Title: Separation of bottom-up and top-down signals in the human somatosensory cortex with 7T fMRI..
Session: Oral Session
Speaker: Ashley York
Abstract: Invasive electrophysiological recordings from animals indicate that, incoming sensory information (bottom-up), terminates in the middle cortical layer, whereas the modified information, via active processes like attention (top-down) terminate in the superficial and deep layers (Fig.1a). Ultra-high field (7T) fMRI can be used to probe activation across cortical depth non-invasively in humans, with recent publications showing examples in the visual [1] and motor [2] cortex. Nevertheless, when using gradient echo BOLD, depth depended variations in activation are easily overshadowed by signal large gradients imposed by the vascular hierarchy [3]. Here we performed a depth-dependent analysis of bottom-up and top-down driven processes in the human primary somatosensory cortex (S1) and show how these can be separated through signal normalization.