Evidence for neural encoding of Bayesian surprise in human somatosensation.

Accumulating empirical evidence suggests a role of Bayesian inference and learning for shaping neural responses in auditory and visual perception. However, its relevance for somatosensory processing is unclear. In the present study we test the hypothesis that cortical somatosensory processing exhibits dynamics that are consistent with Bayesian accounts of brain function.

EEG-fMRI based information theoretic characterization of the human perceptual decision system.

The modern metaphor of the brain is that of a dynamic information processing device. In the current study we investigate how a core cognitive network of the human brain, the perceptual decision system, can be characterized regarding its spatiotemporal representation of task-relevant information. We capitalize on a recently developed information theoretic framework for the analysis of simultaneously acquired electroencephalography (EEG) and functional magnetic resonance imaging data (fMRI) (Ostwald et al.

Supramodal parametric working memory processing in humans.

Previous studies of delayed-match-to-sample (DMTS) frequency discrimination in animals and humans have succeeded in delineating the neural signature of frequency processing in somatosensory working memory (WM). During retention of vibrotactile frequencies, stimulus-dependent single-cell and population activity in prefrontal cortex was found to reflect the task-relevant memory content, whereas increases in occipital alpha activity signaled the disengagement of areas not relevant for the tactile task. Here, we recorded EEG from human participants to determine the extent to which these mechanisms can be generalized to frequency retention in the visual and auditory domains.

Tactile motion and pattern processing assessed with high-field FMRI.

Processing of motion and pattern has been extensively studied in the visual domain, but much less in the somatosensory system. Here, we used ultra-high-field functional magnetic resonance imaging (fMRI) at 7 Tesla to investigate the neuronal correlates of tactile motion and pattern processing in humans under tightly controlled stimulation conditions. Different types of dynamic stimuli created the sensation of moving or stationary bar patterns during passive touch.

Stimulus-dependent EEG activity reflects internal updating of tactile working memory in humans.

Despite recent advances in uncovering the neural signature of tactile working memory processing in animals and humans, the representation of internally modified somatosensory working memory content has not been studied so far. Here, recording EEG in human participants (n = 25) performing a modified delayed match-to-sample task allowed us to disambiguate internally driven memory processing from encoding-related delay activity. After presentation of two distinct vibrotactile frequencies to different index fingers, a visual cue indicated which of the two previous stimuli had to be maintained in working memory throughout a retention interval for subsequent frequency discrimination against a probe stimulus.

Oscillatory correlates of vibrotactile frequency processing in human working memory.

Previous animal research has revealed neuronal activity underlying short-term retention of vibrotactile stimuli, providing evidence for a parametric representation of stimulus frequency in primate tactile working memory (Romo et al., 1999). Here, we investigated the neural correlates of vibrotactile frequency processing in human working memory, using noninvasive electroencephalography (EEG).

Studying the role of human parietal cortex in visuospatial attention with concurrent TMS-fMRI.

Combining transcranial magnetic stimulation (TMS) with concurrent functional magnetic resonance imaging (fMRI) allows study of how local brain stimulation may causally affect activity in remote brain regions. Here, we applied bursts of high- or low-intensity TMS over right posterior parietal cortex, during a task requiring sustained covert visuospatial attention to either the left or right hemifield, or in a neutral control condition, while recording blood oxygenation-level-dependent signal with a posterior MR surface coil. As expected, the active attention conditions activated components of the well-described "attention network," as compared with the neutral baseline.

Neural activity in cortical areas MST and FEF in relation to smooth pursuit gain control.

Two cortical areas that crucially contribute to the generation and maintenance of smooth pursuit eye movements (SPEM) are the medial superior temporal area (MST) and the pursuit area of the frontal eye fields (FEF). They both project to the brainstem premotor structures via different parallel pathways. A special property of the pursuit system is the increased sensitivity to retinal image motion for increasing pursuit velocities (dynamic gain control), which might be attributed to the FEF.

MSTd neurons during ocular following and smooth pursuit perturbation.

MSTd neurons in the behaving monkey were investigated during step-ramp smooth pursuit eye movements (SPEM), short perturbations of the small visual target during ongoing pursuit, and large-field visual stimulation inducing ocular following responses (OFR). Neurons responded with short latencies to visual motion during OFR. In contrast the non-retinal responses during SPEM and perturbations followed the eye movements by 100-150 ms and were in the opposite direction to the OFR response.