Cerebral cortex Flashcards
What is the organisation of the cerebral cortex?
- Cortex forms the outer surface of the forebrain (grey matter)
- 6 distinct layers (“laminae”)
- Cortex covers the other “subcortical” forebrain structures
What are betz cells?
Key characteristic of the primary motor cortex
Project to brain-stem
Very large pyramidal cells
Project from motor cortex to spinal tract
How do betz cells contribute to the Corticospinal tract
Betz cells from the motor cortex initiate, regulate and control voluntary skilled movements
They do this by innervating alpha and gamma motor neurons in the spinal cord
Where does the corticospinal tract cross?
the medulla
This is so limb movements are controlled by the contralateral motor cortex
(The left motor cortex will control the right side of the body and vice versa)
What is Somatotopic motor representation?
different parts of the primary motor cortex send commands to different parts of the body
What is relationship between sensory and motor maps?
Close mirror
Multiple maps : maps reflect sensory motor specialization
What does Electrical stimulation cause?
Brief micro-stimulation (simple movements)
What does Prolonged stimulation cause?
Complex goal-directed actions
What are Secondary motor/ association areas?
areas that are not directly controlling movement but key to motor control
What are the 5 Secondary motor/ association areas?
- Posterior parietal cortex (PPC)
- Supplementary motor area (SMA)
- Pre-motor (PMC)
- Dorsal PM (PMd)
- Ventral PM (PMv)
Describe the Posterior parietal cortex (PPC)
Links frontal cortex (decision-making) with premotor (planning) areas
Receives information from sensory regions
Important for determining potential actions/goals given the environment
Describe the Supplementary Motor area (SMA)
two areas
SMA proper (learning)
Pre-SMA (execution)
- Initiation of internally generated movements (rather than stimulus driven)
Describe the Dorsal Premotor (PMd)
Important in preparation of movement and learning conditional actions
Set related activity (get ready, set, go)
Describe the Ventral Premotor (PMv)
Important for sensory guidance of movement: responsive to tactile, visual and auditory stimuli
Mirror neurons
Where were mirror neurons first reported and why are they important?
in PMv
MNs important for learning through observation also understanding other people’s intentions
What is neuroplasticity?
The ability of the brain to form and reorganise synaptic connections
in response to learning or following injury
Where can neuroplasticity occur?
all areas of the brain but there are very clear examples for the somatotopic maps in S1 and M1
When does sensory remapping occur in somatopic maps?
Rapid changes in somatosensory (or motor maps) evident after change in inputs
What does training do to somatopic maps
expands the map
What does Denervation or amputation do to somatopic maps?
Reduces the map
What does Co- activation do to somatopic maps?
Co- activation (surgically fusing two maps) = fuses the map
How do changes in somatopic maps reflect neuroplasticity?
Long term changes in functional connectivity
Branching of dendritic connections
Neurons appear to “compete” for space in the cortex gets taken over by other inputs
What is Synapse efficacy?
Synapse enables one neuron to communicate with another
What are the 3 components of Pre- synaptic based synapse efficacy?
Increase vesicle volume
Increase availability of vesicles
Increase release probability
What are the 2 components of Synaptic cleft based synapse efficacy
Reduce re-uptake mechanisms
Reduce gap dimensions
What is the component Post- synaptic based synapse efficacy?
Increase receptor density/ area
What is the component of growth based synapse efficacy?
make new synapses
What is Long term synaptic plasticity?
Specific timed patterns of neuronal activity can lead to long-term snaptic changes
What is Long term potentiation (LTP)?
An activity- dependent persistent strengthening of synapses.
What does Long term potentiation (LTP) produce?
a long lasting increase in signal transmission between two neurons.
What is Long- term depression (LTD)
An activity dependent reduction in the efficacy of neuronal synapses.
What does Long- term depression (LTD) produce?
a long lasting decreases in a signal transmission between two neurons
First identified in hippocampus
What is the NMDA channel blocked by?
Mg
What drives out Mg
Concurrent Voltage change
What does glutamate bind to?
NMDA & AMPA receptors
Temporary change in shape of channel, opens up channel
Describe Cooperatively in reference to LTP
LTP requires simultaneous activation of large number of axons (due to large depolarisation)
Describe activation in reference to LTP
When weak synaptic input is paired with strong, then large depolarisation can propagate
causes LTP at synapse with weak input
Describe synapse specific in reference to LTP
If particular synapse is not activated then LTP will not occur even with strong postsynaptic depolarisation
