Neocortical Function

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Bryan Kolb Ian Q. Whishaws

• Fundamentals of
• Human Neuropsychology,
• Sixth Edition
• Chapter 10
• Lecture PPT

Prepared by Gina Mollet, Adams State College
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Neocortical Function
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Portrait Hemispherectomy

• A.R.
• Developed right side weakness, difficulty
  talking, and experienced seizures on the right
  side of his body
• Diagnosed with Rasmussens encephalitis
• Chronic brain infection that leads to loss of
  function in one hemisphere
• Had his left hemisphere surgically removed

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A Hierarchy of Function from the Spinal Cord to
the Cortex

• The brain is organized in a functional hierarchy
• Higher levels provide more precision and
  flexibility
• Levels of function
• Subcortical structures are capable of mediating
  complex behavior
• Brain plasticity
• Brain has the ability to compensate for loss of
  function

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A Hierarchy of Function from the Spinal Cord to
the Cortex

• Behaviors are produced by many different levels
  of the nervous system
• Example Grooming behavior of the rat
• Each layer or region adds a new dimension to the
  behavior

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The Spinal Cord and Reflexes

• What behaviors can be initiated without
  descending control from the brain?
• Reflexes stepping responses, limb approach or
  limb withdrawal to tactile stimuli
• Spinal animal
• Organism whose spinal cord disconnected from the
  brain
• Remain alert
• Can talk and express emotion

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The Hindbrain and Postural Support

• Low Decerebrate
• Individual or animal whose hindbrain and spinal
  cord disconnected from the brain
• Comatose state
• Sensory input cannot reach the upper brain
  resulting in changes in consciousness
• Sensory stimulation elicits movement and
  affective behavior

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The Hindbrain and Postural Support

• Low Decerebrate
• Decerebrate Rigidity
• Stiffness due to excessive muscle tone
• Demonstrate postural reflexes
• Exhibit both quiet sleep and active sleep
  however, any stimulation during active sleep
  reinstates rigidity
• Show sudden collapses similar to narcolepsy
• Persistent vegetative state (PVS)?

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Midbrain and Spontaneous Movement

• High Decerebration
• Midbrain, hindbrain, and spinal cord are
  disconnected from the brain
• Can respond to distant objects moving towards
  them
• Move towards auditory and visual stimuli, but
  show no evidence of vision

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Midbrain and Spontaneous Movement

• High Decerebration
• Effectively perform voluntary movements
• Movements that take an animal from one place to
  another
• Also called appetitive, instrumental, purposive,
  or operant movements
• Effectively perform automatic movements
• Units of stereotyped behavior linked in a
  sequence
• Example grooming, reactions to taste

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Midbrain and Spontaneous Movement

• High Decerebration
• Studies of infants born with little to no cortex
  illustrate that the children show little to no
  spontaneous movement and no habituation
• Cortex is important for attenuating and
  inhibiting movements, but not for movement
  production

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The Diencephalon and Affect and Motivation

• Diencephalic
• Diencephalon, midbrain, hindbrain, and spinal
  cord are disconnected from the brain
• Lack only basal ganglia and cortex
• Do not eat or drink even to sustain themselves
• Behaviors become energized and sustained
• Sham rage
• Sham motivation

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Basal Ganglia and Self-Maintenance

• Decorticate
• Removal of the neocortex basal ganglia and
  brainstem are intact
• Eat and drink enough to sustain themselves
• Normal sleep/wake cycles
• Can sequence series of movements
• Automatic and voluntary behaviors are linked
• Basal ganglia can inhibit or facilitate voluntary
  movements

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The Cortex and Intention

• Cortex
• Allows for sensory discrimination and complex
  learning
• Helps sequence complex movements
• Extends usefulness of all behaviors
• Makes behavior adaptive
• More complex behavior patterns can be generated

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The Structure of the Cortex

• Brodmanns map
• Topographical map of the brain based on anatomy
  and function

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The Structure of the Cortex

• Primary Sensory Cortex
• Primary Motor Cortex
• Association Cortex
• Secondary cortex Elaborates information coming
  from primary areas
• Higher order areas (Tertiary areas) Combine
  information from more than one system

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The Structure of the Cortex

• Flechsig
• Early Myelinating Primary motor and sensory
  areas
• Mid Myelinating Secondary areas
• Late Myelinating Association or Tertiary areas

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The Structure of the Cortex

• Primary Areas
• Bright Color
• Secondary Areas
• Medium Bright
• Tertiary Areas
• Lightest

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Snapshot Mapping the Human Cortex

• About 70 of the cortex is buried in sulci
• Flat maps of the cortex have been created in
  order to study the cortex in the sulci

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Cortical Cells

• Spiny neurons
• Nerve cells in the cortex with dendritic spines
• Excitatory neurons - Use glutamate or aspartate
• Include pyramidal cells and spiny stellate cells

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Cortical Cells

• Aspiny Neurons
• Nerve cells in the cortex without dendritic
  spines
• Interneurons with short axons
• Many different types named for appearance
• Inhibitory neurons - Use GABA

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Cortical Layers, Efferents, and Afferents

• Cortex composed of four to six layers each with
  different functions
• Afferents to the cortex can be
• Specific afferents
• Bring information in and terminate in a discrete
  area
• Nonspecific afferents
• Serve general functions and terminate diffusely

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Cortical Columns, Spots, and Stripes

• Column and module
• Terms for the vertical organization of the cortex
• Evidence from staining and probing illustrates
  patterns of spots or stripes

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Multiple Representations Mapping Reality

• Multiple maps in each sensory modality
• Multimodal or Polymodal Cortex
• Areas of the cortex that functions in two sensory
  systems
• Cortex is an organ of sensory and motor perception

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The Cortex

• Cortical maps determine reality for a species
• Knowledge related directly to the number of maps
• Dogs More complex understanding of smell
• Humans More complex understanding of vision

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Cortical Systems Frontal Lobe, Paralimbic
Cortex, and Subcortical Loops

• Sensory systems project have four principle
  connections in the cortical hierarchy
• Connection to the frontal lobes, paralimbic
  cortex, multimodal cortex, and subcortical
  connections and loops

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Cortical Systems Frontal Lobe, Paralimbic
Cortex, and Subcortical Loops

• Frontal Lobe
• Subdivisions
• Motor Cortex
• Premotor Cortex
• Prefrontal Cortex
• Projections are to the premotor or prefrontal
  cortex
• Projections control movements, orders movement,
  short-term memory for sensory events

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Cortical Systems

• Paralimbic Cortex
• Entorhinal Cortex
• Parahippocampal Cortex
• Cingulate Cortex
• Plays a role in the formation of long-term
  memories

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Cortical Systems

• Subcortical Loops
• Cortical - subcortical connections are reciprocal
  feedback loops or subcortical loops
• Information sent to cortex through subcortical
  structures
• Play a role in amplifying or modulating cortical
  activity

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Cortical Connections, Reentry, and the Binding
Problem

• How does the brain produce our concept of a
  unified and coherent world?
• The binding problem
• Possible solution Intracortical networks of
  connections among subsets of cortical regions
• All cortical areas have internal connections
  among units with similar properties
• Reentry Any cortical area can influence an area
  it receives input from
• Jerison - Information is integrated into
  perception and organized as knowledge and thought

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A Hierarchical Model of Cortical Function

• Luria
• Posterior part of the cortex is the sensory unit
• Anterior part of the cortex is the motor unit
• Three cortical units
• Primary cortex
• Secondary cortex
• Tertiary cortex
• Units work in serial processing
• Each level of processing adds complexity
• The tertiary cortex can activate paralimbic
  cortex

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A Hierarchical Model of Cortical Function

• Problems with Lurias Theory
• Not all areas linked serially
• Zones of the cortex have multiple connections
• We can experience a percept without a specialized
  area for it in the brain
• Possible solutions
• Nonordered neural network
• Distributed hierarchical system - Felleman and
  van Essen

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A Contemporary Model of Cortical Function

• How does information flow in the monkey brain
  when it is looking for jelly beans?
• Proposed hierarchy
• Illustrates efficient and optimal connections to
  complete a task
• Several areas of the brain may be activated
  simultaneously

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Do Human Brains Possess Unique Properties?

• Three allegedly unique properties of humans
• Grammatical language
• Theory of mind
• Certain forms of intelligence, such as intuition
• Special characteristics of the human brain
• Higher density of cortical neurons and a higher
  conduction velocity
• von Economo neurons
• May be associated with theory of mind
• Fail to develop properly in autism

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