Methodological challenges and solutions in auditory functional magnetic resonance imaging

Abstract

Functional magnetic resonance imaging (fMRI) studies involve substantial acoustic noise. This review covers the difficulties posed by such noise for auditory neuroscience, as well as a number of possible solutions that have emerged. Acoustic noise can affect the processing of auditory stimuli by making them inaudible or unintelligible, and can result in reduced sensitivity to auditory activation in auditory cortex. Equally importantly, acoustic noise may also lead to increased listening effort, meaning that even when auditory stimuli are perceived, neural processing may differ from when the same stimuli are presented in quiet. These and other challenges have motivated a number of approaches for collecting auditory fMRI data. Although using a continuous echoplanar imaging (EPI) sequence provides high quality imaging data, these data may also be contaminated by background acoustic noise. Traditional sparse imaging has the advantage of avoiding acoustic noise during stimulus presentation, but at a cost of reduced temporal resolution. Recently, three classes of techniques have been developed to circumvent these limitations. The first is Interleaved Silent Steady State (ISSS) imaging, a variation of sparse imaging that involves collecting multiple volumes following a silent period while maintaining steady-state longitudinal magnetization. The second involves active noise control to limit the impact of acoustic scanner noise. Finally, novel MRI sequences that reduce the amount of acoustic noise produced during fMRI make the use of continuous scanning a more practical option. Together these advances provide unprecedented opportunities for researchers to collect high-quality data of hemodynamic responses to auditory stimuli using fMRI.

Comprehending auditory speech: previous and potential contributions of functional MRI

“…This noise is periodic, with harmonics in the range crucial for speech perception, and thus greatly reduces the audibility of speech signals (Edmister, Talavage, Ledden, & Weisskoff, 1999;Hall et al, 1999;Peelle, 2014). The acoustic properties of the scanner noise can also interact with those of the auditory stimuli, causing some stimuli or experimental conditions to be more affected by scanner noise than others, thus distorting experimental outcomes.…”

“…Others have endeavoured to reduce the magnitude or impact of the acoustic scanner noise itself by noise cancellation or manipulating the parameters of the acquisition sequence (Hall et al, 2009;Peelle et al, 2010;Schmitter et al, 2008). For a helpful and succinct description of these approaches, we highly recommend Peelle (2014).…”

“…Price, 2012), and in the specific methodological challenges of examining auditory processing with fMRI (Peelle 2014). For this review, we felt that it was timely to limit our discussion to the use of fMRI in the investigation of speech comprehension.…”

“…At a neural level, listening to speech in the context of scanner noise engages compensatory neural activity associated with modulation of attention and cognitive control. In addition, the response of the auditory cortex can become saturated, reducing the dynamic range of the response to auditory stimuli (Langers, Van Dijk, & Backes, 2005;Peelle, Eason, Schmitter, Schwarzbauer, & Davis, 2010;Peelle, 2014). The challenge of acoustic noise has been addressed through the development of "sparse sampling", where a delay of ~6 to 18 seconds is introduced between successive acquisitions to allow for the presentation of auditory stimuli in relative quiet (Edmister et al, 1999;Hall et al, 1999).…”

How to study spoken language understanding: a survey of neuroscientific methods

“…In the behavioural literature on speech understanding researchers typically work hard to achieve high-fidelity presentation of clear speech or in some cases use the presence of background noise to deliberately perturb spoken language understanding (Pisoni, 1996). Speech presented in conjunction with noisy neuroscientific methods necessarily leads to challenges or compromises in experimental designresearchers should either acknowledge that they are studying speech comprehension in the presence of significant background noise, or use sparse or offline methods in which speech presentation is timed to avoid noisy periods of data collection or brain stimulation (Devlin & Watkins, 2007;Hall et al, 1999;Peelle, 2014;Perrachione & Ghosh, 2013;Schwarzbauer, Davis, Rodd, & Johnsrude, 2006). In many cases, however, the additional methodological issues that arise for auditory, but not visual stimuli, have resulted in researchers taking the easier but rather limiting approach of studying language comprehension using written rather than spoken language.…”