Biology subjects

Moisa, M.

Publications and source records attributed to Moisa, M..

6 recordsLinked to original sources

bioRxiv2025

Risk preferences causally rely on parietal magnitude representations: Evidence from combined TMS-fMRI

Risk preferences have traditionally been considered as stable traits that reflect subjective-valuation processes in prefrontal areas. More recently, however, it has been suggested that risk preferences may also be shaped by how choice problems are perceived and processed in perceptual brain regions. Specifically, the acuity of the parietal approximate number system (ANS), which encodes payoff magnitudes for different choice options, has been shown to correlate with both risk preferences and choice consistency. However, this correlational relationship leaves open the question whether parietal magnitude representations in fact causally underlie choice. Here, we provide direct evidence for such a key causal role of parietal magnitude representations in economic choice, using continuous theta-burst transcranial magnetic stimulation (cTBS), combined with functional MRI (fMRI) and numerical population receptive field (nPRF) modeling. Our stimulation protocol targeted numerosity-tuned regions in the right parietal cortex, identified through nPRF modeling of individual fMRI data (n=35; within-subject design). The stimulation successfully perturbed neural processing, as evidenced by decreased amplitude of numerical magnitude-tuned responses and less accurate multivariate decoding of presented magnitudes from unseen data that were not used for model fitting. In line with a perceptual account of risky choice, the reduction in neural information capacity was also reflected in noisier behavioral responses. Moreover, a computational cognitive model fitted to choice behavior revealed that perturbing the ANS specifically increased the noisiness of small-magnitude representations. This perturbation made small magnitudes to be perceived as larger than they actually are, leading to more risk-seeking behavior. Finally, individual estimates of the cTBS effect on cognitive noise correlated with the corresponding decrease in amplitude of numerical magnitude-tuned fMRI responses, further solidifying the role of the parietal ANS in economic choice. In conclusion, our study demonstrates that the precision of parietal magnitude representations causally influences economic decision-making, with noisier encoding promoting biased risk-taking as formalized in recent perceptual models of risky choice.

neuroscience↗

bioRxiv2024

Enhancing altruism by electrically augmenting frontoparietal gamma-band phase coupling

Cooperation, productivity, and cohesion in human societies depend on altruism, the tendency to share resources with others even though this is costly. While altruism is a widely shared social norm, people vary strongly in their inclination to behave altruistically, in particular across situations with different types of inequality in resource distribution. What neurobiological factors underlie this variability? And can these be targeted by interventions to enhance altruistic behavior? Here, we build on recent EEG findings that altruistic choices during disadvantageous inequality correlate with oscillatory gamma-band coherence between frontal regions (representing others interest) and parietal regions (representing neural evidence accumulation). We apply a transcranial alternating current stimulation (tACS) protocol designed to exogenously enhance this fronto-parietal coherence and find that this leads to increased altruism, specifically during disadvantageous inequality as hypothesized based on the EGG findings. Computational modeling reveals that this transcranial entrainment does not just add noise to the decision process but specifically increases the weight individuals assign to other-regarding concerns during choices. Our findings show that altruism can be enhanced by neurostimulation designed to enhance oscillatory synchronization between frontal and parietal areas. This establishes a neural basis for altruism and identifies a neural target for interventions aimed at improving prosocial behavior.

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bioRxiv2021

Disrupting inferior frontal cortex activity alters affect decoding efficiency from clear but not from ambiguous affective speech

The evaluation of socio-affective sound information is accomplished by the primate auditory cortex in collaboration with limbic and inferior frontal cortex (IFC)--often observed during affective voice classification. Partly opposing views have been proposed, with IFC either coding cognitive processing challenges in case of sensory ambiguity or representing categorical object and affect information for clear voices. Here, we presented clear and ambiguous affective speech to two groups of human participants during neuroimaging, while in one group we inhibited right IFC activity with transcranial magnetic stimulation. IFC activity inhibition led to faster affective decisions, more accurate choice probabilities, reduced auditory cortical activity and increased fronto-limbic connectivity for clear affective speech. This indicates a more intermediate functional property of the IFC than assumed--namely with normal activity representing a more deliberate form of affective sound processing (i.e., enforcing cognitive analysis) that flags categorical sound decisions with precaution (i.e., representation of categorical uncertainty). TeaserInferior frontal cortex enforces cognitive analyses during affect decisions with different levels of sensory ambiguity.

neuroscience↗

bioRxiv2021

Causal evidence for a domain-specific role of left superior frontal sulcus in human perceptual decision-making

Humans and animals can flexibly choose their actions based on different information, ranging from objective states of the environment (e.g., apples are bigger than cherries) to subjective preferences (e.g., cherries are tastier than apples). Whether the brain instantiates these different choices by recruiting either specialised or shared neural circuitry remains debated. Specifically, domain-general accounts of prefrontal cortex (PFC) function propose that prefrontal areas flexibly process either perceptual or value-based evidence depending on what is required for the present choice, whereas domain-specific theories posit that PFC sub-areas, such as the left superior frontal sulcus (SFS), selectively integrate evidence relevant for perceptual decisions. Here we comprehensively test the functional role of the left SFS for choices based on perceptual and value-based evidence, by combining fMRI with a behavioural paradigm, computational modelling, and transcranial magnetic stimulation. Confirming predictions by a sequential sampling model, we show that TMS-induced excitability reduction of the left SFS selectively changes the processing of decision-relevant perceptual information and associated neural processes. In contrast, value-based decision making and associated neural processes remain unaffected. This specificity of SFS function is evident at all levels of analysis (behavioural, computational, and neural, including functional connectivity), demonstrating that the left SFS causally contributes to evidence integration for perceptual but not value-based decisions.

neuroscience↗

bioRxiv2018

Shared neural mechanisms between imagined and perceived egocentric motion

Many cognitive and social processes involve mental simulations of a change in perspective. Behavioral studies suggest that such egocentric mental rotations rely on brain areas that are also involved in processing actual self-motion, thus depending on vestibular input. In a combined galvanic vestibular stimulation (GVS) and functional Magnetic Resonance Imaging (fMRI) study, we investigated the brain areas that underlie both simulated changes in self-location and the processing of vestibular stimulation within the same individuals. Participants performed an egocentric mental rotation task, an object-based mental rotation task, or a pure lateralization task during GVS or sham stimulation. At the neural level, we expected an overlap between brain areas activated during vestibular processing and egocentric mental rotation (against object-based mental rotation) within area OP2 and the Posterior Insular Cortex (PIC), two core brain regions involved in vestibular processing. The fMRI data showed a small overlap within area OP2 and a larger overlap within the PIC for both egocentric mental rotation against object-based mental rotation and vestibular processing. GVS did not influence the ability to perform egocentric mental rotation.\n\nOur results provide evidence for shared neural mechanisms underlying perceived and simulated self-motion. We conclude that mental rotation of ones body involves neural activity in the PIC and area OP2, but the behavioral results also suggest that those mental simulations of ones body might be robust to modulatory input from vestibular stimulation.

neuroscience↗

bioRxiv2017

Concurrent tACS-fMRI Reveals Causal Influence Of Power Synchronized Neural Activity On Resting State fMRI Connectivity

Resting state fMRI (rs-fMRI) is commonly used to study the brains intrinsic neural coupling, which reveals specific spatiotemporal patterns in the form of resting state networks (RSN). It has been hypothesized that slow rs-fMRI oscillations (<0.1 Hz) are driven by underlying electrophysiological rhythms that typically occur at much faster timescales (>5 Hz); however, causal evidence for this relationship is currently lacking. Here we measured rs-fMRI in humans while applying transcranial alternating current stimulation (tACS) to entrain brain rhythms in left and right sensorimotor cortices.\n\nThe two driving tACS signals were tailored to the individuals alpha rhythm (8-12 Hz) and fluctuated in amplitude according to a 1 Hz power envelope. We entrained the left versus right hemisphere in accordance to two different coupling modes where either alpha oscillations were synchronized between hemispheres (phase-synchronized tACS) or the slower oscillating power envelopes (power-synchronized tACS).\n\nPower-synchronized tACS significantly increased rs-fMRI connectivity within the stimulated RSN compared to phase-synchronized or no tACS. This effect outlasted the stimulation period and tended to be more effective in individuals who exhibited a naturally weak interhemispheric coupling. Using this novel approach, our data provide causal evidence that synchronized power fluctuations contribute to the formation of fMRI-based RSNs. Moreover, our findings demonstrate that the brains intrinsic coupling at rest can be selectively modulated by choosing appropriate tACS signals, which could lead to new interventions for patients with altered rs-fMRI connectivity.\n\nSignificance StatementResting state fMRI has become an important tool to estimate brain connectivity. However, relatively little is known about how slow hemodynamic oscillations measured with fMRI relate to electrophysiological processes.\n\nIt was suggested that slowly fluctuating power envelopes of electrophysiological signals synchronize across brain areas and that the topography of this activity is spatially correlated to resting state networks derived from rs-fMRI. Here we take a novel approach to address this problem and establish a causal link between the power fluctuations of electrophysiological signals and rs-fMRI via a new neuromodulation paradigm, which exploits these power-synchronization mechanisms.\n\nThese novel mechanistic insights bridge different scientific domains and are of broad interest to researchers in the fields of Medical Imaging, Neuroscience, Physiology and Psychology.

neuroscience↗