Impacto de la estimulación sonora durante diferentes etapas del sueño en pacientes con acúfeno

It is known that auditory information is continuously processed both during wakefulness and sleep. Consistently, it has been shown that sound stimulation mimicking tinnitus during sleep decreases the intensity of tinnitus and improves the patients’ quality of life. The mechanisms underlying this effect are not known. To begin to address this question, eleven patients suffering from tinnitus were stimulated with sound mimicking tinnitus at different sleep stages; 4 were stimulated in N2, 4 in stage N3 (slow waves sleep) and 3 in REM sleep (stage with Rapid Eyes Movements). Patients’ sleep stage was monitored through polysomnography, for sound stimulation application. Tinnitus level reported by subjects were compared the days before and after stimulation and statistically analyzed (paired Student t test). All patients stimulated at stage N2 reported significantly lower tinnitus intensity the day after stimulation, while none stimulated during stage N3 and only one out of three stimulated during REM sleep showed changes. These results are consistent with studies showing that sound stimulation during N2 (sleep stage with spindles) changes power spectrum and coherence of electroencephalographic signals, and suggest that the N2 sleep stage is a critical period for reducing tinnitus intensity using this therapeutic strategy, during which auditory processing networks are more malleable by sound stimulation.Es sabido que la información auditiva se procesa continuamente durante la vigilia y el sueño. Se ha demostrado que la estimulación con sonido que imita el tinnitus, aplicada durante el sueño, disminuye la intensidad del tinnitus y mejora la calidad de vida de los pacientes. Los mecanismos que subyacen a esta mejoría no se conocen, aunque en la etapa de sueño con husos (N2) fueron demostrados los principales cambios en los espectros de potencia y la coherencia en las ondas electroencefalográficas durante la estimulación sonora. Once pacientes que padecen tinnitus fueron estimulados por sonido (imitando el tinnitus) en diferentes etapas del sueño; 4 fueron estimulados en N2, 4 en la etapa N3 (sueño de ondas lentas) y 3 durante el sueño REM (estadio con movimientos oculares rápidos). Los pacientes fueron registrados con una polisomnografía, para el diagnóstico de etapas del sueño y la aplicación de la estimulación del sonido. Los valores de intensidad del tinnitus se compararon los días anterior y posterior a la estimulación y se analizaron estadísticamente (prueba t de Student pareada). Todos los pacientes estimulados en la etapa N2 mostraron una disminución estadísticamente significativa en la intensidad del tinnitus el día después de la estimulación, mientras que ninguno de los pacientes estimulados en la etapa N3 mostró cambios en la intensidad, y solo uno de los tres estimulados durante el sueño REM tuvo cambios. Los resultados sugieren que la etapa de sueño N2 sería el período en que el sonido estimulante interactuaría con las redes de procesamiento auditivo, reduciendo la intensidad del tinnitus

Sleep and sensory information

The information coming from the outer and the inner worlds during life is a meaningful influence on the brain phenotypical development and, in our particular topic, on sleep organization. In early developmental stages, from phylogenetic and ontogenetic viewpoints, the sensory information constitutes a relevant drive controlling the brain function and the general physiology. Each brain develops genetically conditioned, although a germane component is the sensory information from both the two worlds and the way the brain handled it throughout life, i.e., an endless process. The natural light-dark sequence, a phylogenically archaic information, through the light receptor and its processing system, profoundly influences the sleep-wakefulness cycle. The circadian rhythm of melatonin secretion -the notion of darkness- is generated in mammals by a central pacemaker located in the suprachiasmatic nuclei of the hypothalamus, largely synchronized by cues from the light-dark cycle. Early in the twentieth century, the concept of the sleep as being the result of a blockade of the auditory inflow was introduced (see 16). Later, Bremer made the proposal of an extensive deafferentation of ascending sensory impulses to the isolated brain that resulted in sleep. He became the outstanding proponent of the deafferentation sleep theory known as the “passive theory”, implicating the existence of a tonus on the central nervous system (CNS) dependent on the sensory information. The activating ascending reticular system described seemed to confirm Bremer’s concepts: every sensory input would also release information (tonus?) to the brain stem activating reticular formation.Sociedad Argentina de Fisiologí

Past, present, and future of sleep medicine research in Latin America.

Sleep medicine is a relatively young field with exponential growth in development and research in the last decades. Parallel to the advances in the United States, Latin America also had its beginnings in sleep medicine housed in neuroscience laboratories. Since the very first Latin American meeting in 1985, and the first sleep society in 1993, sleep research has undergone significant development in subsequent years. From contributions in animal research that allowed understanding of the activity of the brain during sleep to the studies that improved our knowledge of sleep disorders in humans, Latin America has become a scientific hub for expansion of sleep research. In this article, we present a historical account of the development of sleep medicine in Latin America, the current state of education and the achievements in research throughout history, and the latest advances in the trending areas of sleep science and medicine. These findings were presented during World Sleep Society meeting in Vancouver in 2019 and complement the work on sleep societies and training published by Vizcarra-Escobar et al in their article Sleep societies and sleep training programs in Latin America (J Clin Sleep Med. 2020;16(6):983-988)