Bi150 PS5_Answers_2011

Bi150 PS5_Answers_2011 - PS5 Answer Key Problem 1....

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PS5 Answer Key Problem 1. Measuring Brain Activity (1.5 points) Brain Measurement Techniques fMRI EEG PET Patch-clamp (microelectrode recording) Light microscopy Lesion A. (0.3 point) Rank in order the above brain measurement techniques in terms of their spatial resolution, from lowest (1) to highest (6), with which they can measure brain activity (directly or indirectly). 1. EEG 2. Lesion/PET 3. PET/Lesion 4. fMRI/light microscopy 5. light microscopy/fMRI 6. patch clamp B. (0.3 point) Rank in order the above techniques in terms of their temporal resolution, again from lowest (1) to highest (6), with which they can measure brain activity. 1. Lesion 2. PET 3. Light microscopy/fMRI 4. fMRI/light microscopy 5. EEG 6. Patch-clamp C. (0.4 point) Pick the one measure that provides the strongest causal evidence that a given brain region is necessary for a particular function. Give a brief explanation for your answer. Lesion experiments provide the only causal evidence for the function of a brain region/area because the other techniques that we have for measuring brain activity can only give correlative data between an action/behavior and brain activity. Lesioning is causal because loss of some function when all else in the brain is unperturbed directly implicates that brain area/region in that function lost. D. (0.5 point) Functional MRI is used to make claims about neuronal activity in different parts of the brain. However, it does not directly measure electrophysiology. Briefly describe what physiological parameter(s) fMRI actually measures, and how this measurement is thought to be related to neuronal activity.
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PS5 Answer Key The physiological parameters that are measured are the following: hemodynamic response changes in blood flow and/or oxygenation changes in hemoglobin oxygenation PARTS of the below should be sufficient to get full credit: Measuring changes in oxygen content of the blood in the brain indicates brain activity because when neurons become active, they require an enormous amount of metabolic energy. This high- energy demand is due to the high energy cost of the dynamic electrophysiological states that they go through. Therefore, oxygen comes into high demand because of a need to oxidatively phosphorylate, and produce new stores of ATP for the continued function and viability of the neuron. The change in oxyhemoglobin relative to deoxyhemoglobin causes small local changes in the magnetic field in the brain which in turn influence one of the relaxation time constants measured in fMRI (so-called T2*). By using an appropriate pulse sequence, the change in this relaxation time constant for protons (hydrogen atoms) can be measured as a function of time and spatial location in the brain.
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PS5 Answer Key Problem 2. Sensorimotor System (1.5 points) A. (0.3 point) Even with our eyes closed, we generally still know where our arms and legs are located. a.
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This note was uploaded on 01/03/2012 for the course BI 150 taught by Professor Kennedy,m during the Fall '08 term at Caltech.

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Bi150 PS5_Answers_2011 - PS5 Answer Key Problem 1....

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