Prof. Dr. Cornelius Schwarz
Universität Tübingen
The Slip hypothesis: Temporally Local Coding and Perception of Tactile Stimuli in Rodents and Humans
Prof. Dr. Christoph Braun
Universität Tübingen und University University of Trento, Italy
Beyond the Basics: Exploring the Dynamic Nature of the Somatosensory System
Abstracts
Prof. Dr. Cornelius Schwarz
Werner Reichardt Center for Integrative Neuroscience, Tubingen University, Germany Hertie Institute for Clinical Brain Research, Dept. Cognitive Neurology, Tubingen, Germany
The Slip hypothesis: Temporally Local Coding and Perception of Tactile Stimuli in Rodents and Humans
- The Slip hypothesis: Temporally Local Coding and Perception of Tactile Stimuli in Rodents and Humans
Perceptual systems may have evolved to employ specific physical features characteristic or even unique of the sensory signal at hand, rather than implement generic mathematical analysis of sensory data. Further, perceptual computation may involve neural as well as pre-neuronal elements, the latter based in the physics of the world. In the touch system, one such specific, pre-neuronal element is the phenomenon of biomechanical, frictional events, which are generated by the relative movement of the integument in touch with object surfaces. These short, high amplitude, vibrotactile events are called stick-slip movements (‘slips’). Biomechanical evidence from the rodent whisker system showed that the kinematic outlay of slips carries rich information about the objects touched. Neurophysiological evidence from recordings of primary afferents and the first synaptic station in the brain stem, showed that the early whisker-related tactile system responds in an utmost precise fashion to the kinematics of short vibrotactile events, and that there is almost no integration of the vibrotactile signal beyond the typical duration of slips. In S1, the neuronal population responds very well to changes in the kinematic outline of vibrotactile events, but rather poorly to event rate changes. Matchingly, psychophysical results, which we carried out in rodents as well as the fingertip system in humans, indicate that local kinematic shape of short events dominates perception while integration of event rate has a comparatively poor perceptual effect. In summary, the available data suggests an alternative possibility to think about tactile (neuronal) coding, compared to the one the field has followed as its dominant theory for decades: the tactile system may detect local (shorter than 10 ms) kinematic patterns in the vibrotactile signal, rather than doing extensive integration across time to come up with ‘intensity’ (sum of signal), or ‘frequency (sum of spectral components).
Prof. Dr. Christoph Braun
MEG Center, Tubingen University University of Trento, Dept. Psychology & Cognitive Science, DiPSCo, Rovereto, Italy
Beyond the Basics: Exploring the Dynamic Nature of the Somatosensory System
- Beyond the Basics: Exploring the Dynamic Nature of the Somatosensory System
Although it has been shown that the somatosensory system is a highly dynamic and adaptive system that constantly adjusts to stimuli, tasks, and expectations, in our models, the somatosensory system is often viewed as a static sensory apparatus that simply extracts and forwards information to higher brain areas for processing. This limited view ignores the complexity and adaptability of the somatosensory system, including both bottom-up and top-down processing. Oversimplified models in the study of somatosensory processing might have important implications. First, simplified studies that only focus on individual aspects may result in incomplete or misleading responses and may not provide a complete understanding of somatosensory processing. Second, it is emphasized that the somatosensory system does not necessarily process sensory information based on physical dimensions but rather on dimensions that help solve the sensory problem. Third, it will be argued that studying the somatosensory system in more naturalistic conditions can provide a more complete understanding of somatosensory processing. To illustrate these points, this talk will discuss differences in the estimation of somatosensory processing of time and space, highlighting the dynamic nature of the somatosensory system. Overall, this talk emphasizes the need to move beyond simplistic views of somatosensory processing and embrace the complexity and adaptability of this important sensory system.