Prof. Greg Francis 5/23/081Brain scansIIE 269: Cognitive PsychologyGreg FrancisLecture 03How to study the brain without killingsomeone.Scanning Technology provides insight into brainprocesses EEG recordings MRI PET scans Functional MRI Non-invasive Maps of brain activityElectroencephalogram EEG The brainproduceselectrical activity Put electrodeson the headEEG Watch the electrical current change through time whilereading sentences Good temporal resolution Poor spatial resolutionSemanticanomalyBrain maps You can analyze the EEG signals in many different ways Compare the signal strength for different situations Ayahuasca is a Brazilian psychoactive teaBrain maps You can analyze the EEG signals in many different ways Can be used to diagnose attention deficit disorderProf. Greg Francis 5/23/082Spatial resolution You never reallyknow which partof the brain ismaking thecurrent Lots of work toimproveMagnetic Resonance Imaging Magnetic fieldforces protons inyour body to lineup pulses of radiointo fieldbouncesprotons around as they returnto normalposition, theyemit a signalthat can bedecoded into amapMagnetic Resonance Imaging MRI Scans: Like an x-ray machine, butcan look at soft tissue (like lungs, heart,..) Very good spatial resolutionMagnetic Resonance Imaging MRI Scans: Like an x-ray machine, but can look at softtissue (like ankles, (former undergraduate) brain,..) Very good spatial resolution millimetersMRI Scans MRI providesa “slice” at atime Take multipleslices to buildup full imageNobel prizewinning work!MRI Scans Very good spatialresolution(millimeters) Cross-section(s) Make a movie Viewing from above Going from bottom totopProf. Greg Francis 5/23/083MRI Scans Can identifyanatomicaldifferences betweenbrains Alcoholic has largerventricles and thinnercorpus callosum Note comparingacross brains is a bittricky! Everyone’s brain is abit differentMRI Scans 3-D maps Normal Ataxia: loss of motorcontrolMRI Scans Non-invasive, no side effects Allows early detection of brain disease,tumors,… Fantastic spatial resolution But… it only shows structure no way to know what a brain area doesPositron Emission Tomography PET scans track concentrations ofradioactivity higher radioactivitycorresponds to higher bloodflow In the brain, higher bloodflow corresponds to strongerneural activityPositron Emission Tomography Radioactive blood flows allover the body Most normal uptake from Brain Heart Kidneys BladderPET Scans Plot concentrationof radioactivity witha color or grayscalecode to show mostactive regions ofthe brain note fuzzinessProf. Greg Francis 5/23/084PET Scans Differences in activity can be found for differentconditionsPET Scans Like MRI, thescanner takesslices of the brain The resolution ofthe scancorresponds to thesize of a “voxel”PET Scans Images are almostalways fuzzy because Limits of the scanningtechnology Blood flow spreadsradiation around nearbyareas Radiation is sampledover time The person moveshis/her head during thescanningPET Scans Useful for identifyingbrain deficits Yellow area is a tumor,which processesglucose faster thannormal cells Spatial resolution islimited (centimeters) Temporal resolution islimited by decay rate ofradioactive substance seconds to minutesFunctional MRI Just like MRI, but with a new analysis MRI differentiates between different types of tissue (celltypes) Functional MRI differentiates between active andinactive neurons» concentration of oxygen Very good spatial resolution millimeters Pretty good temporal resolution < a secondFunctional MRI Color maps showstrongest“responses” More next time e.g., during a taskthat requires covertspatial attentionProf. Greg Francis 5/23/085Functional MRI When moving apointer to a targetbox “activity” in areasinvolved in vision,planning, and motorcontrolSome misconceptions Brain scans tell us how the brain works in fact, the scans just tell us approximatelywhere in the brain something occurs sometimes it can tell approximately when Brain scans demonstrate a physiologicalbasis to things that were thought to beemotionally or cognitively based e.g., MRI scans of stutters in fact, all behavioral traits are physiologicallybasedConclusions Lots of research in this area Technology is improving in many ways There 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)Next time How do we use brain scans to studycognition? How good are the scans? What does the color actually represent inthose pictures? How to read someone’s