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XII: Experience and Critical Periods (aka, Plastics)XIII: Brain Diseases IXIV: Brain Diseases IIXV: Genetics and Human Brains: Clues from AbnormalitiesXVI: Reflections on Higher Brain Functions

Lecture XII: Plasticity

Neuromorphological

On the Cellular Level (Hebb Rule)

Functional

Adult

Early

Molding

Tweeking

Neuromorphological PlasticityOrganization

guided by input

Whisker and Neuronal

Connections (9)Periphery input to

cortex No Genetic

Predisposition

Human: Visual Cortex (11)

Experiment: Label Eye-Specific Neurons (12)

October 11, 2010 XII. Experience & Critical Periods (aka Plastics) 5

Labeled axons from visual thalamus to visual cortex in monkeys of different ages

Axons related to left eye are red and those related to right eye are blue

Neuromorphological PlasticityOrganization

guided by input

Whisker and Neuronal

Connections (9)Periphery input to

cortex No Genetic

Predisposition

Human: Visual Cortex (11)

Don’t use it, lose it. (14,15)

Experiment: Label Eye-Specific Neurons (12)

Wide Branching to Delineated (13)

Functional Plasticity

Reinforcing Good Connections

Ends with Puberty

Early vs Late Bilinguals (21,22,23,24)

October 11, 2010 XII. Experience & Critical Periods (aka Plastics) 8

“Early” bilingual subject -

Broca’s Area (Brodmann’s 44+)

“Late” bilingual subject -

Broca’s Area (Brodmann’s 44+)

Language Production

Functional Plasticity

Reinforcing Good Connections

Early vs Late Bilinguals (21,22,23,24)

Ends with Puberty

Lose unused neurons (25)

Adult PlasticityReinforcement

through experience; adjustments

Demo Quickly learned and lost (half-life)

Hebb Rule

1. Increase post-synaptic sensitivity (38)2. Create new synapses (39)

Persistent firing of a cell by a different neuron results in metabolic or growth process change (37).

October 11, 2010 XII. Experience & Critical Periods (aka Plastics) 12

October 11, 2010 XII. Experience & Critical Periods (aka Plastics) 13

Lecture XII: Brain Disease: Parkinson’s

• Phenotype: Characterized by an inability to initiate movement (walking) or terminate movement, tremors at rest, rigidity and minimal facial expressions. • Pathophysiology: Loss of Substantia nigra results in lost dopaminergic neurons• Loss of thalamic output from basal ganglia• Reduced excitation of motor neurons in the superior collicus and cortex

October 13, 2010 Lecture XIII. Brain Diseases - I. 15

Substantia Nigra

THE BRAIN ATLAS, 3rd ed p 74

October 13, 2010 Lecture XIII. Brain Diseases - I. 16

THE BRAIN ATLAS, 3rd ed p 139

Substantia Nigra

Globus Pallidus

Caudate Nucleus & Putamen

Subthalamic Nucleus

Substantia Nigra

Thalamus

Decreased Excitation of Cortex

Globus Pallidus

Caudate Nucleus & Putamen

Subthalamic Nucleus

Substantia Nigra

Thalamus

Increased Excitation