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The capacity to initiate actions endogenously is critical for goal-directed behavior. Spontaneous voluntary actions are typically preceded by slow-ramping medial frontal cortex activity that begins around two seconds before movement, which may reflect spontaneous fluctuations that influence action timing. However, the mechanisms by which these slow ramping signals emerge from single-neuron and network dynamics remain poorly understood. Here, we developed a spiking neural network model that produces spontaneous slow ramping activity in single neurons and population activity with onsets ∼2 seconds before threshold crossings. A key prediction of our model is that neurons that ramp together have correlated firing patterns before ramping onset. We confirmed this model-derived hypothesis in a dataset of human single neuron recordings from medial frontal cortex. Our results suggest that slow ramping signals reflect bounded spontaneous fluctuations that emerge from quasi-winner-take-all dynamics in clustered networks that are temporally stabilized by slow-acting synapses. HIGHLIGHTS: 1. We reveal a mechanism for slow-ramping signals before spontaneous voluntary movements. 2. Slow synapses stabilize spontaneous fluctuations in spiking neural network. 3. We validate model predictions in human frontal cortical single neuron recordings. 4. The model recreates the readiness potential in an EEG proxy signal. 5. Neurons that ramp together had correlated activity before ramping onset.

The covid-19 pandemic has widened political and social divides in the US – a trend most notable by the emergence of anti-science and ideological movements bent on hindering governments’ actions by disseminating disinformation. Thus, certain views, often found at the fringe of the marketplace of ideas, have pervaded into mainstream media to the point of influencing the 2020 presidential elections, for example. Overall, the spread of conspiracy theories has led to increased distrust in institutions, reduced social engagement and greater hesitancy towards evidence-based health practices towards Covid-19. As a prominent example, while evidence indicates that vaccination is currently the most reliable strategy for protecting vulnerable populations and preventing overwhelming hospitalizations, disinformation has increased overall hesitancy in the general population. Previous work indicates that motivations to support conspiratorial thinking is heterogenous—while some individuals may be prone to support such views for epistemic reasons (e.g., wanting to better understand), others may do so due to existential (e.g., wanting to be safe) or social (e.g., wanting to protect or belong to one’s group) motives. Our research aims to explore heterogeneity in conspiracy theory related to Covid-19. As part of this effort, we collected longitudinal data from a large sample size (N>600) of US residents across multiple waves of the same participants during the pandemic, starting April 2020. Participants completed a series of self-reported questionnaire and experimental tasks, while we also recorded demographics information. Our measures included various psychological assessments, race attitudes, and covid-related questions. Participants also completed a questionnaire concerning their views on various aspects pertaining to Covid-19 vaccination, news media, and government to examine whether they support conspiracy theories. Moreover, they performed a target discrimination task, in which they were asked to indicate whether a visual stimulus, embedded within noise, was a face or a house. Critically, the task involved a detection component where the target stimulus was absent for 30% of trials. In this way, we estimated participants’ tendency to detect patterns when none were present, based on a signal-detection theoretic framework. To explore heterogeneity for conspiracy theory of Covid-19, our analyses will comprise structural equation modelling and latent profile analysis based on personality traits, psychological wellbeing, and socio-political views. With this approach, we aim to understand the extent to which these factors promote conspiracy theories of Covid-19 in different ways. Last, we will investigate how this effects vaccine hesitancy.

In 1957, Craig Mooney published a set of human face stimuli to study perceptual closure: the formation of a coherent percept on the basis of minimal visual information. Images of this type, now known as "Mooney faces", are widely used in cognitive psychology and neuroscience because they offer a means of inducing variable perception with constant visuo-spatial characteristics (they are often not perceived as faces if viewed upside down). Mooney's original set of 40 stimuli has been employed in several studies. However, it is often necessary to use a much larger stimulus set. We created a new set of over 500 Mooney faces and tested them on a cohort of human observers. We present the results of our tests here, and make the stimuli freely available via the internet. Our test results can be used to select subsets of the stimuli that are most suited for a given experimental purpose.

International audience; In physics “entrainment” refers to the synchronization of two coupled oscillators with similar fundamental frequencies. In behavioral science, entrainment refers to the tendency of humans to synchronize their movements with rhythmic stimuli. Here, we asked whether human subjects performing a tapping task would entrain their tapping to an undetected auditory rhythm surreptitiously introduced in the guise of ambient background noise in the room. Subjects performed two different tasks, one in which they tapped their finger at a steady rate of their own choosing and one in which they performed a single abrupt finger tap on each trial after a delay of their own choosing. In both cases we found that subjects tended to tap in phase with the inducing modulation, with some variability in the preferred phase across subjects, consistent with prior research. In the repetitive tapping task, if the frequency of the inducing stimulus was far from the subject’s own self-paced frequency, then entrainment was abolished, consistent with the properties of entrainment in physics. Thus, undetected ambient noise can influence self-generated movements. This suggests that uncued decisions to act are never completely endogenous, but are subject to subtle unnoticed influences from the sensory environment.

While there have been numerous studies of the vestibular system in mammals, less is known about the brain mechanisms of vestibular processing in humans. In particular, of the studies that have been carried out in humans over the last 30 years, none has investigated how vestibular stimulation (VS) affects cortical oscillations. Here we recorded high-density electroencephalography (EEG) in healthy human subjects and a group of bilateral vestibular loss patients (BVPs) undergoing transient and constant-velocity passive whole body yaw rotations, focusing our analyses on the modulation of cortical oscillations in response to natural VS. The present approach overcame significant technical challenges associated with combining natural VS with human electrophysiology and reveals that both transient and constant-velocity VS are associated with a prominent suppression of alpha power (8–13 Hz). Alpha band suppression was localized over bilateral temporo-parietal scalp regions, and these alpha modulations were significantly smaller in BVPs. We propose that suppression of oscillations in the alpha band over temporo-parietal scalp regions reflects cortical vestibular processing, potentially comparable with alpha and mu oscillations in the visual and sensorimotor systems, respectively, opening the door to the investigation of human cortical processing under various experimental conditions during natural VS.