Biology subjects

Spagna, A.

Publications and source records attributed to Spagna, A..

8 recordsLinked to original sources

bioRxiv2025

Right-hemisphere frontoparietal oscillations precede conscious report of visual targets.

What neural events precede conscious reports? Hemisphere-asymmetric attentional networks are causally related to conscious perception (Bartolomeo et al., 2025; Kaufmann et al., 2024), but their spectrotemporal dynamics remain unclear. Here, we used magnetoencephalography to examine brain oscillations occurring in human participants (male and female) before a near-threshold target during the cue-target period. In 67% of trials, a supra-threshold visual cue appeared near the target placeholder box, indicating that the target would appear at that location (valid condition). In the remaining 33% of trials, the target appeared at the opposite location (invalid condition). We analyzed brain oscillations, coherence, and theta-gamma phase-amplitude (PAC) coupling in 18 regions of interest involved in attentional and perception (Martin-Signes et al., 2024). Results revealed that: (1) Report of validly cued targets was preceded by early ([~]58 ms post-cue) beta-band activity in the right-hemisphere superior parietal lobule. (2) Report of invalidly cued targets was preceded by late ([~]166 ms post-cue) beta-band activity in the right temporo-occipital (TO) region, PAC in the right lateral visual cortex, and low gamma coherence between this region and the left temporo-parietal junction, (3) Unreported invalidly cued targets were preceded by PAC in the right TO, and by high gamma coherence between this region and the right middle frontal gyrus suggesting a pre-target bias. We show that conscious report is preceded by temporally dissociable, frequency-specific reconfigurations of right-lateralized attentional networks, with an early parietal beta-mediated orienting window and a later ventral beta- and gamma-mediated window that predict conscious reports before target onset. Significance statementConscious perception depends not only on sensory signals, but also on how attentional networks prepare the brain in advance. Using MEG and a spatial cueing task with near-threshold targets, we show distinct right-hemisphere beta- and gamma-band dynamics predicting whether an upcoming stimulus will be reported or missed. Validly cued reports rely on early beta activity in the right superior parietal lobule, whereas invalid reports and omission errors are linked to later beta activity in the right temporo-occipital region, early theta-gamma coupling between this region and the right middle frontal gyrus, and theta-gamma phase-amplitude coupling. These findings reveal hemisphere-asymmetric spectrotemporal signatures by which attention biases predictive processing and shapes the conscious report of future stimuli, informing theories of conscious perception.

neuroscience↗

bioRxiv2023

Present: flexible neuroscience- and technology-driven frameworks for the study of classroom engagement

Classroom engagements impact on academic success is crucial. However, the contributions of affective, cognitive, and behavioral components of engagement remain uncertain. We conducted two studies using non-invasive, research-based approaches to clarify these contributions. Study 1 employed portable EEG headsets to measure cognitive engagement, in-class quizzes assessed content retention, and post-class subjective questionnaires indexed affective engagement by measuring feelings of learning and engagement. Content retention predicted subjective measures, while the EEG theta/beta ratio was negatively related to content retention but positively related to subjective measures. Study 2 featured embedded measures of content retention, confidence, engagement, background knowledge, and indexed behavioral engagement looking at nonverbal behavior quantified via video camera recordings. Confidence and engagement were significantly correlated with each other and with particular facial muscle, gaze direction, and head pose movements. We discuss how these approaches enable real-time studies of classroom engagement and can be integrated to develop neurofeedback interventions.

neuroscience↗

bioRxiv2023

Ultra-high field fMRI of visual mental imagery in typical imagers and aphantasic individuals

Most of us effortlessly describe visual objects, whether seen or remembered. Yet, around 4% of people report congenital aphantasia: they struggle to visualize objects despite being able to describe their visual appearance. What neural mechanisms create this disparity between subjective experience and objective performance? Aphantasia can provide novel insights into conscious processing and awareness. We used ultra-high field 7T fMRI to establish the neural circuits involved in visual mental imagery and perception, and to elucidate the neural mechanisms associated with the processing of internally generated visual information in the absence of imagery experience in congenital aphantasia. Ten typical imagers and 10 aphantasic individuals performed imagery and perceptual tasks in five domains: object shape, object color, written words, faces, and spatial relationships. In typical imagers, imagery tasks activated left-hemisphere frontoparietal areas, the relevant domain-preferring areas in the ventral temporal cortex partly overlapping with the perceptual domain-preferring areas, and a domain-general area in the left fusiform gyrus (the Fusiform Imagery Node). The results were valid for each individual participant. In aphantasic individuals, imagery activated similar visual areas, but there was reduced functional connectivity between the Fusiform Imagery Node and frontoparietal areas. Our results unveil the domain-general and domain-specific circuits of visual mental imagery, their functional disorganization in aphantasia, and support the general hypothesis that conscious visual experience - whether perceived or imagined - depends on the integrated activity of high-level visual cortex and frontoparietal networks.

neuroscience↗

bioRxiv2022

The Interplay of Attention and Conscious Perception: Evidence from Human Intracerebral Recordings and Computational Modeling

How do attention and consciousness interact in the human brain? Rival theories of consciousness disagree on the role of fronto-parietal attentional networks in conscious perception. We recorded neural activity from 727 intracerebral contacts in 13 epileptic patients, while they detected near-threshold targets preceded by attentional cues. Unsupervised clustering revealed three patterns: (1) Attention-enhanced conscious report accompanied sustained right-hemisphere fronto-temporal activity, in networks connected by the superior longitudinal fasciculus (SLF) II-III, and late accumulation in bilateral dorso-prefrontal and right-hemisphere orbitofrontal cortex (SLF I-III). (2) Attentional reorienting affected conscious report through early, sustained activity in a right-hemisphere network (SLF III). (3) Conscious report accompanied left-hemisphere dorsolateral-prefrontal activity. Task modeling with recurrent neural networks identified specific excitatory and inhibitory interactions between attention and consciousness, and their causal contribution to conscious perception of near-threshold targets. Thus, distinct, hemisphere-asymmetric fronto-parietal networks support attentional gain and reorienting in shaping human conscious experience. One-Sentence SummaryIntracerebral recordings, tractography and modeling reveal the interaction of attention and consciousness in the human brain.

neuroscience↗

bioRxiv2020

Distinct Contributions of Nonpredictive and Predictive Peripheral Cues to Visual Conscious Perception: an MEG study

How do attentional networks influence conscious perception? To answer this question, we used magnetoencephalography (MEG) in human participants, and assessed the effects of spatially nonpredictive or predictive supra-threshold peripheral cues on the conscious perception of near-threshold Gabors. Three main results emerged. (1) As compared with invalid cues, both nonpredictive and predictive valid cues increased conscious detection. Yet, only predictive cues shifted the response criterion towards a more liberal decision (i.e., willingness to report the presence of a target under conditions of greater perceptual uncertainty) and affected target contrast leading to 50% detections. (2) Conscious perception following valid predictive cues was associated to enhanced activity in frontoparietal networks. These responses were lateralized to the left hemisphere during attentional orienting, and to the right hemisphere during target processing. The involvement of frontoparietal networks occurred earlier in valid than in invalid trials, a possible neural marker of the cost of re-orienting attention. (3) When detected targets were preceded by invalid predictive cues, and thus reorienting to the target was required, neural responses occurred in left hemisphere temporo-occipital regions during attentional orienting, and in right hemisphere anterior insular and temporo-occipital regions during target processing. These results confirm and specify the role of frontoparietal networks in modulating conscious processing, and detail how invalid orienting of spatial attention disrupts conscious processing. Significance StatementDo we need to pay attention to external objects in order to become aware of them? Characterizing the spatiotemporal dynamics of attentional effects on visual perception is critical to understand how humans process and select relevant information. Participants detected near-threshold visual targets preceded by supra-threshold spatial cues with varying degrees of predictivity, while their brain activity was recorded using magnetoencephalography. Results demonstrated that valid predictive cues biased participants conscious perception through an early recruitment of frontoparietal regions, and that attentional costs associated to invalid predictive cues were related to activation of the right hemisphere ventral network. This work characterizes the neural dynamics associated with the cost of attentional reorienting on conscious processing.

neuroscience↗

bioRxiv2020

Supramodal executive control of attention: evidence from unimodal and crossmodal dual conflict effects

Although we have demonstrated that the executive control of attention acts supramodally as shown by significant correlation between conflict effects measures in visual and auditory tasks, no direct evidence of the equivalence in the computational mechanisms governing the allocation of executive control resources within and across modalities has been found. Here, in two independent groups of 40 participants, we examined the interaction effects of conflict processing in both unimodal (visual) and crossmodal (visual and auditory) dual-conflict paradigms (flanker conflict processing in Task 1 and then in the following Task 2) with a manipulation of the stimulus onset asynchrony (SOA). In both the unimodal and the crossmodal dual-conflict paradigms, the conflict processing of Task 1 interfered with the conflict processing of Task 2 when the SOA was short, reflecting an additive interference effect of Task 1 on Task 2 under the time constraints. These results suggest that there is a unified entity that oversees conflict processing acting supramodally by implementing comparable mechanisms in unimodal and crossmodal scenarios.

neuroscience↗

bioRxiv2020

Visual mental imagery engages the left fusiform gyrus, but not the early visual cortex: a meta-analysis of neuroimaging evidence

The dominant neural model of visual mental imagery (VMI) stipulates that memories from the medial temporal lobe acquire sensory features in early visual areas. However, neurological patients with damage restricted to the occipital cortex typically show perfectly vivid VMI, while more anterior damages extending into the temporal lobe, especially in the left hemisphere, often cause VMI impairments. Here we present two major results reconciling neuroimaging findings in neurotypical subjects with the performance of brain-damaged patients: (1) a large-scale metaanalysis of 46 fMRI studies, of which 27 investigated specifically visual mental imagery, revealed that VMI engages fronto-parietal networks and a well-delimited region in the left fusiform gyrus. (2) A Bayesian analysis showing no evidence for imagery-related activity in early visual cortices. We propose a revised neural model of VMI that draws inspiration from recent cytoarchitectonic and lesion studies, whereby fronto-parietal networks initiate, modulate, and maintain activity in a core temporal network centered on the fusiform imagery node, a high-level visual region in the left fusiform gyrus.

neuroscience↗

bioRxiv2018

Right hemisphere superiority for executive control of attention

Over forty years have passed since the first evidence showing the unbalanced attentional allocation of humans across the two visual fields, and since then, a wealth of behavioral, neurophysiological, and clinical data increasingly showed a right hemisphere dominance for orienting of attention. However, inconsistent evidence exists regarding the right-hemisphere dominance for executive control of attention, possibly due to a lack of consideration of its dynamics with the alerting and orienting functions. In this study, we used a version of the Attentional Network Test with lateralized presentation of the stimuli to the left visual field (processed by the right hemisphere, RH) and right visual field (processed by the left hemisphere, LH) to examine visual field differences in executive control of attention under conditions of alerting or orienting. Analyses of behavioral performance (reaction time and error rate) showed a more efficient executive control (reduced conflict effect) in the RH compared to the LH for the reaction time, under conditions of increased alerting and of informative spatial orienting. These results demonstrate the right-hemisphere superiority for executive control, and that this effect depends on the activation of the alerting and orienting functions.

neuroscience↗