Synaptogenesis

Creation of synapses between neurons.

Pathway Formation

Establishing neural pathways for communication.

Cell Proliferation

Radial glial cells produce neurons and astrocytes.

Transcription Factors

Proteins determining cell fate during division.

Cell Migration

Movement of cells to their final locations.

Pyramidal Cells

Neurons that migrate vertically along glial fibers.

Inhibitory Interneurons

Cells migrating laterally from different origins.

Subplate Layer

Initial residence of first migrating cells.

Cortical Plate

Destination for migrating neurons in the cortex.

Layer VI Neurons

First cortical layer formed during migration.

Cell Differentiation

Neurons acquire specific characteristics at destination.

Cortical Protomap

Blueprint for cortical area development.

Radial Unit Hypothesis

Neurons follow radial glial guides during migration.

Thalamic Input

Influences cortical differentiation during development.

LGN Input

Essential for monkey striate cortex differentiation.

Pathway Selection

First phase in forming neural pathways.

Target Selection

Second phase determining pathway endpoints.

Address Selection

Final phase ensuring precise connectivity.

Growth Cone

Tip of a growing axon.

Axon Guidance

Mechanisms directing axon growth to targets.

Pioneer Neurons

Neurons that lead axon growth directionally.

Chemoattractant

Substance that attracts growing axons, e.g., netrin.

Chemorepellent

Substance that repels growing axons, e.g., slit.

Optic Chiasm

Site where optic nerve fibers cross over.

Topographic Maps

Organized neural connections based on spatial information.

Chemoaffinity Hypothesis

Theory that axons connect based on chemical signals.

CNS Regeneration

Ability of axons to regenerate in amphibians, not mammals.

Ephrins

Repulsive signals guiding retinal axon direction.

Retinotectal Projection

Mapping of retinal inputs to tectum.

Neuromuscular Synapse Formation

Process of synapse development at muscle junctions.

CNS Synapse Formation

Steps for establishing synapses in the central nervous system.

Dendritic Filopodium

Protrusion that contacts axons during synapse formation.

Synaptic Vesicles

Contain neurotransmitters at presynaptic membrane.

Postsynaptic Receptors

Proteins accumulating on postsynaptic membrane for signaling.

Cell and Synapse Elimination

Reduction of neurons and synapses for brain function.

Apoptosis

Programmed cell death crucial for development.

Trophic Factors

Supportive proteins like nerve growth factor.

Synapse Elimination

Removal of synapses at neuromuscular junction.

Activity-Dependent Synaptic Rearrangement

Changes in synaptic patterns due to neural activity.

Critical Period

Time frame for significant synaptic plasticity.

Synaptic Segregation

Refinement of synaptic connections in visual pathways.

Retinal Waves

In utero activity influencing synaptic segregation.

Hebbian Modifications

Synaptic changes based on correlated activity.

Ocular Dominance Columns

Visual cortex structures for segregated eye input.

Synaptic Rearrangement

Changes in synaptic connections due to experience.

Monocular Deprivation

Experiment affecting ocular dominance and synaptic competition.

Ocular Dominance Shift

Change in visual processing due to eye activity.

Cortical Binocularity

Ability to process inputs from both eyes.

Cortical Synaptic Plasticity

Mechanisms for modifying synaptic strength and connections.

Synapse Activity

Correlates with multiple inputs on postsynaptic neuron.

Excitatory Synaptic Transmission

Involves glutamate receptors for signal transmission.

AMPA Receptors

Glutamate-gated ion channels facilitating synaptic transmission.

NMDA Receptors

Unique receptors with voltage-gated and calcium-conducting properties.

Calcium Flux

Signals pre- and postsynaptic coactivation levels.

Long-Term Potentiation (LTP)

Strengthening of synaptic transmission due to NMDA activation.

Hebbian Detectors

NMDA receptors detect simultaneous presynaptic and postsynaptic activity.

Biochemical Mechanisms

Triggered by Ca2+ entry, modifying synaptic effectiveness.

Testing LTP

Monitor synaptic strength before and after NMDA activation.

Long-Term Depression (LTD)

Opposite of LTP, involves loss of synaptic AMPA receptors.

Monocular Deprivation Consequences

Leads to loss of synaptic influence on cortical neurons.

Critical Periods

Times when synaptic plasticity is heightened during development.

Axon Growth Cessation

Hypothesis for the end of plasticity in the brain.

Mature Synaptic Transmission

When synaptic connections stabilize and plasticity diminishes.

Cortical Activation Constraints

Limits on activation may affect synaptic plasticity.

Intrinsic Inhibitory Circuitry

Matures later, influencing plasticity and recovery.

Brain Development Circuitry

Formation and refinement of neural connections during growth.

Environmental Influence

Affects brain modification throughout an individual's life.

Visual System Plasticity

Critical periods observed in sensory and motor systems.

Reduced Visual Responsiveness

Result of brief monocular deprivation on visual processing.