**2. PAG as a key point in vocalization**

The PAG presents a large number of afferences. The most important have their origin from the prefrontal cortex, amygdala and hypothalamus. Its efferent projections to different pontine nuclei allow it to coordinate different patterns of cardiorespiratory and motor responses depending on the type of stimulus. Other functions of PAG include thermoregulation, participation in wakefulness and sleep mechanisms, or modulation of neuropathic pain or urination. At the clinical level, we know that its activity is modified in different neurodegenerative processes such as Alzheimer's and multisystemic atrophy [6–9].

All these higher structures that project to the PAG integrate visual, auditory and somatosensory information in the context of basic mechanisms for survival, maintaining an efferent tone on the PAG which, in turn, projects on the pontomedullary respiratory nuclei involved in respiratory rhythmogenesis to change from eupnea to a rhythm adapted to vocalization or growling. Specifically, the nRA is the perfect target to convert passive breathing into active breathing to generate motor activities that produce changes in abdominal pressure, in addition to modifying the activity of the motor neurons that are located in the nA and that control the caliber of the pharynx and larynx [10, 11]. Stimulation of PAG and nRA is known to produce vocalization [12] and lesions in PAG cause mutism in animals and humans [13, 14] and vocalization and problems in the production of voice when lesions occur in nRA [15]. However, the electrophysiological influence of PAG on these pontomedullary nuclei has not yet been described.
