Psychology 110B Introduction to Neurons The stuff of the brain and mind

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Psychology 110BIntroduction to NeuronsThe
stuff of the brain and mind
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Review

• Cerebral cortex
• 4 lobes
• 2 hemispheres
• Motor area
• Sensory areas
• Association areas

• Nervous system
• Central
• Spinal cord
• Brain
• Cortex, etc
• Peripheral
• Sensory
• Motor
• Autonomic
• Skeletal

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Review

• Perception cognition
• Connects the hemispheres
• Limbic system
• Drives
• Memory
• Emotion
• Sensory relay station
• Rapid motion
• Life support homeostasis

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Functionaldifferentiation

• Cortical regions with specialized functions
• Motion
• Speech production
• Modulation of emotion
• Speech comprehension
• Hearing
• Vision

Topographic organization
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Hemispheric asymmetry of higher functions

• Left
• Language
• Brocas area
• Wernickes area
• Putting it all together

• Right
• Visuospatial
• Faces
• Maps

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Neuroimaging

• Goal discover, identify, and take pictures of
  the regions of the brain that are actively
  supporting mind and behavior
• The underlying assumption
• Active neurons require nourishment
• Blood ? oxygen, hemoglobin, sugars, etc.
• More activity, more bloodflow
• Measure bloodflow, infer neural activity

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PETPositron Emission Tomography

• Radioisotopic tracer injected into bloodstream
• Oxygen 15 decays to Nitrogen a positron
• Half-life 80 seconds
• Positron annihilates an electron
• Reaction generates 2 gamma rays travelling in
  opposite directions

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PETPositron Emission Tomography

• Patterns of gamma ray emissions locate where
  isotope decayed
• Density of decay is proportional to bloodflow
• More bloodflow is inferred to reveal more neural
  activity

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Neuroimages using PET
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fMRI Functional Magnetic Resonance Imagery

• A strong external magnet polarizes iron ions in
  hemoglobin
• The polarized ions create a secondary, induced
  magnetic field
• and radio waves
• at characteristic
• frequencies

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Neurons

• The elementary units of the information
  processing system
• Integrate and transmit pulses of electrical
  charge
• Are linked by chemical neurotransmitters

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A neuron its parts
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Neural communication

• Neurons form chains and networks through which
  they send packets of information

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Neural communication

• Neurons form chains and networks through which
  they send packets of information

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Neural communication

• Neurons form chains and networks through which
  they send packets of information

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Neural communication

• Neurons form chains and networks through which
  they send packets of information

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Key terms in neural communication

• Terminal button
• Neurotransmitters
• Synapse
• Dendrite
• Soma, cell body
• Axon
• Myelin

• Excitatory connection
• Inhibitory connection
• Activation level
• Threshold
• Repolarization
• Action potential
• Depolarization
• Spreading activation
• Plasticity

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Graded chemical communication
Neurotransmitters
Terminal Button
Dendrite
Soma
Synapse
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Neurotransmitters

• Hundreds of neurons release chemical
  neurotransmitters that adhere to the dendrites of
  a target neuron
• Glutamate
• Acetylcholine
• Dopamine
• Serotonin
• Norepinephrine
• ...

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Excitatory connections

• Excitatory connections increase the rate of
  firing of the target neuron

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Inhibitory connections

• Inhibitory connections decrease the rate of
  firing of the target neuron

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Chemical communication between neurons at the
synapse becomes electrical communication within
the neuron
Axon
Soma
Myelin
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Activation Threshold

• The target neuron accumulates these packets of
  information
• The accumulation is called its activation level
• The threshold is its limited capacity for
  information

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Repolarization

• When the amount of information reaches its
  threshold, (i.e, when it fills up with
  information),
• it becomes fully (re)polarized
• and generates an action potential, a brief
  quantum of electrical charge that travels down
  its axon to its terminal buttons

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Action potential
The action potential is a quantum (an
all-or-nothing unit ) of electric charge
The charge travels down the axon to the terminal
buttons
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Depolarization
The cell body depolarizes when
the action potential travels down the axon to the
terminal buttons.
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From electrical communication within the neuron
to chemical communication at the synapse

• When the action potential reaches the terminal
  buttons, they release chemical neurotransmitters
  across the synapse with the the next target
  neuron
• Information flows from one neuron to the next

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Neural communication

• The transmission of information is known as
  spreading activation

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The brain is a neuronal information processing
system

• Billions of neurons
• that are arrayed in networks
• energized by spreading activation
• The neural networks form specialized regions with
• Topographic organization
• Highly precise interconnections
• Localization of function

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Neuronal plasticity

• Learning causes neurons to develop new neurons
  and more terminal buttons and to make more
  synaptic connections
• This plasticity
• Is most rapid in young children
• Is most evident in the hippocampus
• Declines with age

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Summary

• Information is represented in patterns of
  spreading activation across interconnected
  networks of neurons
• Localization of function
• Different parts of the brain contain networks of
  neurons that process different types and sources
  of information and direct different behaviors
• Limbic system gt Emotion
• Frontal cortex gt Reason, judgment

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The brain is the most complex thing we know about

• Normal behavior requires all the parts to work
  together
• Multiple patterns of spreading neural activation
  must interact seamlessly
• It usually works.
• Sometimes it doesn't

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Psychoactive drugs

• Either enhance or block synaptic transmission
• Three mechanisms

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At the terminal button

• Either facilitate the release of the
  neurotransmitter
• Speed, cocaine
• Or inhibit the release of the neurotransmitter
• Antipsychotics

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Within the synapse

• Either facilitate the reuptake of the
  neurotransmitter
• Or inhibit the reuptake of the neurotransmitter
• Clinical antidepressants, Zoloft (?)

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At the dendrite

• Either block access
• Caffeine (blocks inhibitory connections)
• Or act like a neurotransmitter
• LSD, psilocybin,nicotine,
• Valium (increases inhibitory connections)

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Questions?