Presentation on theme: "SLEEP-ASSOCIATED CHANGES IN THE MENTAL REPRESENTATION OF SPOKEN WORDS (DUMAY & GASKELL, 2007) Alison Trude PSYC 525 15 September 2010."— Presentation transcript:
SLEEP-ASSOCIATED CHANGES IN THE MENTAL REPRESENTATION OF SPOKEN WORDS (DUMAY & GASKELL, 2007) Alison Trude PSYC 525 15 September 2010
Lexical Memory How do we know when a new lexical entry has been integrated into memory? Competition when compatible with input +
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
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
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
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
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”).
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 *
Results Free Recall task: AM group did worse @ 12 hr, better after sleep PM group improved @ both 12 and 24 hr
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
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
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
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?