Biology subjects

Gulbinaite, R.

Publications and source records attributed to Gulbinaite, R..

7 recordsLinked to original sources

bioRxiv2023

Spatiotemporal resonance in mouse primary visual cortex

Human primary visual cortex (V1) responds more strongly, or resonates, when exposed to [~]10, [~]15-20, [~]40-50 Hz rhythmic flickering light. Full-field flicker also evokes perception of hallucinatory geometric patterns, which mathematical models explain as standing-wave formations emerging from periodic forcing at resonant frequencies of the simulated neural network. However, empirical evidence for such flicker-induced standing waves in the visual cortex was missing. We recorded cortical responses to flicker in awake mice using high spatial resolution widefield imaging in combination with high temporal resolution glutamate-sensing fluorescent reporter (iGluSnFR). The temporal frequency tuning curves in the mouse V1 were similar to those observed in humans, showing a banded structure with multiple resonance peaks (8 Hz, 15 Hz, 33 Hz). Spatially, all flicker frequencies evoked responses in V1 corresponding to retinotopic stimulus location, but some evoked additional peaks. These flicker-induced cortical patterns displayed standing wave characteristics and matched linear wave equation solutions in an area restricted to the visual cortex. Taken together, the interaction of periodic traveling waves with cortical area boundaries leads to spatiotemporal activity patterns that may affect perception.

neuroscience↗

bioRxiv2023

Using the SSVEP to measure the SNARC-spatial attention effects in a parity judgment task

Mental representation of numbers in the brain has been described as spatially organized on what is known as the "mental number line," with small numbers to the left and large numbers to the right. This representation leads to the "SNARC effect" (Spatial-Numerical Association of Response Codes), which refers to (1) improved behavioral performance for "congruent" conditions (e.g., left-handed response to small numbers) as compared to "incongruent" conditions (e.g., right-handed response to small numbers) and (2) perceiving numbers induces an automatic shift in covert spatial attention. Nonetheless, there is scarce physiological evidence for (or against) the prediction that number magnitude induces an automatic shift of spatial attention. Here we recorded EEG during the bimanual SNARC-parity judgment task (classifying numbers as odd or even) in attempt to find electrophysiological evidence for number-magnitude-induced automatic shifts of spatial attention. Attention was measured using the SSVEP (steady-state visual evoked potential) from four task-irrelevant flickering frequencies (two to the left: 15 and 20 Hz and two to the right: 24 and 17.14 Hz) in combination with an optimal spatial filtering method. EEG analysis was performed on the flicker frequencies closest to the fixation point: 20 and 24 Hz for the left and right visual hemifields, respectively. We replicated the expected behavioral patterns predicted by the SNARC effect, such that participants performed better for congruent conditions than on incongruent conditions. We observed significant changes in the SSVEP amplitude with respect to the baseline for the left (20 Hz) and right (24 Hz) flicker for both the congruent and incongruent conditions. Statistically significant differences between the congruent and incongruent conditions were larger for the congruent conditions for the flicker stimuli on the left. Together, these findings support the hypothesis that when numbers are part of the task, but their magnitude is not relevant, the SNARC-spatial attention effect is elicited as a cognitive effect resulting from the mental representation of numbers and its relationship with the space representation, more than merely a motor effect.

physiology↗

bioRxiv2022

Random Tactile Noise Stimulation Reveals Beta-Rhythmic Impulse Response Function of the Somatosensory System

Both passive tactile stimulation and motor actions result in dynamic changes in beta-band (15-30 Hz Hz) oscillations over somatosensory cortex. Similar to alpha-band (8-12 Hz) power decrease in the visual system, beta-band power also decreases following stimulation of the somatosensory system. This relative suppression of alpha and beta oscillations is generally interpreted as an increase in cortical excitability. Here, next to traditional single-pulse stimuli, we employed a random intensity continuous right index finger tactile stimulation (white noise), which enabled us to uncover an impulse response function (IRF) of the somatosensory system. Contrary to previous findings, we demonstrate a burst-like initial increase rather than decrease of beta activity following white noise stimulation (human participants, N = 18, 8 female). These beta bursts, on average, lasted for 3 cycles and their frequency was correlated with resonant frequency of somatosensory cortex, as measured by a multi-frequency steady-state somatosensory evoked potential (SSSEP) paradigm. Furthermore, beta-band bursts shared spectro-temporal characteristics with evoked and resting-state beta oscillations. Taken together, our findings not only reveal a novel oscillatory signature of somatosensory processing that mimics the previously reported visual IRFs, but also point to a common oscillatory generator underlying spontaneous beta bursts in the absence of tactile stimulation and phase-locked beta bursts following stimulation, the frequency of which is determined by the resonance properties of the somatosensory system. Significance StatementThe investigation of the transient nature of oscillations has gained great popularity in recent years. The findings of bursting activity rather than sustained oscillations in the beta-band has provided important insights into its role in movement planning, working memory, inhibition and reactivation of neural ensembles. In this study, we show that also in response to tactile stimulation the somatosensory system responds with [~]3 cycle oscillatory beta-band bursts, whose spectro-temporal characteristics are shared with evoked and resting-state beta-band oscillatory signatures of the somatosensory system. As similar bursts have been observed in the visual domain, these oscillatory signatures might reflect an important supramodal mechanism in sensory processing.

neuroscience↗

bioRxiv2019

Attention differentially modulates the amplitude of resonance frequencies in the visual cortex

Rhythmic visual stimuli (flicker) elicit rhythmic brain responses at the frequency of the stimulus, and attention generally enhances these oscillatory brain responses (steady state visual evoked potentials, SSVEPs). Although SSVEP responses have been tested for flicker frequencies up to 100 Hz [Herrmann, 2001], effects of attention on SSVEP amplitude have only been reported for lower frequencies (up to ~30 Hz), with no systematic comparison across a wide, finely sampled frequency range. Does attention modulate SSVEP amplitude at higher flicker frequencies (gamma band, 30-80 Hz), and is attentional modulation constant across frequencies? By isolating SSVEP responses from the broadband EEG signal using a multivariate spatiotemporal source separation method, we demonstrate that flicker in the alpha and gamma bands elicit strongest and maximally phase stable brain responses (resonance), on which the effect of attention is opposite: positive for gamma and negative for alpha. Finding subject-specific gamma resonance frequency and a positive attentional modulation of gamma-band SSVEPs points to the untapped potential of flicker as a non-invasive tool for studying the causal effects of interactions between visual gamma-band rhythmic stimuli and endogenous gamma oscillations on perception and attention.

neuroscience↗

bioRxiv2018

Midfrontal theta phase coordinates behaviorally relevant brain computations during response conflict

Neural oscillations are thought to provide a cyclic time frame for orchestrating brain computations. Following this assumption, midfrontal theta oscillations have recently been proposed to temporally organize brain computations during conflict processing. Using a multivariate analysis approach, we show that brain-behavior relationships during conflict tasks are modulated according to the phase of ongoing endogenous midfrontal theta oscillations recorded by scalp EEG. We found reproducible results in two independent datasets, using two different conflict tasks: brain-behavior relationships (correlation between reaction time and theta power) were theta phase-dependent in a subject-specific manner, and these \"behaviorally optimal\" theta phases were also associated with fronto-parietal cross-frequency dynamics emerging as theta phase-locked beta power bursts. These effects were present regardless of the strength of conflict. Thus, these results provide empirical evidence that midfrontal theta oscillations are involved in cyclically orchestrating brain computations likely related to response execution during the tasks rather than purely related to conflict processing. More generally, this study supports the hypothesis that phase-based computation is an important mechanism giving rise to cognitive processing.

neuroscience↗

bioRxiv2017

Individual alpha peak frequency predicts 10 Hz flicker effects on selective attention

Rhythmic visual stimulation (\"flicker\") is primarily used to \"tag\" processing of low-level visual and high-level cognitive phenomena. However, preliminary evidence suggests that flicker may also entrain endogenous brain oscillations, thereby modulating cognitive processes supported by those brain rhythms. Here we tested the interaction between 10 Hz flicker and endogenous alpha-band (~10 Hz) oscillations during a selective visuospatial attention task. We recorded EEG from human participants (both genders) while they performed a modified Eriksen flanker task in which distractors and targets flickered within (10 Hz) or outside (7.5 or 15 Hz) the alpha band. By using a combination of EEG source separation, time-frequency, and single-trial linear mixed effects modeling, we demonstrate that 10 Hz flicker interfered with stimulus processing more on incongruent than congruent trials (high vs. low selective attention demands). Crucially, the effect of 10 Hz flicker on task performance was predicted by the distance between 10 Hz and individual alpha peak frequency (estimated during the task). Finally, the flicker effect on task performance was more strongly predicted by EEG flicker responses during stimulus processing than during preparation for the upcoming stimulus, suggesting that 10 Hz flicker interfered more with reactive than proactive selective attention. These findings are consistent with our hypothesis that visual flicker entrained endogenous alpha-band networks, which in turn impaired task performance. Our findings also provide novel evidence for frequency-dependent exogenous modulation of cognition that is determined by the correspondence between the exogenous flicker frequency and the endogenous brain rhythms.\n\nSignificanceHere we provide novel evidence that the interaction between exogenous rhythmic visual stimulation and endogenous brain rhythms can have frequency-specific behavioral effects. We show that alpha-band (10 Hz) flicker impairs stimulus processing in a selective attention task when the stimulus flicker rate matches individual alpha peak frequency. The effect of sensory flicker on task performance was stronger when selective attention demands were high, and was stronger during stimulus processing and response selection compared to the pre-stimulus anticipatory period. These findings provide novel evidence that frequency-specific sensory flicker affects online attentional processing, and also demonstrate that the correspondence between exogenous and endogenous rhythms is an overlooked prerequisite when testing for frequency-specific cognitive effects of flicker.

neuroscience↗

bioRxiv2016

The triple-flash illusion reveals a driving role of alpha-band reverberations in visual perception

The modulatory role of spontaneous brain oscillations on perception of threshold-level stimuli is well established. Here, we provide evidence that alpha-band (7-14 Hz) oscillations not only modulate but also can drive perception. We used the \"triple-flash\" illusion: Occasional perception of three flashes when only two spatially-coincident veridical ones are presented, separated by ~100 ms. The illusion was proposed to result from superposition of two hypothetical oscillatory impulse response functions (IRF) generated in response to each flash (Bowen, 1989). In Experiment 1, we varied stimulus onset asynchrony (SOA) and validated Bowen's theory: the optimal SOA for illusion to occur was correlated, across subjects, with the subject-specific IRF period. Experiment 2 revealed that pre-stimulus parietal alpha EEG phase and power, as well as post-stimulus alpha phase-locking, together determine the occurrence of the illusion on a trial-by-trial basis. Thus, oscillatory reverberations create something out of nothing - a third flash where there are only two.

neuroscience↗