09-28 Intro to Cog Sci Lecture 8

09-28 Intro to Cog Sci Lecture 8 - Introduction to...

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Introduction to Cognitive Science Lecture 8: 9/28/09 Basic strategies: - Look at it: Histology and modern-day variants - Poke it: Single unit stimulation and recording - Electroencephalogram (measuring electrical activity) Event-Related Potential - EEGs tend to reflect overall global brain activity - ERPs are designed to get around this, by averaging many trials together, to cancel out noise! - E.g. How quickly does the brain process sound? You cannot play a sound and then look at the EEG only. This is because there is lots of unrelated nonsense. Therefore, you play this over hundreds of times. Average all responses event related potential - This is a great technology for looking at when, not where things happen (it has great temporal resolution ) MEG & SQUIDs - MEG = magnetoencephalogram – presents challenges and advantages; the main advantage is better spatial resolution than EEG (because the skull itself has electrical resistances; skull doesn’t have magnetic resistance. Electrical and magnetic fields of the same object are orthogonal. Therefore, if we use MEG – it will be 90 degrees off from an EEG - Magnetic fields are very weak. Signals are fast and weak. So we need gradiometers which are really fast and sensitive. PET (positron emission tomography) - inject a radioactive tracer into the brain stem - it accumulates in the brain, especially active parts - as it decays, it emits positrons - almost immediately, they hit electrons, producing gamma rays - detecting these with an array of scanners can reconstruct where positrons were emitted The Nature of fMRI fMRI advantages - completely safe and noninvasive for all - safe for repeated and extended use - no special preparation (e.g. eating); but no metal - great spatial resolutions (approx 1.5 mm, PET = 4 mm) - signal strong enough to look at individuals - Anatomical + functional scans in same session - Bad temporal resolution (1 s, EEGs = ms) - fMRI measures the corresponding plumbing in the brain around neural firing patterns, NOT the patterns
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This note was uploaded on 01/28/2010 for the course CGSC 110 at Yale.

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09-28 Intro to Cog Sci Lecture 8 - Introduction to...

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