Biology subjects

Ribeiro, M. J.

Publications and source records attributed to Ribeiro, M. J..

5 recordsLinked to original sources

bioRxiv2026

Impaired Sensory-motor Reconfiguration and Pupil-linked Arousal in Aging

Mounting evidence indicates impairments of decision-making and brainstem arousal systems in aging. To shed light on the relationship between these phenomena, we compared behavior and dynamics of pupil-linked arousal between older and younger adults during compositionally structured tasks. The main task required continuous online inference about hidden changes in the stimulus-response mappings required for reporting a perceptual categorization judgment. Accuracy in that task was reduced in older compared to younger adults, impairment specifically reflecting objective and subjective difficulty in switching between stimulus-response mappings: there was no age difference in tasks requiring only the online inference or only the perceptual categorization under stable stimulus-response mappings. Participant[s] pupils reliably dilated during the categorization judgment as well as moments of high probability of switches in the online inference process in both age groups. But only when the switches prompted a change in stimulus-response association in the main task, were these pupil responses deteriorated in older compared to younger adults. We propose that impaired cognitive engagement of arousal in aging might limit the sensory-motor reconfigurations required for behavioral flexibility. SIGNIFICANCE STATEMENTAging affects decision-making, but the computational and physiological basis of these alterations are poorly understood. Here, we show that older people are impaired in switching the association between sensation and action to support flexible decision-making. This flexible switching process recruits pupil-linked arousal systems of the brainstem in a manner that is altered in older compared to younger individuals. By contrast, we find that several other computational processes required for complex decision-making, including rapid online inference about uncertain environments, and the associated pupil-linked arousal responses, are largely unaffected in older people. Our findings implicate an aberrant cognitive recruitment of brainstem arousal systems in age-related problems in decision-making.

neuroscience↗

bioRxiv2024

The influence of sensory noise, confidence judgments, and accuracy on pupil responses and trial-by-trial reaction time adjustments in young and older people

We investigated the association between pupil responses, decision confidence and decision accuracy, their relationship with behavioural adjustments important for optimal task performance, and if these were altered in older adults. We tested young and older adults, including men and women, with a dot motion direction discrimination task, while measuring task-related pupil responses. Feedback was provided after each trial. Participants were instructed to report perceived motion direction and simultaneously their decision confidence. Older adults were overconfident in the presence of high sensory noise and in incorrect trials. Young peoples pupil responses reflected performance lapses. This effect was reduced in older people that showed blunted pupil responses to lapses and to negative feedback. Low confidence, errors, and larger pre-feedback pupil responses were associated with slower reaction time on the subsequent trial. The effects of errors and pupil were stronger in the older group. In conclusion, older peoples blunted pupil responses following lapses suggest reduced awareness of their own abilities and internal brain state and might impair adjustment of behaviour for optimal performance.

neuroscience↗

bioRxiv2024

The cortical heartbeat-evoked potential is modulated by heart rate in a task and mental effort dependent manner

Cardiac cycle duration, or interbeat interval (IBI), is the period from one heartbeat to the next. IBI changes from cycle to cycle. Periods with longer IBI are associated with higher sensitivity to external sensory stimuli (exteroception). Warning cues induce a state of attentive anticipation characterized by an increase in IBI (anticipatory cardiac deceleration) and faster reaction times. Ageing reduces the increase in IBI induced by warning cues and response speed. However, it is unclear which mechanism, if any, connects IBI with reaction time. The heartbeat-evoked potential (HEP) is a cortical response evoked by the heartbeat, modulated by attention and associated with sensitivity to external sensory stimuli. HEP might be affected by IBI and mediate the association between cardiac output and cortical processing. We investigated if the HEP was affected by warning cues as well as spontaneous fluctuations in IBI. To explore the impact of age-related changes in cardiac responses, we included young and older people [N = 33/29; 26/23 women; mean age 23/61 years]. We analysed the electroencephalograms and electrocardiograms simultaneously acquired during auditory cued simple reaction time and go/no-go tasks. The warning cue did not induce significant changes in the HEP. Yet, fluctuations in IBI (not locked with the warning cue) affected the HEP and HEP amplitude was associated with average reaction time in the older group. However, on a trial-by-trial basis, reaction time was independent from IBI fluctuations. In conclusion, we found no evidence that the HEP mediates the effect of attention orienting on reaction time.

neuroscience↗

bioRxiv2021

Slow fluctuations in ongoing brain activity decrease in amplitude with ageing yet their impact on task-related evoked responses is dissociable from behaviour

In humans, ageing is characterized by decreased brain signal variability and increased behavioural variability. To understand how reduced brain variability segregates with increased behavioural variability, we investigated the association between reaction time variability, evoked brain responses and ongoing brain signal dynamics, in young (N = 36) and older adults (N = 39). We studied the electroencephalogram (EEG) and pupil size fluctuations to characterize the cortical and arousal responses elicited by a cued go/no-go task. Evoked responses were strongly modulated by slow (< 2 Hz) fluctuations of the ongoing signals, which presented reduced power in the older participants. Although variability of the evoked responses was lower in the older participants, once we adjusted for the effect of the ongoing signal fluctuations, evoked responses were equally variable in both groups. Moreover, the modulation of the evoked responses caused by the ongoing signal fluctuations had no impact on reaction time, thereby explaining why although ongoing brain signal variability is decreased in older individuals, behavioural variability is not. Finally, we showed that adjusting for the effect of the ongoing signal was critical to unmask the link between neural responses and behaviour.

neuroscience↗

bioRxiv2019

Postdoc X-ray in Europe 2017: work conditions, productivity, institutional support and career outlooks

1.Executive SummaryThis survey and data analysis were conducted by the European Network of Postdoctoral Associations (ENPA) with the aim of assessing the current research and work conditions, aspirations and support received by postdoctoral researchers working in Europe. The Results section is structured into three main parts. The first one describes the study sample of European postdoctoral researchers, including participants demographics, funding sources and income, research outputs, and teaching opportunities. The second section focuses on their professional aspirations and institutional support provided. The third part describes the level of engagement of postdoctoral researchers and their institutions in working towards better research conditions and career development, and what initiatives are emerging within this community. Our Conclusions section pulls together this comprehensive analysis, highlighting some of the most concerning issues currently affecting postdoctoral researchers in Europe. We also make a number of recommendations that would significantly improve the career expectations and aspirations of postdoctoral researchers. These are listed below. Conclusions and recommendationsO_LILonger postdoctoral periods in Southern Europe despite higher publication metrics Recommendation Institutions in Southern Europe should develop clear criteria to support postdoctoral researchers career progression. C_LIO_LISouthern and Eastern Europe pay the lowest salaries and have the lowest number of foreign postdoctoral researchers Recommendation The salary differences across European countries should be addressed as this could be a barrier to mobility and knowledge exchange from higher to lower pay regions. C_LIO_LILack of access to funding is a significant concern of postdoctoral researchers Recommendation Discrepancies in access to funding should be minimized across the different European areas. C_LIO_LIPostdoctoral researchers in Europe work longer hours than required by contract Recommendation The culture of overwork in the research environment should be addressed in order to protect researchers against the risks associated with long hours at work. C_LIO_LIThe majority of full-time postdoctoral work contracts includes an exclusivity clause Recommendation Inclusion of exclusivity clauses in contracts for postdoctoral researchers should be optional in order to allow them to enhance their employability outside academia. C_LIO_LIPostdoctoral researchers career development is poorly supported by their institutions Recommendation Postdoctoral researchers career prospects and career management should be much more supported by institutions in coordination with postdoctoral associations. C_LIO_LILack of postdoctoral representation in governance is linked to unclear institutional duties and rights Recommendation Institutional governance bodies should include postdoctoral researcher representatives. This would ensure that the views of this vital staff group are heard, as well as making postdoctoral researchers feel more engaged with their own institutions. A flexible and proactive communication strategy at the institution and research group level should be developed, taking into account the sometimes transient nature of postdoctoral researchers posts. C_LIO_LIResearchers show higher engagement with their local postdoctoral associations than with workers unions Recommendation Postdoctoral associations are an essential way to advocate for postdoctoral researchers at the governance level. Institutions should engage with, promote and support the work of postdoctoral associations. C_LI

scientific communication and education↗