Biology subjects

Meirhaeghe, N.

Publications and source records attributed to Meirhaeghe, N..

7 recordsLinked to original sources

bioRxiv2026

Reciprocal Fronto-Parietal Interactions Support Motor Anticipation during Sequential Reaching

Motor planning is a highly flexible process that adapts to changing behavioral demands. Frontal and parietal circuits are considered as critical nodes that support planning processes. However, it remains unclear whether the coordination of motor and parietal areas is preserved or adjusted in response to varying behavioral contexts. To address this open question, we trained two rhesus macaques to perform a visually-guided sequential reaching task, in which they could adapt their behavior to varying degrees of target predictability within the sequence. Analysis of eye and hand movements revealed distinct visuomotor strategies that were reflected in corresponding neural activity patterns. During motor anticipation, the direction of the upcoming reach toward predictable targets could be decoded from preparatory neural activity prior to target onset both in motor regions (PMd/M1) and parietal area 7A, whereas during reactive movements directional information emerged only after target onset. Using feature-specific information transfer analysis, we found that information about the upcoming movement direction was transmitted between 7A and PMd/M1 through bidirectional interactions. This pattern of interactions was preserved during motor anticipation and shifted earlier in time with respect to target onset. Our findings thus support a reciprocal fronto-parietal network that flexibly adjusts the timing of preparatory activity as different strategies are employed under varying behavioral constraints. Contrary to classical hierarchical models predicting serial activation across parietal and motor areas, parietal-to-motor interactions did not precede motor-to-parietal interactions, consistent with a heterarchical organization of cortical processing during flexible motor planning.

neuroscience↗

bioRxiv2022

Parallel planning through an optimal neural subspace in motor cortex

How do patterns of neural activity in motor cortex contribute to the planning of a movement? A recent theory developed for single movements proposes that motor cortex acts as a dynamical system whose initial state is optimized during the preparatory phase of the movement. This theory makes important yet untested predictions about preparatory dynamics in more complex behavioral settings. Here, we analyzed preparatory activity in non-human primates planning not one, but two movements simultaneously. As predicted by the theory, we found that parallel planning was achieved by adjusting preparatory activity within an optimal subspace to an intermediate state reflecting a tradeoff between the two movements. The theory quantitatively accounted for the relationship between this intermediate state and fluctuations in the animals behavior down at the trial level. These results uncover a simple mechanism for planning multiple movements in parallel, and further point to motor planning as a controlled dynamical process.

neuroscience↗

bioRxiv2021

Parametric control of flexible timing through low-dimensional neural manifolds

Biological brains possess an unparalleled ability to adapt behavioral responses to changing stimuli and environments. How neural processes enable this capacity is a fundamental open question. Previous works have identified two candidate mechanisms: a low-dimensional organization of neural activity and a modulation by contextual inputs. We hypothesized that combining the two might facilitate generalization and adaptation in complex tasks. We tested this hypothesis in the framework of flexible timing tasks where dynamics play a key role. Examining trained recurrent neural networks, we found that confining the dynamics to a low-dimensional subspace allowed tonic inputs to parametrically control the overall input-output transform, enabling generalization to novel inputs and adaptation to changing conditions. Reverse-engineering and theoretical analyses demonstrated that this parametric control relies on a mechanism where tonic inputs modulate the dynamics along non-linear manifolds in activity space while preserving their geometry. Comparisons with data from behaving monkeys confirmed the behavioral and neural signatures of this mechanism.

neuroscience↗

bioRxiv2021

A precise and adaptive neural mechanism for predictive temporal processing in the frontal cortex

The theory of predictive processing posits that the nervous system uses expectations to process information predictively. Direct empirical evidence in support of this theory however has been scarce and largely limited to sensory areas. Here, we report a precise and adaptive neural mechanism in the frontal cortex of non-human primates consistent with predictive processing of temporal events. We found that the speed at which neural states evolve over time is inversely proportional to the statistical mean of the temporal distribution of an expected stimulus. This lawful relationship was evident across multiple experiments and held true during learning: when temporal statistics underwent covert changes, neural responses underwent predictable changes that reflected the new mean. Together, these results highlight a precise mathematical relationship between temporal statistics in the environment and neural activity in the frontal cortex that could serve as a mechanistic foundation for predictive temporal processing.

neuroscience↗

bioRxiv2019

Selective facilitation of egocentric mental transformations under short-term microgravity

Understanding the impact of microgravity on human cognitive performance is crucial to guarantee the safety and success of future long-term manned missions. The effects of weightlessness on key mental processes such as spatial abilities are in particular not fully characterized. In this study, we examine the influence of microgravity on perspective-taking abilities--a type of mental operation especially relevant in the context of collaborative teamwork between free-floating astronauts. Twelve subjects performed a cooperative task in virtual-reality under both normal and short-term microgravity conditions during a parabolic flight. The task involved various degrees of mental transformations, and required subjects to perform actions instructed by a fellow astronaut aboard a virtual spacecraft. The experimental design allowed us to control for nuisance variables, training effects, and non-gravity related factors of parabolic flights. Overall, our results indicated that microgravity has a facilitatory effect on perspective-taking abilities. Notably, this facilitation was selective to conditions requiring subjects to rotate their perspective around their line of sight, i.e., for mental rotations in the frontal plane. Moreover, microgravity affected subjects differently depending on their visual field dependence, as determined via a classic rod-and-frame test. Specifically, improvement in performance was more pronounced in field-independent subjects. Together, these results shed light on a long standing debate about the impact of microgravity on egocentric mental imagery, and have direct operational consequences for future long-term missions.

neuroscience↗

bioRxiv2019

Reinforcement regulates timing variability in thalamus

Learning reduces variability but variability can facilitate learning. This paradoxical relationship has made it challenging to tease apart sources of variability that degrade performance from those that improve it. We tackled this question in a context-dependent timing task requiring humans and monkeys to flexibly produce different time intervals with different effectors. Subjects timing variability featured two novel and context-specific sources of variability: (1) slow memory-contingent fluctuations of the mean that degraded performance, and (2) fast reinforcement-dependent regulation of variance that improved performance. Signatures of these processes were evident across populations of neurons in multiple nodes of the cortico-basal ganglia circuits. However, only in a region of the thalamus involved in flexible control of timing were the slow performance-degrading fluctuations aligned to performance-optimizing regulation of variance. These findings provide direct evidence that the nervous system makes strategic use of exploratory variance to guard against other undesirable sources of variability.

neuroscience↗

bioRxiv2018

Bayesian computation through cortical latent dynamics

Statistical regularities in the environment create prior beliefs that we rely on to optimize our behavior when sensory information is uncertain. Bayesian theory formalizes how prior beliefs can be leveraged, and has had a major impact on models of perception 1, sensorimotor function 2,3, and cognition 4. However, it is not known how recurrent interactions among neurons mediate Bayesian integration. Using a time interval reproduction task in monkeys, we found that prior statistics warp the underlying structure of population activity in the frontal cortex allowing the mapping of sensory inputs to motor outputs to be biased in accordance with Bayesian inference. Analysis of neural network models performing the task revealed that this warping was mediated by a low-dimensional curved manifold, and allowed us to further probe the potential causal underpinnings of this computational strategy. These results uncover a simple and general principle whereby prior beliefs exert their influence on behavior by sculpting cortical latent dynamics.

neuroscience↗