What have we done so far?
What are the neural processes underlying unconscious and conscious processing after somatosensory stimulation?
Using fMRI, we have identified cortical processing after subliminal finger stimulation (Blankenburg et al., 2003a; Taskin et al., 2008), and using EEG and rsfMRI we have identified modulations of alpha rhythm as a target mechanism regulating access to conscious experience (Schubert et al., 2006, 2009; Ritter et al., 2009; Reinacher et al., 2009; Nierhaus et al., 2015). As putative modulating factors, we investigate the impact of vigilance, attention (Schubert et al., 2008; Goltz et al., 2013, 2015), and peripheral noise (Iliopoulos et al., 2014).
What is the structural and functional organization of the human primary and secondary somatosensory cortex and how does it reflect somatosensory perception?
We were among the first to differentiate finger representations in different subareas of SI (Kurth et al., 2000), distal to proximal finger somatotopy (Blankenburg et al., 2003b), and somatotopic organization within SII (Ruben et al., 2001) in human subjects. Recently, we have shown that sensorimotor somatotopy may be delineated even without any stimulation only based on resting-state fMRI (Long et al., 2014). Currently, we are investigating somatotopic patterns of BOLD activation and deactivation in SI upon peripheral electrical stimulation (Project Taskin) and their relationship to different types of somatosensory perception.
What are the behavioral and neural effects of stroke affecting the somatosensory system and how can we improve behavioral outcome?
We investigate cerebral reorganization after somatosensory stroke and its clinical & behavioral consequences (Taskin et al., 2006; Preusser et al., 2015), particularly the delayed development of pain (Central poststroke pain, CPSP), and its neurophysiological underpinnings (Krause et al., 2012, 2015). We aim at performing preventive and therapeutic clinical trial in patients after somatosensory stroke (Jungehülsing et al., 2013).
Can our findings be generalized beyond the somatosensory system?
To address this question, some studies are performed on other sensory systems (mainly the visual system) for example in order to generalize our hypothesis on the functional role of background alpha rhythms (Moosmann et al., 2003; Becker et al., 2008, 2011) and its role after subliminal stimulation (Bareither et al., 2014), or to assess the possibility of investigating cortical organization and plasticity only based on resting-state fMRI (Striem-Amit et al., 2015).
What are potential methodological improvements to noninvasively study human neurophysiology?
We have worked on combining fMRI with neurophysiological methods such as EEG, TMS, and TDCS. Already in 2002, we have simultaneously recorded SEPs and evoked BOLD (Thees et al., 2002) and subsequently we identified BOLD correlates of occipital and Rolandic alpha rhythms (Moosmann et al., 2003; Ritter et al., 2009). In cooperation with Gabriel Curio’s group we were even able to simultaneously assess evoked spike burst upon somatosensory stimulation and associated BOLD signal in human subjects noninvasively (Ritter et al., 2008; Freyer et al., 2009). In order to study the somatosensory system in a more ecologically valid context (e.g., in walking subjects, at a patient’s bedside etc.), we established noninvasive optical recordings of somatosensory cortical maps with multichannel near-infrared spectroscopy (Koch et al., 2010).