Thread View: sci.cognitive
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Started by Stephen Hicks
Sun, 17 May 1998 00:00
Getting more out of PET and fMRI!
Author: Stephen Hicks
Date: Sun, 17 May 1998 00:00
Date: Sun, 17 May 1998 00:00
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I can suggest an area that definately needs some mathematical help. Interpreting the PET and fMRI images of humans "in thought". The method commonly used is merely subtracting the highest changes in energy from a baseline taken previously. This is a misleading technique that presents the researcher with those famous "Modes of Cognition" pictures that frequently cover psychological journals. You could explore better ways to extract information from these images rather then using the feeble "Subtraction Technique". For example: The temporal resolution for PET is around 40 seconds as positrons must be given time to accumulate in the sensors. So assuming that during that time the neurons under that "bright spot" were continuously "on" is a misinterpretation. The region may have lit up very brightly only for a second, or it may have flickered intermediately throughout the 40 secs, or indeed any permutation of the two factors, length of time, and energy released. The variables- -The amount of radiation collected. (read off the scan) -The energy output of the neurons in that specific region. (easy if they are just cortical neurons, calculate their density, plus their individual power needs (rem: most PET measure only change in blood flow!) ) -The amount of time elapsed during the scan. You should be able to get a better idea about what the region was doing during that time, eg. how long it was on and how long it was off, would tell you the frequency of those neurons. At any rate it would be far more informative then what we presently do!
Re: Getting more out of PET and fMRI!
Author: Greig de Zubicaray
Date: Sun, 17 May 1998 00:00
Date: Sun, 17 May 1998 00:00
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On Sun, 17 May 1998 01:37:38 +1000, Stephen Hicks <oleosat@bigfoot.com> wrote: | I can suggest an area that definately needs some mathematical help. | Interpreting the PET and fMRI images of humans "in thought". The method | commonly used is merely subtracting the highest changes in energy from a | baseline taken previously. This is a misleading technique that presents | the researcher with those famous "Modes of Cognition" pictures that | frequently cover psychological journals. You could explore better ways | to extract information from these images rather then using the feeble | "Subtraction Technique". You're a little out of date. fMRI investigations routinely employ parametric and event-related designs these days. Besides, the subtraction paradigm is still quite useful if used appropriately. Greig de Zubicaray _______________________________ Neuroimaging Programme Centre for Magnetic Resonance, The University of Queensland Brisbane. QLD. 4072. Australia Tel: 617 33654250 Fax: 617 33653833
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