Setting the Scene

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Setting the Scene

• Why study the brain?
• Hard science of behavior
• To validate soft sciences of behavior
• Obsessive Compulsive Syndrome Example
• Intellectual curiosity about ourselves
• To understand the physiological basis of
  disorders and disease

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Ontongeny recapitulates Phylogeny

• Ontogeny The origin and development of an
  individual organism from embryo to adult.
• Phylogeny The evolutionary development and
  history of a species or higher taxonomic grouping
  of organisms.

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• Development of brain are animals like us? Good
  models?
• Are primates good models for humans?
• Joaquin Fuster, Goldman-Rakic
• Are humans good models for humans?
• Talairach parietal

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Ways to study the brain

• Disorders and Insult
• Psychological Schizophrenia, Depression
• Anatomical Parkinsons, Alzheimers
• Trauma, stroke
• Animal models
• Anatomy
• Comparitive, system level
• Microstructure

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Ways to study the brain

• Human neuroimaging
• EEG
• PET
• fMRI
• MEG
• Near Infrared
• Optical Surface
• ?????

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Complexity

• The brain is COMPLEX
• How many neurons?
• On average, for a given neuron, how many neurons
  connect to it?
• DLPFC neuron morphology vs. APFC morphology
• evolution

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Things that affect processing in the brain
Time course Spatial extent Neuronal
system cellular Chemical Anatomical Geneti
c Malady
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What is information?

• Grandmother cell (Barlow 1972)
• just as physical stimuli directly cause receptors
  to initiate neural activity, so the active
  high-level neurons directly and simply cause the
  elements of our perception
• What is a spike train?
• Chemical activity?
• Electrical field?
• Oscillation?

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Neurons

• IPSP
• Operates by INCREASING the negative charge
• Positively charged Ions are admitted to interior
  of neuron
• Potassium, chloride
• Changing spontaneous firing rate

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Chemical Events at The Synapse

• Does the action potential travel across the
  synapse?
• How might you be able to tell?
• Sherrington thought the communication was still
  too fast to be chemical, and assumed it was
  electrical

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Synaptic transmission

• T. R. Elliott
• Noted that adrenaline affected muscles and other
  organs (pupils, stomach, heart) similarly to
  stimulation of the sympathetic nervous system
  (1905)
• Otto Loewi
• Stimulated vagus nerve or, later, accelerator
  nerve to slow or speed heart
• Collected fluid from heart and applied it to
  heart of another frog
• Had same effect on second frogs heart
• Could not be electricity
• 1920

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Synaptic transmission

• What must occur for chemical synaptic
  transmission to take place?
• Create the transmitters
• Get them to the right place
• Release them at the right time
• They do something on receiving cell
• Chemicals (and transporters) are recycled

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Neurotransmitter categories

• Amino acids - contain amine group NH2
• Peptides chains of amino acids
• Acetylcholine NH2 replaced by N(CH3)3
• Monoamines non-acidic transmitter containing
  NH2
• Purines includes adenosine and derivatives
• Gases ?

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Neurotransmitters

• NO nitric oxide gas produced by neurons
• May dilate vessels
• RCBF in PET

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Where do Neurotransmitters come from?

• Synthesized in the body, often in the neuron,
  from nutrients
• Examples
• Choline
• From cauliflower, milk
• or can be created from
• Lecithin, present in several
• foods
• Choline converted into acetylcholine

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Where do Neurotransmitters come from?

• Acetylcholine is synthesized in the synaptic
  terminal

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Where do Neurotransmitters come from?

• Cholinergic system
• Calcium influx causes hundreds of vesicles
  containing thousands of ACh molecules to be
  released (exocytosis )

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Where do Neurotransmitters come from?

• End plate on muscle
• Causes contraction
• miniature end plate potentials (mepps).

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ACh

• Two kinds of receptors for ACh
• Two types of nicotinic receptors
• Neuromuscular junction of skeletal muscle (end
  plate) (nicotinic muscle, Nm ), neuron to neuron
  connections, nicotinic neuronal, Nn

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Peptides

• Synthesized in cell body (soma)
• Transported along axons to terminals
• 1 mm/day to 100 mm/day
• May take days or weeks to replenish peptides for
  long axoned neurons
• Peptides are not recycled

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Transmission across membrane

• Voltage-controlled calcium gates
• Calcium entering cell causes excytosis, lasting
  1-2 ms
• Amount released is variable
• Cleft, or gap between neurons, app. .05 microns
  wide
• 10 microseconds to diffuse across cleft
• Total transmission lt 2 ms