PSYC 251 Exam 2 Unit 4: Working Memory and Cognitive Control

Atkinson and Shiffrin’s Modal Model of Memory

Proposed that transient memories are processed in two stages:

1. Sensory memory

   1. Large capacity, very short duration, one for each sense.

2. Short-term memory (working memory)

   1. Holds about seven chunks of information for as long as it is attended/rehearsed; helps select information for long-term storage

Partial Report Technique (Sperling, iconic sensory memory)

Have participants only report one row of letters, signaled by a tone after representation

Again only 3 letters - but 3 letters from any given row

Suggests sensory store holds a complete snapshot of the world, but that it fades very rapidly

Short-term memory (working memory)

Transient representations of information maintained in consciousness

1. Multimodal (general for senses)

2. Small capacity

3. Quick decay <1 min and displaced by new info (overwriting)

4. Rehearsal preserves info in STM

5. Encoding and retrieval Processes transfer to/from LTM

Long-term memory

Declarative and non-declarative

Learned through repetition

Infinite capacity

1. not in consciousness

2. slower access

3. forgotten more slowly

Tripartite Model (Baddeley) - working memory

1. Phonological loop - inner voice

2. Visuospatial sketchpad - inner eye

3. Central executive - manipulator that controls information processing and attention

Phonological loop

The inner voice

stores about 2 seconds of auditory info

Visuospatial sketchpad

The inner eye

Central executive

The working part of your mind; monitors and manipulates working memory buffers

Exerts cognitive control over behavior; provides complex organization in response to environmental demands

The most important component of working memory; but also the least understood

Prefrontal Cortex

Prominent role in working memory, executive function, and cognitive control

Mammals with better working memory and executive function tend to have proportionately larger PFC areas.

PFC damage examples

Often causes dysexecutive syndrome, a decrease in working memory and executive function

1. Chef became aimless in the kitchen, moving aimlessly between tasks

2. Accountant became unreliable, couldn’t maintain relationships, and went bankrupt, couldn’t stick to plans

High degree of distractibility

PFC and dysexecutive syndrom effects

• Decreased digit span

• Poor memory updating (N-back)

• Poor planning (Tower of Hanoi)

• Poor task switching with perseverance (Wisconsin card sorting - learn first rule, unable to switch to new rule)

• Poor overall IQ

PFC Lesions

In animal models, lesions produce disruptions in short-term memory

Impaired performance on a spatial delayed-response task (monkey eye tracking study)

Lateral PFC

Most involved in working memory and executive function

Provides focused control over working memory, despite distractions

Dorsolateral PFC (DLPFC)

Manipulation

Neurons show working memory specific activity (encoding, storage, retrieval activate separate neurons)

Ventral LPFC

simple maintenance

(other cortical areas activated during rehearsal)

Posterior brain regions - PFC

The PFC activates these regions where info was initially processed while that info is being maintained in working memory

Abstract-to-concrete goals in Lateral PFC

Goals may be represented from abstract to concrete along the anterior-posterior axis of the PFC

Schizophrenia - working memory

Poor working memory, especially tasks involving central executive function (manipulation, cognitive control)

Altered frontal lobe function, esp in the DLPFC

Defective dopamine processing in the PFC

• Worse performance on Wisconsin card sorting test

ADHD

Changes in dopamine function cause changes in executive function tasks and PFC activation

ADHD associated with poor working memory and cognitive control perhaps due to dopaminergic dysfunction and/or noisy inputs from the basal ganglia to the PFC