Nonlinear effects in hemodynamic response in primary auditory cortex associated with temporal patterns of acoustic history
Abstract
A novel approach is proposed to model nonlinear hemodynamic response (HDR) effects in primary auditory cortex, arising from temporal patterns of systematic confound of imaging acoustic noise (IAN) and a desired auditory stimulus as investigated using functional magnetic resonance imaging (fMRI). The proposed state-dependent linear-time-invariant system model is demonstrated to account for nonlinearities associated with the temporal pattern of stimulus history. It was found that acoustic history of more than 16s can influence the response to a short auditory stimulus. Results revealed hemispheric response asymmetries, including right primary auditory cortex being more sensitive to the presence of IAN. The shape of HDR and extent of activation were nonlinearly modulated by the temporal pattern of acoustic history. Nonlinearities in HDR due to these modulating effects can negatively affect detection of activation. In addition to auditory-related brain areas, non-auditory areas such as visual cortex and hippocampus were also found to activate during acoustic stimulation. Therefore, IAN may negatively affect non-auditory fMRI experiments. Constant presence of IAN during experiments with short repetition times may delay and reduce auditory responses due to elevated baseline blood flow levels. Thus, comparison of results across studies with different imaging paradigms, imaging parameters, or stimulus histories may be problematic, and requires inclusion of effects of confounds to maximize sensitivity and specificity.
Degree
Ph.D.
Advisors
Talavage, Purdue University.
Subject Area
Biomedical engineering|Electrical engineering
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