working towards mind reading

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

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