Thermal stimulation of pressure phosphenes

Abstract

Synesthesia of vision and somatosensory is based on physiology of interconnection of neurons in different nuclei of thalamus or areas of cerebral cortex. Work studied effect on the intensity of pressure phosphenes (PP) of various methods of heating eyes and hands, as well as manual influence on cervical spine. Along with subjective assessments of the PP intensity, EEG and ECG were used for chronometry of bioelectrical activity of brain and heart. From analysis of frequency and amplitude spectra of EEG, it was concluded that mechanism of PP generation is dominated by processes of redistribution and recombination of charges in retinal and LGB layers. Stimulation of PP by heating hands was associated with convergence of LGB neurons and neurons of thalamus nuclei, which are responsible for thermoreception and are adjacent to LGB. Enhancement of effect of PP stimulation by heating hands in water and in sauna was explained by resonant mechanism of heat transfer from heated water to water of physiological fluids of epidermis and water associated with proteins of ion channels of thermoreceptor membranes. It was suggested that breakdown of water clusters in physiological fluids of epidermis at temperature above 42 C promotes to transformation of thermoreceptors into pain receptors.

Connection of brain glymphatic system with circadian rhythm

“…However, taking into account the isotropic distribution of the density of capillaries [50] and current dipoles in the "synaptic brain" [51][52][53] over the cortex, it can be assumed that the specific power of the electrical activity of the cortex, and hence ΨEEG, have similar values throughout the scalp. This confirms the closeness of (Vν) values at all standard points of the scalp in the synchronous frequency and amplitude EEG spectra [57], as well as the observation that during sleep, high ν and low V (~10 Hz, ~0.01 mV) pass into high V and slow NREM sleep waves (0.5-4 Hz, 0.2 mV) [54,55]. This implies a qualitative dependence for the EEG spectra:…”

Thermo- and photoreceptors of eyes as regulators of circadian rhythm and glymphatic system

“…GS2 is characterized by rapid eye movements, dreams, and, unlike GS1, a sharp increase in cerebral blood flow with expansion of the lumens of arterioles and capillaries [42, 43]. Considering the synesthesia of vision with almost all somatosensory systems [17, 60], we cannot exclude the convergence of the nervous systems of thermoreceptors and oculomotor muscles in the mechanism of synchronization of their activity [41]. Rapid eye movement enhances the communication of thermoreceptors of the cornea and cells of the ganglion layer of the retina through nerve connections with the thalamus, hypothalamus and midbrain substance.…”

“…Corneal thermoreceptors with TRPV1 channels have maximum sensitivity at T∼40 °C [75], close to the pain threshold of 42 °C [17, 60, 76]. In the range from 25 to ∼40 °C, the E A value of the ion current in the TRPV1 channel and in the bath buffer solution is 21 kJ/mol (Fig.…”

“…These E A values correlate with the E A of rotational-translational diffusion of water (τ D , D w ) and electrolytes (T 1 ) in the corresponding T ranges [30]. The increase in the E A ion current in TRPV1 at T>40 °C to 48 kJ/mol is apparently due to the specific molecular mechanism of the TRPV1 response to T above the pain threshold [17, 75]. The average E A current value in TRPV1 in the range of 33-42 °C is ∼34 kJ/mol, which coincides with the E A (33 kJ/mol) TD of the rate of impulse transmission by the saltatory mechanism in the myelinated fiber (Fig.…”

“…The high sensitivity of corneal cold receptors is due to their membrane voltage-gated cation channels TRPM8 [15, 16]. Cells of the ganglion layer complete the transformation of light information into optic nerve impulses, which, after primary processing in the thalamus, are fan-fed to the visual area of the cerebral cortex [17]. At the same time, in the ganglion layer, ∼1-2% of cells (ipRGC) are classified as special – they synchronize their physiology and activity with the circadian «light-dark» cycle [18].…”