Prof. Greg Francis 1/2/12 PSY 200: Intro. to ... - Purdue University

Prof. Greg Francis 1/2/12DifferencesWe have to look for differences in activityAlzheimer’s patients have reduced brain activityA simple experimentSuppose you run an fMRI experiment where a person alternatesbetween seeing a blank screen and a faceYou take multiple fMRI scans with half recording brain activity duringthe blank and half recording brain activity during the faceAdd them up pixel by pixel for each conditionViewing blankViewing facePurdue UniversityPurdue UniversitySubtraction methodSubtract the fMRI signals produced by one condition from the fMRIsignals produced by another conditionThe difference map indicates those brain regions that are involved inthe different cognitive tasksIt requires a sophisticated statistical analysis to avoid false positives!Viewing blankViewing facePurdue UniversityDifference mapWhat is usuallyreported is just thedifference mapColors mark placesin the brain that arestatistically differentbetween conditions Czisch et al. (2009)for rare tones vs.frequent tonesThe map would bedifferent if itcompared rare tonesversus speechReportingPurdue UniversityFunctional MRIFunctional MRIColor maps showstrongest“responses”e.g., during a taskthat requires covertspatial attentioncompared to one thatdoes not requireattentionWhen moving apointer to a targetbox compared to nomovement “activity” in areasinvolved in vision,planning, and motorcontrolPurdue UniversityPurdue UniversityPSY 200: Intro. to Cognitive Psychology 4

Prof. Greg Francis 1/2/12LimitationsBrain scans do not really tell us how the brainworks the scans just tell us approximately where in the brainsomething occurs sometimes it can tell approximately whenEven trying to find the place may be problematic Lots of cognitive abilities involve many different areasof the brainMost of the time theories of cognition are derivedfrom experimental psychology Brain studies explore how to implement the theoriesPurdue UniversityCommon misconceptionBrain scans demonstrate a physiological basis tothings that were thought to be emotionally orcognitively based e.g., MRI scansof stutters in fact, allbehavioral traitsare physiologicallybasedPurdue UniversityConclusionsLots of research in this areaTechnology is improving in many waysThere are many other types of scanningtechnologies Computerized Axial Tomography (CAT) Diffusion tensor imaging (DTI) Single Photon Emission Computed Tomography(SPECT) Near Infrared Spectroscopic Imaging (NIRSI) Magnetoencephalography (MEG) Positron Emission Tomography (PET)Purdue UniversityNext timeHow do we use brain scans to studycognition?How good are the scans?What is really being measured?How to read someone’s mind.Purdue UniversityPSY 200: Intro. to Cognitive Psychology 5