成果selfreqavg b 1简介自要求.pdfVIP

selfreqavg,selfreqcomb

1Introduction

selfreqavgandselfreqcombareprogramsforcomputingtheamplitudeandphaseofthe

hemodynamicresponseatacertainfrequency.Thisistypicallydoneinretinotopic(orphase

encoding)studies.Theseprogramsaremeanttoreplaceanalyseandcombineforphaseen-

codingstudies.Theparadigmconsistsofaperiodicallyvaryingstimulus(eg,arotatingspoke

orexpanding/contractingring).Thestimulusischaracterizedbyitsfundamentalfrequency,

direction,andtype.Thetheamplitudeandphaseofhemodynamicresponseatthestimulation

frequencyaremeasuredbycomputingtheFFToftheboldsignal.Thesignificanceoftheeffect

isassesedwithanF-testinthefollowingway.AnF-ratioiscomputedastheratioofthesignal

powertothenoisepower.Thesignalpoweristhepoweratthefundamental.Thenoisepoweris

sumoftheremainingspectrumexcludingthefollowingcomponents:harmonicsofthestimulus,

componentswithinonefrequencybinofthefundamentalandharmonics,andthefirstthreebins.

selfreqavgcomputestheamplitude,phase,andnoisedirectlyfromtherawMRsignal.self-

reqcombcombinestheresultsfromseveralinvokationsofselfreqavgintoasingleaverage.This

isdonebyseparatelyaveragingtherealandimaginarycomponentsofthefundamentalaswellas

averagingthenoisepower.Theaveragerealandimaginarycomponentsareusedtorecompute

thepoweratthefundamentalwhichisthenusedtoperformtheF-testasdescribedabove.The

softwareappropriatelyhandlesthecasewheretheinputsmayhavedifferentdegrees-of-freedom

(eg,differentnumberoftimepoints).

2Questions,Comments,andBugReports

Thesoftwareauthorsareinterestedinyourquestions,comments,andbugreports.However,

sincethesoftwareisfree,ourresponsivenesstoyourneedsmaybelimitted.Togetth