The Brain and BehaviorOutline
• 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
• Communication• Coordination• Control• Cognition• Complexity
Outline: Start With A Mechanistic View
• 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
• None• Nerve net• Segmented• Cephalization: an organizing principle (brain-
mind correlation not always obvious!)• Kineses• Taxes• Reflexes
Evolution
Brain Structure
Brain Structure
Brain Structure
DRUGS
Evolution
• 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
• 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
• 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
• 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-or-none 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-or-none law:• Once it’s launched, further increases in
stimulus intensity have no effect on its magnitude.
• Frequency signals intensity
Outline
• 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
• 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
• Reflexes
• Voting behavior
• Mirror neurons
• Other examples to follow
Reflexes: A model
Outline
• 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
• 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 non-
primary 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=rel
ated
• 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