Biases in the perception of self-motion during whole-body acceleration and deceleration

International audienceSeveral studies have investigated whether vestibular signals can be processed to determine the magnitude of passive body motions. Many of them required subjects to report their perceived displacements offline, i.e., after being submitted to passive displacements. Here, we used a protocol that allowed us to complement these results by asking subjects to report their introspective estimation of their displacement continuously, i.e., during the ongoing body rotation. To this end, participants rotated the handle of a manipulandum around a vertical axis to indicate their perceived change of angular position in space at the same time as they were passively rotated in the dark. The rotation acceleration (Acc) and deceleration (Dec) lasted either 1.5 s (peak of 60 • /s 2 , referred to as being " High ") or 3 s (peak of 33 • /s 2 , referred to as being " Low "). The participants were rotated either counterclockwise or clockwise, and all combinations of acceleration and deceleration were tested (i.e., AccLow-DecLow; AccLow-DecHigh; AccHigh-DecLow; AccHigh-DecHigh). The participants' perception of body rotation was assessed by computing the gain, i.e., ratio between the amplitude of the perceived rotations (as measured by the rotating manipulandum's handle) and the amplitude of the actual chair rotations. The gain was measured at the end of the rotations, and was also computed separately for the acceleration and deceleration phases. Three salient findings resulted from this experiment: (i) the gain was much greater during body acceleration than during body deceleration, (ii) the gain was greater during High compared to Low accelerations and (iii) the gain measured during the deceleration was influenced by the preceding acceleration (i.e., Low or High). These different effects of the angular stimuli on the perception of body motion can be interpreted in relation to the consequences of body acceleration and deceleration on the vestibular system and on higher-order cognitive processes

Do Gravity-Related Sensory Information Enable the Enhancement of Cortical Proprioceptive Inputs When Planning a Step in Microgravity?

International audienceWe recently found that the cortical response to proprioceptive stimulation was greater when participants were planning a step than when they stood still, and that this sensory facilitation was suppressed in microgravity. The aim of the present study was to test whether the absence of gravity-related sensory afferents during movement planning in microgravity prevented the proprioceptive cortical processing to be enhanced. We reestablished a reference frame in microgravity by providing and translating a horizontal support on which the participants were standing and verified whether this procedure restored the proprioceptive facilitation. The slight translation of the base of support (lateral direction), which occurred prior to step initiation, stimulated at least cutaneous and vestibular receptors. The sensitivity to proprioceptive stimulation was assessed by measuring the amplitude of the cortical somatosensory-evoked potential (SEP, over the Cz electrode) following the vibration of the leg muscle. The vibration lasted 1 s and the participants were asked to either initiate a step at the vibration offset or to remain still. We found that the early SEP (90–160 ms) was smaller when the platform was translated than when it remained stationary, revealing the existence of an interference phenomenon (i.e., when proprioceptive stimulation is preceded by the stimulation of different sensory modalities evoked by the platform translation). By contrast, the late SEP (550 ms post proprioceptive stimulation onset) was greater when the translation preceded the vibration compared to a condition without pre-stimulation (i.e., no translation). This suggests that restoring a body reference system which is impaired in microgravity allowed a greater proprioceptive cortical processing. Importantly, however, the late SEP was similarly increased when participants either produced a step or remained still. We propose that the absence of step-induced facilitation of proprioceptive cortical processing results from a decreased weight of proprioception in the absence of balance constraints in microgravity

Automatic testing of cognitive performance in baboons maintained in social groups

International audienceLaboratory procedures used to study the cognitive functions of primates traditionally have involved removal of the subjects from their living quarters to be tested singly in a remote experimental room. This article presents an alternative research strategy favoring testing primates while they are maintained in their social group. The automatic learning device for monkeys (ALDM) is a computerized test system controlled by an automatic radio frequency identification of subjects. It is provided ad lib inside the social group of monkeys, for voluntary self-testing on a 24-h schedule. Nine baboons were tested with ALDM during a 7-month period. Experiments were performed to assess learning in motor control and abstract reasoning tasks. The results revealed high trial frequencies and excellent learning performance, even in tasks involving the highest cognitive complexities. A different study using ALDM with a group of 3 rhesus monkeys revealed social influences on learning. Beyond its interest for cognitive psychologists, ALDM is of interest for pharmacologists; and cognitive neuroscientists working with nonhuman primates. ALDM also can serve as an enrichment tool for captive animals and may be used to study a variety of species other than primates

Beyond the Reward Pathway: Coding Reward Magnitude and Error in the Rat Subthalamic Nucleus

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The experimental emergence of convention in a non-human primate

International audienceConventions form an essential part of human social and cultural behaviour and may also be important to other animal societies. Yet, despite the wealth of evidence that has accumulated for culture in non-human animals, we know surprisingly little about non-human conventions beyond a few rare examples. We follow the literature in behavioural ecology and evolution and define conventions as systematic behaviours that solve a coordination problem in which two or more individuals need to display complementary behaviour to obtain a mutually beneficial outcome. We start by discussing the literature on conventions in non-human primates from this perspective and conclude that all the ingredients for conventions to emerge are present and therefore that they ought to be more frequently observed. We then probe emergence of conventions by using a unique novel experimental system in which pairs of Guinea baboons (Papio papio) can voluntarily participate together in touch-screen based cognitive testing and we show that conventions readily emerge in our experimental setup and that they share three fundamental properties of human conventions (arbitrariness, stability and efficiency). These results question the idea that observational learning, and imitation in particular, is necessary to establish conventions, they suggest that positive reinforcement is enough

Different populations of subthalamic neurons encode cocaine vs. sucrose reward and predict future error

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Measuring social networks in primates: wearable sensors versus direct observations

International audienceTechnology, Japan Network analysis represents a valuable and flexible framework to understand the structure of individual interactions at the population level in animal societies. The versatility of network representations is moreover suited to different types of datasets describing these interactions. However, depending on the data collection method, different pictures of the social bonds between individuals could a priori emerge. Understanding how the data collection method influences the description of the social structure of a group is thus essential to assess the reliability of social studies based on different types of data. This is however rarely feasible, especially for animal groups, where data collection is often challenging. Here, we address this issue by comparing datasets of interactions between primates collected through two different methods: behavioral observations and wearable proximity sensors. We show that, although many directly observed interactions are not detected by the sensors, the global pictures obtained when aggregating the data to build interaction networks turn out to be remarkably similar. Sensors data yield moreover a reliable social network already over short timescales and can be used for long term campaigns, showing their important potential for detailed studies of the evolution of animal social groups

Contraction of the stapedius and tensor tympani muscles explored by tympanometry and pressure measurement in the external auditory canal

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Exploring the middle ear function in patients with a cluster of symptoms including tinnitus, hyperacusis, ear fullness and/or pain

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