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Brain and Behaviour 2 > Brain Mechanisms Of Action And Decision Making > Flashcards

Brain Mechanisms Of Action And Decision Making Flashcards

1
Q

What are the 3 broad functions of the nervous system?

A
  • Sensory input
  • Processing
  • Sensory output
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2
Q

Function of the motor cortex

A

Planning, initiating and driving voluntary movement

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3
Q

Function of the brainstem centres

A

Basic movement and postural control

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4
Q

Function of the basal ganglia

A

Gating proper initiations of movement

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5
Q

Function of the cerebellum

A

Sensory motor coordination

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6
Q

The basics of movement

A

1) simple reflex (mediated at the level of the spinal cord
2) posturing and postural change
3) locomotion
4) sensory orientation
5) species specific action patterns
6) acquired skills e.g hobbies

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7
Q

Different levels of control over movement

A
  • Voluntary: under conscious control by the brain
  • Rhythmic: can also be controlled voluntarily , but timing and spatial organisation is to a large extent controlled autonomously by spinal cord circuits known as central pattern generators
  • Reflexes: stereotyped responses to specific stimuli that are generated by simple neural circuits in the spinal cord or brain stem
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8
Q

Leprosy

A
  • Cause by a bacterium infection
  • Peripheral nerves thicken in leprosy, disrupting afferent and efferent signals
  • Thermal sensation usually the first to go, followed by pain touch. Inability to feel pain can result in severe limb damage over time
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9
Q

Afferent signals

A

These are nerve impulses or sensory signals that travel from the peripheral sensory organs (e.g skin) towards the central nervous system (CNS). They provide the CNS with information about the external or internal environment for appropriate response

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10
Q

Efferent signals

A

These are nerves impulses that travel from the CNS to peripheral parts of the body such as muscles. These signals transmit motor commands and initiate actions

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11
Q

Basic sensorimotor transformation process (reflex action)

A

Sensory inputs > spinal cord and brainstem circuits (loud circuit neurons that coordinate the reflex) > lower motor neurons > skeletal muscles

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12
Q

Muscles variants

A
  • All voluntary and reflex muscles are brought about by making striated muscles contract
  • There are three main types:
    > Cardiac muscles: specialised tissue found only in the heart
    > Smooth muscles: found around blood vessels, glands, gut and bronchioles
    > Skeletal muscles: when at least one end (the origin) is connected to a bone through a tendon
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13
Q

The role of skeletal muscles in voluntary movement

A
  • In terms of voluntary movement control, striated skeletal muscles play a large role
  • Muscle fibres are striated because of regular bands composed of proteins: actin (thin) and myosin (thick)
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14
Q

How do muscles contract?

A
  • Muscles fibres are stimulated by a nerve impulse
  • Acetylcholine is released at the neuromuscular junction (the chemical synapse between a motor neuron and a muscle fibre
  • This causes ion channels to open, ultimately allowing calcium ions to enter the muscle, triggering a contraction
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15
Q

Sarcomere

A

The basic functional unit of striated muscle

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16
Q

Motor neuron

A
  • A motor neuron sends signals through efferent connections
  • Voluntary muscle contraction is therefore initiated by nerve impulses from the CNS
  • A single motor neuron will control several muscle fibres: this is known as innervation
  • A motor unit is the motor neuron and all the fibres it controls
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17
Q

The role of acetylcholine

A

It is a neurotransmitter that is important in triggering a cascade of events that lead to the release of calcium ions, and in turn movement

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18
Q

Acetylcholine receptors disrupters

A

1) Curare toxin:
> This causes the receptor to be blocked in muscle tissue. This results in the inhibition of muscles due to being unable to respond to motor nerve stimulus
> It is formed from plants

2) Myasethenia gravis:
> This is an abnormality in acetylcholine receptors
> People with this condition are very weak as they can only activate a few fibres of their striated muscle fibres

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19
Q

How do we make sustained movement?

A

1) Action potential travels down to lower motor neuron leading to a muscle twitch
2) A train of APs spaced apart result in a sequence of twitches
3) If they arrive rapidly, the muscle contractions will add up and give rise to large and prolonged contractions
4) Tectonic contractions derive fro multiple motor neurons activating many muscle fibres simultaneously
5) TCs are needed for sustained, strong muscle contractions

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20
Q

Motor pool recruitment

A
  • This refers to the sum of all the motor neurons working together
  • Each muscle fibre responds to one motor unit
  • If you want a concerted effort, you need to recruit more and more motor units. This known as motor pool recruitment
  • The more force power required to complete the action , the greater the recruitment needed
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21
Q

Hypotonia

A

Decreased muscle tone

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22
Q

Motor neuron problems

A
  • Lower motor neurons can be damaged in motor neuron disease, in a trauma where a peripheral nerve is cut, in polio, or by alcohol. Such damage leads to lower motor neuron syndrome
  • Symptoms include: paralysis, muscular wasting, no reflexes, fasciculation
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23
Q

Fasiculation

A

Muscle twitching

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24
Q

Motor programs

A

This is an abstract representation of movement that centrally organises and controls the many degrees of freedom involved in performing an action

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25
Q

Equivalence

A

This refers to the idea that your movements are independent of your muscle groups e.g you can write your name with any part of your body

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26
Q

Supplementary motor cortex (SMA)

A

Controls well learned actions that do not place strong demands on monitoring the environment

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27
Q

Primary motor cortex (PMC)

A
  • Responsible for the execution of all voluntary movements of the body
  • Located in the frontal lobe
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28
Q

Posterior parietal cortex (PPC)

A
  • The planning area
  • Also involved in spatial reasoning and attention
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29
Q

Premotor cortex (PMA)

A
  • Links actions with physical objects
  • Selects sequences of appropriate movements
  • Modulates primary motor cortex
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30
Q

Somatotropic organisation

A
  • This refers to the organisation of the motor and sensory strips in the brain to control movement and process sensations
  • Left hemisphere section controls the body’s right side and received information from the right side as well. Right hemisphere vice versa
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31
Q

Primary somatosensory cortex (PSC)

A
  • Processes sensory input from the skin, muscles and joints
  • Located in the parietal lobe
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32
Q

Evidence for a cortical ‘map’: apraxia

A
  • This refers to an inability to carry out movements in response to commands
  • Damage to the posterior parietal cortex in the dominant hemisphere
  • Difficulty in motor planning to perform tasks or movements when asked
  • There are two variants:
    1) Ideomotor- semantic disruption
    2) Ideational- inappropriate selection
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33
Q

Evidence for a cortical ‘map’: anticipatory firing

A
  • This refers to the phenomenon where neurons or neural circuits in the brain activate before the onset of an expected action
  • Mushiake et al (1991) supports this idea using monkeys. They were taught to perform an action in response to a cue whilst monitoring brain activity during the preparation and execution phases of the task
  • They found that the neurons in the premotor cortex showed significant firing before movement onset, especially during preparatory phase. This activity was related to planning the sequence of movements rather than a single movement. Neurons in the primary motor cortex were more involved during the execution of the action rather than the planning
34
Q

Motor coordination factors to consider

A
  • Position of perspective in relation to body
  • The hand and arm relative to everything else
  • Feedback
  • Speed and height
35
Q

Graded goal selection

A
  • Decision making involves a graded process, where the brain accumulates evidence gradually based on the sensory input
  • The strength of the evidence determines the level of neural activity, reflecting the likelihood of a particular choice
36
Q

Competitive dynamics

A
  • Neurons representing different goals or options compete thought reciprocal inhibition
  • This competition ensures that only the strongest representation (the most supported option is selected)
37
Q

Threshold-based decision

A
  • The decision occurs when the neural activity for one option surpasses a decision threshold, triggering a motor response
38
Q

Roitman and Shadlen (2002): graded evidence accumulation and competitive goal selection

A
  • Looked at monkeys who completed a two-choice motion discrimination task:
  • Monkeys viewed random dot stimulus where a subset of dots moved coherently in one of two directions. The task required the monkeys to decide the direction of motion and indicate their choice by an eye movement. Activity was recorded from neurons in the LIP during the decision-making progress
  • Graded evidence accumulation: LIP neurons showed firing rates proportional to the strength of motion evidence. As evidence increase, the firing rate of neurons associated with chosen target increased
  • Competition between alternatives: The neurons associated with competing targets exhibited mutual inhibition. The competition resolved as evidence accumulated, with activity for the alternative target decreasing as evidence revealed it was the incorrect target
  • Threshold crossing for decision: A decision was made when the accumulated evidence in favour of one target reached a threshold
39
Q

Sensorimotor transformation: reaching

A

This system is responsible for transforming visual information about the
location of objects in extrapersonal space into the direction of a reaching
movement (a visuomotor transformation). A path connects the parieto-occipital
extrastriate area (PO), the mediodorsal parietal (MDP), the medial intraparietal
(MIP) and the dorsal premotor area (PMd)

40
Q

Sensorimotor transformation: grasping

A

This system is responsible for transforming visual information about the properties of objects, such as shape and size, into commands for effective grasping. A path connects the dorsal extrastriate (ES) cortex with the anterior intraperietal suculus (AIP), and then the ventral premotor area (PMv)

41
Q

Motor coordination solutions

A
  • Attention to environment
  • Goal selection
  • Sensorimotor transformations
42
Q

Optic Ataxia

A
  • An inability to reach accurately under visual guidance
43
Q

Milner and Goodale (1995): posting task study

A
  • Investigated into the distinction between the brain’s ventral and dorsal streams in visual processing
  • Thos research focused on a patient DF who had visual agnostic, with damage to part of the ventral stream (impaired perception of objects shapes, but retained ability to interact with objects)
  • He was asked to interact with a mail slot in two ways:
    > Perceptual matching: match the orientation of a card to the slot without moving it (ability to visually perceive orientation of the slot)
    > Action-oriented task: post the card into the slot (ability to act and correctly orient card to insert it)
  • Poor performances in perceptual matching task, due to not identifying or matching the orientation of the slot. This highlights inability to use the ventral stream of object recognition and perception
  • Normal performance in action-oriented task, successfully posting the card, demonstrating that her dorsal stream was intact to guide her actions
  • This study provides evidence that the ventral and dorsal streams have severe distinct functions
44
Q

Dual-stream hypothesis

A
  • The brain processes visual information through two distinct pathways:
    > Ventral stream: involved in object recognition and identification
    > Dorsal stream: involved in spatial processing and guiding actions
45
Q

Linking sequences (role of SMA)

A
  • The SMA is essential for generating linked self-generated movements. Without it, we would not be able to perform well learned movements and rely on external cues to get things done
  • The SMA and pre-motor cortex have distinct roles:
    > SMA: responsible for uncued, internally guided movements
    > Pre-motor cortex: more involved in movements triggered by external stimuli
  • This dissociation ensures that the brain can manage both cued and uncued actions efficiently
  • Deactivation of the SMA produces severe disruption of learned sequences
46
Q

The role of the cerebellum in error correction

A
  • Signals leaving the motor cortex go through the cerebellum. It also gets signals on what the body is doing from the spinal cord
  • It compared the two and adjusts what you do to produce smooth motion. It can be referred to as the ‘stabiliser’
47
Q

The role of the cerebellum in motor learning

A
  • Cerebellar neuronal circuits learn to make more accurate movement over time
  • After the motor act has been repeated many times, the successive steps of motor act become gradually easier
  • Once the cerebellum has perfectly learned it’s role in different patterns of movements, it establishes a specific motor program for each of these learned movements
48
Q

Ballistic movements

A
  • These movements include writing, typing, talking, running etc
  • These movements occur rapidly, so almost impossible to depend for their control on the sensory feedback
  • Once the movement is activated, there is no way to modify it’s present course by any sensory feed-back control mechanism
49
Q

Cerebellum: inputs and outputs

A
  • Inputs: sensory and motor signals from spinal cord, brainstem and cortex
  • Outputs: adjust motor plans via connections to to the motor cortex, brainstem and spinal cord to ensure smooth and coordinated movements
50
Q

Reentrant circuits

A

The neural pathways in which information flows through a loop, allowing a continuous feedback and modification of activity between interconnected brain regions. They are essential for dynamic processes

51
Q

Cerebellar dysfunction

A

1) Cerebella ataxia: error in range and direction of movement. Uncontrolled eye movements, slurred speech
2) Hypometria and response delays: delayed response. Hypometria refers to movements short of the intended goal
3) Dysdiadochoki nesia: impaired ability to perform rapid alternating movements

52
Q

Alcohol and field sobriety tests (FST)

A
  • The FST allows police to gauge the extent to which you have been on the sauce
  • The cerebellum is sensitive to the ethanol found in booze
  • Cerebellum reliant aspects of the FST: walking in a straight line, touching the tip of the nose with eyes closed, quality control of bad ideas
53
Q

Key components of the basal ganglia loop

A

1) Cerebral cortex: sends excitatory inputs to the basal ganglia, initiating the loop
2) Basal ganglia: processes and modulates signals from the cortex
3) Thalamus: refines the singles from the basal ganglia back to the cortex
4) Other connections: links with the brainstem and spinal cord for motor execution

54
Q

There are three primary pathways in the basal ganglia loop

A

1) Primary pathway: facilitates movements by activating motor programs (cortex > striatum > globus pallidius interna (GPi) > thalamus > cortex)
2) Indirect pathway: inhibits competing or unnecessary motor programs (cortex > striatum > GPi > subthalamic nucleus > GPi > cortex)
3) Hyperdirect pathway: provide rapid inhibitory control over the thalamus to suppress actions immediately

55
Q

Hypokinesia vs hyperkinesia

A
  • Hypokinesia: insufficient direct pathway output (excess indirect pathway output)
  • Hyperkinesia: the opposite
56
Q

Parkinson’s disease

A
  • Resting tremor in limbs (4-5 Hz) that disappears on movement or during sleep
  • Muscle rigidity: resistance to passive movement (jerky movement)
  • Akinesia: general paucity of involuntary movement
  • Bradykinesia: slowness
57
Q

Huntington’s disease

A
  • Progressive disease causing involuntary muscle jerks
  • It will ultimately affect the whole body
  • Also intellectual deterioration, depression and occasionally psychoticism
  • Genetically determined (single dominant gene)
  • Degeneration of the output neurons from striatum, reducing inhibitory modulation
58
Q

What is executive control for?

A

1) When we need to plan
2) When we need to troubleshoot problems
3) Dealing with novel or unplanned situations
4) Overcoming a habitual response
5) Dealing with danger or difficulty

59
Q

The prefrontal cortex (PFC)

A
  • It is involves in attention, memory, task completion, emotion and engagement
60
Q

The key PFC players

A
  • Dorsolateral prefrontal cortex (DLPFC): plays a role in memory, attention, goal setting, motivation
  • Lateral prefrontal cortex (LPFC): subjective self, consciousness, emotion
  • Ventrolateral prefrontal cortex (VLPFC): social and emotional functions, self-regulation
61
Q

Initiation vs inhibition

A
  • Initiation is the selection of desired behaviour (the oddball task)
  • Inhibition is the suppression of unimportant or distracting behaviour (go-no go task):
    1) restraining potential end behaviour
    2) preventing information from interfering with processing
    3) stopping inappropriate actions
    4) removing irrelevant information from working memory
62
Q

Tasks to measures attention in cognitive tasks

A
  • Oddball task (Schruder, 2017): involves presenting a sequence of repetitive stimuli with occasional infrequent (odd) stimuli. The participant is required to respond to the odd stimuli
  • Go/no-go task (Cornet, 2015): measures response inhibition and ability to suppress automatic responses. Participants must respond to certain stimuli and inhibit responses to others
63
Q

Ventromedial prefrontal cortex (VMPFC)

A
  • It is important in establishing links between stimulus and actions
  • Critical for adaptive learning: reward and punishment
  • Also involved with social decision making, emotional regulation and moral judgements
  • It creates a mental model of the world. The central feature is the ability to recognise and create rules for behaviour that generalise across contexts
64
Q

Cognitive flexibility- allowing us to adapt

A
  • The ability to adjust one’s thinking from old situations to new situations
  • The ability to overcome habitual responses and adapt to new situations
  • The ability to switch between different rules and concepts
65
Q

Smith et al (2003): A-not-B task

A
  • An object is placed at location A multiple times as the infant watches. The objects is then hidden at location B in full view of the infant
  • The task measures the infant’s ability to recognise the new location of the object, instead of searching for it at location A
  • Infants under 10 months tend to make preservation errors, suggesting they have difficulty in inhibiting their previous action adapting to the new location, reflecting limited cognitive flexibility
  • Infants around 1 year old typically pass this task, showing greater development of cognitive flexibility
66
Q

Wisconsin card sorting task (WCST)

A
  • Participant is presented with a set of cards, with an initial rule being stated (e.g sort by colour). This rule changes without warning during the study and the participant has to figure out what the new rule is based on feedback (correct or incorrect)
  • The main aim is to test task switching ability
  • Patients with damage in the lateral prefrontal cortex have difficulty on this task often leading to rule preservation
67
Q

Disrupted initiation (as a result of a stroke)

A
  • The medial PFC is essential for goal directed behaviour and initiation
  • A stoke in lateral parts but not ventromedial parts show aboulia: lethargy, quiet withdrawals, answer questions but act slower, easily distracted, cannot sustain a movement
68
Q

Alien hand syndrome

A
  • A neurological disorder in which the afflicted person’s hand appears to take on a mind of it’s own
  • Can occur though unilateral or bilateral damage to the frontal lobe. It can only occur after strokes, surgery, tumours and infections
69
Q

Motor skill

A
  • This refers to the ability to solve a motor problem correctly, quickly, rationally and resourcefully
  • Thus motor acts are not carried out in isolation from cognitive mechanisms. Many motor deficits and syndromes are associated with cognitive problems
70
Q

Making a decision (in the context of free will)

A

1) It arises endogenously, not in direct response to an external stimulus or cue
2) There are no externally imposed restrictions or compulsions that directly or immediately control subjects initiation and performance of the act
3) Subjects feel introspectively that they are performing the act on their own initiative and that they are free to start or not start the act of they wish

71
Q

Making a decision (the three conditions)

A

1) At least two possible choices
2) Expectations can be predicted about the outcomes
3) Value of outcome can be assessed

72
Q

Normative theories

A
  • Concerned with optimal decision making; provides an evaluative standard for behaviour
  • Based on probability and expected value
  • We use these concepts to build decision models
73
Q

Issues with using normative theories

A
  • Expected value has limitations
  • Biases become more obvious when risks are increased e.g people may prefer to avoid a loss, even if the expected value suggests the potential gain outweighs the risk
  • In high-risk scenarios, emotional and psychological factors override the calculation of expected value
  • Utility: recognising the limitations of expected value, normative theories incorporate utility, which reflects the psychological rather than economic value of outcomes. Utility considers how much a person subjectively values an outcome rather than it’s objective monetary value
74
Q

Framing effects

A
  • A ‘framing effect’ is a cognitive bias that occurs when the way information is presented influences how we make decisions. This can lead to different choices even when the options are the same
75
Q

Prospect Theory (Tversky and Khaneman)

A
  • Predicts what people will do, not what they should do
    1) Reference dependence: people make decisions based on anticipated gains and losses relative to the current state
    2) Probability weighting: probabilities are subjectively assessed, often overestimating unlikely events
76
Q

Prospect theory: mapping loss aversion

A
  • Risk aversion (don’t want to a risk) for high-probability gains (e.g prefer certain outcomes over risky ones)
  • Risk seeking for low-probability (e.g buying lottery tickets): the reward is worth the risk
  • Risk aversion for low-probability losses (e.g paying for insurance): no need to take a risk
  • Risk seeking for high-probability losses (e.g gambling to break even)
77
Q

Heuristics in decision making

A
  • These are mental shortcuts used for quick decision-making under constraints
  • There are 3 main types:
    1) Availability heuristic: decisions based on the ease with which examples come to mind (the available information you can think of at the time) e.g viewing planes as dangerous due to hearing about multiple plane crashes recently
    2) Representativeness heuristic: judgements based on stereotypes or perceived generalisations
    3) Anchoring and adjustment bias: over-reliance on initial information (anchor) and insufficient adjustments
78
Q

Nash equilibrium

A
  • A stable state where no player can improve their outcome by changing their strategy while others keep theirs unchanged
79
Q

What can we take from the prisoner’s dilemma?

A
  • Highlights the importance of social context in decision-making and the role of prosocial behaviour
  • Sometimes, the optimal outcome is not the most ‘selfish’ one
  • In a real-life context, it highlights the idea that societies generally preserve rules that encourage prosocial behaviour
80
Q

Neural mechanisms in rewards

A
  • Primary reinforcers: direct benefits, water, food, sex, pleasure
  • Secondary reinforcers: when rewards can be used to gain other rewards, no value in itself
  • Aversive: removal of reinforcers, aversive stimuli
81
Q

The neurotransmitter dopamine

A
  • Dopamine is associated with pleasure, motivation and reward prediction
  • Very useful, but also has a key role in addiction
  • Addiction: overstimulation of opioid receptors and increased tolerance
  • Mobile games and loot boxes are designed to exploit cognitive biases

Brain and Behaviour 2 (4 decks)

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