Biology subjects

Gavenas, J.

Publications and source records attributed to Gavenas, J..

3 recordsLinked to original sources

bioRxiv2024

Pupil dilations prior to freely timed actions reflect the reported timing of conscious intention

Freely timed actions are typically preceded by a slow anticipatory buildup of cortical brain activity, which has been extensively studied. However, such free actions are also preceded by slow pupil dilations in both humans and other animals, which have barely been examined. We investigated the neurocognitive significance of antecedent pupil dilations (APDs) in a voluntary-action paradigm. Participants performed self-paced actions and reported the timing of movement, conscious intention, or other events using a clock. APDs began a second or more before movement, and control conditions suggest that they did not reflect processing related to reporting demands, motor execution, or general anticipation. Critically, APD timing covaried with the reported timing of intention awareness but did not covary with the reported timing of overt movement or an external stimulus. Furthermore, decoding algorithms could distinguish APDs with above-chance accuracy more than 500 milliseconds before button-press. Our results suggest that APDs reflect a shift in awareness prior to movement onset and potentially offer a non-invasive method of predicting spontaneous movements before they occur. Highlights: 1. Freely timed movements are preceded by antecedent pupil dilations (APDs). 2. APDs do not reflect reporting, motor execution, or general anticipation. 3. APDs are informative of upcoming movements 500+ milliseconds before button-press. 4. APD timing specifically correlates with timing of intention awareness.

neuroscience↗

bioRxiv2023

Probing for Intentions: The Early Readiness Potential does not Reflect Awareness of Motor Preparation

Voluntary actions are typically preceded by the Readiness Potential (RP), a negative midfrontal EEG deflection that begins [~]2 seconds before movement. What cognitive and neural process the RP reflects and how it relates to conscious intention remain unclear due to conflicting findings. We investigated the neural basis and cognitive significance of the RP in a novel probe-based paradigm. Contrary to prior reports, we found that pre-probe RP buildups were not related to reported awareness of motor preparation. Computational modeling suggested that the best explanation for these results is via metacognitive access to stochastic accumulation. Reported preparation was also related to beta desynchronization over contralateral motor cortex shortly before probe onset. We conclude that the RP may be metacognitively accessible in response to external task demands but does not reflect the onset of a conscious intention. We discuss implications of these findings for voluntary action initiation and intention awareness. HighlightsO_LIWe investigate the mechanisms underlying voluntary action initiation in a new probe paradigm. C_LIO_LIContrary to prior results, the readiness does not reflect reported awareness of motor preparation. C_LIO_LIComputational modeling supports stochastic accumulation over linear ballistic accumulation and classic RP models. C_LIO_LIReported awareness of motor preparation may emerge from metacognitive access to stochastic accumulation. C_LIO_LITime-frequency analysis suggests reported awareness may also relate to pre-probe beta desynchronization. C_LI

neuroscience↗

bioRxiv2023

Slow ramping emerges from spontaneous fluctuations in spiking neural networks

Highlights1. 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 capacity to initiate actions endogenously is critical for goal-directed behavior. Spontaneous voluntary actions are typically preceded by slow-ramping activity in medial frontal cortex 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.

neuroscience↗