Working Memory II Working memory executive control and

Working Memory II Working memory, executive control, and prefrontal cortex Cognitive Science, 9. 012 Nuo Li 4/27/06

What is working memory? Active maintenance of goal related information in the face of distractors and interference. It’s task dependent and involves some degree of cognitive control.

What is working memory? Some defining characteristics: - goes on in consciousness accessible to explicit form of expression (declarative memory) elaboration of short-term memory selective involves cognitive processing (e. g. recognition)

Atkinson & Shiffrin (1971) • • • Parallel processing of inputs Information are selected for entry into STM = Working Memory = Control processes – Selection – Rehearsal – Coding – Decision making

Baddeley & Hitch (1974) WM = Executive Control + Domain Specific Modules

Outline • Working memory (WM) and short-term memory (STM) • WM, controlled attention, and fluid intelligence • Role of pre-frontal cortex (PFC) • Mapping from functions to structures • Representation

Outline • Working memory (WM) and short-term memory (STM) - WM Tasks - STM Tasks - Distinctions between WM and STM • WM, controlled attention, and fluid integellence • Role of pre-frontal cortex (PFC) • Mapping from functions to structures • Representation

WM tasks Reading span (Daneman & Capenter, 1980) Subject read (or listen to) a list of 2 to 6 sentences. Afterward, the subject recalled the last word of each sentence.

Demo For many years, mywas family friend have been working the air. farm. SPOT Because We were the 50 room miles outstuffy. atand sea Bob before went weoutside lost sight for of some theon fresh land. BAND TRIAL ANSWER: SPOT, TRIAL, BAND

WM tasks Reading span (Daneman & Capenter, 1980) Subject read (or listen to) a list of 2 to 6 sentences. Afterward, the subject recalled the last word of each sentence. Operation span (Turner & Engle 1989) Subject solved a string of arithmetic operations and then read aloud a word that followed the string. After a series of such operation-word strings, the subject recalled the word.

Demo Is (8/4)-1=1? Is (6 x 2)-2 =10? Is (10 x 2)-6=12? Bear Dad Beans Answer: Bear, Dad, Beans

WM tasks (Memory span tasks) Reading span (Daneman & Capenter, 1980) Subject read (or listen to) a list of 2 to 6 sentences. Afterward, the subject recalled the last word of each sentence. Operation span (Turner & Engle 1989) Subject solved a string of arithmetic operations and then read aloud a word that followed the string. After a series of such operation-word strings, the subject recalled the word. Counting span (Case, Kurland, & Goldberg 1982) Subject is presented with up to eight displays. Each display consists of different number of targets, and two other kinds of distracters, all randomly placed. Subject is required to count the targets aloud, and report the final tally. After the series of displays, the subject is required to report previous final tally in order

Demo Answer: 5 8 6 3 9 9

WM tasks These tasks are thought to reflect some fundamental aspect of cognition. Score on these tasks predict a range of cognitive functions: - Reading & listening comprehension - Following directions - Vocabulary learning - Note taking - Writing - Reasoning - Bridge playing - Computer language learning - etc

STM Tasks Wechsler Digit Span Task Forward Span The examiner verbally present digits at a rate of one per second. Subject is asked to repeat the digits. The number of digits increases by one until the participant consecutively fails two trials of the same digit span length. Backward Span The backward test requires the participant to repeat the digits in reverse order.

WM & STM What’s the difference?

WM & STM Brown–Peterson distractor task: Recall trigram of consonants (e. g. GKT, WCH, …) after performing a number of algebraic computations (e. g. , counting backwards by 3’s). Keppel and Underwood (1962) found that forgetting in the Brown– Peterson distractor task depends on where in the experimental session performance is assessed. (On the very first trial, the recall performance was near perfect). Goes against the classic notion of information has to be rehearsed in order to be retained. Proactive interference plays an important role in short-term retention

Effect of Proactive Interference Others also found similar effects: Rosen & Engle (1998) Subjects (with high and low WM score) learn to associate 12 cue word with 3 list of other 12 words. Instruction emphasized accuracy Example: list 1: bird-bath; list 2: bird-dawn; list 3: bird-bath; (re-learn) Measured both timing and accuracy. Result: List 1: same List 2: low WM made more error (showed intrusion from list 1) List 3: high WM responded slower than low WM subjects, even slower than themselves on trial 1. Conclusion: information in list 1 is suppressed better for the high WM subjects, which affected their performance on later trials.

Effect of Proactive Interference Kane & Engle (2000) Subject (with high and low WM score) had 3 trial in which they saw 10 words to recall. The subject performed a rehearsal preventative task for 16 s. Result: Trial 1: high WM and low WM subject performed the same (60%) Subsequence trials: low WM had steeper decline in recall performance Adding secondary preventative task (adding interference load) The two group performed the same. Conclusion: When add more interference load, high WM subjects were hurt more, suggest that under normal condition, high WM subjects allocate more attentional control to combat the interference.

WM & STM Storage of information. Limitation: How many item can be stored. WM Different from passive storage, WM is active maintenance of goal related information relevent to a task in the face of proactive distractors. There is addition of mental “work” (cognitive processing) and its combination w/ “memory”. ( more than just STM), involves recognition & comprehension. Limitation: memory component & control component

Outline • Working memory (WM) and short-term memory (STM) • WM, controlled attention, and fluid intelligence • Role of pre-frontal cortex (PFC) • Mapping from functions to structures • Representation

WM is Capacity Limited Memory capacity vs. Cognitive control capacity “Greater working memory capacity does not mean that more items can be maintained as active, but this is a result of greater ability to control attention, …ability to use attention to avoid distraction. ” -Engle RW

Model of WM, Engle WM = STM + controlled attention Three components: 1. a store in the form of long-term memory traces active above threshold 2. processes for achieving and maintaining that activation 3. Controlled attention (capacity limited, individual performance difference arise)

Model of WM, Engle Central Executive Magnitude of this link is determined by the extent to which the procedures for achieving the maintaining activation are routinized or attention demanding. Thus, it is assumed that, in intelligent, well-educated adults, coding and rehearsal in a digit span task would be less attention demanding than in a 4 -year old children. Strategies, procedures for maintaining activation a. b. Could be phonological, visual spatial, motor, auditory, etc More or less attention demanding depending on the task and subject (working memory capacity, controlled attentions) a. b. c. Achieve activation through controlled retrieval Maintain activation (to the extent that maintenance activities are attention demanding). Blocking interference through inhibition of distraction STM Activated portion of long term memory LTM

Empirical Support Two questions: 1) Is separate construct of STM and WM necessary? 2) Once the common variance to WM and STM is removed, do the WM residual variance (which should reflect controlled attention) correlate with the residual for general fluid intelligence?

Empirical Support 133 subjects performed 8 different tasks Operation span . 77. 49 Reading span . 63 WM . 61 . 81. 91 counting span COMMON backward span forward span General fluid intelligence . 85 . 67. 79 . 29 Ravens standard progressive matrices test . 74 Cattell fair test of intelligence STM. 12 . 71 Forward span w/ similar sounding word Engle et al (1999)

WM and Fluid Intelligence • Controlled attention is closely related to general fluid intelligence • Performance task on WM task predicts performance on other cognitive tasks e. g. performance on reading span task correlates well with reading comprehension

WM and Fluid Intelligence Antisaccade Task Pro-saccade cue Anti-saccade cue Identification of target by pressing key A target Identification of target by pressing key Require suppression of the natural tendency to saccade to the flashed cue. WM span assessed on operation-span task. Kane et al (1999)

WM and Fluid Intelligence Result Reflexive Eye Movement Reaction Time Eye movement not monitored in this case Kane et al (1999)

WM and Fluid Intelligence Stroop task Result

WM and Fluid Intelligence Dichotic listening task Subjects repeat aloud words presented to one ear while ignoring information presented to the other ear. At some point, subject’s first name is spoken to the ignored ear. Report whether they heard their name during the trial. Result 20% high WM span subject reported 65% low WM span subject reported Conclusion High WM span people suppressed distractor information better

Current WM Models ? Engle Baddeley & Hitch Central Executive Strategies, procedures for maintaining activation STM LTM

Outline • Working memory (WM) and short-term memory (STM) • WM, controlled attention, and fluid intelligence • Role of pre-frontal cortex (PFC) • Representation • Mapping from functions to structures

PFC Anatomy Dorsolateral Input mainly from medial, dorsolateral cortical areas. (somatosensory, visuospatial information) Lateral Inputs mainly from ventrolateral and ventromedial cortical areas (auditory, visual pattern information) Segregation of functions? More on that later…

PFC Deficits in Human Wisconsin card sorting Results: No difficulty learning the rule initially. (memory component) But once learning a rule, patient could not switch.

PFC Deficits in Human Other cognitive tasks: Stroop task London tower All these cognitive task involves a memory component Q: deficit in memory component vs. executive control?

PFC Deficits in Human Owen et al (1996) spatial Task: Find the hidden squares Result: Normal controls: developed successful self-ordered search strategy Temporal lob lesion patients: only failed on most difficult task PFC lesion: failed on most easy task Conclusion: prefrontal contribution to WM is the mediation of problem-solving strategies and not in memory per se. verbal visual

PFC Deficits in Human Other memory tasks Shimamura 1995 Inability to suppress irrelevent information, sensitive to proactive interference

PFC Deficits in Human Recall temporal-sequence Milner & Petrides, 1984 Shimamura 1995 Deficits in recalling temporal ordering, but no deficit in recognition.

PFC Anatomy in Other Species

PFC Deficit in Nonhuman Primates Working memory task Associative memory task PFC lesioned primates: Deficit in working memory task, but not in discrimination task PFC lesioned primates also show deficit in spatialdelayed alternation task

PFC Deficit in Nonhuman Primates Lateral PFC Lesion: Slower to learn new criteria when the diagnostic dimension is changed. Orbital PFC Lesion: Learn new criteria normally, slower to relearn. Dias, Robbins & Roberts, 1996

PFC Deficit in Nonhuman Primates Funahashi , Bruce, & Goldman-Rakic (1993) Delayed saccade task Fixation Point Target Saccade! After dorsolateral PFC lesion Error on contralateral visual field Performance decay with time

PFC Neural Response Anti-saccade task Error Trials Funahashi, Chafee, & Goldman-Rakic (1993)

PFC Deficits Dorsolateral - Spatial delayed response - Spatial delayed alternation task - No deficit in discrimination Lateral - Object alternation - Delayed non-match to sample Orbital - Deficits in olfactory, taste, visual and auditory discrimination - Discrimination reversal learning.

Outline • Working memory (WM) and short-term memory (STM) • WM, controlled attention, and fluid intelligence • Role of pre-frontal cortex (PFC) • Mapping from functions to structures • Representation

Verbal storage+processing

Verbal storage Activation in left posterior parietal cortex (Brodmann’s area) 3 frontal sites (Broca’s area) Left supplementary motor and premotor area storage 0 - and 1 -back Item recognition Storage+process 2 - and 3 -back Free recall Smith & Jonides, 1999 (review)

Visuospatial visual spatial

Visuospatial Spaital (blue) Object (red) Smith & Jonides, 1999 (review)

Some insights from Imaging studies • Imaging studies show that working memory is mediated by frontal cortex and a collection of posterior regions differing in the types of information maintained. • Posterior cortical regions seem to specialize in the type of information held in working memory • Frontal area may have a special role in integrating different type of information

Outline • Working memory (WM) and short-term memory (STM) • WM, controlled attention, and fluid intelligence • Role of pre-frontal cortex (PFC) • Mapping from functions to structures • Representation

WM Representation Domain general vs. Domain specific? Engle Baddeley & Hitch Central Executive Strategies, procedures for maintaining activation STM LTM

Domain General? Rao, Rainer, & Miller (1997) Conclusion: More than half of the neuron (64/123) contain both “what” and “where” information

But wait… Cue Delay Response Wilson, Scalaidhe, Goldman-Rakic 1993 Lateral PFC 24/31 selective for pattern 6/31 selective for both 1/31 selective for spatial information Conclusion: segregation of “what” (lateral) and “where” (dorsolateral)

Thank you!

Backup slides

PFC Neural Response Primate performing a delayed response task PFC Neurons Milner & Petrides (1984)

PFC Neural Response Cue-delay-saccade Funahashi , Bruce, & Goldman-Rakic (1989) Q: memory of cue vs. motor preparation?

PFC Neural Response Quintana & Fuster (1992) Dissociation of memory of cue from motor preparatory cue

PFC Neural Response Delayed match-to-sample task Rainer Asaad & Miller (1998)

Spatial Jonides, Smith, Koeppe, Awh, Minoshima, Mintun. (1993) Areas for spatial memory task

Domain General? Cross-modal processing Suchan, Linnewerth, Koster, Daum, & Schmid (2006)