Chp 4: Principles of Neocortical Function Flashcards
Case study: Michelle
Suffer stroke in womb
- born with half a brain (no left hem: lang/ recognise objects)
-Not the case for Michelle - Has issue control right side of body
- Few prob with lang
Can tell you the exact weekday of a date
- Has issue with tasks for visual skills (Rey Complex Figures Test)
Shifted language functionality to the right side, but at the cost of the right side’s functions
Neuroplasticity is a competitive process
- Brain always competes for more territory
Case Study: Brain Plasticity – Jody
- Epileptic seizures (unable to use left side of body)
- All seizure came from right hemisphere
Rasmussen’s Encephalitis
- Inflammation in the brain
- Most often to restricted to one hemisphere
Hemispherectomy (cutting)
- removed right hemisphere)
Rare, one hemisphere
Similarity Jody and Michelle
Both patients are still able to walk, but they still are miss the fine manual dexterity
Neocortex: fine precise action
A Hierarchy of Function from the Spinal Cord to the Cortex (what do the higher levels do?)
The brain is organized in a functional hierarchy
◦ Higher levels provide more precision and flexibility
Patient A.R. could function so well with much of his brain gone because of: (2)
1.Brain plasticity
◦ Brain has the ability to compensate for loss of function
2.Levels of function
◦ Subcortical structures are capable of mediating complex behavior
- Comes at a cost due to competitive nature of neuroplasticity
Behaviors are produced by many different levels of the nervous system
◦ Example: grooming behaviour of the rat
◦ Each layer or region adds a new dimension to the behavior
- Grooming behaviour is the product of many brain areas:
- Spinal cord, hindbrain, midbrain,
diencephalon, basal ganglia and cortex - Functions are not replicated, but behaviours
are enriched
Central Nervous System Hierarchy
- Spinal Cord (spinal)
- Hindbrain (low decerebrate)
- Midbrain (high decerebrate)
- Hypothalamus, thalamus (diencephalic)
- Basal Ganglia (decorticate)
- Cortex (normal)
CNS Hierarchy: The Spinal Cord and Reflexes (Spinal) (3)
What behaviors can be initiated without descending control from the brain?
- Spinal animal
◦ Organism whose spinal cord disconnected from the brain
◦ Reflexes: stepping responses, limb approach or limb withdrawal to tactile stimuli
◦ Can make automatic stepping movements
CNS Hierarchy: Hindbrain and Postural Support (low decerebrate) (8)
Low Decerebrate
◦ Individual or animal whose hindbrain and spinal cord disconnected from the brain
◦ Comatose state
- No longer showing alertness
- Sensory input cannot reach the upper brain resulting in changes in consciousness
◦ Sensory stimulation elicits movement and affective behavior
◦ 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)
CNS Hierarchy: Midbrain and Spontaneous Movement (high decerebrate) (7)
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
- but can orient towards it
◦ 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, lick, taste more, cough, spit
◦ 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
CNS Hierarchy: The Diencephalon and Affect and Motivation (Hypothalamus, thalamus (diencephalic))
Diencephalic
◦ Diencephalon, midbrain, hindbrain, and spinal cord are disconnected from the brain
- Lack only basal ganglia and cortex
◦ Still not eating/drinking to sustain themselves
◦ Behaviors become energized and sustained
◦ Sham rage – inappropriately displayed (posterior hypothalamus)
◦ Sham motivation– referring to hyperactivity
CNS Hierarchy: Basal Ganglia and Self-Maintenance (Decorticate) (6)
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 behaviours are linked
◦ Basal ganglia can inhibit or facilitate voluntary movements
CNS Hierarchy: The Cortex and Intention (normal) (6)
(what does the cortex do?)
Decorticate animal can’t
- Build nest, hoard food, make skilled movements using tongue and limbs
Cortex
◦ Allows for sensory discrimination and complex learning
◦ Helps sequence complex movements
◦ Extends usefulness of behaviours
◦ Makes behavior adaptive
◦ More complex behavior patterns can be generated
Differences on the layers in motor vs. sensory cortex
- Layer 4 is larger than the in sensory cortex, input aspects is bigger, thicker (post central gyrus)
- Layer 5 is thicker for output in motor cortex (pre central gyrus)
Korbinian Brodmann’s map
- Cytoarchitectonic map
◦ Topographical map of the brain
based on anatomy and function
Darkest coloured regions
- Come to myelinations first
- Then slowly to secondary
- Then to lightest coloured areas (tertiary)
