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
Brain Structure (midline)
Structure: Central Core
Structure: X-Ray View
Methods for studying the brain
• Single-cell and population recordings
– Animal studies
– Surgical patient studies
• Stimulation
– Animal studies
– Surgical patient studies
• Damage
– Animal lesions
– Human injury
– Human surgical lesions
• Neuroimaging
• Electroencephalogram (EEG) recording
– Electrodes are placed on the surface of the
scalp and record/amplify the electrical
signal given off by the brain
– Event Related Potentials (ERPs) are used
to study how the brain responds to different
stimuli or events
CT scan
MRI scan
Functional Magnetic Resonance Imagingin (fMRI)
– Measures changes in blood-oxygenlevel-dependent (BOLD) activation
– Areas of the brain that are engaged
more in a task, require oxygen rich
blood
– Result show a very small but highly
significant percent change in BOLD
activation (the entire brain is active all
the time)
Connectivity measures
Functional connectivity – uses resting-state fMRI data to chart
cortical regions with temporal synchrony (correlation of
activation patterns)
Structural connectivity –
measures the movement of
water molecules to chart the
white matter tracts
(visualizing anatomy)
Diffusion Tensor Imaging (DTI)
Diffusion Spectrum Imaging (DSI)
Homunculus Map of Human Cortex
Homunculus Map of Human Cortex
What does the homunculus tell us?
• Localization of motor
and sensory function
• Topographical
organization
• Cortical representation
related to function not
mass
Cortical Damage
• Much of what we know about the cortex
comes from studying brain damage
• Damage at identifiable sites can
produce:
• Disorders of planning or social cognition
• Apraxias (disorders in action)
• Agnosias (disorders in perception)
• Aphasias (disorders of language)
Case Study: Phineas Gage
Disorders of Planning and Social
Cognition
• Caused by damage to prefrontal area
– Disrupts executive control– processes that
allow us to direct and regulate our own
cognitive activities
• e.g., setting priorities, planning, strategizing,
ignoring distracters
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
– Patient video
• Prosopagnosia: inability to recognize faces (fusiform face
area)
– Patient video
– Patient video
• Neglect Syndrome: complete inattentiveness to stimuli on
one side of the body
– Patient video
• 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
– Patient video
• Agrammaticism
• Anomia
• Difficulty with articulation
• Wernicke’s Aphasia: disturbance in speech
comprehension, caused by damage to Wernicke’s
area
– Patient video
• Disruption in recognition of spoken words
• Disruption in comprehension of the meaning of words
• Inability to convert thought into words
Aphasias
Localization of Function
• Different regions of the brain serve
specialized functions
• Sensory Information
• Motor Control
• Planning and Social Cognition
• Perception
• Language
Connectivity
Congenital Prosopagnosics
show typical BOLD
activation to faces but
severe behavioral deficit in
face processing
DTI show degradation of
tracts connecting posterior
and anterior regions
engaged in face processing
(Thomas et al., 2009)
Connectivity
• Autism – Neurodevelopmental disorder
marked by social and communicative deficits
and presence of repetitive behaviors
• Underconnectivity theory – autism phenotype
comes from reduction in global connectivity
(long distance connections between frontal
and parietal/occipital regions) and increase in
local connectivity (particularly in visual areas)
Temple Grandin underconnectivity
Association cortex – regions not receiving direct
sensory input. Involved in perception, language,
social and executive functioning.
Comparison of human
and macaque monkey
brain show that major
areas of cortical
expansion occur in
association cortex
(Van Essen & Dierker, 2007)
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
Split brain patient
Phantom Limb Pain
• Amputees often feel pain in a limb after
it has been removed
– Mirror box therapy video
• Sensation in limb can be felt when
touching other areas of body (most
common: lost hand feels touch of face)
Neural remapping
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
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