Biology subjects

Roder, B.

Publications and source records attributed to Roder, B..

3 recordsLinked to original sources

bioRxiv2022

Crossmodal visual predictions elicit spatially specific early visual cortex activity but later than real visual stimuli

Previous studies have indicated that crossmodal visual predictions are instrumental in controlling early visual cortex activity. The exact time course and spatial precision of such crossmodal top-down influences on visual cortex have been unknown. In the present study, participants were exposed to audio-visual combinations comprising one of two sounds and a Gabor patch either in the top left or in the bottom right visual field. Event related potentials (ERP) were recorded to these frequent crossmodal combinations (Standards) as well as to trials in which the visual stimulus was omitted (Omissions) or the visual and auditory stimuli were recombined (Deviants). Standards and Deviants elicited an ERP between 50 and 100 ms of opposite polarity known as a C1 effect commonly associated with retinotopic processing in early visual cortex. In contrast, a C1 effect was not observed in Omission trials. Spatially specific Omission and Mismatch effects (Deviants minus Standards) started only later with a latency of 230 ms and 170 ms, respectively. These results suggest that crossmodal visual predictions control visual cortex activity in a spatially specific manner. However, visual predictions do not elicit neural responses that mimic stimulus-driven activity but rather seem to affect early visual cortex via distinct neural mechanisms.

neuroscience↗

bioRxiv2018

Alpha-band oscillations reflect external spatial coding for tactile stimuli in sighted, but not in congenitally blind humans

We investigated the function of oscillatory alpha-band activity in the neural coding of spatial information during tactile processing. Sighted humans concurrently encode tactile location in skin-based and, after integration with posture, external spatial reference frames, whereas congenitally blind humans preferably use skin-based coding. Accordingly, lateralization of alpha-band activity in parietal regions during attentional orienting in expectance of tactile stimulation reflected external spatial coding in sighted, but skin-based coding in blind humans. Here, we asked whether alpha-band activity plays a similar role in spatial coding for tactile processing, that is, after the stimulus has been received. Sighted and congenitally blind participants were cued to attend to one hand in order to detect rare tactile deviant stimuli at this hand while ignoring tactile deviants at the other hand and tactile standard stimuli at both hands. The reference frames encoded by oscillatory activity during tactile processing were probed by adopting either an uncrossed or crossed hand posture. In sighted participants, attended relative to unattended standard stimuli suppressed the power in the alpha-band over ipsilateral centro-parietal and occipital cortex. Hand crossing attenuated this attentional modulation predominantly over ipsilateral posterior-parietal cortex. In contrast, although contralateral alpha-activity was enhanced for attended versus unattended stimuli in blind participants, no crossing effects were evident in the oscillatory activity of this group. These findings suggest that oscillatory alpha-band activity plays a pivotal role in the neural coding of external spatial information for touch.

neuroscience↗

bioRxiv2017

Infants Are Superior In Implicit Crossmodal Learning And Use Other Learning Mechanisms Than Adults

While adults have to continuously adapt their internal representations of the sensory world, infants need to first acquire these models. We used event-related potentials to test the hypothesis that infants extract crossmodal statistics implicitly while adults learn them when task relevant. Six-month-old infants and adults were passively exposed to frequent standard audio-visual combinations (A1V1, A2V2, p=0.35 each), rare recombinations of the standard stimuli (A1V2, A2V1, p=0.10 each), and a rare deviant audio-visual combination with an infrequent auditory and visual element (A3V3, p=0.10). While both infants and adults differentiated between rare deviants and standards at early processing stages, only infants discriminated standards from recombined stimuli at a later processing stage. A second experiment revealed that adults discriminated recombined from standard combinations only when crossmodal combinations were task relevant. These results demonstrate a heightened sensitivity for crossmodal statistics in infants and a change in learning mode from infancy to adulthood.

neuroscience↗