Transcript Brain Organizing Principles and Functions

The Brain and Behavior
Outline
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Functions
Evolution: structure and behavior
Basic Unit: The Neuron
Generation: How does a signal get started?
Action Potential: How does a signal move?
Synapses: What does the signal do?
Reflexes: A model
Brain Organizing Principles and Functions
Functions
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Communication
Coordination
Control
Cognition
Complexity
Outline: Start With A
Mechanistic View
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Functions
Evolution: structure and behavior
Basic Unit: The Neuron
Generation: How does a signal get started?
Action Potential: How does a signal move?
Synapses: What does the signal do?
Reflexes: A model
Brain Organizing Principles and Functions
Evolution
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None
Nerve net
Segmented
Cephalization: an organizing principle (brainmind correlation not always obvious!)
• Kineses
• Taxes
• Reflexes
Evolution
Brain Structure
Brain Structure
Brain Structure
DRUGS
Evolution
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None
Nerve net
Segmented
Cephalization: organizing principle + brain-function rel.
Kineses
Taxes
Reflexes
Reflexes
• Kinesis (potato bug)
• Taxis (moth / maggot / fly / tick)
• Reflex: (knee jerk)
– Descartes 161 St. Germaine on the Seine
– Pineal
– Mechanist
Reflexes
• Braightenberg: Vehicles
Outline
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Functions
Evolution: structure and behavior
Basic Unit: The Neuron
Generation: How does a signal get started?
Action Potential: How does a signal move?
Synapses
Reflexes: A model
Brain Organizing Principles and Functions
The Neuron
• 100 billion
• Varied in size, shape, function
• Function of neuron sending signals in
real time (ex.)
• What is the signal? - electrical /
chemical
Outline
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Functions
Evolution: structure and behavior
Basic Unit: The Neuron
Generation: How does a signal get started?
Action Potential: How does a signal move?
Synapses
Reflexes: A model
Brain Organizing Principles and Functions
Origin of nerve signal
• Function of neuron sending signals in
real time (ex.)
• What is the signal? - electrical /
chemical
Generation
• Two forces:
– Electrical (ionic)
– Chemical (concentration)
– Give rise to steady-state voltage “resting
potential”
– Universal in cells
Outline
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Functions
Evolution: structure and behavior
Basic Unit: The Neuron
Generation: How does a signal get started?
Action Potential: How does a signal move?
Synapses
Reflexes: A model
Brain Organizing Principles and Functions
Action Potential
Movement of a Signal
Action Potential
• Cell actions
• Speed: Muller (light), Helmholtz (43
m/sec)
• Refractoriness
• All or none law
• Coding of intensity: analog-digital +
recruitment (organizing principle)
Neuron Communication
• Propagation is much faster if the axon is
myelinated:
• Depolarization proceeds down the axon by
a number of skips or jumps.
• The action potential obeys the all-ornone law:
• Once it’s launched, further increases in
stimulus intensity have no effect on its
magnitude.
Neuron Communication
• Propagation is much faster if the axon is
myelinated:
• Depolarization proceeds down the axon by
a number of skips or jumps.
• The action potential obeys the all-ornone law:
• Once it’s launched, further increases in
stimulus intensity have no effect on its
magnitude.
• Frequency signals intensity
Outline
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Functions
Evolution: structure and behavior
Basic Unit: The Neuron
Generation: How does a signal get started?
Action Potential: How does a signal move?
Synapses
Reflexes: A model
Brain Organizing Principles and Functions
Synapses: What happens when
signal reaches end of neuron?
• Two types of actions - excitatory /
inhibitory
• Chemical model with multiple &
functionally different neurotransmitters
• Temporal & spatial summation
Synapses
Release of Neurotransmitter
Synapses
Outline
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Functions
Evolution: structure and behavior
Basic Unit: The Neuron
Generation: How does a signal get started?
Action Potential: How does a signal move?
Synapses
Reflexes: A model
Brain Organizing Principles and Functions
A Model for building behavior
out of simple building blocks
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Reflexes
Voting behavior
Mirror neurons
Other examples to follow
Reflexes: A model
Outline
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Functions
Evolution: structure and behavior
Basic Unit: The Neuron
Generation: How does a signal get started?
Action Potential: How does a signal move?
Synapses
Reflexes: A model
Brain Organizing Principles and Functions
Principles and Functions
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Cephalization
All-or-None Law
Frequency Coding of Intensity
Doctrine of Specific Nerve Energies
Localization of Function (+ Integration)
Topographic Projection (& Distortion)
Split Brain (Crossed Connections)
Connectivity & Functional Connectivity
Neuro-plasticity & Reorganization
Brain Structure (midline)
Structure: Central Core
Structure: X-Ray View
Localization of Function
• Different parts of the brain serve
specialized functions
• Sensory Information
• Motor Control
• Perception
• Language
• Planning and Social Cognition
Localization of Function
Localization/Topographic Projection
Localization/Topographic Proj.
Localization/Topographic Proj.
Cerebral Cortex
• Most projection areas have contralateral
organization:
– Left hemisphere receives information from
right side of body (sensory), or controls
right side of body (motor)
– Right hemisphere receives information
from left side of body (sensory), or controls
left side of body (motor)
Split Brain
Split Brain
Cortical Damage
• Much of what we know about the cortex
comes from studying brain damage.
• Damage at identifiable sites can
produce:
• Apraxias (disorders in action)
• Agnosias (disorders in perception)
• Aphasias (disorders of language)
• Disorders of planning or social cognition
Apraxias
• Difficulty in carrying out purposeful
movements without the loss of muscle
strength or coordination
– Disconnection between primary and nonprimary motor areas
– Able to carry out each part of a complex
movement, but disruption lies in
coordination of the movements
Agnosias
• Visual agnosia: disturbance in recognizing visual stimuli despite
the ability to see and describe them
• Prosopagnosia: inability to recognize faces (fusiform face area)
– http://www.youtube.com/watch?v=vwCrxomPbtY&feature=related
– http://www.youtube.com/watch?v=VKa-PuJCrO4&feature=related
• Neglect Syndrome: complete inattentiveness to stimuli on one
side of the body
– http://www.youtube.com/watch?v=ADchGO-0kGo&feature=related
• Akinetopsia: inability to perceive movement
– “I see the world in snapshots – like frames of a move but most of
the frames are missing”
Aphasias
• Broca’s Aphasia: disturbance in speech production,
caused by damage to Broca’s area
– http://www.youtube.com/watch?v=f2IiMEbMnPM
• Agrammaticism
• Anomia
• Difficulty with articulation
• Wernicke’s Aphasia: disturbance in speech
comprehension, caused by damage to Wernicke’s
area
– http://www.youtube.com/watch?v=aVhYN7NTIKU&feature=r
elated
• Disruption in recognition of spoken words
• Disruption in comprehension of the meaning of words
• Inability to convert thought into words
Disorders of Planning and Social
Cognition
• Caused by damage to prefrontal area
– Disrupts executive control– processes that
allow us to direct our own cognitive
activities
• e.g., setting priorities, planning, strategizing,
ignoring distractors
Plasticity
• The brain is plastic—subject to alteration in the
way it functions, such as:
• Changes in the brain’s overall architecture
• The central nervous system can grow new neurons:
• But appears unable to do so with cortical injury
• This promotes stability in the brain’s connections but
is an obstacle to recovery from brain damage.
Plasticity
• Neurons are subject to alteration in the
way they function, such as:
• Changes in how much neurotransmitter a
presynaptic neuron releases
• Changes in neuron sensitivity to
neurotransmitters
• Creating new connections by growing new
dendritic spines