Systems Physiology II 6010

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Systems Physiology II 6010
Lecture 14 Higher Cortical Function
Bradley Greger, PhD
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The Cerebral Cortex

• Cortex bark
• CPU of the brain
• Outermost structure of the telencephalon
• Sulci
• Gyri
• Increased surface area
• More computing power in limited cranial cavity

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The lobes of the telencephalon

• Frontal
• Primary motor cortex
• Parietal
• Primary somatosensory cortex
• Occipital
• Primary visual cortex
• Temporal
• Primary auditory cortex

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Categories of cerebral cortex

• Primary Cortex First cortical area processing
  sensory input or motor output (17,41, 4, 3-1-2)
• Secondary Cortex Second stage of cortical
  processing (18, 42, 5, 6)
• Tertiary Cortex Multi-modal (association)
  cortex (everything else)

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Non-human primate cerebral cortex

• Source of most scientific knowledge of cortical
  physiology
• Cortical areas defined by electrophysiology,
  anatomical connectivity, and cytoarchitecture
• Limited electrophysiology in humans
• Lesions and imaging (fMRI, PET,) in humans
• Homologous areas???

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Different types of cerebral cortex

• Neocortex
• Six layers
• What is usually meant by cerebral cortex
• Paleocortex
• Three layers
• Parahippocampal gyrus
• Cingulate gyrus
• Archicortex
• Three layers
• hippocampus

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The six neocortical layers

• Layer 1 molecular
• Mostly axons and dendrites
• Layer 2 external granular
• Layer 3 external pyramidal
• Corticocortical efferents
• Layer 4 internal granular
• Thalamic afferents
• Layer 5 internal pyramidal
• Subcortical efferents
• Layer 6 multiform layer
• Thalamic efferents

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Cytoarchitecture

• Different cortical areas exhibit different
  cytoarchitectonics
• Different cell types and cortical layers

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Cytoarchitectonic boundaries

• Changes in cytoarchitecture can be used to
  differentiate cortical areas

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Neocortical cell types

• Pyramidal spiny excitatory principal cell
  output
• Inter-neurons non-spiny inhibitory
  intra-area modulation

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Cortical Columns

• Primary computational unit of the cortex
• Neurons in column process similar types of
  information
• Similar response fields

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Cerebral cortical hierarchies

• Feedforward
• Terminate in layer 4
• Feedback
• Terminate outside layer 4
• Lateral
• Terminate throughout the layers of a column

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Cerebral cortical hierarchies

• Clear hierarchical arrangement close to primary
  cortical areas
• Much of tertiary associational cortical areas on
  the same hierarchical level

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Response Fields

• How neurons encode information
• What input (sensory stimulus, movement, thought,
  .) causes a neuron to change its firing rate

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Response Field Circuits

• Simple response fields early in the cortical
  processing stream
• More complex response fields arise later in the
  cortical processing stream out of convergent
  inputs
• Feedback and lateral connections also influence
  response fields

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Very abstract response fields

• Multi-modal comprising multiple sensory systems
• What do cognitive response fields look like?

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Higher cortical processing

• Language processing
• Wernickes area
• Comprehension
• Syntax
• Brocas area
• Motor control for speech
• Aphasia
• Wernickes
• Articulate speech
• Nonsense speech
• No comprehension
• Brocas
• Non-articulate speech
• Can comprehend language

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Higher cortical processing

• Corpus Callosum
• Fiber pathway connecting hemispheres
• Hemispheric lateralization
• Language, Wernikes only on one side
• Humans only
• The split brain
• Callosotomy prevent seizure spreding
• Hemispheres cannot share information

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Higher cortical processing

• The parietal lobe
• The where pathway
• Hemi-neglect
• In ability to represent the contra-lesion side of
  space

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Higher cortical processing

• The pre-frontal lobe
• Unique to humans
• Personality, decision making,
• The case of Phineas Gage
• Spike through pre-frontal cortex
• Massive change in personality
• Frontal Lobotomy

http//video.google.com/videoplay?docid-288333418
6873702319hlen-GB
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Very Simplified Brain Schematic

• Multiple data streams flow into and out of
  cerebral cortex
• Primary information processing

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Very Simplified Brain Schematic

• Reticular activating system and other biogenic
  amine producing nuclei
• Modulate state of cerebral cortex

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Very Simplified Brain Schematic

• Cerebro-cerebellar system
• Shapes cerebral cortical processing to aid in
  coordination of movement and motor learning

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Very Simplified Brain Schematic

• Cerebro-Basal Ganglia system
• Shapes cerebral cortical processing to aid in
  suppression of unwanted cortical signals
  (reflexes, movement, thoughts,).

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Very Simplified Brain Schematic

• Cerebro-Limbic system
• Encodes memories and adds emotional sensation to
  sensory input and memories