https://www.pisavisionlab.org Research centre dedicated to frontier, interdisciplinary research of human perception Mon, 16 Oct 2023 13:42:44 +0000 en-US hourly 1 https://wordpress.org/?v=6.4.13 https://www.pisavisionlab.org/2022/05/25/short-term-plasticity-in-the-human-visual-thalamus/ Wed, 25 May 2022 10:24:19 +0000 https://www.pisavisionlab.org/?p=4157 eLife 11:e74565. While there is evidence that the visual cortex retains a potential for plasticity in adulthood, less is known about the subcortical stages of visual processing. Here, we asked whether short-term ocular dominance plasticity affects the human visual thalamus. We addressed this question in normally sighted adult humans, using ultra-high field (7T) magnetic resonance imaging combined with the paradigm of short-term monocular deprivation. With this approach, we previously demonstrated transient shifts of perceptual eye dominance and ocular dominance in visual cortex (Binda et al., 2018). Here, we report evidence for short-term plasticity in the ventral division of the pulvinar (vPulv), where the deprived eye representation was enhanced over the nondeprived eye. This vPulv plasticity was similar as previously seen in visual cortex and it was correlated with the ocular dominance shift measured behaviorally. In contrast, there was no effect of monocular deprivation in two adjacent thalamic regions: dorsal pulvinar and Lateral Geniculate Nucleus. We conclude that the visual thalamus retains potential for short-term plasticity in adulthood; the plasticity effect differs across thalamic subregions, possibly reflecting differences in their corticofugal connectivity. Jan W Kurzawski, Claudia Lunghi, Laura Biagi, Michela Tosetti, Maria Concetta Morrone, Paola Binda https://www.pisavisionlab.org/2022/05/25/short-term-plasticity-in-the-human-visual-thalamus/elife-74565-v2/https://doi.org/10.7554/eLife.74565 https://www.pisavisionlab.org/2022/05/25/contextual-information-modulates-pupil-size-in-autistic-children/ Wed, 25 May 2022 10:32:09 +0000 https://www.pisavisionlab.org/?p=4161 Front Neurosci. 2022 Apr 1;16:752871 Recent Bayesian models suggest that perception is more “data-driven” and less dependent on contextual information in autistic individuals than others. However, experimental tests of this hypothesis have given mixed results, possibly due to the lack of objectivity of the self-report methods typically employed. Here we introduce an objective no-report paradigm based on pupillometry to assess the processing of contextual information in autistic children, together with a comparison clinical group. After validating in neurotypical adults a child-friendly pupillometric paradigm, in which we embedded test images within an animation movie that participants watched passively, we compared pupillary response to images of the sun and meaningless control images in children with autism vs. age- and IQ-matched children presenting developmental disorders unrelated to the autistic spectrum. Both clinical groups showed stronger pupillary constriction for the sun images compared with control images, like the neurotypical adults. However, there was no detectable difference between autistic children and the comparison group, despite a significant difference in pupillary light responses, which were enhanced in the autistic group. Our report introduces an objective technique for studying perception in clinical samples and children. The lack of statistically significant group differences in our tests suggests that autistic children and the comparison group do not show large differences in perception of these stimuli. This opens the way to further studies testing contextual processing at other levels of perception. Tortelli C, Pomè A, Turi M, Igliozzi R, Burr DC, Binda P. https://www.pisavisionlab.org/2022/05/25/contextual-information-modulates-pupil-size-in-autistic-children/fnins-16-752871/https://doi.org/10.3389/fnins.2022.752871 https://www.pisavisionlab.org/2022/07/05/attention-cueing-in-rivalry-insights-from-pupillometry/ Tue, 05 Jul 2022 14:34:24 +0000 https://www.pisavisionlab.org/?p=4258 eNeuro 6 June 2022 We used pupillometry to evaluate the effects of attention cueing on perceptual bi-stability, as reported by adult human observers. Perceptual alternations and pupil diameter were measured during two forms of rivalry, generated by presenting a white and a black disk to the two eyes (binocular rivalry) or splitting the disks between eyes (interocular grouping rivalry). In line with previous studies, we found that subtle pupil size modulations (∼0.05 mm) tracked alternations between exclusive dominance phases of the black or white disk. These pupil responses were larger for perceptually stronger stimuli: presented to the dominant eye or with physically higher luminance contrast. However, cueing of endogenous attention to one of the rivaling percepts did not affect pupil modulations during exclusive dominance phases. This was observed despite the reliable effects of endogenous attention on perceptual dominance, which shifted in favor of the cued percept by ∼10%. The results were comparable for binocular and interocular grouping rivalry. Cueing only had a marginal modulatory effect on pupil size during mixed percepts in binocular rivalry. This may suggest that, rather than acting by modulating perceptual strength, endogenous attention primarily acts during periods of unresolved competition, which is compatible with attention being automatically directed to the rivaling stimuli during periods of exclusive dominance and thereby sustaining perceptual alternations. Miriam Acquafredda, Paola Binda and Claudia Lunghi https://www.pisavisionlab.org/2022/07/05/attention-cueing-in-rivalry-insights-from-pupillometry/eneuro-0497-21-2022/https://doi.org/10.1523/ENEURO.0497-21.2022 https://www.pisavisionlab.org/2022/07/05/vision-optimizing-each-glimpse/ Tue, 05 Jul 2022 14:41:23 +0000 https://www.pisavisionlab.org/?p=4262 Current Biology, 2022 A new study uses a rigorous approach to isolate the consequences of eye movements on cortical visual processing, showing that our visual system does not shut down during saccades but specifically modulates sensitivity to selected stimuli. Paola Binda, Maria Concetta Morrone https://www.pisavisionlab.org/2022/07/05/vision-optimizing-each-glimpse/bindamorrone2022-currbiol/https://doi.org/10.1016/j.cub.2022.05.025 https://www.pisavisionlab.org/2022/09/25/short-term-monocular-deprivation-in-adult-humans-alters-functional-brain-connectivity-measured-with-ultra-high-field-magnetic-resonance-imaging/ Sun, 25 Sep 2022 17:33:13 +0000 https://www.pisavisionlab.org/?p=4274 ["live talk"] Vision Science Society meeting 2022 INTRODUCTION: In adult humans, a brief period of monocular deprivation (patching one eye for two hours) induces a form of homeostatic plasticity. Stimuli in the deprived eye are transiently boosted, shifting ocular dominance (e.g., measured with binocular rivalry) and enhancing responses in visual cortex (measured with EEG or fMRI). We asked whether, above and beyond these changes in response amplitude, monocular deprivation also produces a reorganization of visual processing circuits, which we indexed with fMRI functional connectivity. METHODS: Ultra-high field 7T fMRI EPI sequences were acquired in 18 adult normally sighted participants, before and after application of a translucent patch on the dominant eye for two hours. During the acquisitions, a contrast modulated pattern was shown monocularly to the deprived or non-deprived eye and stimulus related activity was regressed out from the fMRI timeseries; in separate sessions, fMRI signals were also recorded in resting state conditions. We analyzed the correlations of the fMRI signal between a priori defined cortical and subcortical regions of interest. Primary visual cortex V1 was used as “seed” area, from which we extracted a reference timeseries and correlated it with timeseries from the other areas to give an index of functional connectivity. RESULTS: After monocular deprivation, V1 increased its functional connectivity with a set of regions primarily located in the ventral visual stream, but also including motor and somatosensory areas. V1 functional connectivity with the lateral geniculate nucleus, its main thalamic input, was unaffected by deprivation. In contrast, a selective post-deprivation increase in functional connectivity was observed for the adjacent ventral pulvinar. CONCLUSIONS: These results suggest that the effects of short-term monocular deprivation involve a transient reorganization of cortical circuits, including both local circuits and long-range projections. They also suggest that ventral pulvinar plays an important and previously unappreciated role in sustaining visual plasticity through adulthood. Acknowledgements European Research Council (ERC): European Union’s Horizon 2020 research and innovation program, grant n. 801715 (PUPILTRAITS) and n. 832813 (GenPercept). Italian Ministry of University and Research: PRIN2017 program (grant n. 2017HMH8FA and n. 2017SBCPZY) and FARE-2 (grant SMILY). 23/05/2022 31/05/2022 Miriam Acquafredda, Francesco Scarlatti, Laura Biagi, Michela Tosetti, Maria Concetta Morrone, Paola Binda https://www.pisavisionlab.org/2022/09/27/impact-of-ketonic-metabolism-on-cortical-visual-processing/ Tue, 27 Sep 2022 07:45:43 +0000 https://www.pisavisionlab.org/?p=4293 ["poster"] Vision Science Society meeting 2022 INTRODUCTION: Abnormal metabolism can impact brain function. For example, obesity is associated with reduced plasticity and ketogenic diets have been employed in some forms of epilepsy. However, the extent to which ketone metabolism affects cortical excitability and neurotransmission is still an open question. Here we tested visual cortex function before and after oral supplementation of the main ketone body, Beta-Hydroxy Butyrate (BHB). We used Visual Evoked Potentials to evaluate the excitatory and inhibitory (cross-orientation inhibition) components of visual responses, combined with Magnetic Resonance Spectroscopy (MRS) to quantify the concentration of major metabolites and neurotransmitters. METHODS: After overnight fasting, participants (N=9) took an oral supplement that raised the concentration of BHB, inducing a state of ketosis. Steady-state visual evoked potentials were measured in response to a counter-phase flickering sinusoidal grating presented alone or superimposed with an orthogonal grating mask (1 c/deg grating, 50% contrast, temporal frequency 8.33Hz; orthogonal mask: 1 c/deg, 60% contrast, temporal frequency 7.1Hz). 3T MRS scans acquired immediately before and after VEPs measured the levels of BHB, GABA and the standard metabolites (including N-Acetyl Aspartate and Creatine) in a 2.5x2.5 cm voxel in the occipital cortex. RESULTS: Ketosis was associated with enhanced visual responses, as steady-state visual evoked potentials were significantly increased after BHB supplementation (vs. before administration: t(8)= 2.91, p<0.05). This effect was reliably associated with the change in occipital Creatine levels (r(9)= -0.78, p<0.05). Furthermore, the index of excitation/inhibition ratio of VEPs (defined as the VEP amplitude difference with and without the orthogonal mask) correlated strongly with changes in occipital GABA concentrations (r(9)= 0.71, p<0.05). CONCLUSIONS: Increasing the levels of BHB in the brain enhances visual cortex responses. The modulation of the excitation/inhibition ratio correlates with GABA changes, suggesting an effect of BHB in modulating GABAergic inhibition. Acknowledgements: This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program, grant n. 801715 (PUPILTRAITS) and n. 832813 (GenPercept), and by the Italian Ministry of University and Research under PRIN2017 and FARE-2 programmes. 23/05/2022 31/05/2022 Paola Binda, Cecilia Steinwurzel, Giuseppe Andrea Daniele, Eleuterio Ferrannini, Francesca Frijia, Domenico Montanaro, Maria Concetta Morrone https://www.pisavisionlab.org/2022/11/25/short-term-monocular-deprivation-in-adult-humans-alters-functional-brain-connectivity-measured-with-ultra-high-field-magnetic-resonance-imaging-2/ Fri, 25 Nov 2022 11:17:32 +0000 https://www.pisavisionlab.org/?p=4392 ["poster"] XIII Congresso Nazionale AIRMM In adult humans, a brief period (2 hours) of monocular deprivation induces a form of homeostatic plasticity. Stimuli in the deprived eye are transiently boosted, shifting perceptual ocular dominance and enhancing evoked fMRI responses in the visual cortex and in the ventral pulvinar, though not in the lateral geniculate nucleus (LGN). We asked whether, above and beyond these changes in cortical response, monocular deprivation also produces a functional reorganization of visual processing circuits. Ultra-high field 7T fMRI EPI resting-state sequences (with two TRs, 3000 and 1000 ms) were acquired in 20 normally sighted adult participants, before and after the application of a translucent patch on the dominant eye for two hours. During the acquisitions, participants were laying in the scanner with their eyes closed. Functional connectivity was measured by correlating BOLD signals in each cortical voxel with those in subcortical “seed” area (ventral pulvinar or LGN) after filtering and nuisance regression. Using Granger causality, we estimated the directionality of functional connectivity with V1, which was distinct for LGN and ventral pulvinar, and compatible with the role of pulvinar in supporting cortico-cortical loops. Comparing functional connectivity before and after monocular deprivation, we found decreased connectivity of early visual areas (V1-V3) with the ventral pulvinar, but unchanged connectivity with LGN. These results suggest that the ventral pulvinar plays an important and previously unappreciated role in sustaining visual plasticity throughout adulthood, possibly by orchestrating the circuit of cortico-cortical connections that may implement the homeostatic regulation of neural function. 23/11/2022 25/11/2022 Miriam Acquafredda, Laura Biagi, Michela Tosetti, Maria Concetta Morrone, Paola Binda https://www.pisavisionlab.org/2022/11/25/the-visual-system/ Fri, 25 Nov 2022 11:25:05 +0000 https://www.pisavisionlab.org/?p=4396 ["invited talk"] XIII Congresso nazionale AIRMM 24/11/2022 Paola Binda

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