Brain Networks, Neurotransmitters and Psychedelics: Towards a Neurochemistry of Self-Awareness.

PURPOSE OF REVIEW: Self-awareness can be defined as the capacity of becoming the object of one's own awareness and, increasingly, it has been the target of scientific inquiry. Self-awareness has important clinical implications, and a better understanding of the neurochemical basis of self-awareness may help clarifying causes and developing interventions for different psychopathological conditions. The current article explores the relationship between neurochemistry and self-awareness, with special attention to the effects of psychedelics. RECENT FINDINGS: The functioning of self-related networks, such as the default-mode network and the salience network, and how these are influenced by different neurotransmitters is discussed. The impact of psychedelics on self-awareness is reviewed in relation to specific processes, such as interoception, body ownership, agency, metacognition, emotional regulation and autobiographical memory, within a framework based on predictive coding. Improved outcomes in emotional regulation and autobiographical memory have been observed in association with the use of psychedelics, suggesting higher-order self-awareness changes, which can be modulated by relaxation of priors and improved coping mechanisms linked to cognitive flexibility. Alterations in bodily self-awareness are less consistent, being potentially impacted by doses employed, differences in acute/long-term effects and the presence of clinical conditions. Future studies investigating the effects of different molecules in rebalancing connectivity between resting-state networks may lead to novel therapeutic approaches and the refinement of existing treatments.

The cognitive neuroscience of self-awareness: Current framework, clinical implications, and future research directions.

Self-awareness, the ability to take oneself as the object of awareness, has been an enigma for our species, with different answers to this question being provided by religion, philosophy, and, more recently, science. The current review aims to discuss the neurocognitive mechanisms underlying self-awareness. The multidimensional nature of self-awareness will be explored, suggesting how it can be thought of as an emergent property observed in different cognitive complexity levels, within a predictive coding approach. A presentation of alterations of self-awareness in neuropsychiatric conditions will ground a discussion on alternative frameworks to understand this phenomenon, in health and psychopathology, with future research directions being indicated to fill current gaps in the literature. This article is categorized under: Philosophy > Consciousness Psychology > Brain Function and Dysfunction Neuroscience > Cognition.

Self-awareness in Dementia: a Taxonomy of Processes, Overview of Findings, and Integrative Framework.

PURPOSE OF REVIEW: Self-awareness, the capacity of becoming the object of one's own awareness, has been a frontier of knowledge, but only recently scientific approaches to the theme have advanced. Self-awareness has important clinical implications, and a finer understanding of this concept may improve the clinical management of people with dementia. The current article aims to explore self-awareness, from a neurobiological perspective, in dementia. RECENT FINDINGS: A taxonomy of self-awareness processes is presented, discussing how these can be structured across different levels of cognitive complexity. Findings on self-awareness in dementia are reviewed, indicating the relative preservation of capacities such as body ownership and agency, despite impairments in higher-level cognitive processes, such as autobiographical memory and emotional regulation. An integrative framework, based on predictive coding and compensatory abilities linked to the resilience of self-awareness in dementia, is discussed, highlighting possible avenues for future research into the topic.

Simultaneous measurement of in-plane and out-of-plane displacement fields in scattering media using phase-contrast spectral optical coherence tomography.

The use of phase-contrast spectral optical coherence tomography to measure two orthogonal displacement components on a slice within a scattering medium is demonstrated. This is achieved by combining sequential oblique illumination of the object and recording two interferograms before plus two after the deformation. The proposed technique is illustrated with results from a sample undergoing simple shear. Depth-resolved out-of-plane and in-plane sensitivities of 0.14 and 4.2 microm per fringe are demonstrated up to a depth of 400 microm in a water-based polymer.

Adaptive phase-shifting algorithm for temporal phase evaluation.

Most standard temporal-phase-shifting (TPS) algorithms evaluate the phase by computing a windowed Fourier transform (WFT) of the intensity signal at the carrier frequency of the system. However, displacement of the specimen during image acquisition may cause the peak of the transform to shift away from the carrier frequency, leading to phase errors and even unwrapping failure. We present a novel TPS method that searches for the peak of the WFT and evaluates the phase at that frequency instead of at the carrier frequency. The performance of this method is compared with that of standard algorithms by using numerical simulations. Experimental results from high-speed speckle interferometry studies of carbon fiber panels are also presented.

Effects of random vibration in high-speed phase-shifting speckle pattern interferometry.

The influence of random vibrations on the performance of a dynamic phase-shifting speckle pattern interferometer is investigated by means of experiments and numerical simulations. Two aspects are evaluated: first, temporal unwrapping reliability, second, vibration-induced phase noise. The former is found to be a significant constraint, even for peak velocities well below the Nyquist velocity limit of the interferometer. Shorter sampling windows and higher framing rates are shown to increase the unwrapping success rate, but longer windows reduce the phase error. Three analytical criteria for determining the expected unwrapping success rate are proposed and compared.