Acute cerebellar ataxia and myoclonus with or without opsoclonus: a para-infectious syndrome associated with COVID-19.

BACKGROUND AND PURPOSE: Patients with COVID-19 can have central or peripheral neurological manifestations. METHODS: The cases of two patients with acute cerebellar ataxia and myoclonus associated with COVID-19 are reported (with Video S1) and five previously reported patients are discussed. RESULTS: Acute cerebellar ataxia and myoclonus started between 10 days and 6 weeks after the first manifestations of COVID-19. Opsoclonus or ocular flutter was present in four patients. Patients were treated with intravenous immunoglobulins and/or steroids except for one patient, resulting in a striking improvement within a week. CONCLUSION: Acute cerebellar ataxia and myoclonus with or without opsoclonus belongs to the wide spectrum of neurological manifestations associated with COVID-19. It is important to recognize this possible manifestation since early treatment allows for rapid recovery.

Primate Ventromedial Prefrontal Cortex Neurons Continuously Encode the Willingness to Engage in Reward-Directed Behavior.

To survive in their complex environment, primates must integrate information over time and adjust their actions beyond immediate events. The underlying neurobiological processes, however, remain unclear. Here, we assessed the contribution of the ventromedial prefrontal cortex (VMPFC), a brain region important for value-based decision-making. We recorded single VMPFC neurons in monkeys performing a task where obtaining fluid rewards required squeezing a grip. The willingness to perform the action was modulated not only by visual information about Effort and Reward levels but also by contextual factors such as Trial Number (i.e., fatigue and/or satiety) or behavior in recent trials. A greater fraction of VMPFC neurons encoded contextual information, compared with visual stimuli. Moreover, the dynamics of VMPFC firing was more closely related to slow changes in motivational states driven by these contextual factors rather than rapid responses to individual task events. Thus, the firing of VMPFC neurons continuously integrated contextual information and reliably predicted the monkeys's willingness to perform the task. This function might be critical when animals forage in a complex environment and need to integrate information over time. Its relation with motivational states also resonates with the VMPFC's implication in the "default mode" or in mood disorders.

Reading wild minds: A computational assay of Theory of Mind sophistication across seven primate species.

Theory of Mind (ToM), i.e. the ability to understand others' mental states, endows humans with highly adaptive social skills such as teaching or deceiving. Candidate evolutionary explanations have been proposed for the unique sophistication of human ToM among primates. For example, the Machiavellian intelligence hypothesis states that the increasing complexity of social networks may have induced a demand for sophisticated ToM. This type of scenario ignores neurocognitive constraints that may eventually be crucial limiting factors for ToM evolution. In contradistinction, the cognitive scaffolding hypothesis asserts that a species' opportunity to develop sophisticated ToM is mostly determined by its general cognitive capacity (on which ToM is scaffolded). However, the actual relationships between ToM sophistication and either brain volume (a proxy for general cognitive capacity) or social group size (a proxy for social network complexity) are unclear. Here, we let 39 individuals sampled from seven non-human primate species (lemurs, macaques, mangabeys, orangutans, gorillas and chimpanzees) engage in simple dyadic games against artificial ToM players (via a familiar human caregiver). Using computational analyses of primates' choice sequences, we found that the probability of exhibiting a ToM-compatible learning style is mainly driven by species' brain volume (rather than by social group size). Moreover, primates' social cognitive sophistication culminates in a precursor form of ToM, which still falls short of human fully-developed ToM abilities.

Handedness in gestural and manipulative actions in male hunter-gatherer Aka pygmies from Central African Republic.

OBJECTIVES: All human populations display a right-biased handedness. Nonetheless, if studies on western populations are plenty, investigations of traditional populations living at subsistence levels are rare. Yet, understanding the geographical variation of phenotypes of handedness is crucial for testing evolutionary hypotheses. We aimed to provide a preliminary investigation of factors affecting handedness in 25 Aka pygmies from Central African Republic when spontaneously gesturing or manipulating food/tools (Nactions = 593). MATERIALS AND METHODS: We recorded spontaneous behaviors and characterized individuals' hand preference using GLMM with descriptive variables as target position, task complexity (unimanual/bimanual), task nature (food/tool manipulation, gesture), and task physical/cognitive constraints (precision or power for manipulative actions and informative content for gestures). RESULTS: Individuals were lateralized to the right (93%, N = 15) when manipulating food/tools but not when gesturing. Hand preference was affected by target position but not by task complexity. While nonexplicitly informative gestures were more biased to the right compared to explicitly informative ones, no differences were found within food/tool manipulation (power or precision vs. none). DISCUSSION: Although we do not intend to assume generalizable results due to our reduced sample, our observations provide additional information on handedness in a contemporary traditional society. Especially, the study mainly evidenced considerable cultural effects in gestures while also supporting theories considering active tool manipulation as one of the overriding factor in human handedness evolution.

Noradrenaline and dopamine neurons in the reward/effort trade-off: a direct electrophysiological comparison in behaving monkeys.

Motivation determines multiple aspects of behavior, including action selection and energization of behavior. Several components of the underlying neural systems have been examined closely, but the specific role of the different neuromodulatory systems in motivation remains unclear. Here, we compare directly the activity of dopaminergic neurons from the substantia nigra pars compacta and noradrenergic neurons from the locus coeruleus in monkeys performing a task manipulating the reward/effort trade-off. Consistent with previous reports, dopaminergic neurons encoded the expected reward, but we found that they also anticipated the upcoming effort cost in connection with its negative influence on action selection. Conversely, the firing of noradrenergic neurons increased with both pupil dilation and effort production in relation to the energization of behavior. Therefore, this work underlines the contribution of dopamine to effort-based decision making and uncovers a specific role of noradrenaline in energizing behavior to face challenges.

Free hand hitting of stone-like objects in wild gorillas.

The earliest stone tool types, sharp flakes knapped from stone cores, are assumed to have played a crucial role in human cognitive evolution. Flaked stone tools have been observed to be accidentally produced when wild monkeys use handheld stones as tools. Holding a stone core in hand and hitting it with another in the absence of flaking, free hand hitting, has been considered a requirement for producing sharp stone flakes by hitting stone on stone, free hand percussion. We report on five observations of free hand hitting behavior in two wild western gorillas, using stone-like objects (pieces of termite mound). Gorillas are therefore the second non-human lineage primate showing free-hand hitting behavior in the wild, and ours is the first report for free hand hitting behavior in wild apes. This study helps to shed light on the morphofunctional and cognitive requirements for the emergence of stone tool production as it shows that a prerequisite for free hand percussion (namely, free hand hitting) is part of the spontaneous behavioral repertoire of one of humans' closest relatives (gorillas). However, the ability to combine free hand hitting with the force, precision, and accuracy needed to facilitate conchoidal fracture in free hand percussion may still have been a critical watershed for hominin evolution.

Assessing value representation in animals.

Among all factors modulating our motivation to perform a given action, the ability to represent its outcome is clearly the most determining. Representation of outcomes, rewards in particular, and how they guide behavior, have sparked much research. Both practically and theoretically, understanding the relationship between the representation of outcome value and the organization of goal directed behavior implies that these two processes can be assessed independently. Most of animal studies essentially used instrumental actions as a proxy for the expected goal-value. The purpose of this article is to consider alternative measures of expected outcome value in animals, which are critical to understand the behavioral and neurobiological mechanisms relating the representation of the expected outcome to the organization of the behavior oriented towards its obtention. This would be critical in the field of decision making or social interactions, where the value of multiple items must often be compared and/or shared among individuals to determine the course of actions.

Retrospective revaluation and its neural circuit in rats.

Contingency learning is essential for establishing predictive or causal judgements. Retrospective revaluation captures essential aspects of the updating of this knowledge, according to new experience. In the present study, retrospective revaluation and its neural substrate was investigated in a rat conditioned magazine approach. One element of a previously food-reinforced Tone-Light compound stimulus was either further reinforced (inflation) or extinguished (extinction). These treatments affected the predictive value of the alternate stimulus (target), but only when the target was a weakly salient stimulus such as a Light, and the inflation/extinction procedure concerned the more salient element, that is the Tone. As the predictive value of the Light was decreased in comparison with a relevant control group, this revaluation was interpreted as backward blocking, and not unovershadowing. This observation challenges retrospective revaluation models focused on acquisition and prediction error detection, and is better accounted for by retrieval-based associative theories such as the comparator model (Miller and Matzel) [5]. Immunohistochemical detection of the Fos protein after the test phase revealed activation of the orbitofrontal and infralimbic cortices as well as nucleus accumbens core and shell, in rats that exhibited retrospective revaluation. Our results suggest that rats integrate successive experiences at the retrieval stage of retrospective revaluation, and that prefronto-accumbal interactions are involved in this function.