Brain Imaging

MRI Magnetic Resonance Imaging A strong magnetic field is passed over the body to pick up radio waves from hydrogen atoms in water molecules.  Different areas of the brain have different densities (and so different amounts of water in their tissues). These emit differing amounts of radio waves, producing different amounts of shading on the image produced. The image produced is very detailed (it has high spatial resolution), but can not show brain activity, only structure (so it has very low temporal resolution).

MRI

Video Understanding MRI’s

Relevant Study GO Choose one of the following and complete a GO: Ashtari et al 2009 OR Maguire 2000 http://www.pnas.org/content/97/8/4398.full

fMRI Functional Magnetic Resonance Imaging Another technique for measuring brain activity is functional MRI. fMRI detects changes in blood flow without using a radioactive tracer. When a particular site in the brain is more active, blood flows to that area. This blood brings oxygen to the hard-working brain cells. By tracking variations in blood flow, functional MRI can detect activity in the brain as it happens. An MRI machine has a giant magnet. Certain atoms (like hydrogen, a major component of water) give off a wave of energy when surrounded by a magnetic field. Inside the magnetic field of an MRI machine, hydrogen molecules in the water in blood release pulses of energy. The amount of energy released reflects blood flow, and therefore brain activity. A sensor detects this energy and a computer turns it into a picture.

Video Understanding fMRI’s

Pros and Cons Decent Temporal Resolution (it can  1-2 seconds). This is a big advantage over MRI which is just a structural scan - it can't show the activity of the brain at all. Measuring blood oxygenation is an indirect measure of brain activity. This has two problems. A) We can't be sure that areas with the most deoxygenated blood are actually the most active. B) Even if the area is more active, knowing activity levels does not help us to find out what that part of the brain actually does! Is it an on switch, or an off switch? Is it a connection? Does it do the job alone or with the help of other areas? Just looking at brain activity can't always help us to answer these questions. The technique is incredibly complex to analyse mathematically. One problem with this, is that very complicated analyses may be suggesting relationships that aren't actually there are all! This has been a major source of debate in Psychology in the past few years.

Relevant Studies Harris and Fiske, 2006 OR Kringlebach and Berridge, 2009

Discuss… Read the article: http://www.bbc.com/news/science-environment-27221632 Watch the video: The most important…

Discuss… What are general issues to consider? Strengths and limitations?

PET Scans Research PET scans using links provided: http://learn.genetics.utah.edu/content/neuroscience/brainimaging/  http://www.petscaninfo.com/zportal/portals/pat/brain  https://www.youtube.com/watch?v=GHLBcCv4rqk  Include:  Description of how it works and what it shows/is used for  Pros and cons  one relevant study (Tierney et al (2001) - PET evaluation of bilingual language compensation following early childhood brain damage- https://www.ncbi.nlm.nih.gov/pubmed/11163369