SYNAESTHESIA. Hao Ye PSYC 182: Illusions and the Brain Spring 2008

Transcription

1 SYNAESTHESIA Hao Ye PSYC 182: Illusions and the Brain Spring 2008

2 synaesthesia (synesthesia): a neurological condition in which stimulation of one sensory pathway causes involuntary experiences in another sensory pathway * wikipedia

3 SPECIFICATION inducer - stimulus that triggers synaesthesia concurrent - synaesthetic experience itself inducer concurrent e.g. grapheme color (most common)

4 PREVALENCE 1 in 20 (Galton, 1883) 1 in 200 (Ramachandran & Hubbard, 2001b) 1 in 2000 (Baron-Cohen et. al. 1996) 1 in 25,000 (Cytowic, 1989)

5 HERITABILITY high prevalence among relatives 6-7 : 1 ratio of females : males x-linked dominance? theoretical ratio is 2 : 1 reporting bias?

6 GENETICS discordant female monozygotic twins Smilek et. al., 2002 x - inactivation? discordant male monozygotic twins Smilek et. al., 2005

7 SEX DIFFERENCES recent studies suggest 1:1 ratio Stephen, 2004 Simner et. al., 2005 age of subjects? developmental changes complex genetic and environmental interactions

8 DRUGS MDMA (ecstasy) LSD sex differences females report larger perceptual effects of MDMA (weight-adjusted dosages)

9 ARTISTS metaphors in art loud colors, blue music, etc. famous artists Kandinsky, Nabokov, Liszt, Rimsky-Korsakov

10 HSGS INDEX Hao s Synaesthetic Google Search Index: HSGS = hits name hits name+adj Rimsky-Korsakov: HSGS = 20.2 Beethoven: HSGS = 202.6

11 IS IT REAL? hypotheses strong memory association metaphorical actual percept

12 HOW DO WE TEST? performance on perceptual tasks improved performance on certain tasks decreased performance on other tasks

13 POP-OUT TEST (NORMAL)

14 POP-OUT TEST (SYNAESTHETE)

15 STROOP TASK GREEN RED BLUE YELLOW BLUE YELLOW BLUE YELLOW RED GREEN YELLOW GREEN

16 STROOP-LIKE TASK FOR SYNAESTHETES a b Congruent Congruent Incongruent Incongruent Tasks used to examine the influence of

17 THEORIES cross-wiring defective synaptic pruning excessive synaptic connections cross-activation epileptic patients V4 (color area) adjacent to fusiform gyrus (grapheme area)

18 INDUCER conscious processing unconscious processing concept-driven solution to arithmetic problem interfered with color patch naming

19 CROWDING

20 PERIPHERY

21 NEURAL LOCATION? varies by subject lower synaesthesia higher synaesthesia concurrent is usually not complex inducer can be highly complex

22 UNCONSCIOUS PRIMING ELIMINATED AUTOMATIC BINDING OF COLOUR AND ALPHANUMERIC FORM IN Mattingley et. al.

23 SUMMARY 15 subjects experiments color association consistency standard Stroop task (color-naming of color words) Stroop task (color-naming of letters) Stroop task (color-naming of primed targets)

24 COLOR ASSOCIATION 150-item list (letters, numbers, words) subjects describe synaesthetic color (or arbitrary color) synaesthetes tested 3 months later controls tested 1 month later

25 RESULTS Consistency (%) Letters Arabic numerals Number words Weekdays Months First names Place names Occupations Animals Other nouns Abstract words

26 STANDARD STROOP TASK results as expected all subjects slower on incongruent items no difference between synaesthetes and controls

27 SYNAESTHETIC STROOP TASK I subjects name color of stimuli for synaesthetes: congruent w/ synaesthetic color incongruent w/ synaesthetic color neutral (non-alphanumeric) blocked or randomized

28 RESULTS Voice onset time (ms) a b c 0 Congruent Incongruent Congruent Incongruent Congruent Incongruent Neutral Synaesthetic condition

29 SYNAESTHETIC STROOP TASK II masked achromatic prime three durations (28 ms, 56 ms, 500 ms) subjects name color of target patch for synaesthetes: congruent w/ synaesthetic color incongruent w/ synaesthetic color

30 PRIME IDENTIFICATION 100 Prime identification (% correct) Synaesthetes Group Controls

31 TARGET PATCH IDENTIFICATION a 650 c Voice onset time (ms) Congruent Incongruent Neutral Congruent Incongruent b 650 d Voice onset time (ms) Congruent Incongruent Neutral Congruent Incongruent Synaesthetic condition

32 PRIME PROCESSING letters instead of colored target patch congruent (a A) incongruent (b A) unconscious priming prime durations of 28 ms and 56 ms slower at incongruent condition

33 CONCLUSIONS Task I (name color of letter) blocking benefitted synaesthetes in congruent condition Task II (name color of patch) weak color percept for neutral stimuli results in incongruency unconscious processing results in no effect of congruency