Biology subjects

Ruiz, M. H.

Publications and source records attributed to Ruiz, M. H..

3 recordsLinked to original sources

bioRxiv2024

Cardiac Cycle Modulates Alpha and Beta Suppression during Motor Imagery.

IntroductionThe baroreceptor hypothesis posits that baroreceptors, located on the cardiac walls, are most active during systole, translating cardiac contraction information to the brain. Studies within this context have suggested that the systolic phase, characterised by increased noise, may compromise the processing of sensory stimuli. Although the effect of systolic and diastolic cardiac cycle phases on cognition, perception, and action has been widely documented, there remains a gap in applying these interoceptive insights to enhance assistive technologies such as brain-computer interfaces (BCIs). In the context of BCIs, motor imagery (MI) --the mental rehearsal of movement--serves as a widely used control paradigm, yet its modulation through the cardiac cycle has not been empirically tested. Bridging this gap, this study examined how the cardiac cycle phases influence MI by assessing their effect on contralateral suppression of alpha (8-13 Hz) and beta (14-30 Hz) activity in primary sensorimotor cortices. Materials & MethodsTwenty-nine participants performed left/right thumb abductions based on the direction of an arrow presented on the screen to get familiarised with kinesthetic sensations. They then completed a MI task of the same movements. We recorded both electroencephalography (EEG) and electrocardiography (ECG), focusing our analysis on data epochs aligned with the experimental cue, based on whether it occurred during the systolic or diastolic phase of the cardiac cycle. Time-frequency analysis of source-reconstructed data assessed cue-induced changes in power spectral density (PSD) within the alpha and beta bands in the postcentral and precentral gyrus. ResultsWe found that alpha and beta suppression in the contralateral primary motor and somatosensory cortex was more pronounced when the cue fell during the diastolic phase of the cardiac cycle than during the systolic phase. Validating the main results, an analysis with circular statistics revealed that trials with particularly pronounced contralateral alpha and beta suppression featured cues with latencies clustering during diastole, the quietest time of the cardiac cycle. Accompanying the EEG effects, EMG activity on the side of the movement was enhanced during diastole. ConclusionThese findings provide evidence that MI performance can be enhanced by considering the cardiac cycle phases, offering promising implications for BCI-based applications. O_LIKey point 1: The phases of the cardiac cycle influence motor imagery performance. C_LIO_LIKey point 2: Alpha and beta contralateral suppression over sensorimotor cortices is more pronounced when movement direction is cued during diastole. C_LIO_LIKey point 3: Contralateral suppression is more likely to cluster during the quietest time of the diastolic phase: between the T-wave and the P-wave. C_LI

neuroscience↗

bioRxiv2024

Frequency-specific changes in prefrontal activity associated with maladaptive belief updating in volatile environments in euthymic bipolar disorder

Bipolar disorder (BD) involves altered reward processing and decision-making, with inconsistencies across studies. Here, we integrated hierarchical Bayesian modelling with magnetoencephalography (MEG) to characterise maladaptive belief updating in this condition. First, we determined if previously reported increased learning rates in BD stem from a heightened expectation of environmental changes. Additionally, we examined if this increased expectation speeds up belief updating in decision-making, associated with modulation of rhythmic neural activity within the prefrontal, orbitofrontal, and anterior cingulate cortex (PFC, OFC, ACC). Twenty-two 22 euthymic BD and 27 healthy control (HC) participants completed a reward-based motor decision-making task in a volatile setting. Hierarchical Bayesian modelling revealed BD participants anticipated greater environmental volatility, resulting in a more stochastic mapping from beliefs to actions and paralleled by lower win rates and a reduced tendency to repeat rewarded actions than HC. Despite this, BD individuals adjusted their expectations of action-outcome contingencies more slowly, but both groups invigorated their actions similarly. On a neural level, while healthy individuals exhibited an alpha-beta suppression and gamma increase during belief updating, BD participants showed dampened effects, extending across the PFC, OFC, and ACC regions. This was accompanied by an abnormally increased beta-band directed information flow in BD. Overall, the results suggest euthymic BD individuals anticipate environmental change without adequately learning from it, contributing to maladaptive belief updating. Alterations in frequency-domain amplitude and functional connectivity within the PFC, OFC, and ACC during belief updating underlie the computational effects and could serve as potential indicators for predicting relapse in future research.

neuroscience↗

bioRxiv2022

Modulation of motor vigour by expectation of reward probability trial-by-trial is preserved in healthy ageing and Parkinson's disease patients

Motor improvements, such as faster movement times or increased velocity, have been consistently associated with reward magnitude in deterministic contexts. Yet whether individual inferences on reward probability influence motor vigour dynamically remains undetermined. Here we investigated how dynamically inferring volatile action-reward contingencies modulated motor performance trial-by-trial in healthy younger (HYA, 37) and older adults (HOA, 37), and in medicated Parkinsons Disease patients (PD, 20). We conducted an online study that coupled a standard one-armed bandit decision-making paradigm with a motor sequence task and used a validated hierarchical Bayesian model to fit trial-by-trial data. Our results showed that stronger predictions about the tendency of the action-reward contingency led to faster performance tempo on a trial-by-trial basis without modulating reaction times (RT). Using Bayesian linear mixed models, we demonstrated in HYA, HOA and PD a similar sensitivity (slope) of execution tempo to inferences about the reward probabilities, despite HOA and PD being generally slower than HYA (intercept). In a second experiment in HYA (39), we additionally showed that subjective inferences about credit assignment - whether lack of reward is associated with an incorrect decision or execution error - led to a similar modulation of motor vigour by reward expectation. Our study is the first to reveal that the dynamic updating of beliefs about volatile action-reward contingencies positively biases motor performance through faster execution tempo, without affecting RT. We also provide novel evidence for a preserved sensitivity of motor vigour to inferences about the action-reward mapping in ageing and medicated PD. SIGNIFICANCE STATEMENTNavigating a world rich in uncertainty relies on updating beliefs about the probability that our actions lead to reward. Here we investigated how inferring the action-reward contingencies in a volatile environment modulated motor vigour trial-by-trial in healthy younger and older adults, and in Parkinsons Disease patients on medication. We found an association between trial- by-trial predictions about the tendency of the action-reward contingency and performance tempo, with stronger expectations speeding performance. We additionally provided evidence for a similar sensitivity of performance tempo to the strength of these predictions in all groups. Thus, dynamic beliefs about the changing relationship between actions and their outcome invigorated motor performance. This positive bias was not compromised by age or Parkinsons disease.

neuroscience↗