M7, T4, action disorganization syndrome

Question 1

Action disorganising syndrome

Answer 1

• Impairment in completing everyday routine multi-step tasks
• Cognitive in nature (i.e., not due to impaired object recognition or a motor impairment)

*look up image

Question 2

Characteristics of action disorganising syndrome

Answer 2

• Use objects inappropriately even if they recognize the object (object substitution)
• Leave out actions needed to complete a given task (omission)
• Add other actions in that are not needed to complete a given task (addition)
• Complete actions required for a given task in the wrong order
• Repeat some actions required for a given task multiple times (perseverations)
• Spatial/quality errors (using a tool in the wrong spatial plane)

Question 3

Patient HG (Humphreys, Forde and Riddoch) daily impairments

Answer 3

• Making a cup of tea
• Making a sandwich
• Packing a lunchbox
• Gift wrapping
• Preparing toast and cereal
• Painting a block of wood

Question 4

Patient HG (Humphreys, Forde and Riddoch) errors

Answer 4

Tended to omit key actions
(e.g., failing to add milk to a cup of tea),
perseverate
(e.g., keep adding sticky tape to wrapping paper unnecessarily) and
ordering errors
(e.g. putting cheese on bread before buttering it)

Question 5

Action coding scheme

Answer 5

The action coding scheme (ACS) was developed by Schwartz et al. to systematically describe how everyday mutli-step tasks are performed

Hierarchical coding scheme with ‘A1 components’ and ‘A2 behaviours’

Question 6

Component acts (A1s) and A2 behaviours

Answer 6

component acts (A1s)=
the smallest component of a behavioural sequence that achieves a concrete, functional result or transformation, describable as the movement of an object from one place to another, or as a change in the state of an object (teabag in tea pot, water in tea pot)

Consecutive component acts are linked together into A2 behaviours -> they are higher order groupings of actions that reflect an overall goal in the multi-step task (prepare tea in tea pot)

Question 7

Performance of multistep tasks described via A1 acts and A2 behaviours

Answer 7

• A1 acts are performed consecutively, and not drawn randomly from different A2s.
• That is, all A1 actions in a given A2 should be completed before A1 actions from the next A2 are executed
• To assess everyday action - calculate the rate of A1s executed that do not fall into the correct A2 group in a sequence
  -> For example, when making tea, someone might complete the A1 (A2a) “teabag in tea pot” followed by the A1 (A2b) “milk in cup” followed by (A2a) “water in tea pot” followed by (A2b) “sugar in cup”, regardless of the A2 grouping.

Question 8

Schwartz et al 5 groups of errors that can be made during multi-step tasks, Action Coding Scheme

Answer 8

1. Place and Object substitutions (putting an object in the wrong place, such as pouring milk in a teapot).
2. Anticipations (performing actions in the wrong sequence, such as drinking from a cup with milk only, before tea was added)
3. Tool substitutions (such as brushing hair with a toothbrush)
4. Quality errors (performing an action correctly, but doing so clumsily)
5. Omissions (forgetting a step, such as not adding a teabag to a teapot)

Question 9

Schwartz et al ACS to study how ADS patient HH performed everyday actions

Answer 9

• Scored how HH made cups of coffee over 28 testing sessions
• Made 97 errors in total
• 31% of his A1 actions were independent of a common A2 group
• Mostly made place and object substitution errors, some anticipation errors, and a few tool substitutions, quality errors and omissions
  -> The independent A1 errors HH made might be due to top-down goal states being weakened, thus resulting in environmental, bottom up saliency driving action executions

Question 10

Competitive queuing model

Answer 10

*look up image

Hierarchical Model of action execution
1. Goal Unit = top down signal
2. Basic- level component actions
3. Object Representations = perceptual and semantic system stores providing bottom up activation

Which basic level action is activated in a given moment depends on the competition between the top down signal (goal unit) and bottom up information from the environment (object representation).

Question 11

Understanding the meaning of lines competitive queuing model

Answer 11

• The width of the lines going from the goal unit to the basic level actions indicates the strength of the top down signal and helps determine what order actions should be completed in (activation gradient)
• Novel tasks have less well defined activation gradients (i.e. top down signal telling you what order to do things in).
• Here, incorrect actions may be selected and there would be prolonged competition between top down and bottom up signals about what actions should be completed in what order

Question 12

Competitiveness of the competitive queuing model

Answer 12

• Goal units are competitive with one another meaning that normally, only one goal unit will be active at a given time
• Component actions are competitive with one another meaning that normally, only one component action will be active at a given time.
• Once a component action “wins” the competition, it sends the information off to other systems to determine the precise motor representations needed for the action

Question 13

Object substitution errors, damage to connections between object reps and basic level comp actions - Competitive queuing model in ADS

Answer 13

• Object representations are activated normally (i.e. perceptual and semantic knowledge of what an object is, is normal) BUT
• Connections between the object representations and the basic level component actions may be damaged
• In turn, the basic level actions could be subject to interference from other semantically and/or visually related objects
  -> This could result in a basic level action being performed for the wrong object
  -> e.g. teabag put directly into kettle instead of teapot

Question 14

Object substitution errors, impaired top down activation - Competitive queuing model in ADS

Answer 14

• impaired top down activation from the goal unit or damage to the basic component action level itself could cause object substitution errors.
  = ”poor task-specification of component actions”
• If basic level actions are not fully defined in long term memory, it is possible that actions are generated for objects that are only partially associated with the action are executed.
  -> If presented with a toothbrush, it might afford a similar action as a hairbrush and result in an object substitution error and the brushing of hair with the toothbrush

Question 15

Omission errors, Competitive queuing model in ADS

Answer 15

• In non-ADS individuals, omission errors occur when people are exposed to some sort of dual-task cognitive load (e.g. make a cup of tea, but while you do it, stand on one foot and count backwards from 100)
• Cognitive load might decrease activation from the goal unit towards basic level component actions, resulting in an action being omitted during the action sequence
  -> Secondary tasks ‘steal’ cognitive resources

Question 16

Two types of perseveration errors, competitive queuing model in ADS

Answer 16

1. Immediate perseverations = repeating the same task, over and over again immediately (e.g., continuously adding sugar to tea)
   -> due to damaged links between basic level component actions that normally compete with one another so only one act is active at a given time
2. Delayed perseverations = repeating the action again after some interval (e.g., going back and adding more sugar after some time has passed)
   -> occur after damage to the activation gradient (top down signal from goal unit)
   -> result is no one unit “most” activated at one time in a sequence, therefore, patient will go back and repeat the action

Question 17

Perseverations and environmental triggers

Answer 17

Perseverations also likely to occur when objects in the environment trigger an already completed action to be activated again

They become re-activated because there is some sort of damage to the top down gradient which impairs competition between the goal unit and object representation levels of the model

Question 18

Stored knowledge impairment for routine actions, competitive queuing model in ADS

Answer 18

• ADS patients have impaired long term knowledge of action sequences (e.g. difficulties verbally recalling the steps taken to make a cup of tea), even if semantic knowledge of objects remains normal (e.g. knowing what a teapot is)
• Reflects impairment to goal unit (knowledge about actions) with no damage to object representation level

Question 19

Working memory impairments, competitive queuing model in ADS

Answer 19

• Those with ADS may have “resource deficits” or lowered working memory capacity – in particular for action working memory.
• ADS patients show improved performance on daily tasks when “copying” rather than following written instructions.
  -> This finding suggests that ADS patients can bypass the use of working memory to complete a task and copy what they see.
  -> Could be achieved via mirror neurons in the brain that directly translate seen gestures into motor actions