8: The Sensorimotor System Flashcards
Three main principles of the sensorimotor system…
- It is hierarchically organised.
- Motor output is guided by sensory input.
- Learning changes the nature and locus of sensorimotor control.
Posterior parietal association cortex (PPC)…
Plays role in combined spatial information about body parts and object to be interacted with, and attention.
Damage to PPC…
- ‘Apraxia’ - inability to perform specific voluntary actions, e.g. those performed on request.
- ‘Contralateral neglect’ – inability to respond to contralateral stimuli – patients cannot recognise the left side of their environment.
What is the involvement of the cerebellum and the basal ganglia in the sensorimotor system?
Not actually part of hierarchical system of sensorimotor functioning, but instead interact with its components on various levels. Help with co-ordination of activities.
Cerebellum and basal ganglia roles…
Major roles in motor learning. Involvement is in relaying descending motor signals from primary and secondary motor cortex and also relaying feedback from motor responses from somatosensory systems. Also some cognitive functions too.
What are the 4 descending motor pathways and their overall role?
4 main pathways: two descending in ventromedial region, two descending in the dorsolateral region. These interact to co-ordinate voluntary movement.
What is the role of the dorsolateral tracts?
Involved in finer movements of wrists, hands, fingers, and toes. Limbs, basically.
What is the role of ventromedial tracts?
Involved in control of posture and whole body movements.
Theory of central sensorimotor programmes…
Most complex processes are a combination of well-established simpler processes performed by the lower-level components of the sensorimotor system.
Motor equivalence…
The way that the same movement can be carried out by different muscles for each time.
Response chunking hypothesis…
Practice helps development of chunks or sequences of behaviour by combining smaller, individual responses. Similar principle to cognitive chunking.
Dorsolateral prefrontal association cortex…
This relays output from PPC to the secondary motor cortex, primary motor cortex, and the prefrontal eyefield.
Role in stimuli assessment and generating voluntary reactions.
Secondary motor cortex…
These receive communication from association cortex.
What constitutes a secondary motor cortex is its connection with association and secondary motor areas.
Mirror neurons…
Neurons that are fired when observing another perform a goal-directed action, or when undertaking some goal yourself.
Live in the ventral premotor cortex. Also found in posterior parietal lobe.
These play a role in social cognition, as neurons fire when there is an understanding of the action.
Primary motor cortex…
Major point of convergence and departure (hub) of sensorimotor signals.
Conventional view of primary motor cortex function is that it is mapped ‘somatotopically’.
Stereognosis…
Process of identifying objects by touch. Thought that neurons in PMC encoded the direction of movement.
Motor pool…
A group of motor neurons that innervate (stimulates nerve muscle fibres).
Golgi tendon organs…
Type of muscle receptor.
Live in tendons. These respond to increase in muscle tension by exciting inhibitory interneurons in spinal cord to help tense muscles relax if in danger of being damaged.
Muscle spindles…
Type of muscle receptor.
Live IN muscle tissue. These responds to changes in muscle length.
What is the function of the stretch reflex?
Function of the stretch reflex is to control the body’s position and minimalise the influence of external forces on it.
Recurrent collateral inhibition…
Involves ‘Renshaw cells’, which are inhibitory interneurons in the sgm. It is classed as a negative feedback mechanism as it attempts to restabilise muscles by REDUCING the rate of excitatory neurons being fired.
Motor equivalence…
When the same basic movement can be carried out in several different ways.
The central sensorimotor programs for many species-typical behaviors are…
Established without explicit practice of said behaviours.
Response Chunking Hypothesis…
Practice combines the central sensorimotor programs that control individual response into programs that control sequences (chunks) of behavior.
During the learning process a shift occurs whereby…
Control is shifted from the higher levels of the sensorimotor system down to the lower levels. Automaticity…
Sensorimotor areas activated by performing a newly learned sequence of finger movements…
Clear Skies Present a Pleasant Day
- Cerebellum
- Supplementary motor area
- Primary motor and somatosensory cortexes
- Posterior parietal cortex
- Dorsolateral prefrontal cortex
Sensorimotor areas activated by performing a well-practiced sequence of finger movements…
Clear Skies Present a Pleasant Day (-P)
- Cerebellum
- Posterior parietal cortex
- Primary motor and somatosensory cortexes
- Supplementary motor area
- Premotor cortex
