5.3.2. Психофизиология

Rehabilitation robotics aims to promote activity-dependent reorganization of the nervous system. However, people with paralysis cannot generate sufficient activity during robot-assisted rehabilitation and, consequently, do not benefit from these therapies. Here, we developed an implantable spinal cord neuroprosthesis operating in a closed loop to promote robust activity during walking and cycling assisted by robotic devices. This neuroprosthesis is device agnostic and designed for seamless implementation by nonexpert users. Preliminary evaluations in participants with paralysis showed that the neuroprosthesis enabled well-organized patterns of muscle activity during robot-assisted walking and cycling. A proof-of-concept study suggested that robot-assisted rehabilitation augmented by the neuroprosthesis promoted sustained neurological improvements. Moreover, the neuroprosthesis augmented recreational walking and cycling activities outdoors. Future clinical trials will have to confirm these findings in a broader population.

Childbirth is a life-changing event in a mother’s life. While the transition to motherhood has recently been recognized as one of the most neuroplastic periods in adulthood, no study has yet explored whether the hippocampus and amygdala change during the peripartum in relation to childbirth experience and perinatal depression symptoms. In this longitudinal neuroimaging study, we assessed 88 first-time gestational mothers in late pregnancy and early postpartum and 30 nulliparous control women. We used optimized high-resolution MRI scans to quantify volumetric changes in the hippocampus and amygdala, along with their substructures. We found that increases in depression symptoms during the peripartum were positively correlated with changes in the right amygdala. A more challenging birth experience was associated with bilateral increases in hippocampal volume. These findings show that studying the neuroanatomical changes during the transition to motherhood can inform not only about adaptive processes but also about potential vulnerabilities, highlighting the importance of tracking perinatal experiences to enhance women’s health.

The excitation-inhibition ratio is a key functional property of cortical microcircuits which changes throughout an individual’s lifespan. Adolescence is considered a critical period for maturation of excitation-inhibition ratio. This has primarily been observed in animal studies. However, there is limited human in vivo evidence for maturation of excitation-inhibition ratio at the individual level. Here, we developed an individualized in vivo marker of regional excitation-inhibition ratio in human adolescents, estimated using large-scale simulations of biophysical network models fitted to resting-state functional imaging data from both cross-sectional (n = 752) and longitudinal (n = 149) cohorts. In both datasets, we found a widespread decrease in excitation-inhibition ratio in association areas, paralleled by an increase or lack of change in sensorimotor areas. This developmental pattern was aligned with multiscale markers of sensorimotor-association differentiation. Although our main findings were robust across alternative modeling configurations, we observed local variations, highlighting the importance of methodological choices for future studies.

By adulthood, humans rapidly identify objects from sparse visual displays and across large disruptions to their appearance. What are the minimal conditions needed to achieve robust recognition abilities and when might these abilities develop? To answer these questions, we investigated the upper limits of children’s object recognition abilities. We found that children as young as 3 years successfully identified objects at speeds of 100 milliseconds (both forward and backward masked) under sparse and disrupted viewing conditions. By contrast, a range of computational models implemented with biologically informed properties or optimized for visual recognition did not reach child-level performance. Models only matched children if they received more object examples than children are capable of experiencing. These findings highlight the robustness of the human visual system in the absence of extensive experience and identify important developmental constraints for building biologically plausible machines.

Humans lack memories for specific events from the first few years of life. We investigated the mechanistic basis of this infantile amnesia by scanning the brains of awake infants with functional magnetic resonance imaging while they performed a subsequent memory task. Greater activity in the hippocampus during the viewing of previously unseen photographs was related to later memory-based looking behavior beginning around 1 year of age, suggesting that the capacity to encode individual memories comes online during infancy. The availability of encoding mechanisms for episodic memory during a period of human life that is later lost from our autobiographical record implies that postencoding mechanisms, whereby memories from infancy become inaccessible for retrieval, may be more responsible for infantile amnesia.

Voluntary, flexible stopping of speech output is an essential aspect of speech motor control, especially during natural conversations. The cognitive and neural mechanisms of speech inhibition are not well understood. Here we have recorded direct high-density cortical activity while participants engaged in continuous speech production and were visually cued to stop speaking. Neural recordings revealed distinct activity in the premotor frontal cortex correlated with stopping speech. This activity was found in largely separate cortical sites from regions encoding vocal tract articulatory movements. Moreover, this activity primarily occurred with abrupt stopping in the middle of an utterance, rather than naturally completing a phrase. Electrocortical stimulation at many premotor sites with inhibitory stop activity caused involuntary speech arrest, which contradicts previous clinical interpretations of this effect as evidence for critical centres of speech production. Together, these results suggest a previously unknown premotor cortical network that supports the inhibitory control of speech, providing implications for understanding both natural and altered speech production.

What determines who becomes and stays friends? Many factors are linked to friendship, including physical proximity and interpersonal similarities. Recent work has leveraged neuroimaging to detect similarities among friends by capturing how people process the world around them. However, given the cross-sectional nature of past research, it is unknown if neural similarity precedes friendship or only emerges among friends following social connection. Here we show that similarities in neural responses to movie clips—acquired before participants met one another—predicted proximity in a friendship network eight months later (that is, participants with similar responses were more likely to be friends rather than several degrees of separation apart). We also examined changes in distances between participants in their shared social network, which resulted from the formation, persistence and dissolution of friendships, between two months and eight months after they met each other. Compared with people who drifted further apart, people who grew closer over this six-month period had been more neurally similar as strangers. In addition, analyses controlling for sociodemographic similarities showed that whereas these similarities appeared to drive the differences in pre-existing neural similarities between friends and dyads of a social distance of 3, they did not account for the more extensive links between pre-existing neural similarities and the tendency for people to grow closer together, rather than drift farther apart, over time. Thus, whereas some friendships may initially form due to circumstance and dissolve over time, later-emerging and longer-lasting friendships may be rooted in deeper interpersonal compatibilities that are indexed by pre-existing neural similarities. The localization of these results suggests that pre-existing similarities in how people interpret, attend to and emotionally respond to their surroundings are precursors of future friendship and increased social closeness.

Understanding how animals and humans learn from experience to make adaptive decisions is a fundamental goal of neuroscience and psychology. Normative modelling frameworks such as Bayesian inference1 and reinforcement learning2 provide valuable insights into the principles governing adaptive behaviour. However, the simplicity of these frameworks often limits their ability to capture realistic biological behaviour, leading to cycles of handcrafted adjustments that are prone to researcher subjectivity. Here we present a novel modelling approach that leverages recurrent neural networks to discover the cognitive algorithms governing biological decision-making. We show that neural networks with just one to four units often outperform classical cognitive models and match larger neural networks in predicting the choices of individual animals and humans, across six well-studied reward-learning tasks. Critically, we can interpret the trained networks using dynamical systems concepts, enabling a unified comparison of cognitive models and revealing detailed mechanisms underlying choice behaviour. Our approach also estimates the dimensionality of behaviour3 and offers insights into algorithms learned by meta-reinforcement learning artificial intelligence agents. Overall, we present a systematic approach for discovering interpretable cognitive strategies in decision-making, offering insights into neural mechanisms and a foundation for studying healthy and dysfunctional cognition.

Recently acquired memories are reactivated in the hippocampus during sleep, an initial step for their consolidation1,2,3. This process is concomitant with the hippocampal reactivation of previous memories4,5,6, posing the problem of how to prevent interference between older and recent, initially labile, memory traces. Theoretical work has suggested that consolidating multiple memories while minimizing interference can be achieved by randomly interleaving their reactivation7,8,9,10. An alternative is that a temporal microstructure of sleep can promote the reactivation of different types of memories during specific substates. Here, to test these two hypotheses, we developed a method to simultaneously record large hippocampal ensembles and monitor sleep dynamics through pupillometry in naturally sleeping mice. Oscillatory pupil fluctuations revealed a previously unknown microstructure of non-REM sleep-associated memory processes. We found that memory replay of recent experiences dominated in sharp-wave ripples during contracted pupil substates of non-REM sleep, whereas replay of previous memories preferentially occurred during dilated pupil substates. Selective closed-loop disruption of sharp-wave ripples during contracted pupil non-REM sleep impaired the recall of recent memories, whereas the same manipulation during dilated pupil substates had no behavioural effect. Stronger extrinsic excitatory inputs characterized the contracted pupil substate, whereas higher recruitment of local inhibition was prominent during dilated pupil substates. Thus, the microstructure of non-REM sleep organizes memory replay, with previous versus new memories being temporally segregated in different substates and supported by local and input-driven mechanisms, respectively. Our results suggest that the brain can multiplex distinct cognitive processes during sleep to facilitate continuous learning without interference.

Актуальность. В современной психологии практически отсутствуют диагностические методики, чувствительные к выраженности зрительного неглекта в зависимости от структурированности зрительного поля и его нагруженности стимулами с учетом этой структуры. Цель. Разработать и апробировать методику, позволяющую анализировать выраженность проявлений синдрома неглекта в зрительном поле в зависимости от структурированности и загруженности стимулами. Выборка. В исследовании приняли участие 50 испытуемых в возрасте от 29 до 75 лет (Мвозраст = 58,5; SD = 18,82; 14 женщин), пациенты с неврологическими нарушениями различной этиологии с локализацией очага повреждения в области правого полушария головного мозга, из них 30 пациентов с синдромом неглекта. Методы. Исследование было выполнено с использованием комплексного нейропсихологического обследования по А.Р. Лурии, включающего оценку состояния высших психических функций, количественные методы оценки неглекта, а также разработанную методику «Красные фигуры». Авторская методика состоит из трех серий, последовательно предъявляемых на портативном планшете; они включают в себя набор геометрических фигур красного цвета. Каждая серия отличается от другой количеством стимулов, предъявляемых в правой половине экрана. Результаты. Разработана методика «Красные фигуры», направленная на диагностику синдрома неглекта в зрительной сфере. Проверены психометрические свойства данного теста. Шкалы показали достаточный уровень согласованности по показателям найденных фигур слева и по времени (показатели α-Кронбаха варьируют от 0,716 до 0,881). Все шкалы теста имеют отличное от нормального распределение данных по критерию Колмогорова — Смирнова (p < 0,001), кроме шкалы времени в 3-й серии (p = 0,2). Представлены корреляции, описательная статистика шкал. Выводы. Для исследования синдрома неглекта в зрительной сфере предложена методика, позволяющая оценить нарушения в данной сфере с варьированием структурированности и загруженности стимулами зрительного поля; получены доказательства ее надежности и валидности.