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Coma and Disorders of Consciousness
Published in Alexander R. Toftness, Incredible Consequences of Brain Injury, 2023
We can get a bit more specific. Comas usually result from damage to the reticular activating system in the brain stem or from “global brain dysfunction” such that there is extensive damage in many parts of the brain and they are unable to effectively communicate with one another (Schnakers & Majerus, 2018, p. 3). In contrast, UWS indicates an intact reticular formation, but damage has disrupted “the flow of information from the midbrain to the cortex” (Bleck, 2003). Such damage may be to the underlying white matter of the brain or to the thalamus in each of the brain's hemispheres (Schnakers & Majerus, 2018).
Functional Neurology
Published in James Crossley, Functional Exercise and Rehabilitation, 2021
The reticular activating system (RAS) is the part of the brain that guides attention. The RAS filters and extracts extraneous sensory information. The RAS is like a GPS for the brain, directing attention to where we need it. Selective attention is why it is easy to pick out our own name from a nearby conversation. Hearing our name alerts the brain that a conversation is relevant, attracting attention.
Assessing Paediatric Development in Psychiatry
Published in Cathy Laver-Bradbury, Margaret J.J. Thompson, Christopher Gale, Christine M. Hooper, Child and Adolescent Mental Health, 2021
The reticular activating system is the underlying constellation of basic cortical nuclei and a series of diffuse fibre networks that link these nuclei with key midline subcortical structures and the whole of the higher cortex. The neuronal processes involved in keeping a subject awake and alert utilise, in general, the neurotransmitter noradrenaline. Its counterpart, which is inhibitory in nature and sleep-inducing, is the anticholinergic pathway. Other associative neurotransmitter pathways exist and are further involved in this sleep/wake balance. These pathways vary in degrees of activation and inhibition during rapid eye movement (REM) sleep versus non-REM sleep. The hypothalamus and the pineal gland are involved in further regulating the sleep/wake cycle. This involves the release of cortisol and melatonin in diurnal patterns.
Effectiveness of structured early mobilization protocol on mobility status of patients in medical intensive care unit
Published in Physiotherapy Theory and Practice, 2022
Aishwarya Gatty, Stephen Rajan Samuel, Gopala Krishna Alaparthi, Dattatray Prabhu, Madhusudan Upadya, Shyam Krishnan, Sampath Kumar Amaravadi
Improvement in mobility status of patients in the intervention groups could be associated with several positive effects of early mobilization. It increases arousal via activation of the reticular activating system and priming of the various organ systems involved and cerebral electrical activity. It also decreases effects of sedation (Dean and Butcher, 2012). These effects could have improved the mental status, thereby increasing the scores. Mental status can be enhanced by management of sedation and delirium which is necessary to mobilize patients (Clemmer, 2014). This can be done by implementation of ABCDE bundle which includes daily sedation awakening trials, breathing coordination, assessment, preventing delirium, and implementing early mobility (Bassett et al., 2015). More improvement in scores could have been possible if early mobilization would have been executed as a part of this bundle in our study.
An exploration of higher-level language comprehension deficits and factors influencing them following blast TBI in US veterans
Published in Brain Injury, 2020
Judith R. Koebli, Venugopal Balasubramanian, Genevieve Pinto Zipp
How do these abnormalities correlate with neurobehavioral symptoms? Bigler (28) stated that slight changes in the upper brainstem and reticular activating system will affect consciousness. Mechanical compression of the perirhinal and entorhinal cortices will affect the input and or output to the hippocampus through the fornix and the connection with the anterior thalamus and cingulated. The medial temporal lobe and basal forebrain are associated with emotional regulation. Stretching of the internal carotid artery is associated with posttraumatic migraines. The symptom of fatigue is associated with hormonal changes from the disruption of hypothalamic-pituitary area. Speed of processing is slowed after a concussion. This is correlated to the compromise of the integrity of white matter pathways. Long-coursing axons are more vulnerable for inter-hemispheric connections (29), such as the corpus callosum and anterior commissure. Finally, autopsy studies found axonal injury in the fornix (30,31). The fornix is a white matter structure that contains projecting axons from the hippocampus. The hippocampus is important for memory. Therefore, disruption in the fronix integrity may cause the disruption in short-term memory (28).
Pharmacokinetic and pharmacodynamic of the cognitive enhancer modafinil: Relevant clinical and forensic aspects
Published in Substance Abuse, 2020
Ana Sousa, Ricardo Jorge Dinis-Oliveira
Additionally, recent studies suggest that modafinil might increase electrotonic coupling among cortical neurons via of gap junctions and connexins87 and that its awakening effect depends on integral interconnections between the rostral brain and lower brainstem.88 Electrical coupling in the reticular activating system synchronizes the activity across populations of cells and because modafinil increases this coupling, it induces arousal.87 They also support that brain targets for modafinil are in the locus coeruleus, dorsal pontine tegmentum, substantia nigra, tuberomammillary nucleus and dorsolateral hypothalamic area.88 The presence of many existing hypotheses simply reflects the complexity of the mode of action of modafinil. Still, modafinil differs from other classical psychostimulants, namely amphetamine, methylphenidate and caffeine, because it inducts soft waking without sleep rebound and has a limited addiction, tolerance and neuronal and behavioral excitation potential.23,88–90 Armodafinil and modafinil are pharmacologically similar both in animal and in vitro studies, independently of all the questions about their mechanism of action.91