Although it is known that high-field magnet >= 7T increases BOLD signal and better localize neuronal-specific signal in cortical region [1,2], source of BOLD during resting-state fMRI (rsfMRI) and sensitivity/specificity to small signaled neuronal activation, e.g., spontaneous baseline function is unclear. In addition, it is question how the increased and better localized BOLD signal at 7T affects on brain baseline connection during resting status compared to those at 3T. Small-scale connectivity research (e.g., within same functional domain) is relatively rare compared to large-scale connectivity study, possibly due to low BOLD sensitivity and specificity. In this study, we investigated source of rsfMRI BOLD (comparing with stimulus-evoked fMRI) and possible detection of small-scaled connectivity in primary motor cortex by using high-resolution fMRI at 7T.All MRI was performed with a whole-body 7T and 3T scanner (Siemens Medical Imaging, Erlangen, Germany) equipped with multi-channel RF coil (1-ch Tx & 8-ch Rx @7T; 12-ch Rx @3T). All procedures followed the guidelines of approved IRB. Three healthy volunteers were included in the study. Functional task: The subject was asked to stay without motion with eye closed over all fMRI procedure. Localization of primary motor cortex was performed by functional mapping with right-hand motor task (20-s hand-grasping & 10-s resting; 3 times repetition) commanded via a speaker in magnet room. RsfMRI experiment was carried out without any task for whole brain and also primary motor cortex area, at low- and high-resolution; ~200 volumes for ~6 min, 3 times repetition. Those activations of fMRI vs. rsfMRI were compared at 7T vs. 3T and low- vs. high-resolution. Functional/anatomy MRI: Localization of primary motor cortex was performed by functional mapping of right-hand motor task. Imaging orientation was axial or oblique-tilted axial, respectively for inter-hemispheric and small-scale within primary motor cortex connectivity study with corresponding appropriate filed of view. Gradient echo EPI sequence that is sensitive to BOLD signal was used for all functional studies; TR/TE = 2,000/20(<30 @3T) msec. Spatial in-plane resolution was 1.6×1.6 mm2 and 2.7×2.7 mm2 for high- and low-resolution EPI image covering two hemispheres, respectively. Slice thickness was 2 mm for 20 slices. For primary motor cortex high-resolution functional MRI, 1×1×2 mm3 resolution images were acquired at 7T only. After acquisition of functional EPI data, high-resolution anatomy images were acquired with T1-weighted MPRAGE or T2*-weighted GRE sequence at 0.5×0.5×2 mm3 for primary motor cortex (Fig. 4D) and 2×2×2 mm3 for whole brain, respectively. Imaging and data analysis: All fMRI data series was co-registered to the first time point image by affine rigid body transformation. Independent component analysis (ICA) method (FSL, http://www.fmrib.ox.ac.uk/fsl/) was applied to get the activation maps as well as the activation time-course. The high-frequency component of fMRI data was filtered out with cutoff frequency of 0.08 Hz. The activation patterns were compared for fMRI vs. rsfMRI, 3T vs. 7T, and high vs. low-resolution, with regard to spatial distribution and functional connectivity.Activation patterns of task-evoked fMRI and spontaneous-evoked rsfMRI were well coincident to each other (Fig. 1). High-resolution rsfMRI BOLD could detect the activation map in motor cortex gyrus at 7T (Fig. 2B) but failed at 3T (Fig. 2C). Hemispheric connection of baseline motor function was well detected in all rsfMRI data, but the separation of the connectivity between left and right hemisphere was consistently observed under high-signal BOLD at 7T from all subjects (Fig. 3). However, it was showed that the signals of fMRI and rsfMRI were dominant in surrounding drain vessels even at 7T (Fig. 4A,B). RsfMRI BOLD activation source at 7T are dominated by draining blood vessel artifacts, but located always near the activated grey mater region. A large-scale connection between two hemispheres can be decomposed to smaller-scale functional connection by using rsfMRI at 7T. Effect of draining artifacts and BOLD signal on detectability of small-scale brain connectivity needs to be further studied.