In mammals, efferent projections to the cochlear receptor are constituted by olivocochlear (OC) fibers that originate in the superior olivary complex. Medial and lateral OC neurons make synapses with outer hair cells and with auditory nerve fibers, respectively. In addition to the OC system, there are also descending projections from the auditory cortex that are directed towards the thalamus, inferior colliculus, cochlear nucleus, and superior olivary complex. Olivocochlear function can be assessed by measuring a brainstem reflex mediated by auditory nerve fibers, cochlear nucleus neurons, and OC fibers. Although it is known that the OC reflex is activated by contralateral acoustic stimulation and produces a suppression of cochlear responses, the influence of cortical descending pathways in the OC reflex is largely unknown. Here, we used auditory cortex electrical microstimulation in chinchillas to study a possible cortical modulation of cochlear and auditory nerve responses to tones in the absence and presence of contralateral noise. We found that cortical microstimulation produces two different peripheral modulations: (i) changes in cochlear sensitivity evidenced by amplitude modulation of cochlear microphonics and auditory nerve compound action potentials and (ii) enhancement or suppression of the OC reflex strength as measured by auditory nerve responses, which depended on the intersubject variability of the OC reflex. Moreover, both corticofugal effects were not correlated, suggesting the presence of two functionally different efferent pathways. These results demonstrate that auditory cortex electrical microstimulation independently modulates the OC reflex strength and cochlear sensitivity.

Evidence shows that selective attention to visual stimuli modulates the gain of cochlear responses, probably through auditory-cortex descending pathways. At the cerebral cortex level, amplitude and phase changes of neural oscillations have been proposed as a correlate of selective attention. However, whether sensory receptors are also influenced by the oscillatory network during attention tasks remains unknown. Here, we searched for oscillatory attention-related activity at the cochlear receptor level in humans. We used an alternating visual/auditory selective attention task and measured electroencephalographic activity simultaneously to distortion product otoacoustic emissions (a measure of cochlear receptor-cell activity). In order to search for cochlear oscillatory activity, the otoacoustic emission signal, was included as an additional channel in the electroencephalogram analyses. This method allowed us to evaluate dynamic changes in cochlear oscillations within the same range of frequencies (1–35 Hz) in which cognitive effects are commonly observed in electroencephalogram works. We found the presence of low frequency (<10 Hz) brain and cochlear amplifier oscillations during selective attention to visual and auditory stimuli. Notably, switching between auditory and visual attention modulates the amplitude and the temporal order of brain and inner ear oscillations. These results extend the role of the oscillatory activity network during cognition in neural systems to the receptor level.

21 Evidence shows that selective attention to visual stimuli modulates the gain of 22 cochlear responses, probably through auditory-cortex descending pathways. At the cerebral 23 cortex level, amplitude and phase changes of neural oscillations have been proposed as a 24 correlate of selective attention. However, whether sensory receptors are also influenced by 25 the oscillatory network during attention tasks remains unknown. Here, we searched for 26 oscillatory attention-related activity at the cochlear receptor in humans. We used an 27 alternating visual/auditory selective attention task and measured electroencephalographic 28 activity simultaneously to distortion product otoacoustic emissions (a measure of cochlear 29 receptor-cell activity). In order to search for cochlear oscillatory activity, the otoacoustic 30 emission signal, was included as an additional channel in the electroencephalogram 31 analyses. This method allowed us to study dynamic changes of cochlear oscillations in the 32 same range of frequencies (1-35 Hz) in which cognitive effects are commonly observed in 33 electroencephalogram works. We found the presence of low frequency (<10 Hz) brain and 34 cochlear amplifier oscillations during periods of selective attention to visual and auditory 35 stimuli. Notably, switching between auditory and visual attention modulates the amplitude 36 and the temporal order of brain and inner ear oscillations. These results extend the role of 37 the oscillatory activity network during cognition in neural systems to the receptor level.38

In this chapter we discuss the polymodal activation of thermo-TRP channels using as exemplars two of the best characterized members of this class of channels: TRPM8 and TRPV1. Since channel activation by temperature is the hallmark of thermo-TRP channels, we present a detailed discussion on the thermodynamics involved in the gating processes by temperature, voltage, and agonists. We also review recently published data in an effort to put together all the pieces available of the amazing puzzle of thermo-TRP channel activation. Special emphasis is made in the structural components that allow the channel-forming proteins to integrate such diverse stimuli, and in the coupling between the different sensors and the ion conduction pathway. We conclude that the present data is most economically explained by allosteric models in which temperature, voltage, and agonists act separately to modulate channel activity.

Background Education and health are crucial topics for public policies as both largely determine the future wellbeing of the society. Currently, several studies recognize that physical activity (PA) benefits brain health in children. However, most of these studies have not been carried out in developing countries or lack the transference into the education field. The Cogni-Action Project is divided into two stages, a cross-sectional study and a crossover-randomized trial. The aim of the first part is to establish the associations of PA, sedentarism, and physical fitness with brain structure and function, cognitive performance and academic achievement in Chilean schoolchildren (10–13 years-old). The aim of the second part is to determinate the acute effects of three PA protocols on neuroelectric indices during a working memory and a reading task. Methods PA and sedentarism will be self-reported and objectively-assessed with accelerometers in a representative subsample, whilst physical fitness will be evaluated through the ALPHA fitness test battery. Brain structure and function will be assessed by magnetic resonance imaging (MRI) in a randomized subsample. Cognitive performance will be assessed through the NeuroCognitive Performance Test, and academic achievement by school grades. In the second part 32 adolescents (12–13 year-old) will be cross-over randomized to these condition (i) “Moderate-Intensity Continuous Training” (MICT), (ii) “Cooperative High-Intensity Interval Training” (C-HIIT), and (iii) Sedentary condition. Neuroelectric indices will be measures by electroencephalogram (EEG) and eye-tracking, working memory by n-back task and reading comprehension by a reading task. Discussion The main strength of this project is that, to our knowledge, this is the first study analysing the potential association of PA, sedentarism, and physical fitness on brain structure and function, cognitive performance, and academic achievement in a developing country, which presents an important sociocultural gap. For this purpose, this project will use advanced technologies in neuroimaging (MRI), electrophysiology (EEG), and eye-tracking, as well as objective and quality measurements of several physical and cognitive health outcomes. Trial registration ClinicalTrials.gov identifier: NCT03894241 Date of register: March 28, 2019. Retrospectively Registered. Electronic supplementary material The online version of this article (10.1186/s12887-019-1639-8) contains supplementary material, which is available to authorized users.