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Nisha Dalal, Virginia Flanagin, Stefan Glasauer; Spatio-temporal uncertainty and cortical-hippocampal interactions: fMRI study. Journal of Vision 2015;15(12):991. doi: 10.1167/15.12.991.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: The hippocampus interacts with early visual cortex in a stimulus-dependent way. Previously our lab reported that when participants watched movement through a virtual tunnel there was a weaker correlation between the hippocampus and primary visual cortex than with videos where the phase content was scrambled (Figure S1). The hippocampus may provide an important function in interpreting unpredictable input. Here, we test this hypothesis using a similar fMRI paradigm, together with univariate and representational similarity analyses. Methods and results: We measured 27 healthy participants (mean age 25.6±3.8 years, 14 females) while watching three different types of videos (Figure S1): a. virtual tunnel, b. phase scrambled and c. noise videos. Phase scrambled videos share the same low level statistical properties of tunnel videos but lack the recognizable features such as edges, shapes etc. 1. Univariate group level analysis: Stronger activity of higher visual areas in processing of virtual tunnels compared to phase scrambled and noise video was found (n=27, p< 0.05, FDR corrected, T=2.62). Also, hippocampus and early visual areas were found highly active for noise videos compared to tunnel and phase scrambled videos (n=27, p< 0.05, FDR corrected, T=3.04). 2. Representational similarity analysis: Time dissimilarity matrices (TDMs) were created from unnormalized and unsmoothed ROI data from different regions using the RSA toolbox (Figure S2). Candidate Representational Dissimilarity Matrices (RDMs) were created using entropy and mutual information of the stimuli. Candidate RDMs correlate strongly (p< 0.005, FDR corrected signed rank test with subject as random effect) with TDMs, but none of them could completely describe them. Conclusion and future work: We found increase in hippocampal activity with increase in entropy of the visual input, independent of its meaning. Our next step will be to evaluate how the temporal characteristics of hemodynamic response are reflected during time-continuous perception of stimuli.
Meeting abstract presented at VSS 2015
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