Wietske van der ZwaagNeuroscience Symposium
The Neuroscience Symposia are organized weekly by the Netherlands Institute for Neuroscience. The presentations are given by researchers from the institute or by guest speakers. The title and content of the symposium is usually made known in the week prior to the presentation.
Colloquium room – Netherlands Institute for Neuroscience
Speaker Spinoza Centre
Perception of spatial quantities like the number and sizes of objects is implicated in many perceptual
and cognitive functions, including foraging, attention control, decision making and mathematics. Using 7T fMRI and neural model-based analyses, we have revealed extensive and overlapping networks of neural populations showing selective responses to object number (numerosity) and size. These populations are organized into topographic maps, with numerosity and size preferences changing gradually across the cortical surface, mirroring the layout of early sensory cortices. We have recently extend this approach to temporal quantities, the duration and frequency of visual events. We hypothesized that human neural populations may exhibit tuned responses to visual event timing. We displayed visual events (a circle appearing and disappearing) that gradually varied the time between circle appearance and disappearance (duration) and/or the time between consecutive circle appearances (period, i.e. 1/frequency). We summarized the fMRI responses to these events using neural models tuned to event duration and period. These models also accounted for the precise timing of events, and scaling of response amplitudes with event frequency, recent advances that have allowed inclusion of neural response dynamics into fMRI analyses. The resulting models captured fMRI responses well in several widely-separated temporo-occipital, parietal and frontal areas, partially overlapping with the maps of numerosity, object size and visual field position. Within these areas, we reveal topographic organization of event timing preferences. We also reveal
hierarchical transformations of timing representations between these timing maps. Overall, our results show that, various spatial and temporal quantities are processed in related networks of topographic maps, in regions implicated in object recognition, motion perception, attention control, decision-making and mathematics. Topographic maps group neurons with similar response preferences, thereby making neural processing more efficient by minimizing connection distances. We propose that such organization may be found for many cognitive functions. This allows characterization of neural computations and response selectivity underlying human cognition even at the limited spatial and temporal resolution of fMRI.
4:00 pm – Imaging the human brain’s representations of space, number and timing
5:00 pm – Discussion and drinks