1. SLEEP-ASSOCIATED CHANGES IN THE MENTAL REPRESENTATION OF SPOKEN WORDS (DUMAY & GASKELL, 2007) Alison Trude PSYC 525 15 September 2010

2. Lexical Memory  How do we know when a new lexical entry has been integrated into memory?  Competition when compatible with input +

3. Fictitious Word Learning (Gaskell & Dumay, 2003)  Participants heard nonwords w/ high overlap w/ real words (e.g., cathedruke)  Good performance on 2-Alternative Forced Choice Task  Indicates good phonological learning- can recognize what they heard A cathedruke B cathedruce

4. Fictitious Word Learning (Gaskell & Dumay, 2003)  Then, participants completed a Pause Detection task to check for lexical competition  Previous research showed that words w/ more lexical competitors before the pause had longer PD times  Effect of learning “cathedruke” only seen at retest (7 days later) cathedr_al Did you hear a pause? Y N

5. The Lexicalization Delay  Subsequent studies showed that lexicalization effects took 24 hours to emerge  Sleep shown to play a role in memory consolidation in many domains (e.g., procedural, perceptual, motor skills, some areas of speech)  During sleep, new information can be gradually transferred to LTM, thus preventing catastrophic interference

6. Design  2 groups learned 24 novel wds; tested 12 and 24 hours later (PD, 2-AFC & free recall of novel wds) PM Group AM Group Exposure/Test Retest 12 hours

7. Some more details…  Participants learned 24 novel words that were made up of real words + addt’l syllable (e.g., “shadowks”)  Did 2-AFC task with these stimuli (“shadowks” vs. “shadowkt”)  Also did free recall of novel words  During PD, participants heard 48 real words- 24 that had a novel word competitor and 24 that did not. Heard in context consistent w/ competitor (“shadow_k”).

8. Results  Lexical competitor effect:  RT baseline – RT competitor  So, a negative # means slower (more competition) for comp. than for baseline  At 12 hr, only PM group show effect, at 24 hour, both groups  AM group had slept by then *

9. Results  Free Recall task:  AM group did worse @ 12 hr, better after sleep  PM group improved @ both 12 and 24 hr

10. Discussion  Lexicalization of phonological forms is associated with sleep  Why did free recall get better with sleep?  Strengthening of episodic (phonological) information, or, perhaps lexicalization provides a boost  Compatible with models that use lexicalization delay to prevent overwriting

11. Why does sleep help?  Circadian rhythm: Sleep irrelevant, but something happens at a particular point in circadian cycle  Lack of input: little speech input during sleep, so less competition, better chance to consolidate  Sleep is essential: process that allows lexicalization to happen is specific to sleep  Some evidence that particular configurations of REM/non- REM sleep affect performance  Hippocampus may gradually feed new info into LTM (neocortical store)  Next step: associate stages of word learning with specific brain regions

12. Hot off the presses!  AMLaP 2010  Magnitude of change in competition was correlated with count of sleep spindles (Tamminen et al.)  MEG study (Gagnepain et al.)  Posterior effect for consolidated words  Frontal effect for non-consolidated words  Time-locked to different parts of the stimuli

13. Lingering questions…  Ways to test whether sleep is necessary vs. other possible options (e.g., lack of input)?  Different types of memory needed at various levels of language processing/encoding?  Reasons for improvement on free recall task?