Biology subjects

Pitts, M.

Publications and source records attributed to Pitts, M..

8 recordsLinked to original sources

bioRxiv2026

A late meta-stable code of conscious access in the absence of report

One of the most widely recognised neural correlates of consciousness, the P3b, has been challenged in recent years as a neural signal linked to conscious processing, due to its absence in no-report paradigms. Here, we test whether, even in the absence of a P3b, a period of late metastable brain activity may provide a more general signature of conscious access to perceptual information. To this end, we leverage modern advances in electroencephalography (EEG) analyses, re-examining four datasets from no-report inattentional blindness experiments--all of which failed to find a P3b for consciously seen task irrelevant stimuli-- using cross-time multivariate decoding analyses on the EEG data. We find robust temporal generalization of decoding for consciously seen stimuli across different stimulus types (shapes, faces, words), independent of report requirements and regardless of whether a P3b was evoked. This temporal generalization occurred most consistently 200-400 milliseconds post-stimulus onset, suggesting a meta-stable neural code for conscious processing in a time window typically associated with cognitive access to perceptual content. These consistent temporal generalization patterns across stimulus types indicate a potentially universal signature of conscious access.

neuroscience↗

bioRxiv2024

Human motion data expansion from arbitrary sparsesensors with shallow recurrent decoders

Advances in deep learning and sparse sensing have emerged as powerful tools for monitoring human motion in natural environments. We develop a deep learning architecture, constructed from a shallow recurrent decoder network, that expands human motion data by mapping a limited (sparse) number of sensors to a comprehensive (dense) configuration, thereby inferring the motion of unmonitored body segments. Even with a single sensor, we reconstruct the comprehensive set of time series measurements, which are important for tracking and informing movement-related health and performance outcomes. Notably, this mapping leverages sensor time histories to inform the transformation from sparse to dense sensor configurations. We apply this mapping architecture to a variety of datasets, including controlled movement tasks, gait pattern exploration, and free-moving environments. Additionally, this mapping can be subject-specific (based on an individuals unique data for deployment at home and in the community) or group-based (where data from a large group are used to learn a general movement model and predict outcomes for unknown subjects). By expanding our datasets to unmeasured or unavailable quantities, this work can impact clinical trials, robotic/device control, and human performance by improving the accuracy and availability of digital biomarker estimates.

systems biology↗

bioRxiv2024

No Electrophysiological Evidence for Semantic Processing During Inattentional Blindness

A long-standing question concerns whether sensory input can reach semantic stages of processing in the absence of attention and awareness. Here, we examine whether the N400, an event related potential associated with semantic processing, can occur under conditions of inattentional blindness. By employing a novel three-phase inattentional blindness paradigm designed to maximise the opportunity for detecting an N400, we found no evidence for it when participants were inattentionally blind to the eliciting stimuli (related and unrelated word pairs). In contrast, when minimal attention was allocated to the same task-irrelevant word pairs, participants became aware of them, and a small N400 became evident. Finally, when the same stimuli were fully attended and relevant to the task, a robust N400 was observed. In addition to univariate ERP measures, multivariate decoding analyses were unable to classify related versus unrelated word pairs when observers were inattentionally blind to the words, with decoding reaching above-chance levels only when the words were (at least minimally) attended. Our results also replicated several previous studies by finding a "visual awareness negativity" (VAN) that distinguished task-irrelevant stimuli that were perceived compared with those that were not perceived, and a P3b (or "late positivity") that was evident only when the stimuli were perceived and task relevant. Together, our findings suggest that semantic processing might require at least a minimal amount of attention.

neuroscience↗

bioRxiv2023

An adversarial collaboration to critically evaluate theories of consciousness

Different theories explain how subjective experience arises from brain activity1,2. These theories have independently accrued evidence, yet, confirmation bias and dependence on design choices hamper progress in the field3. Here, we present an open science adversarial collaboration which directly juxtaposes Integrated Information Theory (IIT)4,5 and Global Neuronal Workspace Theory (GNWT)6-10, employing a theory-neutral consortium approach11,12. We investigate neural correlates of the content and duration of visual experience. The theory proponents and the consortium developed and preregistered the experimental design, divergent predictions, expected outcomes, and their interpretation12. 256 human subjects viewed suprathreshold stimuli for variable durations while neural activity was measured with functional magnetic resonance imaging, magnetoencephalography, and electrocorticography. We find information about conscious content in visual, ventro-temporal and inferior frontal cortex, with sustained responses in occipital and lateral temporal cortex reflecting stimulus duration, and content-specific synchronization between frontal and early visual areas. These results confirm some predictions of IIT and GNWT, while substantially challenging both theories: for IIT, a lack of sustained synchronization within posterior cortex contradicts the claim that network connectivity specifies consciousness. GNWT is challenged by the general lack of ignition at stimulus offset and limited representation of certain conscious dimensions in prefrontal cortex. Beyond challenging the theories themselves, we present an alternative approach to advance cognitive neuroscience through a principled, theory-driven, collaborative effort. We highlight the challenges to change peoples mind 13 and the need for a quantitative framework integrating evidence for systematic theory testing and building.

neuroscience↗

bioRxiv2023

A novel signature of visual awareness independent of post-perceptual processing

What are the neural processes associated with perceptual awareness that are distinct from pre-conscious sensory encoding and post-perceptual processes such as reporting an experience? Here, we used electroencephalography (EEG) and a no-report visual masking paradigm with parametric manipulations of stimulus visibility to search for neural signatures associated with perceptual awareness independent from both early sensory processing and subsequent reporting. Specifically, we manipulated the time between stimuli and subsequent masks in a linear manner (i.e., 17ms, 33ms, 50ms, 67ms, and 83ms) such that observers awareness of the stimuli increased in a non-linear fashion (i.e., stimuli were never seen at the two shortest time intervals, always seen at the two longest intervals, and seen approximately 50% of the time at the intermediate interval). Moreover, we manipulated the task across blocks to create separate report and no-report conditions. Overall, we found one neural signal that was closely associated with perceptual awareness, independent from the task: a fronto-central event-related potential (ERP), from [~]250-300ms, that we refer to as the N2. In contrast, earlier ERP signals were linked with the linear manipulation of stimulus strength regardless of visibility, while later candidate signatures, such as P3b and temporal generalization of decoding, were present in the report condition but absent in the no-report condition suggesting a closer association with task performance than perceptual awareness. Taken together, these findings inform current debates regarding theories of consciousness and offer new avenues for exploring the neural mechanisms supporting conscious processing. Significance statementWhat differentiates conscious and unconscious processing in the brain? Here, we identify an electrophysiological signature of perceptual awareness using a combination of visual psychophysics and electroencephalography (EEG). In addition, we used a newly developed "no-report" paradigm, in which observers did not report anything about their perceptual experience to separate neural signals associated with consciousness from those associated with the act of reporting (i.e., memory, motor planning, etc.). Using this no-report paradigm was critical because several other candidate signatures of conscious processing were present when observers reported their experiences but completely disappeared when observers did not report their experiences. These findings open the door to future research interested in the neural mechanisms associated of conscious processing.

neuroscience↗

bioRxiv2021

Brain networks in human conscious visual perception

Consciousness is not explained by a single mechanism, rather it involves multiple specialized neural systems overlapping in space and time. We hypothesize that synergistic, large-scale subcortical and cortical attention and signal processing networks encode conscious experiences. To identify brain activity in conscious perception without overt report, we classified visual stimuli as perceived or not using eye measurements. Report-independent event-related potentials and functional magnetic resonance imaging (fMRI) signals both occurred at early times after stimuli. Direct recordings revealed a novel thalamic awareness potential linked to conscious visual perception based on report. fMRI showed thalamic and cortical detection, arousal, attentional salience, task-positive, and default mode networks were involved independent of overt report. These findings identify a specific sequence of neural mechanisms in human conscious visual perception. One-Sentence SummaryHuman conscious visual perception engages large-scale subcortical and cortical networks even without overt report.

neuroscience↗

bioRxiv2021

The Consciousness Theories Studies (ConTraSt) database: analyzing and comparing empirical studies of consciousness theories

Understanding how consciousness arises from neural activity remains one of the biggest challenges for neuroscience. Numerous theories have been proposed in recent years, each gaining independent empirical support. Currently, there is no comprehensive, quantitative and theory-neutral overview of the field that enables an evaluation of how theoretical frameworks interact with empirical research. We provide a birds eye view on studies that interpreted their findings in light of at least one of four leading neuroscientific theories of consciousness (N=412 experiments), asking how methodological choices of the researchers might affect the final conclusions. We found that supporting a specific theory can be predicted solely from methodological choices, irrespective of findings. Furthermore, most studies interpret their findings post-hoc, rather than a-priori testing critical predictions of the theories. Our results highlight challenges for the field and provide researchers with a unique, open-access website to further analyze trends in the neuroscience of consciousness.

neuroscience↗

bioRxiv2020

Distinguishing the neural correlates of perceptual awareness and post-perceptual processing

To identify the neural correlates of perceptual awareness, researchers often compare the differences in neural activation between conditions in which an observer is or is not aware of a stimulus. While intuitive, this approach often contains a critical limitation: In order to link brain activity with perceptual awareness, observers traditionally report the contents of their perceptual experience. However, relying on observers reports is problematic because it is difficult to know if the neural responses being measured are associated with conscious perception or with post-perceptual processes involved in the reporting task (i.e., working memory, decision-making, etc.). To address this issue, we combined a standard visual masking paradigm with a recently developed "no-report" paradigm in male/female human participants. In the visual masking paradigm, observers saw images of animals and objects that were visible or invisible depending on their proximity to masks. Meanwhile, on half of the trials, observers reported the contents of their perceptual experience (i.e., report condition), while on the other half of trials they refrained from reporting about their experiences (i.e., no-report condition). We used electroencephalography (EEG) to examine how visibility interacts with reporting by measuring the P3b event related potential (ERP), one of the proposed canonical "signatures" of conscious processing. Overall, we found a robust P3b in the report condition, but no P3b whatsoever in the no-report condition. This finding suggests that the P3b itself is not a neural signature of conscious processing and highlights the importance of carefully distinguishing the neural correlates of perceptual awareness from post-perceptual processing. Significance statementWhat are the neural signatures that differentiate conscious and unconscious processing in the brain? Perhaps the most well-established candidate signature is the P3b event-related potential (ERP), a late slow wave that appears when observers are aware of a stimulus, but disappears when a stimulus fails to reach awareness. Here, however, we found that the P3b does not track what observers are perceiving but instead tracks what observers are reporting. When observers are aware of simple visual stimuli, the P3b is nowhere to be found unless observers are reporting the contents of their experience. These results challenge the well-established notion of the P3b as a neural marker of awareness and highlight the need for new approaches to the neuroscience of consciousness.

neuroscience↗