Cortical Motor Areas Flashcards
Primary Motor Cortex
Aka M1, found anterior to the central fissure (located in precentral gyrus). M1 neurons code for the direction in which limb is meant to travel. They fire in relation to the target location - end point of movement.
- It is somatotopically organized - mainly contralateral control
Plays a major role in initiating body movements
Where does M1 receive its inputs from?
Secondary motor areas, prefrontal cortex, and primary somatosensory cortex
What are the effects of damage to M1?
Mostly contalateral deficits; have trouble with the opposite side of your body.
- Cause astereognosia
- Cause response weakness
- Cause difficulty in moving body parts independently but not paralyze in the long term
What are the secondary motor areas?
Higher-level programming of movements (one level higher than primary motor cortex)
What cortices are in the secondary motor areas?
Premotor cortex and Supplementary Motor Area (SMA)
Premotor Cortex
Anterior to the primary motor cortex.
Neurons often fire in preparation of movement
Premotor cortex would fire before each action
Ex). fire clap fire turn
Supplementary Motor Area (SMA)
Neurons often fire during sequences of movements
SMA would fire before each sequence
Ex). fire turn, reach, grab
How are the two secondary motor areas similar?
Anatomically:
- reciprocally connected with M1
- reciprocally connected with each other
- both have direct output to the brain stem
Functionally:
- electrical stimulation elicits complex movements of body parts
- neurons fire prior to and during voluntary movements
What are the effects of damage to the secondary motor areas?
- cause more complex movement disorders
- cause difficulty in developing appropriate movement strategy
What are the Sensorimotor Association Areas?
The cognitive aspects of motor control, the area of the integration of higher order thinking
What cortices are in the Sensorimotor Association Areas?
The dorsolateral Prefrontal Cortex and the Posterior Parietal Cortex
What is the Dorsolateral Prefrontal Cortex
It is the highest in the sensorimotor hierarchy. It mediates planning and decision making for more complex things.
It receives signals from the posterior parietal cortex and it sends projections to areas of secondary motor cortex, to primary motor cortex, and to the frontal eye field.
What is the Posterior Parietal Cortex
It mediates multimodal integration (combination of more than one sensory modality)
It codes information about integrating the location of one’s body parts and object positions.
What are the effects of damage to the posterior parietal cortex?
Apraxia - the inability to plan and properly execute a learned skilled movement following brain damage. It is not a simple motor deficit.
It is often caused by unilateral damage to the left posterior parietal cortex
*the command is understood, but unable to do what’s asked
Contralateral neglect - disturbances of a patient’s ability to respond to stimuli in the opposite side; not a visual problem, they seem to ignore to half of their world
It is usually right parietal damage
What is characteristic of contralateral neglect?
Although people are not consciously aware of stimuli on the neglected side, tests of implicit memory suggest that the information has been processed
