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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