The Brain Mechanisms of Action and Decision Flashcards
What is the role of the basal ganglia in movement?
Gating proper initiation of movement - planning, initiating, and directing voluntary movements.
What is the role of the cerebellum in movement?
Sensory motor coordination.
Basic movements and postural control.
Where do sensory inputs go?
Into the spinal cord and brainstem circuits
What do the upper motor neurones consist of?
Motor cortex and Brainstem centres
What are upper motor neurones?
Confined to the central nervous system - responsible for the initiation of voluntary movements.
What are local circuit neurones?
involved in short non-complex processes locally - short neurones that do not extend very far.
What are lower motor neurones?
The peripheral nervous system that connects the CNS with the muscle to be innervated.
Where do simple reflexes occur?
They are mediated at the level of the spinal cord?
Give an example of posture and postural change
Standing, balancing
Give an example of locomotion
Walking, running
Give an example of sensory orientation
Head turning, eye fixation
Give an example of species specific action patterns
Ingestion, courtship, escape/defence, grooming, gestures
Give an example of acquired skills
Dressing, painting, driving, sports, guitar hero, texting, etc
What is leprosy and how does it affect the PNS? (4)
- Caused by a bacterial infection
- Peripheral nerves thicken, disrupting afferent and efferent signals
- Thermal sensation usually goes first, followed by pain and touch
- Inability to feel pain can result in severe limb damage
What is the difference between afferent and efferent signals?
Efferent pathways carry signals AWAY from the CNS - signals that your brain sends to tell your body to do something.
Afferent signals come from outside stimuli and tell your body what they are sensing e.g. temperature.
What are fasciculations?
Spontaneous contractions
How are all voluntary and reflex movements defined?
By making striated muscles contract
How do we define a skeletal muscle?
When at least one end of a striated muscle is connected to a bone through a tendon
Why are muscle fibres striated?
Because of regular bands composed of proteins actin and myosin.
A sarcomere is the basic unit of striated muscle tissue.
How do we distinguish between actin and myosin?
Actin = thin Myosin = thick
What is a motor unit?
The motor neuron and all the fibres it controls
How do motor neurones control muscles?
It sends efferent signals and voluntary muscle contraction is initiated by nerve impulse via the PNS. A single motor neurone then controls several muscle fibres.
How does Curare toxin affect the nervous system? (4)
- Acetylcholine receptor blocked in muscle tissue
- inhibits muscles within 25 mins
- inability of the muscle to respond to motor nerve stimulus
- no contraction of muscle fibres
How does Myasethenia Gravis affect the nervous system?
- Abnormality in acetylcholine receptors
- People with this condition are very weak as they can only activate a few of their striated muscle fibres
- Trouble smiling
How do we make a sustained movement? (3)
- single action potential travels to a lower motor neurone and leads to a single muscle twitch
- a train of action potentials give rise to a sequence of twitches
- if they arrive within 10-100ms of each other, the contractions add up and give rise to large and prolonged contractions.
What are tetanic contractions?
Large and prolonged contractions
How can lower motor neurones be damaged? (4)
- Motor neurone disease
- Trauma where a peripheral nerve is cut
- Polio
- Alcohol
What are the symptoms of lower motor neurone syndrome? (4)
- Paralysis
- Muscle wasting
- No reflexes
- Fasciculation
What is a motor program?
An abstract representation of movements that centrally organise and control the many degrees of freedom involved in performing an action
What is the role of the SMA?
Supplementary Motor Area - well-learned actions that do not place strong demands on monitoring the environament.
What is the role of the PMC?
Primary Motor Cortex - responsible for the execution of all voluntary movements of the body
- the ‘doing’ area
What is the role of the PPC in decision making?
Posterior Parietal Cortex - the ‘planning’ area.
Also involved in spatial reasoning and attention.
What is the role of the PMA?
Premotor Area - links action with visual objects.
Selects sequences of appropriate movements.
Modulates primary motor cortex.
An ‘intention’ area.
What is somatotopic organisation?
The point-for-point correspondence of an area of the body to a specific point on the nervous system.
What is apraxia?
The inability to carry out movements in response to commands
- damage to the posterior parietal cortex
- difficulty in motor planning to perform tasks or movements when asked
- this is despite understanding the command and being motivated
How would we describe the organisation of our motor areas?
Hierarchical
What is special about a sea squirt?
- The larva is relatively complex
- Contains a primitive spinal cord, a tail for swimming, brain-like ganglion
- This is because once a sea squirt finds somewhere to live, it doesn’t need to move
Why does cerebellum mean little brain?
- Takes up 10% of the brain
- Packs a high number of neurones
Which parts of the brain are involved in the ‘reaching’ action?
Transforming visual info about the location of objects in extrapersonal space into the direction of a reaching movement - path connects the parieto-occipital extriate area (PO) and the dorsal premotor area (PMd)
Give examples of sensorimotor transformations
Reaching, grasping
What parts of the brain are involved in the ‘grasping’ action?
Transforming visual info about the properties of objects such as shape and size, into commands for effective grasping - path connects the dorsal extriate (ES) cortex and the ventral premotor area (PMv)
Why is the parietal cortex important for object manipulation?
Supports our sense of spatial awareness and helps us to direct eye movements and reaching and grasping and point in object manipulation, and also our sense of touch.
Also has strong connections with the frontal lobe.
What is optic ataxia? (3)
- Inability to reach accurately under visual guidance
- Reaching accurately involved reaching in the right direction, with the correct grip scaling and grip orientation
- visual guidance means being able to see both the target and the hand throughout
What type of deficit is optic ataxia?
- Not just due to a single basic sensory or motor deficit
- Can affect one limb or both hemispheres - so it’s not purely physical or spatial disorder
- Can also affect both or one limb in only one hemisphere - so it’s not purely a motor disorder
- It’s a problem of converting visual feedback into actionable motor content
What are linking sequences?
Movements that are chained together to satisfy goals
What does deactivation of the SMA produce?
Severe disruption of learned sequences (SMA)
Why can the cerebellum be called ‘the silent area’?
Because the electrical signals in the cerebellum don’t seem to cause any conscious sensation and rarely causes any motor movement
What is the cerebellum used for in advanced movement? (4)
- Coordination of voluntary motor movement
- Helps maintain balance and equilibrium
- Helps with muscle tone
- Helps with rapid movements
What is error correction?
Cerebellum gets signals from the motor cortex and signals on what the body is doing from the spinal cord and compares the two, adjusting what you do to produce smooth motion
What is motor learning? (3)
- Cerebellar neuronal circuits learn to make more accurate movements over time
- After the motor act has been repeated many times, the motor act becomes gradually more precise.
- Once the cerebellum has perfected the movement, it establishes a specific motor program for each of the learned movements.
What are ballistic movements
- Include writing, typing, talking, running etc.
- Occur so rapidly that is is almost impossible to depend on sensory feedback
- Once movement is activated, there is no way to modify its present course by any sensory feedback control mechanism
What is the inferior olive?
Provides information from your vision and hearing
What is the vestibular nucleus?
plays an essential role in maintaining equilibrium, posture, head position, and clear vision with movement.
What information does your spinal cord input into the cerebellar cortex?
Generally what your body is doing right now.
How can cerebellar dysfunction occur? (5)
- Bleeding in the cerebellum?
- Exposure to mercury/lead/toxins
- Viral infections
- Head trauma
- Faulty genes
What does cerebellar ataxia cause? (4)
- Errors in range and direction of movement
- Uncontrolled eye movements
- Unsteady gait
- Slurred speech
What is hypometria?
Voluntary movements become short of the intended goal
What is Dysdiadochokinesia?
Impaired ability to perform rapid alternating movements
What is the Alcohol and Field Sobriety Test?
FST allows police to gauge the extent you have been drinking.
Cerebellum is sensitive to ethanol.
What does the FST include?
- Walk in a straight line
- Touching the tip of the nose with eyes closed
- Quality control on bad ideas
What is the role of the basal ganglia in advanced movement?
- Inhibits a number of actions generated by the motor cortex
- Release of this inhibition permits the motor cortex to become active
- Provides with the stop and go of movements.
What is the role of the Caudate and Putamen aka the striatum?
Receives inputs
What is the role of the globus pallidus and substantial nigra pars reticulata?
Provides principal output.
What is hypokinesia?
Insufficient direct pathway output.
Excess indirect pathway output.
What is hyperkinesia?
Excess direct pathway output.
Insufficient indirect pathway output.
What is the role of the direct pathway?
Stimulates movement.
What is the role of the indirect pathway?
Inhibits movement
What are the symptoms of Parkinson’s disease? (4)
- Resting tremor in limbs that disappears on movement or during sleep
- Muscle rigidity - jerky movement
- Akinesia - general smallness of involuntary movement
- Bradykinesia (slowness)
Why does Parkinson’s affect movement?
Lack of dopamine means the basal ganglia is running out of the currency it uses to stimulate itself, explaining the struggle with starting and stopping movements.
What is Huntington’s Disease?
- Progressive disease, causing involuntary muscle jerks
- Affects the whole body
- Intellectual deterioration, depression, and occasionally psychoticism
- Genetically determined
- Causes degeneration of the output neurones from the striatum, reducing inhibitory modulation of motor function
Why does Huntington’s affect movement?
Damage to the caudate/putamen means excessive communication between the thalamus and the cortex, making it a hyperkinetic disorder.
What is goal selection?
Selecting goals for action - it is graded and competitive.
Give examples of higher mental functions. (5)
- Judgement
- Future planning
- Social awareness
- Creativity
- Ability to relate emotionally to other people
What is executive control for? (5)
- When we need to plan
- When we need to troubleshoot problems
- Dealing with novel or unplanned situations
- Overcoming a habitual response
- Dealing with danger or difficulty
What is the homunculus problem?
Explaining volitional acts without assuming a cognitive process that is itself volitional (i.e. a man within a man)
What are the 3 elements of conducting executive control?
- Attention
- Cognitive flexibility
- Monitoring
How much of the human cortex does the PFC account for?
29%
What behaviours are the prefrontal cortex linked to? (5)
- Attention
- Memory
- Task completion
- emotion
- coordination
What types of inhibition are carried out in the dorsolateral prefrontal cortex? (4)
- restraining potentiated behaviour
- preventing information from interfering with processing
- restraining inappropriate actions
- removing irrelevant information from working memory
Where does attentional control take place in the brain?
Parietal cortex
Explain what happens during the Stroop task?
- Relies on the links between the DLPFC and anterior cingulate cortex (ACC)
- More errors when there is a mismatch between colour and words
- Low-level features interfere with high-level features
- People with Sz display heightened interference on this task
What is the ventromedial prefrontal cortex important for?
- Establishing the links between stimulus and actions
- Critical for adaptive learning: reward and punishment
- Social decision making, emotional regulation, and moral judgements
What can damage to the vmPFC cause?
- impulsiveness
- increase in jocular attitude
- sexual inhibition
- difficulty in matching your behaviour with social rules expected of you
What is cognitive flexibility?
The ability to switch between different rules and concepts and to adjust one’s thinking from old situations to new situations.
Can be probed using a variety of psychological measures.
How can you measure cognitive flexibility?
- A-not-B task
- Wisconsin Card Sorting Task (WCST)
- Erisken Flanker Task
- Guilford’s Alternative Uses Task
What has the Erikson Flanker test shown us?
ACC is important for detecting some form of conflict in whatever it is you’re looking at.
The dorsal part of the ACC is connected with the prefrontal cortex and the parietal lobe.
How do we measure creativity in Guilford’s Alternative Uses Task test? (4)
- Originality
- Fluency
- Flexibility
- Elaboration
What symptoms occur after a stroke in the medial PFC?
A stroke in the LATERAL parts, but not the VENTROMEDIAL parts show aboulia:
- lethargy, quiet withdrawal
- answer questions but slowly, easily distracted, cannot sustain a movement
What is Alien Hand Syndrome?
- Neurological disorder in which a person’s hand appears to take on a mind of its own
- Can occur through unilateral or bilateral damage to the frontal lobe/corpus collosum
What is the role of the premotor cortex in decision making?
- Response selection
- Execution of simple actions
- Rule making
What is the role of the mid-dorsolateral PFC in decision making?
- Task-switching
- Categorisation of sequences
- Complex stimulus-response sontingencies
- What is the role of the posterior lateral PFC in decision making?
- Selection of sequences of responses
- Categorisation of sequences
- Rule learning
What is the role of the frontopolar cortex in decision making?
- Tracking of goals and subgoals
- Relational integration
- Information-seeking behaviour
What are motor skills?
The ability to solve a motor problem correctly, quickly, rationally, and resourcefully.
How do we make a decision in the context of free will according to Libet 1985?
- arises endogenously
- no externally imposed restrictions that control subjects’ initiation and performance of the act
- subjects feel introspectively that they are performing the act on their own
What are the 3 conditions of making a decision?
- At least 2 possible choices
- Expectations can be predicted about the outcomes
- Value of the outcome can be assessed
What cognitive processes are needed to make a decision?
- Executive control
- Memory
- Reward processing
- Rule processing
etc
What are normative theories of decision making?
- Concerned with optimal decision making.
- Normative = an evaluative standard
- Expected values
- aka how we SHOULD behave
What are the downfalls of normative theories?
- Expected value has limitations
- Biases become more obvious when risks are increased
- This brings in the notion of utility which reflects psychological rather than economic values
What is expected utility?
What something is worth to you
What is rationality theory?
We want to maximise our expected utility.
If we were purely rational then people would all make the same decisions.
Give examples of why utility theory cannot explain human behaviour?
People will pay to avoid risk (e.g. insurance) but will also buy lottery tickets (more than expected value).
What is prospect theory and what does it involve?
Predicts what people WILL do, not what they SHOULD do.
- Reference dependence
- Probability weighting
What is reference dependence in prospect theory?
People make decisions based on anticipated gains and losses compared to their current state.
What is probability weighting in prospect theory?
Probabilities are subjectively assessed e.g. overestimate chance of winning.
Might be more risk-averse if there is a high probability of gains.
What can account for our lack of rationality in certain situations?
Heuristics.
What is bounded rationality?
Human decision-making process where we aim to satisfice rather than optimise.
This allows people to solve problems and quickly within limitations.
What is the availability heuristic?
A bias towards more immediate examples that come to mind.
If something can be recalled more easily, it may be more relevant to you.
What is the representative heuristic?
Mental shortcut that we use when estimating probabilities.
When we’re trying to assess how likely a certain event is, we make our decision by assessing how similar it is to an existing mental prototype.
What is anchoring bias?
When we make assessments by starting from an implicit or explicit initial anchor.
We then rely too heavily on this anchor.
What is adjustment in anchoring?
When we make insufficient adjustments away from the anchor.
What is the Nash Equilibrium?
Decision-making theorem that states a player can achieve the desired outcome by not deviating from their initial strategy - each player’s strategy is optimal when considering the decisions of other players.
Explain the Prisoner’s Dilemma.
Factors in the social context to our decision making.
Shows why two completely rational individuals might not cooperate even if it appears that it is in their best interests to do so.
What are primary reinforcers?
Direct benefits - do not need to be learned.
E.g. water, food, sex, pleasure.
What are secondary reinforcers?
When the reward can be used to gain other rewards - no value in itself.
E.g. money, coupons, etc.
What are aversive stimuli?
Removal of reinforcers - punishment.
How does dopamine affect our decision making?
Modulates the influence of background reward rate on dynamic decisions about when to switch behaviour.
What is the role of heuristics?
They provide shortcuts in our decision making
What is hypokinesia?
Slowness of movement
What is Hemiballismus?
Rare movement disorder characterised by dance like movements (choreas)
- Hyperkinetic movement disorder
What side-effects can you get from DBS? (6)
- Apathy
- Hallucinations
- Hypersexuality
- Cognitive dysfunction
- Depression
- Euphoria
