PSY 3061 1st Edition Lecture 9Outline of Last Lecture I. ElectrophysiologyII. Invasive and noninvasive measuresIII. Event related potentialsIV. Electrophysiology of the PNS Outline of Current Lecture I. Electrophysiology in humansII. How do we measure neural structures noninvasivelyIII. Imaging brain functionIV. Inferring brain functionCurrent LectureI. Electrophysiology in humansa. Most electrophysiology techniques used on humans are noninvasiveb. Noninvasive techniques usually record physiology at skin levelc. Studying neurons with poor spatial resolutiond. Spacial resolution: ability to detect and represent differences in spatial locatione. Temporal resolution: the ability to detect and represent changes in physiologyII. How do we measure neural structures noninvasivelya. Computed tomography is a 3D extension of xray measurementb. Xray measurement is photography of charged particles based on the radiation absorbed and radiation not absorbed by certain tissues; 2D picturec. Can take multiple xrays and combine them for a computed axial tomography (CT)d. MRI: gives highest spatial resolution; gives a bunch of 2D images; assign different intensity levels depending on different tissuesi. Magnet  soil with an electrical currentii. Transceiver/receivers are also coils that stimulate ormeasure the magnetization of what is in the scannerIII. Imaging brain functiona. PET and fMRI measure metabolism and not neurotransmission  indirect measures of neural activityb. Positron emission tomography (PET): radioactive tracer moleculesi. Radioactive tracers to study activity of molecules in the brainii. 2-deoxyglucose is glucose with a radioactive tracer added to itiii. wait for radioactive tracer to be absorbed into tissueiv. radioactive tracers are not stable and decays  gamma particles are emittedv. particles are picked up as bursts of light by surrounding detectorvi. parts of the brain with concentrated tracer are more activevii. red=most, blue=leastviii. not commonly used because it’s radioactive, tracer is expensivec. Functional MRI (fMRI): oxygenated blood flowi. Oxygenated blood has a different magnetization than deoxygenated bloodii. Blood-oxygen-level dependent (BOLD)iii. The brain metabolizes oxygenated blood for energyiv. Regions that are “in use” accumulate more oxygen-rich bloodthan silent brain regionsv. Several snapshots of the BOLD signal are taken over seconds to minutes white a person performs a cognitive taskvi. The BOLD response fluctuates pretty slowlyvii. May take several seconds for it to return to baselineviii. Partial image subtraction: to study how the brain activates during the “task” one must subtract how the brain activates during a baseline stated. Multi-modal imaging: integration of 2 or more brain measures (e.g. combined EEG and MRI)IV. Inferring brain functiona. Removing (lesion) a certain brain part and seeing how it affectsbehaviorb. Aspiration: removal of brain tissue by suctionc. Knife cutsd. Heat  radio-frequency electrical currente. Cryogenic blockade: freezing temporarily disrupts function of a certain brain region. Function regained when