Abstract
The field of cognitive neuroscience is weighing evidence about whether to move from the current standard field strength of 3 Tesla (3T) to ultra-high field (UHF) of 7T and above. The present study contributes to the evidence by comparing a computational cognitive neuroscience paradigm at 3T and 7T. The goal was to evaluate the practical effects, i.e. model predictive power, of field strength on a numerosity task using accessible pre-processing and analysis tools. Previously, using 7T functional magnetic resonance imaging and biologically-inspired analyses, i.e. population receptive field modelling, we discovered topographical organization of numerosity-selective neural populations in human parietal cortex. Here we show that these topographic maps are also detectable at 3T. However, averaging of many more functional runs was required at 3T to reliably reconstruct numerosity maps. On average, one 7T run had about four times the model predictive power of one 3T run. We believe that this amount of scanning would have made the initial discovery of the numerosity maps on 3T highly infeasible in practice. Therefore, we suggest that the higher signal-to-noise ratio and signal sensitivity of UHF MRI is necessary to build mechanistic models of the organization and function of our cognitive abilities in individual participants.
Highlights
Cognitive neuroimaging studies typically require fast whole brain image acquisitions with high signal-to-noise ratio (SNR) and maximal sensitivity to small blood oxygenation level dependant (BOLD) signal changes for reliable detection
The higher percentage BOLD signal change and variance explained at 7T confirms the higher BOLD signal sensitivity and SNR at ultra-high field
These results suggest that future cognitive neuroscience studies may benefit from ultra-high field (UHF) by collecting less data and preserving strong statistical power
Summary
Cognitive neuroimaging studies typically require fast whole brain image acquisitions with high signal-to-noise ratio (SNR) and maximal sensitivity to small blood oxygenation level dependant (BOLD) signal changes for reliable detection. One of the earliest discoveries using UHF in the field of cognitive neuroscience was the existence of topographic maps that represent dimensions of numerical cognition (Cai et al, 2021; Harvey et al, 2013; Harvey and Dumoulin, 2017) Following studies, extended this finding of cognitive topographic maps and uncovered maps representing object size (Harvey et al, 2015), time duration (Harvey et al, 2020; Protopapa et al, 2019) and haptic numerosity (Hofstetter et al, 2021). These discoveries suggested that topographic principles common in primary sensory and motor cortices may be an organizational principle of cognitive functions in association cortex. All these studies used 7T functional MRI (fMRI), and anecdotal reports suggested failure to reconstruct these maps at lower field strengths
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