Biology subjects

Soto-Faraco, S.

Publications and source records attributed to Soto-Faraco, S..

12 recordsLinked to original sources

bioRxiv2024

Single trial characterization of frontal Theta and parietal Alpha oscillatory episodes during Spatial Navigation in humans

Theoretical proposals and empirical findings both highlight the relevance of theta brain oscillations in human Spatial Navigation. However, whilst the general assumption is that the relevant theta band activity is purely oscillatory, most empirical studies fail to disentangle oscillatory episodes from wide band activity. In addition, experimental approaches often rely on averaged activity across trials and subjects, disregarding moment-to-moment fluctuations in Theta activity, contingent on key aspects of the task. Here, we used novel oscillation detection approaches to investigate the dynamics of theta and alpha episodes in human subjects performing a spatial navigation task in a Virtual Reality environment, resolved at single-trial level. The results suggest that bouts of theta oscillatory activity are related to task difficulty and access to previously encoded information, across different timescales. alpha episodes, instead, seem to anticipate successful navigational decisions and could be related to shifts in internal attention.

neuroscience↗

bioRxiv2022

Using occipital α-bursts to modulate behaviour in real-time

Spontaneous oscillatory neural activity can influence the processing of incoming sensory input and subsequent behavioural reactions. Spontaneous oscillatory activity mostly appears in stochastic bursts, but typical trial-averaged approaches fail to capture this. We aimed at relating oscillatory bursts in the alpha band (8-13 Hz) to behaviour directly, via an EEG-based brain-computer interface (BCI) that allowed for burst-triggered stimulus presentation in real-time in a visual detection task. According to alpha theories, we hypothesised that targets presented during alpha-bursts should lead to slower responses and higher miss rates, whereas targets presented in the absence of bursts should lead to faster responses and higher false alarm rates. Our findings support the role of bursts in alpha-oscillations in visual perception and exemplify how real-time BCI systems can be used as a test bench for brain-behavioural theories.

neuroscience↗

bioRxiv2022

Long-range alpha-synchronisation as control signal for BCI: A feasibility study

Shifts in spatial attention are associated with variations in alpha-band (, 8-14 Hz) activity, specifically in inter-hemispheric imbalance. The underlying mechanism is attributed to local -synchronisation, which regulates local inhibition of neural excitability, and fronto-parietal synchronisation reflecting long-range communication. The direction-specific nature of this neural correlate brings forward its potential as a control signal in brain-computer interfaces (BCI). In the present study, we explored whether long-range -synchronisation presents lateralised patterns dependent on voluntary attention orienting and whether these neural patterns can be picked up at a single-trial level to provide a control signal for active BCI. We collected electroencephalography (EEG) data from a cohort of healthy adults (n = 10) while performing a covert visuospatial attention (CVSA) task. The data shows a lateralised pattern of -band phase coupling between frontal and parieto-occipital regions after target presentation, replicating previous findings. This pattern, however, was not evident during the cue-to-target orienting interval, the ideal time window for BCI. Furthermore, decoding the direction of attention trial-by-trial from cue-locked synchronisation with support vector machines (SVM) was at chance-level. The present findings suggest EEG may not be capable of detecting long-range -synchronisation in attentional orienting on a single-trial basis and, thus, highlight the limitations of this metric as a reliable signal for BCI control. SIGNIFICANCE STATEMENTCognitive neuroscience advances should ideally have a real-world impact, with an obvious avenue for transference being BCI applications. The hope is to faithfully translate user-generated brain endogenous states into control signals to actuate devices. A paramount challenge for transfer is to move from group-level, multi-trial average approaches to single-trial level. Here, we evaluated the feasibility of single-trial estimation of phase synchrony across distant brain regions. Although many studies link attention to long-range synchrony modulation, this metric has never been used to control BCI. We present a first attempt of a synchrony-based BCI that, albeit unsuccessful, should help break new ground to map endogenous attention shifts to real-time control of brain-computer actuated systems.

neuroscience↗

bioRxiv2021

Cross-modal Semantic Relationships Guide Spontaneous Orienting in Real-life Scenes

In real-world scenes, the different objects and events available to our senses are interconnected within a rich web of semantic associations. These semantic links help parse information and make sense of the environment. For example, during goal-directed attention, characteristic everyday life object sounds help speed up visual search for these objects in natural and dynamic environments. However, it is not known whether semantic correspondences also play a role under spontaneous observation. Here, we investigated this question addressing whether crossmodal semantic congruence can drive spontaneous, overt visual attention in free-viewing conditions. We used eye-tracking whilst participants (N=45) viewed video clips of realistic complex scenes presented alongside sounds of varying semantic congruency with objects within the videos. We found that characteristic sounds increased the probability of looking, the number of fixations, and the total dwell time on the semantically corresponding visual objects, in comparison to when the same scenes were presented with semantically neutral sounds or just with background noise only. Our results suggest that crossmodal semantic congruence has an impact on spontaneous gaze and eye movements, and therefore on how attention samples information in a free viewing paradigm. Our findings extend beyond known effects of object-based crossmodal interactions with simple stimuli and shed new light upon how audio-visual semantically congruent relationships play out in everyday life scenarios.

neuroscience↗

bioRxiv2021

Association Between Action Video Game Playing Experience and Visual Search in Real-life Multisensory scenes

Prior studies investigating the effects of routine action video game playing have demonstrated improvements in a variety of cognitive processes, including improvements in attentional tasks. However, there is little evidence indicating that the cognitive benefits of playing action video games generalize from simplified unisensory stimuli to naturalistic multisensory scenes - a fundamental characteristic of natural, everyday life environments. In particular, it is unknown whether video game experience has an impact on cross-modal congruence effects when searching through such multisensory scenes. The present pre-registered compared the performance of action video game players (AVGPs) with non-video game players (NVGPs) on a visual search task for objects embedded in video clips of realistic scenes. We run two identical online experiments with gender-balanced samples, for a total N=130. Overall, the data replicated previous findings reporting search benefits when visual targets were accompanied by semantically congruent auditory events, compared to neutral or incongruent ones. However, according to the results, AVGPs did not consistently outperform NVGPs in the search task overall, nor they exploit multisensory cues more efficiently than NVGPs. Exploratory analyses with self-reported gender as a variable revealed a potential difference in response strategy between experienced male and female AVGPs when dealing with cross-modal cues. These findings suggest that the generalization of the advantage of AVG experience to realistic, cross-modal situations should be done with caution, and considering gender-related aspects.

neuroscience↗

bioRxiv2021

The dynamics of decision making and action during active sampling

Embodied Cognition Theories (ECTs) propose that the decision process continues to unfold during the execution of choice actions, and its outcome manifests itself in these actions. Scenarios where actions not only express choice but also help sample information can provide a valuable test of this framework. Remarkably almost no studies so far have addressed this scenario. Here, we present a study testing just this paradigmatic situation with humans. On each trial, subjects categorized a central object image, blurred to different extents (2AFC task) by moving a cursor toward the left or right of the display. Upward cursor movements, orthogonal with respect to choice options, reduced the image blur and could be freely used to actively sample information. Thus, actions for decision and actions for sampling were made orthogonal to each other. We analyzed response trajectories to test a central prediction of ECTs; whether information-sampling movements co-occurred with the ongoing decision process. Trajectory data revealed were bimodally distributed, with one kind being direct towards one response option (non-sampling trials), and the other kind containing an initial upward component before veering off towards an option (sampling trials). This implies that there was an initial decision at the early stage of a trial whether to sample information or not. Importantly, the trajectories in sampling trials were not purely upward, but rather had a significant horizontal deviation that was visible early on in the movement. This result suggests that movements to sample information exhibit an online interaction with the decision process. The finding that decision processes interact with actions to sample information supports the ECT under novel, ecologically relevant constrains.

neuroscience↗

bioRxiv2020

The phase of Theta oscillations modulates successful memory formation at encoding

Several past studies have shown that attention and perception can depend upon the phase of ongoing neural oscillations at stimulus onset. Here, we extend this idea to the memory domain. We tested the hypothesis that ongoing fluctuations in neural activity have an impact on memory encoding using a picture paired-associates task to gauge episodic memory performance. Experiment 1 capitalized on the principle of phase reset. We tested if subsequent memory performance fluctuates rhythmically, time-locked to a reset cue presented before the to-be-remembered pairs. We found indication that behavioral performance was periodically and selectively modulated at theta frequency ([~]4 Hz). In Experiment 2 we focused on prestimulus ongoing activity using scalp EEG recorded while participants performed the pair-associate task. We analyzed subsequent memory performance as a function of theta and alpha activity around the presentation of the to-be-remembered pairs. The results of the pre-registered analyses, using large electrode clusters and generic spectral ranges, returned null results of prestimulus phase-behavior correlation. However, we found that post-stimulus theta-power modulations in left frontal scalp predicted subsequent memory performance. This post-stimulus effect in theta power was used to guide a post-hoc prestimulus phase analysis, narrowed down to more precise scalp location and frequency. This analysis returned a correlation between prestimulus theta phase and subsequent memory. Altogether, these results suggest that the prestimulus theta activity at encoding has an impact on later memory performance.

neuroscience↗

bioRxiv2020

Can the occipital alpha-phase speed up visual detection through a real-time EEG-based brain-computer interface (BCI)?

Electrical brain oscillations reflect fluctuations in neural excitability. Fluctuations in the alpha band (, 8-12 Hz) in the occipito-parietal cortex are thought to regulate sensory responses, leading to cyclic variations in visual perception. Inspired by this theory, some past and recent studies have addressed the relationship between -phase from extra-cranial EEG and behavioural responses to visual stimuli in humans. The latest studies have used offline approaches to confirm -gated cyclic patterns. However, a particularly relevant implication is the possibility to use this principle online for real-time neurotechnology, whereby stimuli are time-locked to specific -phases leading to predictable outcomes in performance. Here we aimed at providing a proof-of-concept for such real-time neurotechnology. Participants performed a speeded response task to visual targets that were presented upon a real-time estimation of the -phase via an EEG closed-loop brain-computer interface (BCI). We predicted, according to the theory, a modulation of reaction times (RTs) along the -cycle. Our BCI system achieved reliable trial-to-trial phase-locking of stimuli to the phase of individual occipito-parietal -oscillations. Yet, the behavioural results did not support a consistent relation between RTs and the phase of the -cycle neither at group nor single participant levels. We must conclude that although the -phase might play a role in perceptual decisions from a theoretical perspective, its impact on EEG-based BCI application appears negligible.

neuroscience↗

bioRxiv2019

Not so automatic: Task relevance and perceptual load modulate cross-modal semantic congruence effects on spatial orienting

Recent studies show that cross-modal semantic congruence plays a role in spatial attention orienting and visual search. However, the extent to which these cross-modal semantic relationships attract attention automatically is still unclear. At present the outcomes of different studies have been inconsistent. Variations in task-relevance of the cross-modal stimuli (from explicitly needed, to completely irrelevant) and the amount of perceptual load may account for the mixed results of previous experiments. In the present study, we addressed the effects of audio-visual semantic congruence on visuo-spatial attention across variations in task relevance and perceptual load. We used visual search amongst images of common objects paired with characteristic object sounds (e.g., guitar image and chord sound). We found that audio-visual semantic congruence speeded visual search times when the cross-modal objects are task relevant, or when they are irrelevant but presented under low perceptual load. Instead, when perceptual load is high, sounds fail to attract attention towards the congruent visual images. These results lead us to conclude that object-based crossmodal congruence does not attract attention automatically and requires some top-down processing.

neuroscience↗

bioRxiv2019

From cognitive control to creativity: The conflict resolution of surrealistic imagery

Surrealistic imagery juxtaposes common visual elements to create un-ordinary associations with semantically conflicting representations. We hypothesize that these images engage the conflict processing network that has been described in cognitive neuroscience theories, and probed with laboratory protocols such as the Stroop or Flanker tasks. We addressed this hypothesis by measuring mid-frontal Theta power using EEG while participants watched surrealistic images through a social media-like interface. Surrealistic images, compared to controls, produced a significant Theta power increase, as predicted from cognitive conflict theory. We also found increased memory for surrealistic images one week after exposure, compared to the controls. These findings provide evidence for the surrealistic artistic strategy to effectively engage viewer s cognitive control and boost memorability. In these studies, we provide validation of cognitive theories in real-life scenarios and insights regarding the use of neural correlates as effectiveness metrics in creative communication, as well as the arts.

neuroscience↗

bioRxiv2019

Integrating When and What Information in the Left Parietal Lobe Allows Language Rule Generalization

A crucial aspect when learning a language is discovering the rules that govern how words are combined in order to convey meanings. Since rules are characterized by sequential co-occurrences between elements (e.g. These cupcakes are unbelievable), tracking the statistical relationships between these elements is fundamental. However, statistical learning alone cannot fully account for the ability to create abstract rule representations that can be generalized, a paramount requirement of linguistic rules. Here, we provide evidence that, after the statistical relations between words have been extracted, the engagement of goal-directed attention is key to enable rule generalization. Incidental learning performance during a rule-learning task on an artificial language revealed a progressive shift from statistical learning to goal-directed attention. In addition, and consistent with the recruitment of attention, fMRI analyses of late learning stages showed left parietal activity within a broad bilateral dorsal fronto-parietal network. Critically, rTMS on participants peak of activation within the left parietal cortex impaired their ability to generalize learned rules to a structurally analogous new language. No stimulation or rTMS on a non-relevant brain region did not have the same interfering effect on generalization. Performance on an additional attentional task showed that rTMS on the same parietal site hindered participants ability to integrate what (stimulus identity) and when (stimulus timing) information about an expected target. The present findings suggest that learning rules from speech is a two-stage process: following statistical learning, goal-directed attention -involving left parietal regions- integrates what and when stimulus information to facilitate rapid rule generalization.

neuroscience↗

bioRxiv2019

Characteristic sounds facilitate object search in real-life scenes

Real-world multisensory events do not only provide temporally and spatially correlated information, but also semantic correspondences about object identity. Semantically consistent sounds can enhance visual detection, identification and search performance, but these effects are always demonstrated in simple and stereotyped displays that lack ecological validity. In order to address identity-based crossmodal relationships in real world scenarios, we designed a visual search task using complex, dynamic scenes. Participants searched objects in video clips from real life scenes with background sounds. Auditory cues embedded in the background sounds could be target-consistent, distracter-consistent, neutral and no sound (just background noise). We found that characteristic sounds enhance visual search of relevant objects in natural scenes but fail to increase the salience of irrelevant distracters. Our findings generalize previous results on object-based crossmodal interactions with simple stimuli and shed light upon how audio-visual semantically congruent relationships play out in real life contexts.

neuroscience↗