Working Memory

Types of memory

• Short-term memory

• Sensory processing

Working memory

• Application of ‘attention to short-term memory

• Hold a series of facts or actions for a few minutes to complete a task

• Very limited capactiy (4-7 ‘chunks’)

Long-term memory

• Turn short/working memory into ‘permanent’

• Huge capacity

What structure is represented by this image?

Prefrontal cortex

Subdivisions of the PFC

• Dorsolateral

• Rostral

• Ventrolateral

• Orbitofrontal

• Dorsomedial

• Ventromedial

Dorsolateral prefrontal cortex

• Brodmann Areas 9+46

• Monitoring and manipulation of working memory content

• Susceptible to Traumatic Brain Injury (TBI)

Role of dorsolateral prefrontal cortex

• Abstract reasoning

• Top-down regulation of attention

• Projects to hippocampus

  encoding long term memory
  recalling memory to replay

• Many many other regions involved in working memory

Testing Cognitive Function

• Wechsler Memory Scale

• Wechsler Adult Intelligence Scale

• Cambridge Neuropsychological test automated battery

• All include multiple tasks, measuring multiple cognitive functions, including working memory

Cognitive Tests

• Standardised - allows comparisons

• Reliable - taking the same test twice gives the same result

• Valid? Does the test measure what it claims to?

• Link from test results to anatomy/neuroscience?

Working memory functions and tests

Maintenance

• Retaining information

• Digit span forward task

• Spatial span forward task

Monitoring

• Attending to info

• N-Back task

Manipulation

• Working with information

• Letter-number sequencing task

Digit span forward task

• Verbal/auditory maintenance

• Administrator recites a series of numbers - 1 per second, monotone delivery

• Subject asked to repeat those numbers

• Length of series increased with each trial

• Task ends when participant fails twice at a specific length

• length = score

Dominance/laterality

Brains composed of two identical hemispheres

• Mirror images

Some functions thought to arise largely in one hemisphere

• Not the same hemisphere in everyone

• Different hemispheres dominant for different behaviours

• Lots of variance

N-Back task

• Remembering backwards

• A series of digits are presented, one at a time (about 15-50 in total)

• Answer ‘yes’ if a digit appeared ‘n’ back

• ‘N’ is the number of digits back you have to remember

The higher the ‘n’ the harder the task

Stimuli can be varied to test different sub-types of working memory

• Letters/words (verbal and auditory)

• Sound (auditory)

• Shapes (spatial)

• Smells (olfactory)

Letter-number sequencing task

• Administrator reads out a string of words and letters

• Participant must first say the number in ascending order and then letters in alphabetical order

• Cut-off when cannot reproduce a certain string length 3 times

• Manipulation of verbal working memory

Attention Deficit Hyperactivity Disorder (ADHD)

Restless, impulsive, difficulty concentrating (age inappropriate)
- 7% worldwide

Multiple subtypes (hyperactive/impulsive/combines, child/adult

Problems with response inhibition

• The ability to ‘resist internal or external interferences to achieve goal directed behaviours’ (Barkley 1997)

Challenges with Working Memory

• Visuospatial more than verbal

• Improves with age

• Improved by methylphenidate

Response inhibition causes, or is it cause by working memory problems?

Neurobiology poorly understood

Train your working memory

• Multiple meta-analytic studies show that working memory training does not improve intelligence etc.

• Short-term effects

• Do not really transfer across WM tasks

• Do not transfer to other cognitive abilities - or academic performance

• Many studies poorly designed/controlled

Schema

• Learned content can be retrieved as one chunk

• The more is learned, the bigger the ‘chunk’ - but it still one chunk

• Is a simple example of how expertise develops

• Examples - area codes, times tables

Neural Efficiency

• Learning results in reduced brain activity

• Seen in working memory and attention areas

• Less processing power required to achieve complete same cognitive task

• IQ may reflect baseline differences in neural efficiency

• Controversial - technology may not be sensitive enough