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Ram Adapa

17 papers in the library · 422 citations · publishing 2011-2026

Papers

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Mapping basal ganglia circuitry in altered states of consciousness: from pathology to pharmacology.

Brain : a journal of neurology August 7, 2026 Dorottya Szocs, Andrea I Luppi, Peter Coppola et al.

The precise neuromodulatory mechanisms underlying consciousness and its disorders, despite growing evidence in both animals and humans, remain poorly understood at the subcortical level. The basal ganglia, a key component of the cortico-basal ganglia-thalamo-cortical loop, are known to play a crucial role in mediating consciousness and behavioural responsiveness to the environment. Here, we...

Diminished functional gradient of the precuneus during altered states of consciousness

bioRxiv December 17, 2024 Dian Lyu, Ram Adapa, Robin Carhart-Harris et al. preprint

Abstract The relationship between the default mode network (DMN) and task-positive networks, such as the frontoparietal control network (FPCN), is a prominent feature of functional connectivity (FC) in the human brain. This relationship is primarily anticorrelated at rest in healthy brains and is disrupted in altered states of consciousness. Although the DMN and FPCN seem to perform distinct...

In vivo mapping of pharmacologically induced functional reorganization onto the human brain’s neurotransmitter landscape

Science Advances June 14, 2023 Leor Roseman, Christopher Timmermann, Daniel Golkowski et al. 65 citations

To understand how pharmacological interventions can exert their powerful effects on brain function, we need to understand how they engage the brain’s rich neurotransmitter landscape. Here, we bridge microscale molecular chemoarchitecture and pharmacologically induced macroscale functional reorganization, by relating the regional distribution of 19 neurotransmitter receptors and transporters...

Distributed harmonic patterns of structure-function dependence orchestrate human consciousness.

Communications Biology January 28, 2023 Andrea I. Luppi, Jakub Vohryzek, Morten L. Kringelbach et al. 98 citations

A central question in neuroscience is how consciousness arises from the dynamic interplay of brain structure and function. Here we decompose functional MRI signals from pathological and pharmacologically-induced perturbations of consciousness into distributed patterns of structure-function dependence across scales: the harmonic modes of the human structural connectome. We show that...

The complexity of the stream of consciousness.

Communications Biology November 3, 2022 Peter Coppola, Judith Allanson, Lorina Naci et al.

Typical consciousness can be defined as an individual-specific stream of experiences. Modern consciousness research on dynamic functional connectivity uses clustering techniques to create common bases on which to compare different individuals. We propose an alternative approach by combining modern theories of consciousness and insights arising from phenomenology and dynamical systems theory....

Mapping Pharmacologically-induced Functional Reorganisation onto the Brain’s Neurotransmitter Landscape

bioRxiv (Cold Spring Harbor Laboratory) July 13, 2022 Andrea I. Luppi, Justine Y. Hansen, Ram Adapa et al. 5 citations preprint

Abstract To understand how pharmacological interventions can exert their powerful effects on brain function, we need to understand how they engage the brain’s rich neurotransmitter landscape. Here, we bridge microscale molecular chemoarchitecture and pharmacologically-induced macroscale functional reorganisation, by relating the regional distribution of 19 neurotransmitter receptors and...

Dopaminergic brainstem disconnection is common to pharmacological and pathological consciousness perturbation

Proceedings of the National Academy of Sciences of the United States of America July 23, 2021 Lennart R.b. Spindler, Andrea I. Luppi, Ram Adapa et al.

Significance Understanding the neural bases of consciousness is of basic scientific and clinical importance. Human neuroimaging has established that a network of interconnected brain regions known as the default mode network disintegrates in anesthesia and after brain damage that causes disorders of consciousness. However, the neurochemical underpinnings of this network change remain largely...

Network dynamics scale with levels of awareness

bioRxiv Preprint Server April 12, 2021 Peter Coppola, Lennart R.b. Spindler, Andrea I. Luppi et al. preprint

Small world topologies are thought to provide a valuable insight into human brain organisation and consciousness. However, functional magnetic resonance imaging studies in consciousness have not yielded consistent results. Given the importance of dynamics for both consciousness and cognition, here we investigate how the diversity of brain dynamics pertaining to small world topology (quantified...

Reorganisation of Brain Hubs across Altered States of Consciousness

Scientific Reports February 25, 2020 Deniz Vatansever, Manuel S. Schröter, Ram Adapa et al.

Patterns of functional interactions across distributed brain regions are suggested to provide a scaffold for the conscious processing of information, with marked topological alterations observed in loss of consciousness. However, establishing a firm link between macro-scale brain network organisation and conscious cognition requires direct investigations into neuropsychologically-relevant...

Fractal dimension of cortical functional connectivity networks & severity of disorders of consciousness

PLoS One February 13, 2020 Thomas F. Varley, Michael M. Craig, Ram Adapa et al.

Recent evidence suggests that the quantity and quality of conscious experience may be a function of the complexity of activity in the brain and that consciousness emerges in a critical zone between low and high-entropy states. We propose fractal shapes as a measure of proximity to this critical point, as fractal dimension encodes information about complexity beyond simple entropy or randomness,...

Consciousness & Brain Functional Complexity in Propofol Anaesthesia

Scientific Reports January 23, 2020 Thomas F. Varley, Andrea I. Luppi, Ioannis Pappas et al. 86 citations

The brain is possibly the most complex system known to mankind, and its complexity has been called upon to explain the emergence of consciousness. However, complexity has been defined in many ways by multiple different fields: here, we investigate measures of algorithmic and process complexity in both the temporal and topological domains, testing them on functional MRI BOLD signal data obtained...

Fractal Dimension of Cortical Functional Connectivity Networks Predicts Severity in Disorders of Consciousness

bioRxiv Preprint Server October 1, 2019 Tf. Varley, M. Craig, Ram Adapa et al. preprint

Recent evidence suggests that the quantity and quality of conscious experience may be a function of the complexity of activity in the brain, and that consciousness emerges in a critical zone on the axes of order/randomness and integration/differentiation. We propose fractal shapes as a measure of proximity to this critical point, as fractal dimension encodes information about complexity beyond...

Placing meta-stable states of consciousness within the predictive coding hierarchy: The deceleration of the accelerated prediction error.

Consciousness and Cognition July 10, 2018 Amirali Shirazibeheshti, J. Cooke, Srivas Chennu et al.

While many studies have linked prediction errors and event related potentials at a single processing level, few consider how these responses interact across levels. In response, we present a factorial analysis of a multi-level oddball task - the local-global task - and we explore it when participants are sedated versus recovered. We found that the local and global levels in fact interact. This...

Ketamine Effects on Memory Reconsolidation Favor a Learning Model of Delusions

PLoS One June 12, 2013 Philip R. Corlett, Victoria C. Cambridge, Jennifer M. Gardner et al. 104 citations

Delusions are the persistent and often bizarre beliefs that characterise psychosis. Previous studies have suggested that their emergence may be explained by disturbances in prediction error-dependent learning. Here we set up complementary studies in order to examine whether such a disturbance also modulates memory reconsolidation and hence explains their remarkable persistence. First, we...

Ketamine administration in healthy volunteers reproduces aberrant agency experiences associated with schizophrenia.

Cogn Neuropsychiatry February 6, 2011 James W. Moore, Danielle C. Turner, Philip R. Corlett et al. 64 citations

INTRODUCTION: Aberrant experience of agency is characteristic of schizophrenia. An understanding of the neurobiological basis of such experience is therefore of considerable importance for developing successful models of the disease. We aimed to characterise the effects of ketamine, a drug model for psychosis, on sense of agency (SoA). SoA is associated with a subjective compression of the...

Exploring the Impact of Ketamine on the Experience of Illusory Body Ownership

Biological Psychiatry 2011 H. Morgan, D. Turner, P. Corlett et al.

Background Our sense of body ownership is profound and familiar, yet it may be misleading. In the rubber-hand illusion, synchronous tactile and visual stimulation lead to the experience that a rubber hand is actually one's own. This illusion is stronger in schizophrenia. Given the evidence that ketamine, a noncompetitive N-methyl-D-aspartate antagonist reproduces symptoms of schizophrenia, we...