Adeerus Ghayan

Neurophology is the study of the relationship between light and photoacceptor molecules in the body, as well as their impact on brain development and functioning. This field encompasses four distinct areas of science. The laws of quantum physics govern the absorption and desorption of light by photoacceptors, while the ensuing cascading reactions are dictated by chemistry. The resulting neurological developments are biological in nature and ultimately manifest in the realm of psychology. The study of neurophology necessitates an understanding of these four scientific disciplines.

Photoacceptors

A photoacceptor is any biological molecule that undergoes a change upon absorbing a photon. There are two types of photoacceptors: ketophores and actophores. It is important not to confuse the term “photoacceptor” with related terms such as “photoactive,” “photoreceptor,” “chromophore,” and “photopigment.”

The term “photoactive” is used in chemical engineering to describe molecules that can undergo a chemical or physical change in response to illumination, such as light-sensitive layers in solar cells. A photoreceptor cell is a subtype of ketophore molecule and a specialised type of neuron found in the retina, capable of visual phototransduction. A chromophore refers to the part of a molecule responsible for its colour. Photopigments are unstable chromophores that undergo a chemical change when they absorb light.

Primary and Secondary Effects

Light exposure has both primary and secondary effects on the human body. Primary effects involve direct photochemical changes in photoacceptors, such as the activation of enzymes and alterations in cellular metabolism, which occur immediately upon exposure to specific wavelengths of light. In contrast, secondary effects arise from these primary changes and include a cascade of biochemical reactions that can influence gene expression and cellular signalling pathways, often manifesting hours or days after the initial light exposure.

Light Properties and Electromagnetic Radiation Spectrum

Light refers to the electromagnetic radiation spectrum, although the term is commonly used to denote visible light. The impact of light on a photoacceptor depends on a variety of factors, the most significant of which is the wavelength of the photon. A photon is a single quantum of light. Different types of light radiation consist of different photons. For DNA-based life forms, the solar spectrum has notable biogenic effects.

Light Absorption in Human Body

Photoacceptors are present throughout the body, even deep within the brain. Their photostimulation and subsequent effects require the absorption of a photon. To understand the impact of light on the brain and body, it is essential to comprehend the photon capacity for body penetration and its relevant properties.

As light travels into the tissue, its intensity decreases due to absorption and scattering. The penetration of light into tissues depends not only on the wavelength but also on the optical properties of the target tissue. Although light attenuation occurs when light passes through bone, this attenuation is not significant.

Photons at wavelengths between 630 nm and 800 nm have been shown to penetrate up to 28 mm, even in layers of tissue with relatively low transparency, such as skin, connective tissue, muscle, bone, and spinal cord. Approximately 6% of the total energy density is detectable at the ventral surface of a living rat.

While considerable research has been conducted on the absorption and penetration properties of light, many published studies have utilised animal models to investigate the effects of light. It is important to note that, although the penetration of light is contingent on the wavelength and specific tissue, significant interspecies differences in penetration have been observed. For instance, at 850 nm, the penetration of energy in humans is nearly three times greater than that in the mouse cortex. While this significant difference in light-tissue interaction can be attributed to variations in water and protein content, the translational implications should be carefully considered when using data from animal models.

Extant research has identified photoacceptors in the eyes, brain, tissues, organs, and blood, which mediate brain development and growth. Evidence also suggests that photons reach these photoacceptors deep within the body. Although there is currently no research on how photoacceptors within the bones may impact the brain, it is known that light does penetrate bone.

To Cite: Adeerus Ghayan. “Neurophology” Islamabad: Subagh (2017).
The entire article is taken from Adeerus Ghayan’s book Neurophology.
Amazon Link: https://www.amazon.com/dp/B076JZF3P7

Further Reading: “Nureeva and Tangora” by Adeerus Ghayan.