How Brain Imaging Helps in the Study of Cognition
HOW CAN BRAIN IMAGING HELP STUDY COGNITION?
Intro * involves analysing activity within brain while performing various cog tasks – allow us to link bhvr & brain function to help understand how info is processed * cog activity assoc w neural activity in brain regions: * on scalp as electrical activity ie MEG, EEG (direct measures) * inside brain by measuring O2 consumption caused by neural activity ie PET, fMRI (indirect) * diff imaging techniques vary in their temp (time-based) and spatial (location) reso
Direct measures
Electrodes attached to head cap & amp – recordings of electrical activity (EEG) or change in mag field (MEG) – filter & statistically analyse – compare for diff tasks
1. Magnetoencephalography (MEG) * magnetic brain measurements * better spatial reso than EEG – mag fields x as blurred/attenuated
2. Electroencephalography (EEG) * electrical – v high temp reso, relatively poor spatial
Indirect measures
Neural activity consumes O2, generate electrical signals – compensate for O2 consumption – more oxy blood pumped into region
1. Positron emission tomography (PET) * radioactive isotopes (O2 15) injected – areas of brain which take up more = more active than other areas * measures blood flow
2. fMRI * measures rel amount of oxy blood flowing to diff parts of brain - oxy blood = neural activity * put subject in big mag field – transmit radio waves – turn off waves transmitter – receive and record waves re-transmitted by subject – reconstruct 3D image * MRI: high reso, one image; fMRI: low reso, many images (2-3s for each, up to 50 mins)
Usefulness Allows us to examine the dynamics of the whole brain – not just small region Understand how many different brain regions interact Examine processes impossible with lesion approach – e.g. memory encoding
Understand the brain regions and networks involved in processes such as language
Intro * involves analysing activity within brain while performing various cog tasks – allow us to link bhvr & brain function to help understand how info is processed * cog activity assoc w neural activity in brain regions: * on scalp as electrical activity ie MEG, EEG (direct measures) * inside brain by measuring O2 consumption caused by neural activity ie PET, fMRI (indirect) * diff imaging techniques vary in their temp (time-based) and spatial (location) reso
Direct measures
Electrodes attached to head cap & amp – recordings of electrical activity (EEG) or change in mag field (MEG) – filter & statistically analyse – compare for diff tasks
1. Magnetoencephalography (MEG) * magnetic brain measurements * better spatial reso than EEG – mag fields x as blurred/attenuated
2. Electroencephalography (EEG) * electrical – v high temp reso, relatively poor spatial
Indirect measures
Neural activity consumes O2, generate electrical signals – compensate for O2 consumption – more oxy blood pumped into region
1. Positron emission tomography (PET) * radioactive isotopes (O2 15) injected – areas of brain which take up more = more active than other areas * measures blood flow
2. fMRI * measures rel amount of oxy blood flowing to diff parts of brain - oxy blood = neural activity * put subject in big mag field – transmit radio waves – turn off waves transmitter – receive and record waves re-transmitted by subject – reconstruct 3D image * MRI: high reso, one image; fMRI: low reso, many images (2-3s for each, up to 50 mins)
Usefulness Allows us to examine the dynamics of the whole brain – not just small region Understand how many different brain regions interact Examine processes impossible with lesion approach – e.g. memory encoding
Understand the brain regions and networks involved in processes such as language