Stapedial muscle electromyography in various diseases

The polyvagal perspective

The polyvagal theory introduced a new perspective relating autonomic function to behavior, that included an appreciation of the autonomic nervous system as a "system," the identification of neural circuits involved in the regulation of autonomic state, and an interpretation of autonomic reactivity as adaptive within the context of the phylogeny of the vertebrate autonomic nervous system. The paper has two objectives: first, to provide an explicit statement of the theory; and second, to introduce the features of a polyvagal perspective. The polyvagal perspective emphasizes how an understanding of neurophysiological mechanisms and phylogenetic shifts in neural regulation leads to different questions, paradigms, explanations, and conclusions regarding autonomic function in biobehavioral processes than peripheral models. Foremost, the polyvagal perspective emphasizes the importance of phylogenetic changes in the neural structures regulating the autonomic nervous system and how these phylogenetic shifts provide insights into the adaptive function and the neural regulation of the two vagal systems.

The Polyvagal Theory: phylogenetic contributions to social behavior

The scientific legacy of Paul MacLean provides important insights into the neural substrate of adaptive social behavior in mammals. Through his research and visionary conceptualizations, current investigators can legitimately study social behavior from a neurobiological perspective. His research and writings provided three important contributions. First, he emphasized the importance of evolution as an organizing principle that shaped both the structure of the nervous system and the adaptive social behavior. Second, by defining the limbic system, he legitimized the biological perspective in the study of emotion. Third, he recognized the important role of the vagal afferents in the regulation of higher brain structures. The paper will focus on the Polyvagal Theory. The Polyvagal Theory is a new conceptualization of the role of vagus and employs several features that MacLean emphasized including the importance of evolution, limbic structures and vagal afferents. The Polyvagal Theory builds on these early findings by MacLean and focuses on the link between phylogenetic changes in the autonomic nervous system and social behavior. By focusing on the phylogenetic changes in the structure of the vagus and the role that the vagus plays in the neural regulation of visceral state, new insights regarding social behavior emerge. Moreover, by articulating the phylogenetically organized hierarchy of neural circuits, insights into benefits of social behavior become evident as do an understanding of the behavioral and physiological features associated with stress and psychiatric disorders.

Acoustic middle ear muscle reflex protection against magnetic coil impulse noise

Electromagnetic stimulation (EMS) of the brain and the intracranial portion of the facial nerve has become a widely used clinical technique. The high intensity impulse noise acoustic artifact generated by some magnetic coils used in EMS has been shown to cause severe cochlear damage in experimental animals. This damage results in permanent threshold shifts throughout the auditory spectrum of the rabbit. As with other impulse and impact noise signals, the duration of the coil impulse noise is too short to be influenced by the normally protective acoustic middle ear muscle reflex. Artificially activating the acoustic reflex with a contralateral broad band noise during exposure to the intense coil artifact reduced the compound threshold shift (CTS) significantly, and the permanent threshold shifts (PTS) to near zero at each tone frequency and noise band tested. The results demonstrate the effectiveness of a suprathreshold sound in activating the acoustic middle ear muscle reflex and protecting against impulse noise-induced hearing loss caused by high frequency magnetic coil acoustic impulses.