Earlyblindindividualsshowsuperiorperformanceacrossawidevarietyofauditoryskills. However, fMRI studies examining neural plasticity resulting from blindness have almost exclusivelyfocusedontechniquesthatpoolinformationacrossvoxels.Asaresult,whilestudies have shown that differences in neural activity between early blind and sighted subjects are correlatedwithbehavioralperformance,justificationsforthesecorrelationsremainatthe`more cortexisbetter'orthe`biggerBOLD(orsometimessmaller)responsesarebetter'levelofexplanation. Wewillexaminethewidespreadalterationsthatoccurwithinauditoryprocessingpathways withinearlyblindindividualsusing`voxel?wiseencoding'modelsthatrepresenteachvoxelas havingatuningfunctionalongdimension(s)ofinterest.Simplelinkingmodelswillallowusto predictbehavioralperformancebasedonthepredictedcorticaldiscriminabilityofstimuli.This will allow us, for the first time, to model quantitatively how neural responses to auditory stimuli might mediatetheenhancedbehavioralabilitiesobservedinearlyblindindividuals.
In Aim1 wewillexaminewhetherearlyblindnessaltersprimaryauditorycortex(PAC).We willbeginbycomparingPACsize,responsivenessandfrequencytuningbandwidthsacrossearly blind and sighted individuals. We will then examine whether tuning for temporal amplitude modulations within primary auditory cortex are also affected by blindness. Computational modelswillbeusedtolinkprimaryauditorycortexneuralresponsestobehavioralperformance acrossavarietyofauditorytasksforblindandsightedindividuals.
In Aim 2 we will use naturalistic stimuli to measure complex auditory spectro?temporal tuninginbothauditoryandoccipitalcortex.Again,computationalmodelswillbeusedtolink eachindividual'sneuralresponsestoauditoryperformanceoncomplexnaturalistictasks. Finally in Aim 3 we will examine auditory motion processing. Although auditory motion responses are found within visual cortical area hMT+ in early blind individuals, it is not clear howtheseresponseshelpearlyblindsubjectstoperceptuallysegregatemovingauditoryobjects in complex auditory environments. We will examine whether hMT+ is tuned for frequency as wellasdirectionofmotionandhowhMT+neuralresponsesmightresultinenhancedbehavioral performanceonauditorymotiontasks.
Individualswhobecomeblindearlyinlifeshowsuperiorperformanceonawiderangeof auditorytasks.However,theneuralbasisofthisimprovedperformanceisstillnotwell understood.UsingacombinationofBOLDneuroimaging,behavioraltestingandcomputational modeling,wewilltrytounderstandthelinkbetweenalteredbrainresponsesandthe extraordinaryabilityofblindpeopletomakesenseoftheauditoryworld.
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