Brain development

Timing

The beginning

Differentiation

Neural tube

Spinal chord and PNS

Spinal chord and PNS Migration of cells from spinal chord to periphery (e.g., gut, heart, peripheral sensory organs.

Development of sensory & motor neurons Alignment of sensory and motor neurons (motor & proprioception) Proper Central Pattern Generators and reflexes require proper development of local circuits

Sense chemical gradients and orient axonal growth Axonal growth cones Sense chemical gradients and orient axonal growth

Setting up the connections Where and when should the axon grow? Decussation

Motor neurons to muscles Setting up innervation

Competition among synapses Synaptic pruning - PNS Competition among synapses

Cells are programed to die unless they get NGF…. Nerve growth factor Cells are programed to die unless they get NGF….

Cell death

Anterior segments Midbrain Mesencephalon Hindbrain Signaling cascades govern Cell differentiation & Migration Diencephalon Telencephalon

Cortical layers Glial fibers

Eyes

Eyes to brain Setting up topography…

Synaptic pruning - CNS

Occular dominance in a neonate monkey V1 Synaptic pruning - CNS Occular dominance in a neonate monkey V1

Synaptic pruning is activity dependent Hebbian learning

Synapses during development

Synaptic plasticity Map space with inter-aural differences

Synaptic plasticity

This shift can only happen in young owls… Synaptic plasticity Axonal projections from the Inferior Coliculus to the visual tectum shift. This shift can only happen in young owls…

A developmental period with enhanced plasticity. Critical periods A developmental period with enhanced plasticity. Imprinting

Critical periods Bird song development

Critical periods

Innervation of primary visual cortex Critical periods Innervation of primary visual cortex