Information Rate in Humans during Visuomotor Tracking

Previous investigations concluded that the human brain’s information processing rate remains fundamentally constant, irrespective of task demands. However, their conclusion rested in analyses of simple discrete-choice tasks. The present contribution recasts the question of human information rate within the context of visuomotor tasks, which provides a more ecologically relevant arena, albeit a more complex one. We argue that, while predictable aspects of inputs can be encoded virtually free of charge, real-time information transfer should be identified with the processing of surprises. We formalise this intuition by deriving from first principles a decomposition of the total information shared by inputs and outputs into a feedforward, predictive component and a feedback, error-correcting component. We find that the information measured by the feedback component, a proxy for the brain’s information processing rate, scales with the difficulty of the task at hand, in agreement with cost-benefit models of cognitive effort

Mental fatigue correlates with depression of task-related network and augmented DMN activity but spares the reward circuit

Long-lasting and demanding cognitive activity typically leads to mental fatigue (MF). Indirect evidence suggests that MF may be caused by altered motivational processes. Here, we hypothesized that if MF consists in an alteration of motivational states, brain functional changes induced by MF could specifically affect the brain motivation circuit. In order to test this hypothesis, we devised a functional neuroimaging protocol to detect altered brain activity in reward-related brain regions in relation to cognitively induced mental fatigue. Twenty-five healthy participants underwent a FATIGUE and a CONTROL session on different days. In the FATIGUE session, MF was induced by performing a demanding cognitive task (adapted Stroop task) during 90 min, whereas in the CONTROL session, participants were asked to read magazines for the same period of time. We measured the neural consequences of the MF induction during a working memory task (Missing Number task) while modulating extrinsic motivation with block-wise variations in monetary reward. We also tracked participants’ momentary fatigue, anxiety state and intrinsic motivation prior to and following the MF inducement and measurement. Accuracy on the Missing Number Task was lower in the FATIGUE than in the CONTROL condition. Furthermore, subjective MF, but not its behavioral manifestations, was associated with hypoactivity of the task-evoked neural responses. Importantly, activity in regions modulated by reward showed no differences between FATIGUE and CONTROL sessions. In parallel, subjective MF correlated with increased on-task activity and resting-state functional connectivity in the default mode network. These results indicate that subjective mental fatigue is not associated with altered activity in the brain motivation circuit but rather with hypoactivity in task-specific brain regions as well as relative increases of activity and connectivity in the default mode network during and after the task.Une nouvelle théorie du coût de la cognition basée sur la théorie de l'information: validation expérimental

Disentangling the involvement of primary motor cortex in value-based reinforcement learning and value-based decision making.

When one makes the decision to act in the physical world, the neural activity in primary motor cortex (M1) encodes the competition between potential action choices. Traditional approaches have viewed this activity as reflecting the unfolding of the outcome of a decision process taking place upstream. However, a recently emerging theoretical framework posits that the motor neural structures directly contribute to the decision process. We recently tested this hypothesis (Zenon et al., 2015, Brain Stimulation) by using continuous theta burst stimulation (cTBS) to alter activity in M1 while participants performed a task that required them to select between two fingers in the right hand based on the color of a stimulus (green or red, explicit instruction). Importantly, this finger choice was biased such that, to earn more money, the subjects also had to take into account the shape of the stimulus (circle or square, undisclosed manipulation). So the motor response depended, on the one hand, on a perceptual decision process, interpreting the color of the stimulus according to instructed rules and, on the other hand, on a value-based decision process relying on reinforcement learning. Interestingly, cTBS over M1 modified the extent to which the value-based process influenced the subjects' decisions whereas it had no effect on their ability to make a choice based on perceptual evidence. Importantly, in that study, cTBS was applied at the very beginning of the experiment, before the subjects had learned the task. Hence, we cannot tell from that work whether the effect of M1 cTBS was due to an alteration of value-based reinforcement learning or of value-based decision making, which takes place once learning is complete. Here, we present a study in which we intend to use the same task but with cTBS applied at different times in order to assess the contribution of M1 to the two value-based processes (learning and decision making). More precisely, the experiment will extend over three sessions, each occurring at 24-hours interval. Each experimental session will consist of six blocks, each lasting about 4 minutes. Pilot data suggest that the value-based process begins to effectively shape the subject decisions in the middle of the second session. Given this, cTBS over M1 will be applied either at the beginning of the first session (before learning) or at the beginning of the third session (after learning). This procedure will allow us to disentangle the involvement of M1 in value-based reinforcement learning and value-based decision making

Disruption of Broca's Area Alters Higher-order Chunking Processing during Perceptual Sequence Learning

Because Broca's area is known to be involved in many cognitive functions, including language, music, and action processing, several attempts have been made to propose a unifying theory of its role that emphasizes a possible contribution to syntactic processing. Recently, we have postulated that Broca's area might be involved in higher-order chunk processing during implicit learning of a motor sequence. Chunking is an information-processing mechanism that consists of grouping consecutive items in a sequence and is likely to be involved in all of the aforementioned cognitive processes. Demonstrating a contribution of Broca's area to chunking during the learning of a nonmotor sequence that does not involve language could shed new light on its function. To address this issue, we used offline MRI-guided TMS in healthy volunteers to disrupt the activity of either the posterior part of Broca's area (left Brodmann's area [BA] 44) or a control site just before participants learned a perceptual sequence structured in distinct hierarchical levels. We found that disruption of the left BA 44 increased the processing time of stimuli representing the boundaries of higher-order chunks and modified the chunking strategy. The current results highlight the possible role of the left BA 44 in building up effector-independent representations of higher-order events in structured sequences. This might clarify the contribution of Broca's area in processing hierarchical structures, a key mechanism in many cognitive functions, such as language and composite actions

Anatomia descritiva comparativa da artéria femoral de cachorro-do-mato, raposa-do-campo e lobo-guará

O objetivo deste estudo foi descrever a anatomia da artéria femoral em canídeos selvagens, como o cachorro do mato (Cerdocyon thous), a raposa do campo (Lycalopex vetulus) e o lobo-guará (Chrysocyon brachyurus). Foram utilizados dois espécimes de cada grupo canídeo. Solução de látex vermelha foi injetada no sistema arterial dos animais, que foram então fixados em solução aquosa de formaldeído a 10% e dissecados seguindo as técnicas rotineiras da anatomia macroscópica. Nos três grupos canídeos, o padrão arterial foi semelhante ao descrito para canídeos domésticos, em que a artéria femoral profunda origina da artéria ilíaca externa, ainda na cavidade abdominal, e envia seu primeiro ramo, a artéria femoral circunflexa lateral. Alguns ramos musculares, uma ou duas artérias femorais caudais e os ramos terminais - a artéria genicular descendente, a artéria safena e a artéria poplítea - são originários da artéria femoral. O padrão de origem desses vasos também mostra semelhanças com as de canídeos domésticos, às vezes formando troncos e ocasionalmente originando individualmente. Assim, pode-se concluir que o padrão anatômico da artéria femoral e seus ramos em canídeos selvagens mostra semelhanças com a dos canídeos domésticos, mas variações inerentes em cada espécie também estão presentes.The goal of this study was to describe the anatomy of the femoral artery in wild canids such as the crab-eating fox (Cerdocyon thous), the hoary fox (Lycalopex vetulus), and the maned wolf (Chrysocyon brachyurus). Two specimens from each canid group were used. Red dyed latex was injected in the arterial system of the animals, which were then fixed in 10% formaldehyde aqueous solution and dissected following the routine techniques in macroscopic anatomy. In the three canid groups, the arterial pattern was similar to that described for domestic canids, in which the deep femoral artery rises from the external iliac artery, still in the abdominal cavity, and sends its first branch, the lateral circumflex femoral artery. A few muscular branches, one or two caudal femoral arteries, and the terminal branches – the descending genicular artery, the saphenous artery, and the popliteal artery – are all originated from the femoral artery. The origin pattern of these vessels also shows similarities with those from domestic canids, sometimes forming trunks and occasionally rising individually. Thus, it can be concluded that the anatomical pattern of the femoral artery and its branches in wild canids shows similarities with that from domestic canids, but inherent variations in each species are also present

ESTUDO ANATÔMICO DAS ARTÉRIAS DO OMBRO DE Cebus libidinosus (RYLANDS, 2000; PRIMATES – CEBIDAE)

As pesquisas nos Cebus libidinosus têm sido incremAs pesquisas nos Cebus libidinosus têm sido in¬crementadas, em razão do pouco conhecimento de sua morfofisiologia e por terem expressivo desenvolvimento psicomotor comparável ao dos primatas do Velho Mundo. A região do ombro merece especial atenção, em virtude dos hábitos arborícolas e as constantes manipulações de objetos. Neste trabalho utilizaram-se 24 exemplares de Cebus libidinosus doados pelo Instituto Brasileiro do Meio Ambiente (IBAMA) de Sete Lagoas, MG, Brasil, sacrificados de acordo com as recomendações do Comitê Brasileiro de Experimentação Animal (COBEA) e inclu¬ídos nas coleções anatômicas da Universidade Federal de Uberlândia (UFU) e Universidade Federal de Goiás (UFG). O sistema arterial destes indivíduos foi injetado com látex corado e posteriormente dissecaram-se as artérias sob lupa estereoscópica. Na maioria dos casos, as artérias encontra¬da, apresentaram relativa correspondência de distribuição e número comparável ao modelo humano e de outros primatas, com variações quanto à frequência e origem dos vasos. De modo geral as artérias do ombro deste Cebídeo se originaram de vasos derivados indiretamente da artéria axilar, uma vez que surgiram como pequenos troncos arte¬riais que se subdividiram, e não como ramos individuais, como descrito nos outros animais estudados, e de modo específico ocorreram variações de todas as estruturas em relação aos outros primatas estudados. PALAVRAS-CHAVES: Anatomia, artérias, Cebus libidinosus, primatas

Spatial and Temporal Dynamics of Attentional Guidance during Inefficient Visual Search

Spotting a prey or a predator is crucial in the natural environment and relies on the ability to extract quickly pertinent visual information. The experimental counterpart of this behavior is visual search (VS) where subjects have to identify a target amongst several distractors. In difficult VS tasks, it has been found that the reaction time (RT) is influenced by salience factors, such as the target-distractor similarity, and this finding is usually regarded as evidence for a guidance of attention by preattentive mechanisms. However, the use of RT measurements, a parameter which depends on multiple factors, allows only very indirect inferences about the underlying attentional mechanisms. The purpose of the present study was to determine the influence of salience factors on attentional guidance during VS, by measuring directly attentional allocation. We studied attention allocation by using a dual covert VS task in subjects who had 1) to detect a target amongst different items and 2) to report letters briefly flashed inside those items at different delays. As predicted, we showed that parallel processes guide attention towards the most relevant item by virtue of both goal-directed and stimulus-driven factors, and we demonstrated that this attentional selection is a prerequisite for target detection. In addition, we show that when the target is characterized by two features (conjunction VS), the goal-directed effects of both features are initially combined into a unique salience value, but at a later stage, grouping phenomena interact with the salience computation, and lead to the selection of a whole group of items. These results, in line with Guided Search Theory, show that efficient and rapid preattentive processes guide attention towards the most salient item, allowing to reduce the number of attentional shifts needed to find the target

Mechanisms of gaze and attention guidance in visual exploration

On average, humans execute over 150,000 saccades each day. Because of the small visual angle subtended by the fovea, exhaustive exploration of the visual surroundings, i.e. complete sampling of the whole visual field, would be much ineffective. Consequently, the decision of where to move the gaze in order to optimize visual information gathering is critical. How the brain achieves this computational conundrum is the central question addressed in the present work.(SBIM 3) -- UCL, 200

Contribution of the basal ganglia to spoken language: Is speech production like the other motor skills?

Two of the roles assigned to the basal ganglia in spoken language parallel very well their contribution to motor behaviour: (1) their role in sequence processing, resulting in syntax deficits, and (2) their role in movement "vigor," leading to "hypokinetic dysarthria" or "hypophonia." This is an additional example of how the motor system has served the emergence of high-level cognitive functions, such as language