https://www.pisavisionlab.org Research centre dedicated to frontier, interdisciplinary research of human perception Thu, 22 Apr 2021 10:07:22 +0000 en-US hourly 1 https://wordpress.org/?v=6.4.13 https://www.pisavisionlab.org/2019/12/27/saccadic-suppression-is-embedded-within-extended-oscillatory-modulation-of-sensitivity-j-neurosci/ Fri, 27 Dec 2019 13:57:14 +0000 https://www.pisavisionlab.org/?p=1621

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Journal of Neuroscience, 37(13), 3661–3670. Action and perception are intimately coupled systems. One clear case is saccadic suppression, the reduced visibility around the time of saccades, which is important in mediating visual stability; another is the oscillatory modulation of visibility synchronized with hand action. To suppress effectively the spurious retinal motion generated by the eye movements, it is crucial that saccadic suppression and saccadic onset be temporally synchronous. However, the mechanisms that determine this temporal synchrony are unknown. We investigated the effect of saccades on contrast discrimination sensitivity over a long period stretching over >1 s before and after saccade execution. Human subjects made horizontal saccades at will to two stationary saccadic targets separated by 20°. At a random interval, a brief Gabor patch was displayed between the two fixations in either the upper or lower visual field and the subject had to detect its location. Strong saccadic suppression was measured between −50 and 50 ms from saccadic onset. However, the suppression was systematically embedded in a trough of oscillations of contrast sensitivity that fluctuated rhythmically in the delta range (at ∼3 Hz), commencing ∼1 s before saccade execution and lasting for up to 1 s after the saccade. The results show that saccadic preparation and visual sensitivity oscillations are coupled and the coupling might be instrumental in temporally aligning the initiation of the saccade with the visual suppression. SIGNIFICANCE STATEMENT Saccades are known to produce a suppression of contrast sensitivity at saccadic onset and an enhancement after saccadic offset. Here, we show that these dynamics are systematically embedded in visual oscillations of contrast sensitivity that fluctuate rhythmically in the delta range (at ∼3 Hz), commencing ∼1 s before saccade execution and lasting for up to 1 s after the saccade. The results show that saccadic preparation and visual sensitivity oscillations are coupled and the coupling might be instrumental in aligning temporally the initiation of the saccade with the visual suppression. Benedetto, A., & Morrone, M. C. https://www.pisavisionlab.org/2019/12/27/saccadic-suppression-is-embedded-within-extended-oscillatory-modulation-of-sensitivity-j-neurosci/3661-full/https://doi.org/10.1523/JNEUROSCI.2390-16.2016 https://www.pisavisionlab.org/2019/12/28/different-responses-of-spontaneous-and-stimulus-related-alpha-activity-to-ambient-luminance-changes-eur-j-neurosci/ Sat, 28 Dec 2019 08:10:52 +0000 https://www.pisavisionlab.org/?p=1682 Download

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European Journal of Neuroscience, 48(7), 2599–2608. Alpha oscillations are particularly important in determining our percepts and have been implicated in fundamental brain functions. Oscillatory activity can be spontaneous or stimulus-related. Furthermore, stimulus-related responses can be phase- or non-phase-locked to the stimulus. Non-phase-locked (induced) activity can be identified as the average amplitude changes in response to a stimulation, while phase-locked activity can be measured via reverse-correlation techniques (echo function). However, the mechanisms and the functional roles of these oscillations are far from clear. Here, we investigated the effect of ambient luminance changes, known to dramatically modulate neural oscillations, on spontaneous and stimulus-related alpha. We investigated the effect of ambient luminance on EEG alpha during spontaneous human brain activity at rest (experiment 1) and during visual stimulation (experiment 2). Results show that spontaneous alpha amplitude increased by decreasing ambient luminance, while alpha frequency remained unaffected. In the second experiment, we found that under low-luminance viewing, the stimulus-related alpha amplitude was lower, and its frequency was slightly faster. These effects were evident in the phase-locked part of the alpha response (echo function), but weaker or absent in the induced (non-phase-locked) alpha responses. Finally, we explored the possible behavioural correlates of these modulations in a monocular critical flicker frequency task (experiment 3), finding that dark adaptation in the left eye decreased the temporal threshold of the right eye. Overall, we found that ambient luminance changes impact differently on spontaneous and stimulus-related alpha expression. We suggest that stimulus-related alpha activity is crucial in determining human temporal segmentation abilities. Benedetto, A., Lozano‐Soldevilla, D., & VanRullen, R. https://www.pisavisionlab.org/2019/12/28/different-responses-of-spontaneous-and-stimulus-related-alpha-activity-to-ambient-luminance-changes-eur-j-neurosci/ejn-13791/https://doi.org/10.1111/ejn.13791