Neuroimaging scientists, neuroscientists and clinicians interested in high resolution MRI and fMRI and advanced receiver coil hardware. To selectively perform imaging of human neocortex at ultra-high resolution, referred to as MR Corticography (MRCoG), receiver coil sensitivity can be focused on the peripheral region of the brain to maximize SNR (Figure 1). Use of smaller loops in high-density coil arrays allow for higher signal at shallower brain depths, introducing a trade off between SNR and coverage depth in the brain (Figure 2). Previous work has shown that these types of coils can achieve higher cortical SNR than standard whole-brain coils [1], particularly at higher resolutions, but the exact loop size to achieve the ideal balance between increased signal and sufficient coverage is unknown. To assess the gains achievable with such novel coil designs, data were collected on three 8-channel coil arrays (Virtumed, LLC), with 70, 40 and 30mm loop diameters. Data were collected on a Siemens 7T Scanner, using simultaneous multi-slice (SMS) EPI [2,3] with a voxel size of 500μm isotropic, SMS 2, IPAT 2, Flip Angle 80°, partial Fourier 5/8, TR=3000ms, TE=26ms, Matrix Size 180x160, 62 slices). Temporal SNR (tSNR) was calculated by dividing the mean of the time-series by the standard deviation, across 25 TRs. BOLD activation was also measured using a visual localizer paradigm, consisting of a flashing checkerboard pattern alternating with a blank screen (18s on, 18s off, repeated 5 times per scan). The visual localizer scans were repeated 3 times for each coil. BOLD activation was also measured using 450μm isotropic voxels (imaging factors same as above except: TE=31ms, Matrix Size 200x180, 50 slices) on the array with the smallest loops (30 mm), using the same visual localizer paradigm, repeated 4 times.The smaller loop diameters yield increased signal in superficial areas of the brain, with this specificity increased for the smallest loops (Figure 3). This increase in superficial signal led to a reduction in signal at the deepest brain areas. Lower signal in one brain hemisphere was likely due to B1 field inhomogeneity using a single transmitter loop in these test coils. For the resolution used (500μm isotropic voxels), the 70mm loop size yielded very low tSNR values and less BOLD activation compared to the loop sizes of 40mm and 30mm. Such gains in tSNR yield increased activation in visual stimulation paradigms, allowing high-resolution fMRI in visual cortex (Figure 4). Robust BOLD activation was achievable at very high isotropic resolution, 450μm, in only 12 minutes of scan time (Figure 5).These results indicate that array coils with smaller loop sizes give sufficient gains in SNR to allow ultra-high resolution fMRI, potentially useful for studying laminar and columnar organization in the human neocortex. Based on these findings of gains in SNR using receiver arrays with small loop diameter, future design of larger arrays with 128 – 256 coil elements using small coils should provide highest SNR in whole brain imaging targeted to neocortex[4]. Such large arrays with small coils may likely have additional gains in spatial sensitivity for acceleration with SMS and parallel imaging.Receiver coil arrays with small loop diameter increase SNR in the peripheral cortex to achieve high resolution in fMRI and neuroimaging.