Imaging correlations in non-communicating patients

The diagnosis and medical management of patients with acute or chronic disorders of consciousness (DOC) are challenging. Motor-independent functional neuroimaging technologies are increasingly employed to study covert cognitive processes in the absence of behavioural reports. Studies with functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) performed in this patient population have utilized active, passive and resting-state paradigms. Active paradigms refer to mental imagery tasks that measure wilful modulation of brain signal in specific brain areas, aiming to detect command-following. Passive paradigms are used to measure brain responses to external sensory stimulation (e.g. auditory, somatosensory and visual). Alternatively, in resting-state paradigms, spontaneous brain function is assessed while subjects receive no external stimulation and are instructed to let their mind wander. Independently from each other, these methods have shown differences between healthy controls and patients, as well as among patients with DOC. However, these techniques cannot yet be used in clinical settings before robust information at the single-subject level will be provided: it is expected that multimodal research will improve the single-patient diagnosis, shed light on the prognostic biomarkers, and eventually promote the medical management of patients with consciousness alterations

Targeting the neurophysiology of cognitive systems with transcranial alternating current stimulation

Cognitive impairment represents one of the most debilitating and most difficult symptom to treat of many psychiatric illnesses. Human neurophysiology studies have suggested specific pathologies of cortical network activity correlate with cognitive impairment. However, we lack (1) demonstration of causal relationships between specific network activity patterns and cognitive capabilities and (2) treatment modalities that directly target impaired network dynamics of cognition. Transcranial alternating current stimulation (tACS), a novel non-invasive brain stimulation approach, may provide a crucial tool to tackle these challenges. We here propose that tACS can be used to elucidate the causal role of cortical synchronization in cognition and, eventually, to enhance pathologically weakened synchrony that may underlie cognitive deficits. To accelerate such development of tACS as a treatment for cognitive deficits, we discuss studies on tACS and cognition (all performed in healthy participants) according to the Research Domain Criteria (RDoC) of the National Institute of Mental Health

Memory Reactivation in Humans (Imaging Studies)

Consistent evidence indicates that sleep participates in memory consolidation processes, possibly through the replay of learning-related neuronal activity. Besides animal data, non-invasive brain imaging studies in man (mostly using positron emission tomography [PET] and functional magnetic resonance imaging [fMRI]) have shown the spontaneous reactivation of cerebral activity in learning-related areas during sleep. Additionally, studies triggering reactivation using contextual cues during sleep have suggested a causal role for neuronal replay and reactivation in memory consolidation processes. Finally, several imaging studies support the hypothesis that post-learning sleep promotes a progressive transfer of information from hippocampus toward neocortical stores over time, as a possible consequence of the neuronal replay. Besides neuroimaging techniques, we argue that replay of neuronal activity may also be investigated and accessed at the behavioural level through the study of dreams and sleep disorders .info:eu-repo/semantics/publishe

Sleep oscillations and aging

Human sleep can be broadly categorized as rapid eye movement (REM) and non-REM (NREM) sleep according to the electrophysiological features and oscillations that characterize these distinct states. The most dramatic changes that occur to sleep are observed over the course of the life span. With aging, the neural oscillations of sleep may provide insight into the physiological changes that accompany aging, may signal poor health and pathology, and explain functional changes in daytime performance, learning, and memory. This review will discuss the age-related changes that occur to the neural oscillations that characterize sleep states, such as sleep spindles, k-complexes, slow waves, and REM-related neural activity. The physiological processes that underlie these changes and the functional significance of the age-related changes in sleep are discussed