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N400
Working towards mind reading
Brain Computer Interfacing
Creating a direct link between your brain and a computer
That sounds an awful lot like mind reading...
Work towards mind reading
BCI
Can a computer detect what I am thinking about?
Not directly (yet)
What can we detect?
• Relaxation (alpha waves)• Imagined movement (ERD/ERS)• Recognition (P300)• Annoying flashing lights (SSVEP)• Priming (N400)• ...
Simple physiological responses
N400
• Discovered during a language study• Reading senseless sentences:
I drink coffee with cream and sugarI drink coffee with cream and socks
ERP7 word sentences
Priming
apple fruit juice
eatingtree
Newton healthy
pickingpearworm
Priming
apple fruit juice
eatingtree
Newton healthy
pickingpearworm
Prime
Probe
Probe
Probe
Probe
Probe
Probe
Probe
Probe
Probe Probe
ERP2 words
How can we use this for mind reading?
1. Let the subject choose his own prime2. Don’t prime on a stimulus, but prime only by
thinking about the object3. Guess the prime by showing different probes
Experimental setup
1. Give one of two possible physical objects to subject
2. Lo beep – close eyes and think about object3. Hi beep – open eyes4. Show a probe word that is related to one of
the two possible objects, record EEG5. Can the computer tell which object was
shown?
ERPonly a probe word
ERPonly a probe word
Future researchbuilding a search tree
Challenges
• When no result: problem in experiment, recording or data processing?Process of elimination
• More neuroscience than computer scienceRead up on neuroscience
• Ambiguous results: only works on some subjectsVerify results with statistics and control scenarios
?