Atkinson and Shiffrin 1968 4 Glanzer and Cunitz

Atkinson and Shiffrin 1968 4

Glanzer and Cunitz 6

Cowan stm = 4 • • • Cowan, N. (2001) The Magical Number 4 in Short-term Memory: A Reconsideration of Mental Storage Capacity. Behavioral and Brain Sciences 24 distinction between a limited-capacity primary memory and an unlimited-capacity secondary memory was described by James (1890), Miller (1956) about 7 chunks in short-term memory (STM) tasks. more as a rough estimate and a rhetorical device than as a real capacity limit. Others have since suggested that there is a more precise capacity limit, but that it is only 3 to 5 chunks. Conditions to test • • (1) when information overload limits chunks to individual stimulus items, (2) when other steps are taken specifically to block the recoding of stimulus items into larger chunks, • - rehearsal and long-term memory cannot be used to combine stimulus items into chunks of an unknown size; • - nor can storage mechanisms that are not capacity-limited, such as sensory memory, allow the capacity-limited storage mechanism to be refilled during recall. • 11 Cowan : under these conditions: a capacity limit << Miller's 7 + 2 chunks : about 4 chunks

Cowan – opposing views • • 12 (1) There are capacity limits but that they are in line with Miller's 7+2 (Lisman & Idiart, 1995). (2) Short-term memory is limited by the amount of time that has elapsed rather than by the number of items that can be held simultaneously (e. g. , Baddeley, 1986). (3) There is no special short-term memory faculty at all; all memory results obey the same rules of mutual interference, distinctiveness, etc. (e. g. , Crowder, 1993). (4) There may be no capacity limits per se but only constraints such as scheduling conflicts in performance and strategies for dealing with them (e. g. , Meyer & Kieras, 1997). (5) There are multiple, separate capacity limits for different types of material (e. g. , Wickens, 1984). (6) There are separate capacity limits for storage versus processing (Daneman & Carpenter, 1980; Halford et al. , 1998). (7) Capacity limits exist, but they are completely task-specific, with no way to extract a general estimate. (This may be the "default" view today. )

1 בעיות של המודל המסורתי • נוירולוגיה • Patients with an STM deficit performed poorly on tasks such as immediate memory span and recency, • but were normal in their long-term memory performance. – • so dissociation into two systems BUT • the problem • if short-term system acts as a crucial antechamber to long-term learning, • such patients should have impaired learning capacity • should show poor performance on a wide range of tasks that were assumed to be dependent on the limited capacity shortterm system. • They showed no evidence of this • with one such patient an efficient secretary • another ran a shop and a family. 13

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Working Memory Retention Systems: A State of Activated Long-Term Memory • • Daniel S. Ruchkin, Jordan Grafman, Katherine Cameron, and Rita S. Berndt Behavioral and Brain Sciences 2003 High-temporal resolution coherence studies • event-related brain potential (ERP) • electroencephalographic (EEG) • STM • the sustained co-activation of • both pre-frontal cortex and the • posterior cortical systems • that participate in the • initial perception • comprehension of the retained information • are involved in its storage. short-term storage mechanisms involve • neural synchrony pre-frontal cortex and posterior cortex, • activation of the long-term memory representations of the material held in short-term memory. • begins during the encoding/comprehension phase • prolonged into the retention phase by attentional drive from pre-frontal cortex control systems. 17

interpretation • the long-term memory systems • • associated with the posterior cortical processors provide the necessary representational basis for working memory, short-term memory decay being due to, primarily, the posterior system. no reason to posit specialized neural systems whose functions are limited to that of short-term storage buffers. Pre-frontal cortex provides the attentional pointer system for maintaining activation in the appropriate posterior processing systems. Limitations on the number of pointers that can be sustained by the pre-frontal control systems determines • short-term memory capacity • displacement of information in short-term memory. 18

anterior posterior LTM 19

WORKING MEMORY • neurological data: at least two STM memory systems • anterior (frontal) • semantic • uses active reverberations • can sustain themselves without repetition, (up to a point) • limited by displacement by competing new information • posterior • phonological • based on rehearsal • temporal decay and need for articulation 20

Working memory • רכיבים • articulatory (phonological) loop • visuo-spatial sketch pad cf Wickens cube • abstract semantic info. • tactile etc • procedural knowledge • a limited capacity attentional control system, the central executive 21

Consolidation of skills Shadmehr and Holcomb 1997 Shadmehr R, Holcomb HH. 1997. Neural correlates of motor memory consolidation. Science, 277: 821 -825, להניע זרוע רובוט - • מטלה ממוחשב positron emission • tomography (PET) • בזמן אמון הדם זרם ל prefrontal cerebral cortex • שתי קבוצות • קבוצה א • למדו וזכרו היטב posterior parietal and • דם זרם ל cerebella • קבוצה ב • ירידה בביצוע בזמן בדיקה 22

Consolidation of skills Shadmehr and Holcomb 1997 שעה - בדיקה שעות 6 חופשי - שעה 1 א אמון חופשי בדיקה 2 אמון 1 ב אמון Shadmehr R, Holcomb HH. 1997. Neural correlates of motor memory consolidation. Science, 277: 821 -825, 23

Conclusions • after practicing a new motor skill, it takes five to six hours for the memory of the new skill to move from a temporary storage site in the front of the brain to a permanent storage site at the back. • If interrupted by practicing another new skill, the learning of the first skill is hindered. • The shift of location of the memory in the brain is necessary to render it invulnerable and permanent. 24

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