Topic 7b: Cognition affordance competition Flashcards
Dorsolateral Prefrontal Cortex (dlPFC)
- Used for
- New or old?
- Connected to …
- Weighs up costs and benefits of an action, and executive control
- One of most recently evolved parts of the brain
- Undergoes prolonged period of maturation, lasting until adulthood
- Heavily connected to the Basal Ganglia and Dopamine
DLPFC lesions cause …
Wisconsin card sort test: cognitive control. Must discover current ‘rule’
Patients with DLPFC lesions persist with unsuccessful strategy (perseverance errors) and/or capricious errors (abandoning successful rule).
Action selection view 1: the central executive
Classical model:
First decide what to do (select) then plan the movement (specify)
Sense, think, act
Motor system is simply the output stage.
Perception > Cognition > Action
Action selection view 2: Affordance competition
Instead of serial perception, cognition and action modules, we have parallel specification and selection systems
Biased competition: potential actions compete against each other within sensorimotor map, influenced by a variety of biasing factors (e.g. reward)
Decision is made through a ‘distributed consensus’
In other words, motor control is decision-making
Affordance model: multiple reach options are initially specified and then gradually eliminated in a competition for overt execution, as more information accumulates.
If central executive, then activity should be zero until action has been selected.
What is the main difference between the classic model and affordance competition?
Classic model: store information, decide then plan one action
Affordance competition: specify both actions then select one (motor cortex is much more involved)
Free will?
Cognition ‘leaking’ into the motor system has ramifications for free will.
Suggests that our ‘conscious self/central executive’ does not initiate (select) behaviour.
Instead, the conscious self is alerted to a given behaviour that the rest of the brain is already planning.
The libet experiment
Asked to choose a random moment to move
Motor system activity measured with EEG
Asked to watch a clock and report its position when the conscious will to move is felt
modern version of the Libet experiment
Similar design as original study, but brain activity now recorded with fMRI and analysed with machine learning techniques (pattern classification)
Decision signals are decodable up to 10 seconds before they become aware
What part of the brain is involved with mental imagery of action?
The Premotor cortex and Supplementary motor area are similarly activated by imagining and executing a movement
Mental rehearsal improves performance
Implications for rehabilitation and brain-machine interfaces
Brain interfaces (BMIs) for rehabilitation
Electrical (as-well as other forms of) stimulation can modulate brain / spinal activity
Huge potential in rehabilitation
Robots can be controlled by mental imagery
Computers learn the distinct electrical brain signals associated with each movement
Summary
Cognition (selection) and motor (specification) systems act in parallel
Cognition ‘leaks’ into motor system which has ramifications for ‘free-will’ and ‘changes-of-mind’.
Mental imagery is similar to motor performance and is key to brain machine interfaces
