Prof. Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 1 Purdue University Brain scans PSY 200 Greg Francis Lecture 04 How to read someone’s mind. Purdue University Scanning  Brain scanning techniques like fMRI provide spatial and temporal patterns of activity across the brain  We want to analyze those patterns to discover how the brain works Purdue University fMRI  Passive listening vs. active listening  Vannest et al. (2009)  Twenty children (ages 11-13) complete three tasks  Passive listening: hear a female speaker tell a 30-second story  Active response: hear the same speaker tell a story in 5 second segments of two sentences. Scanning occurred after the sentences (silence). Answer questions  Random tones: no task, just listen Purdue University fMRI  The colors show the difference maps relative to listening to the tones  Common activity (breathing, digestion, hearing machine noise,…) is subtracted out  The colors are not brain activity! Passive listening Active response Purdue University fMRI  More and different activity for active listening compared to passive listening  (Could it be otherwise?) Passive listening Active response Purdue University fMRI  Does more activity for the active response mean active response listening is “better” than passive listening?  Tested children on comprehension of stories  PL: 75.1% correct, SD=12.7  AR: 79.1% correct, SD=9.1  No real difference in comprehension Passive listening Active responseProf. Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 2 Purdue University Sensory substitution  Some scientists look for replacements to lost perception  For example, there is a tongue display unit that attempts to present spatial information for blind people Purdue University Sensory substitution  People can use a TDU to discriminate shapes  Kaczmarek, Bach-y-Rita & Tyler (1998)  Link to video on class web page Purdue University Sensory substitution  So what happens in the brain?  Are there responses from areas typically involved in shape perception? Or in areas related to touch on the tongue? (or both or neither?) Purdue University Sensory substitution  fMRI differences suggest that using the TDU involves areas of motor cortex  Not areas that are traditionally for visual perception  This is the kind of question that can best be answered with brain scan technology Purdue University Reading minds  Long-term, the goal of fMRI research is to be able to analyze a brain scan and identify what a person is thinking  There are several attempts to do this (Haynes et al., 2006)  Adding or subtracting numbers Purdue University Reading minds  Based on the choice at the end, we can deduce whether the subject chose addition or subtraction for that trial  Make an fMRI scan during the selection process  Whether to add or subtract numbers Scan "now"Or scan"now"Prof. Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 3 Purdue University Mind reading  It is possible to build a recognition system that distinguishes (with 71% accuracy) the brain patterns for addition and subtraction  Depends on the place in the brain  Different places for intention and execution  You can read the mind of these subjects! Purdue University Thought reconstruction  Another research group analyzed fMRI responses to reproduce a shown image Purdue University Thought reconstruction  Performance depends on where the signals come from  Fewer errors for “lower” brain areas  Where do you stop?, the retina?, the lens of the eye? Purdue University Thought reconstruction  These kinds of studies are mostly a demonstration of technology  we already know the brain represents visual information!  Before the study was run, we knew that there were differences in the brain when we see different images  The percept is based on the brain, so there must be differences!  These kinds of studies tell us that the neurophysiological differences between cognitive events can be measured by these brain scanning technologies  A bit like statistical power Purdue University Mind reading with EEG  You can purchase an EEG device to read your mind and control a computer  www.emotiv.com Purdue University Mind reading limits  fMRI: If subjects decide to multiply numbers, a system trained to distinguish between subtraction and addition is clueless  Thought reconstruction: As the number of possible images to be shown increases, it becomes harder to reconstruct the shown image  Emotiv: very limited set of mind reading possibilities  This is a very limited form of mind reading  People do better than this every day by watching people behave (posture, eyes, skin tone)  The military and police are quite interested in these approaches  Companies are interested in identifying what you think  Proctor & GambleProf. Greg Francis 1/2/12 PSY 200: Intro. to Cognitive Psychology 4 Purdue University Problems / limitations with scanning  So much data that is difficult to know what to do with everything  Statistical analysis is complicated  In a small brain scan, you may have 64 x 64 voxels x 10 slices » =40,960 voxels overall  Some of those voxels will give different responses just by chance  Difficult to compare across subjects  Slightly different anatomy  Blurring of images is difficult to deal with  Sometimes blur together brain areas, across a fissure, that are actually far apart on surface of cortex  Some cognitive events are faster than the technology can track  Can only measure the brain, cannot manipulate it Purdue University Statistics  It is easy to do the statistics incorrectly (it has taken a while for the field to sort this out)  Bennett et al. (2010) ran a study where the subject was shown a series of photographs depicting people in social situations with a specified emotional valence, either socially inclusive or socially exclusive. The subject was asked to determine which emotion the individual in the photo must have been experiencing.  fMRI contrasts were computed between the scans for the two types of emotional valence Purdue University Statistics