Biology subjects

Senoussi, M.

Publications and source records attributed to Senoussi, M..

11 recordsLinked to original sources

bioRxiv2026

Parallel control of conjunctive and compositional representations supports dynamic task preparation

People can dynamically and adaptively update task goals in the face of task uncertainty. In this fMRI study, we aimed to investigate the modulation of neural task representations that subserve such flexible task control. On each trial, we asked people to perform one of nine image categorization tasks. During task preparation, participants had to actively infer varying levels of task uncertainty and dynamically modulate their task preparation accordingly. Multivariate pattern analyses demonstrated dissociable uncertainty-driven modulations of conjunctive and compositional task representations in the right frontoparietal network. Specifically, different sub-regions showed diminished conjunctive task representations when task uncertainty increased during task preparation. At the same time, we observed an active maintenance of compositional task representations, suggesting an adaptive cognitive strategy in facilitating compositional task reconfiguration. These findings suggest a mechanism of parallel control on conjunctive and compositional representations that allows for maximizing the advantages of both representational formats, offering new insights into the neural mechanisms underpinning human flexible task preparation.

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bioRxiv2025

Rhythmicity Revisited: Evidence from Robust Behavioral Oscillations

Rhythmic fluctuations in neuronal excitability, called neural oscillations, pervade brain activity. If these oscillations have a functional role in behavior, they should also be expressed in a behavioral signature. However, identifying such a behavioral signature has remained controversial: evidence for behavioral oscillations is not yet firmly established, and aperiodic components can be misidentified as rhythmic. To test their existence while controlling for aperiodic dynamics, we applied a state-of-the-art autoregressive (AR) approach on two datasets: one published dataset, and a new dataset collected with a revised dense-sampling design. In both datasets, AR modeling recovered reliable behavioral oscillations in the theta band. Reanalyses of the published dataset also reproduced the reported theta shift with task demands, with more difficult tasks showing slower theta. In contrast, despite clear rhythmicity, the new dataset showed no consistent frequency shift across conditions. Overall, this study establishes rigorous and robust detection of behavioral oscillations. It also suggests that the frequency modulation of behavioral oscillations by task difficulty requires further study.

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bioRxiv2025

Theta-rhythmic attentional exploration of space

Attention facilitates stimulus processing by selecting specific locations (spatial attention) or features (feature-based attention). It can be sustained on a given location or feature, or re-oriented between locations or between features, enabling attentional exploration. Sustained attention was associated with alpha (8-12Hz1-4) oscillations. More recently, authors suggested that exploratory attention was instead related to theta (4-7Hz; for review5-7). To date, there is no systematic evaluation of attentional exploration across stimulus dimensions (space, features) in relation to theta oscillations. Using attentional cueing and electroencephalography (EEG) in humans, we assessed exploration of stimulus dimension during the (1) precue-to-stimulus (first attentional orienting) and (2) post-stimulus (during stimulus processing) trial periods. In the precue-to-stimulus period, we classified the cued dimension (attending to a location/feature) from EEG topographies to assess the neural dynamics of sustained and exploratory attentional orienting. Temporal generalization matrices showed oscillatory patterns of classification accuracies across time. When attention was sustained on a cued location but explored the feature dimension as the target feature was unknown, only the alpha frequency was observed. When attention was sustained on a cued feature but explored locations, both alpha and theta frequencies were observed. Focusing on post-stimulus theta oscillations revealed increased theta power in invalid trials (attention reorients from the precued distractor location/feature to the target -exploration) relative to valid trials in both feature-based and spatial attention conditions. Post-stimulus theta oscillations further predicted behavioral performance. Together, our results show that while alpha oscillations are associated with sustained attention regardless of the attended dimension, theta oscillations are specifically related to spatial exploration.

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bioRxiv2022

Theta-phase connectivity between medial prefrontal and posterior areas underlies novel instructions implementation

Implementing novel instructions is a complex and uniquely human cognitive ability, that requires the rapid and flexible conversion of symbolic content into a format that enables the execution of the instructed behavior. Preparing to implement novel instructions, as opposed to their mere maintenance, involves the activation of the instructed motor plans, and the binding of the action information to the specific context in which this should be executed. Recent evidence and prominent computational models suggest that this efficient configuration of the system might involve a central role of frontal theta oscillations in establishing top-down long-range synchronization between distant and task-relevant brain areas. In the present EEG study (human subjects, 30 females, 4 males), we demonstrate that proactively preparing for the implementation of novels instructions, as opposed to their maintenance, involves a strengthened degree of connectivity in the theta frequency range between medial prefrontal and motor/visual areas. Moreover, we replicated previous results showing oscillatory features associated specifically with implementation demands, and extended on them demonstrating the role of theta oscillations in mediating the effect of task demands on behavioral performance. Taken together, these findings support our hypothesis that the modulation of connectivity patterns between frontal and task-relevant posterior brain areas is a core factor in the emergence of a behavior-guiding format from novel instructions. Significance statementEveryday life requires the use and manipulation of currently available information to guide behavior and reach specific goals. In the present study we investigate how the same instructed content elicits different neural activity depending on the task being performed. We show that medial prefrontal theta oscillations are larger when novel instructions have to be implemented, rather than simply maintained. Crucially, connectivity between medial prefrontal cortex and posterior areas is strengthened during instructions implementation, suggesting that theta oscillations play a role in setting up a dynamic and flexible network of task-relevant regions optimized for the execution of the instructed behavior.

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bioRxiv2021

Time-based binding as a solution to and a limitation for flexible cognition

Why cant we keep as many items as we want in working memory? It has long been debated whether this resource limitation is a bug (a downside of our fallible biological system) or instead a feature (an optimal response to a computational problem). We propose that the resource limitation is a consequence of a useful feature. Specifically, we propose that flexible cognition requires time-based binding, and time-based binding necessarily limits the number of (bound) memoranda that can be stored simultaneously. Time-based binding is most naturally instantiated via neural oscillations, for which there exists ample experimental evidence. We report simulations that illustrate this theory and that relate it to empirical data. We also compare the theory to several other (feature and bug) resource theories.

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bioRxiv2020

Anticipatory reinstatement of expected perceptual events during visual sequence learning

Being able to predict future events in learned sequences is a fundamental cognitive ability. Successful behavior requires the brain to not only anticipate an upcoming event, but to also continue to keep track of the sequence in case of eventual disruptions, (e.g., when a predicted event does not occur). However, the precise neural mechanisms supporting such processes remain unknown. Here, using multivariate pattern classification based on electroencephalography (EEG) activity and time-frequency amplitude, we show that the visual system represents upcoming expected stimuli during a sequence-learning task. Stimulus-evoked neural representations were reinstated prior to expected stimulus onset, and when an anticipated stimulus was unexpectedly withheld, suggesting proactive reinstatement of sensory templates. Importantly, stimulus representation of the absent stimulus co-occurred with an emerging representation of the following stimulus in the sequence, showing that the brain actively maintained sequence order even when the sequence was perturbed. Finally, selective activity was evident in the alpha-beta band (9-20 Hz) amplitude topographies, confirming the role of alpha-beta oscillations in carrying information about the nature of sensory expectations. These results show that the brain dynamically implements anticipatory mechanisms that reinstate sensory representations, and that allow us to make predictions about events further in the future.

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bioRxiv2020

Language network connectivity increases in prodromal Alzheimer's disease

Language production deficits occur early in the course of Alzheimers disease (AD); however, only few studies have focused on language functional networks in prodromal AD. The current study aims to uncover the extent of language alteration at a prodromal stage, on a behavioral, structural and functional level, using univariate and multivariate analyses. Twenty-four AD participants and 24 matched healthy controls underwent a comprehensive language evaluation, a structural T1-3D MRI and resting-state fMRI. We performed seed-based analyses, using the left inferior frontal gyrus and left posterior temporal gyrus as seeds. Then, we analyzed connectivity between executive control networks and language network in each group. Finally, we used multivariate pattern analyses to test whether the two groups could be distinguished based on the pattern of atrophy within the language network; atrophy within the executive control networks, as well as the pattern of functional connectivity within the language network; and functional connectivity within executive control networks. AD participants had language impairment during standardized language tasks and connected-speech production. Univariate analyses were not able to discriminate participants at this stage, while multivariate pattern analyses could significantly predict the group membership of prodromal patients and healthy controls, both when classifying atrophy patterns or connectivity patterns of the language network. Language functional networks could discriminate AD participants better than executive control networks. Most notably, they revealed an increased connectivity at a prodromal stage. Multivariate analyses represent a useful tool for investigating the functional and structural (re-)organization of the neural bases of language. HighlightsLanguage network connectivity discriminates prodromal AD from healthy controls Language network connectivity increases in prodromal AD Atrophy patterns in the language network do not correlate with connectivity patterns in AD

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bioRxiv2020

Neural representations of task context and temporal order during action sequence execution

Since routine action sequences can share a great deal of similarity in terms of their stimulus response mappings, their correct execution relies crucially on the ability to preserve contextual and temporal information (Lashley, 1951). However, there are few empirical studies on the neural mechanism and the brain areas maintaining such information. To address this gap in the literature, we recently recorded the blood-oxygen level dependent (BOLD) response in a newly developed coffee-tea making task (Holroyd et al., 2018). The task involves the execution of 4 action sequences that each feature 6 decision states. Here we report a reanalysis of this dataset using a data-driven approach, namely multivariate pattern analysis (MVPA), that examines context-dependent neural activity across several predefined regions of interest. Results highlight involvement of the inferior-temporal gyrus and lateral prefrontal cortex in maintaining temporal and contextual information for the execution of hierarchically-organized action sequences. Furthermore, temporal information seems to be more strongly encoded in areas over the left hemisphere.

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bioRxiv2020

Theta oscillations shift towards optimal frequency for cognitive control

Cognitive control is supported by theta band (4-7Hz) neural oscillations coordinating neural populations for task implementation. Task performance has been shown to depend on theta amplitude but a second critical aspect of theta oscillations, its peak frequency, has mostly been overlooked. Using modelling, behavioral and electrophysiological recordings, we show that theta oscillations adapt to task demands by shifting towards the optimal frequency.

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bioRxiv2020

NEURAL OSCILLATIONS DISSOCIATE BETWEEN MAINTENANCE AND PROCEDURALIZATION OF NOVEL INSTRUCTIONS

Humans are capable of flexibly converting symbolic instructions into novel behaviors. Previous evidence and theoretical models suggest that the implementation of a novel instruction requires the reformatting of its declarative content into an action-oriented code optimized for the execution of the instructed behavior. While neuroimaging research focused on identifying the brain areas involved in such a process, the temporal and electrophysiological mechanisms remain poorly understood. These mechanisms, however, can provide information about the specific cognitive processes that characterize the proceduralization of information. In the present study, we recorded EEG activity while we asked participants to either simply maintain declaratively the content of novel S-R mappings or to proactively prepare for their implementation. By means of time-frequency analyses, we isolated the oscillatory features specific to the proceduralization of instructions. Implementation of the instructed mappings elicited stronger theta activity over frontal electrodes and suppression in mu and beta activity over central electrodes. On the contrary, activity in the alpha band, which has been shown to track the attentional deployment to task-relevant items, showed no differences between tasks. Together, these results support the idea that proceduralization of information is characterized by specific component processes such as orchestrating complex task settings and configuring the motor system that are not observed when instructions are held in a declarative format. HighlightsO_LIFrontal theta power is increased during instructions implementation C_LIO_LIAttentional orienting in WM is analogous across maintenance and implementation C_LIO_LIInstructions implementation involves motor recruitment C_LI

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bioRxiv2018

Attention explores space periodically at the theta frequency

Voluntary attention is at the core of cognitive functions. Attention can be sustained at a location, or reoriented in space to allow processing at other locations, critical in an ever-changing environment. Numerous studies have investigated attentional orienting in time and space but little is known about the spatio-temporal dynamics of attentional reorienting. Here, we explicitly manipulated attentional reorienting using a cueing procedure in a 2-AFC orientation discrimination task. At various delays during the task, we interrogated attentional deployment by flashing two probe stimuli. Then, solving a second-degree equation to estimate the report probability at each probe location, we demonstrated that attention reorients periodically at ~4 Hz (theta) between the two stimulus locations. We further observed that each stimulus location is sampled at ~11 Hz (alpha). Finally, we support our mathematical approach using simulations and show that this method is sufficiently powered making it a valuable tool for studying the spatio-temporal dynamics of attention.

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