P184: Activity and functional connectivity of the premotor-parietal network modulate intrinsic power changes of mu rhythms: an EEG-fMRI study

Abstract

P185 – Figure 1. A. Brain regions more activated when using tools compared to neutral objects (bars) in fMRI study with healthy controls. B. Statistical map of the voxels associated with tool use scoring in LBD patients in lesion analyse study using VLSM. acquired brain activity from fifteen healthy participants (age range 21-35), by combining 32-channel MRI-compatible EEG and Siemens 3T-MRI systems. During data acquisition, the participants were awake and not engaged in any tasks with their eyes closed. BOLD-based fMRI signals and surface EEG data were recorded simultaneously for 20 min. Power of mu rhythms was calculated from EEG data at C3 and C4 electrodes within a 3-second time bin, corresponding to a single scan of MRI data (400 data points in total). Using SPM software, voxel-based general linear model analyses were performed in the whole brain to find regions correlated with spontaneous fluctuations of mu rhythm power physically at rest. We found that greater BOLD activities in the IPL and PMv were linked with suppression of mu rhythm power. Furthermore, we discovered that the functional connectivity between IPL and PMv was decreased when the power of mu rhythms was suppressed. We did not find any brain regions showing greater activities or functional connectivity in association with increases of mu rhythm power. We conclude that greater activity but reduced functional connectivity of IPL and PMv are correlated with spontaneous suppression of mu rhythm amplitudes at rest. Our results may provide new insight into mechanisms of spontaneous fluctuations of brain activity or connectivity in a resting state. P185 Investigation of the neural correlates of tool use with activation studies in healthy subjects and lesion studies in brain damaged patients E. Salazar-Lopez1, M.L. Brandi1, G. Goldenberg2, A. Wohlschlaeger3, L. Johannsen1, J. Hermsdoerfer1 1Technische Universitaet Muenchen, Lehrstuhl fuer Bewegungswissenschaft, Muenchen, Germany; 2Klinikum Bogenhausen, Klinik fuer Neuropsychologie, Muenchen, Germany; 3Technische Universitaet Muenchen, Klinikum rechts der Isar, Diagnostische und Interventionelle Neuroradiologie. Neuro-Kopf-Zentrum, Muenchen, Germany Question: Results from brain activation studies in healthy subjects and lesion analyses in brain damage patients are expected to reveal a correspondence between areas activated by task performance with lesioned areas in case of deficits. We are planning to directly compare both approaches to study the neural network of tool use in as similar as possible and as realistic as possible conditions: On the other hand we examined tool use in healthy elderly subjects, during the realization of fMRI. On the other hand we plan to correlate the execution in this task in chronic stroke patients – with apraxia – with their damaged brain areas. Methods: Both experiments used a tool carousel for controlled tool presentation (12 tools of daily life). The fMRI-data was analyzed with SPM8 in a factorial design (object and task) during the planningand action-phase. In the lesion analyze study we score the execution according to an apraxic errors scale and use the voxel based lesion symptom mapping (VLSM), a method that includes mapping the lesion manually, normalizing brain image using cost function masking with SPM8 and making a voxelwise statistical analysis of neurological lesions to define the relationship between tissue damaged and behavior. Results: Besides a clear left-sided lateralization, a wide spread network can be identified with the fMRI analysis (see figure). This is specific to planning tool use and includes parietal cortex (superior and inferior parietal lobule and intraparietal sulcus), frontal cortex (dorsal and ventral premotor cortex