CORTEX
Overview of Topics
Lesson Objectives
Description of the Cerebral Cortex
Techniques for Studying the Cortex
Cortical Layers
Organization of Vertical Units
Organization of Cortex
Motor Areas of the Cerebral Cortex
Functional Unit
Lesson Objectives
- Describe the 6 layers of the cortex, the basic function of each, and discuss the characteristic cells located in each layer .
- Explain the vertical unit organization of the cortex.
- Using the diagram, explain the functional organization of the cortex.
- What is meant by the term functional unit? Explain.
- How does the movement-versus-muscle controversy help explain how dendritic growth can begin to serve to integrate information in the cortex?
Description of Cerebral Cortex
Association - General function of the cortex
- Behavioral flexibility
- Conditioned response (reflex)
General structure of the cortex
- Thickness: 4 mm at precentral gyrus to 1.5 mm (visual)
- Layers: six layers -- two main zones
- Outer--receptive--where incoming fibers synapse
- Inner--efferent--cell bodies of fibers projecting to other areas
- Structure -- vertical units (independent systems which communicate with each other via association of fibers)
Techniques of Studying the Cortex
- Ablations
- Electrophysiological
- Neuroradiological techniques
- Metabolism -- Blood Flow, PET, Beam
- Neuropsychological Assessment
Cortical Layers
Organization of Vertical Units
- Reverberation (feedback of circuits)
- Synchronization
- Recruitment
- Facilitation
- Cytoarchitectonic Areas (based on histological differences)
- Cingulate gyrus-- poorly developed
- Projection areas --great differentiation
- Brodmann areas -- idea that anatomial differences relate to
different functions
- Recent cortical research
- Secondary areas
- Cortico-cortical connections
Organization of Cortex
Projection Areas
- Postcentral gyrus (somatosensory projection)
- Also sensory projections to motor cortex
- Receptive field -- extent of skin area that will activate
a single cell
- Single cells respond to only one type of stimulus
- Cells responding to given type of stimulus tend to lie in
a column
- Columns for different modalities from given areas tend to
lie close together
- Middle 1/3 of the Superior Temporal Cortex
- Occipital Lobe -- area 17 -- visual projection
- Motor Strip -- motor projection cortex.
Association Cortex
- 2nd level - association cortex for modality
- Posterior 1/3 of superior temporal cortex --
- Area 18 & 19 of Occipital cortex -- vision.
- Supramarginal area -- somatosensory.
- Premotor cortex -- motor.
- General Association Cortex
- Prefrontal - planning, regulation, and feedback.
- Inferotemporal cortex & superior parietal -- general sensory
association cortex.
Motor Areas of the Cerebral Cortex
- Motor homunculus - Fritz& Hitzig (1870)
- Cortex arranged according to muscles but arrangement of dentrites according to movement
- Connections are such that large areas of cortex project in
an overlapping fashion to various motor neurons
- Discrete movements - result of complex synaptic interactions
at several levels
- Premotor area (Area 6)
- Stimulation -- more complex body movements than from primary
- Much of this area included in primary motor (body movement)
- Sensory homunculus
Functional Unit
The functional unit is a representation of the manner in which information passes through the nervous system.
| General Motor Association Cortex |
<--- |
General Sensory Association Cortex |
| V |
|
^ |
| Motor Association Cortex |
|
Sensory Association Cortex |
| V |
|
^ |
| Motor Strip |
|
Sensory Projection Cortex |
| V |
|
^ |
| Motor Neuron Pool |
|
Thalamus |
| V |
|
^ |
| Effectors (muscles & glands) |
|
Receptors |
Terms to Know
| Vertical Unit |
Frontal cortex |
Motor homunculus |
| Plexiform layer |
Functional unit |
Sensory homunculus |
| Betz cells |
Fusiform layer |
General motor association areas |
| Small Pyramidal Cell layer |
Parietal Cortex |
Sensory association areas |
| Motor strip |
Brodmann areas |
General sensory association areas |
| Granule cell layer |
Post-central gyrus |
Sensory projection areas |
| Large Pyramidal cell layer |
Premotor cortex |
Cytoarchitectonics |
Links to Associated Areas
