Traditionally thought be a speech-dedicated area, the planum temporale (PT) has been implicated in a host of functions including speech perception, tonal processing, auditory-motor integration, spatial hearing, and audio- visual integration. The present proposal uses the lesion method to test hypotheses regarding the causal role the PT region plays in these functions while at the same time providing important new clinically relevant information. We will assess these functions in a large sample of stroke patients to measure the severity, prevalence and relations between these abilities and correlate deficits with lesion location using voxel-based lesion symptom mapping (VLSM) augmented by additional methods. Healthy controls and a hearing impaired comparison group will also be tested. We propose three specific aims selected for basic science theoretical import and maximal opportunity for future clinical translation.
Aim 1 : Understand the role of spatial hearing in stroke-induced communication impairment. In two experiments with stroke patients we will measure speech in noise comprehension with and without spatial cues as well as non-speech auditory streaming acuity using a rhythmic release from masking paradigm. Lesions associated with these deficits will be mapped with VLSM.
Aim 2 : Understand the neural basis of audiovisual speech integration. AV speech has been shown to improve speech intelligibility over auditory speech alone and could potentially benefit individuals with speech recognition impairments do to aphasia. Our pilot data in stroke patients indeed shows that AV speech can facilitate speech recognition in some patients, but also that it can paradoxically interfere with speech recognition in other patients. The effect it has appears to vary with lesion location. We propose a McGurk task as one probe of AV integration and AV synchrony judgments as a second. Lesions associated with these deficits will be mapped with VLSM.
Aim 3 : Characterize auditory-motor function and organization of the PT region. Auditory-motor integration is unequivocally central to speech development, speech motor control, and speech impairments such as conduction aphasia and possibly stuttering. Here we use repetition tasks with words, non-words and melodic stimuli-which we used to map the auditory-motor circuit in our fMRI research-as one assay of auditory-motor integration in stroke patients to assess speech specificity of the circuit. In addition, we use computational model-driven measurement of the auditory-motor component of a picture-naming task. Lesions associated with these deficits will be mapped with VLSM. -- The present proposal will illuminate the organization of PT region, the relation between different but functionally related speech systems, and potential pathways for clinical translation.
The planum temporale is a brain that plays a central role in several speech functions. This project measures these functions in stroke patients as a means to both understand their role in speech deficits leading to possible new treatments and to map the functional anatomical organization of the planum temporale.
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