Imaging Joy with generalized Slice Dithered Enhanced Resolution (gSLIDER) and SWAT reconstruction: 3T high spatial-temporal resolution fMRI

Jennifer D Townsend^1,2,3,4,5,6Angela Martina Muller^2,3Zanib Naeem^1,2,3Alexander Beckett^7,8Bhavesh Kalisetti^4,5Reza Abbasi-Asl^4,5,9Congyu Liao¹⁰An Thanh Vu^1,2,3*

• ¹Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, United States
• ²San Francisco VA Health Care System, Veterans Health Administration, United States Department of Veterans Affairs, San Francisco, California, United States
• ³Northern California Institute for Research and Education (NCIRE), San Francisco, California, United States
• ⁴Department of Neurology, University of California, San Francisco, San Francisco, California, United States
• ⁵UCSF Weill Institute for Neurosciences, San Francisco, United States
• ⁶School of Medicine, National University of Natural Medicine, Portland, Maine, United States
• ⁷Advanced MRI Technologies (United States), Sebastopol, California, United States
• ⁸Helen Wills Neuroscience Institut, University of California, Berkeley, Berkeley, California, United States
• ⁹Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California, United States
• ¹⁰Radiological Sciences Laboratory, Stanford University, Stanford, California, United States

To facilitate high spatial-temporal resolution fMRI (≦1mm3) at more broadly available field strengths (3T) and to better understand the neural underpinnings of joy, we used SE-based generalized Slice Dithered Enhanced Resolution (gSLIDER). This sequence increases SNR efficiency utilizing sub-voxel shifts along the slice direction. To improve the effective temporal resolution of gSLIDER, we utilized the temporal information within individual gSLIDER RF encodings to develop gSLIDER with Sliding Window Accelerated Temporal resolution (gSLIDER-SWAT). We first validated gSLIDER-SWAT using a classic hemifield checkerboard paradigm, demonstrating robust activation in primary visual cortex even with stimulus frequency increased to the Nyquist frequency of gSLIDER (i.e., TR = block duration). gSLIDER provided ~2x gain in tSNR over traditional SE-EPI. GLM and ICA results suggest improved signal detection with gSLIDER-SWAT’s nominal 5-fold higher temporal resolution that was not seen with simple temporal interpolation. Next, we applied gSLIDER-SWAT to investigate the neural networks underlying joy using naturalistic video stimuli. Regions significantly activated during joy included the left amygdala, specifically the basolateral subnuclei, and rostral anterior cingulate, both part of the salience network; the hippocampus, involved in memory; the striatum, part of the reward circuit; prefrontal cortex, part of the executive network and involved in emotion processing and regulation (bilateral mPFC/BA10/11, left MFG (BA46)); and throughout visual cortex. This proof of concept study demonstrates the feasibility of measuring the networks underlying joy at high resolutions at 3T with gSLIDER-SWAT, and highlights the importance of continued innovation of imaging techniques beyond the limits of standard GE fMRI.