Silent and continuous fMRI scanning differentially modulate activation in an auditory language comprehension task

Abstract

Sparse temporal acquisition schemes have been adopted to investigate the neural correlates of human audition using blood-oxygen-level dependent (BOLD) based functional magnetic resonance imaging (fMRI) devoid of ambient confounding acoustic scanner noise. These schemes have previously been extended to clustered-sparse temporal acquisition designs which record several subsequent BOLD contrast images in rapid succession in order to enhance temporal sampling efficiency. In the present study we demonstrate that an event-related task design can effectively be combined with a clustered temporal acquisition technique in an auditory language comprehension task. The same fifteen volunteers performed two separate auditory runs which either applied customary fMRI acquisition (CA) composed of continuous scanner noise or "silent" fMRI built on a clustered temporal acquisition (CTA) protocol. In accord with our hypothesis, the CTA scheme relative to the CA protocol is accompanied by significantly stronger functional responses along the entire superior temporal plane. By contrast, the bilateral insulae engage more strongly during continuous scanning. A post-hoc region-of-interest analysis reveals cortical activation in subportions of the supratemporal plane which varies as a function of acquisition protocol. The middle part of the supratemporal plane shows a rightward asymmetry only for the CTA scheme while the posterior supratemporal plane exposes a significantly stronger leftward asymmetry during the CTA. Our findings implicate that silent fMRI is advantageous when it comes to the exploration of auditory and speech functions residing in the supratemporal plane.

Overview of potential procedural and participant- related confounds for neuroimaging of the resting state

“…In addition to altering the response of the auditory cortex, 41 such studies have found that scanner noise can interact with stimuli to produce differential activity in, for example, the insula, cingulate gyrus and occipital cortex. 40,42,43 We can thus infer that scanner noise has an effect on these regions in the absence of stimuli, although further research on this front is required. Also of note is the possibility that MRI noise will corrupt EEG data acquired simultaneously during rest using combined fMRI-EEG.…”

Reducing the Interval Between Volume Acquisitions Improves “Sparse” Scanning Protocols in Event-related Auditory fMRI

“…Scanner noise induces a BOLD response in auditory-related cortex areas during trials without a proper auditory stimulus. Most interestingly, this appears to happen differentially for the left and the right hemisphere (Herrmann et al 2000;Tamer et al 2009;Schmidt et al 2008) and in a nonlinear manner (Talavage and Edmister 2004). The degree of nonlinearity varies between left and right hemisphere (Hu et al 2010).…”

“…A variety of names exists to date for similar approaches: Edmister et al (1999) and Talavage et al (1999) presented ''clustered volume acquisition''; Hall et al (1999) called their approach ''sparse temporal sampling''; Eden et al (1999) published the ''behavior interleaved gradients technique''. In the present article we use the term ''sparse design'' for aforementioned approaches and ''clustered-sparse design'' for an extension of this design (Schmidt et al 2008;Zaehle et al 2007). ''Clustered volume acquisition'' refers to the temporal clustering of several slices within one volume and is not to be confused with the clustered-sparse protocol, which refers to the clustering of volumes within one trial.…”

“…As a result, the T1-decay-related signal-to-noise ratio (SNR) improvement (for at least Brain Topogr (2012) 25:182-193 183 the first image per cluster), which the clustered-sparse protocol benefits from, is absent. Especially in studies focusing on auditory-related areas silent protocols, in comparison to conventional continuous acquisition protocols, have been shown to be beneficial in terms of SNR and effective power (Schmidt et al 2008;Gaab et al 2007a, b;Hall et al 1999). However, a slow timing and the resulting inflated duration of the scanning session can make such studies a tedious and gruelling experience for participants.…”

“…To ensure that the BOLD response's peak is sampled, the clustered-sparse temporal acquisition (CTA) protocol has been devised (Zaehle et al 2007;Schmidt et al 2008). Derived from the sparse protocol, the clustered-sparse scheme allows for the collection of a cluster of (usually three) consecutive functional volumes per trial.…”