Timo Torsten Schmidt, BCCN Berlin / GRK 1589 / FU Berlin

Tactile Mental Representations

The human ability to mentally represent and manipulate information in the absence of sensory stimulation is key for any higher cognitive functions. Empirical neuroscientific research on mental imagery (MI) and working memory (WM) addresses the question of how our brain represents various types of mental contents. Critically, most research stems from studies in the visual modality, leaving open the question of whether findings, models and theories generalize to other modalities.

In my work I focused on the mental representation of tactile contents. To empirically address what brain regions code different types of mental content, two fMRI studies on MI, one WM EEG study and four fMRI WM decoding studies were conducted. We found that posterior parietal regions and primary somatosensory cortex code spatial features of tactile stimuli. In contrast, when participants memorized more abstract stimulus features such as vibratory frequency, intensity or duration, the prefrontal cortex was found to exhibit multivariate parametric codes specific to the mental content. This finding was also replicated in the visual and auditory modalities.

These results support the view that the abstractness of a mental representation determines which brain regions exhibit content-specific codes, where the gradient of abstractness stretches from sensory to categorical or parametric content types. This gradient maps onto the hierarchical organization of the cortex. In parallel, predictive brain mechanisms also rely on the hierarchical interaction of bottom-up and top-down processes. I will suggest mechanisms for how these well-established hierarchical processing principles relate to the representation of mental contents.

Additional Information

Phd thesis defence in the GRK 1589 "Sensory Computation in Neural Systems"

Organized by

Felix Blankenburg / Robert Martin