Part 4: Managing Stimulants 3.0 Lighting and Olfactory Stimulants.

Our circadian rhythm is a 24-hour cycle that is part of the body’s internal clock, running in the background to carry out essential functions and processes synchronized to the 24-hour cycle of the sun. The body follows circadian rhythms that are synchronized with a master clock in your brain, this clock is directly influenced by environmental cues, especially light. This is why the most important and well-known circadian rhythm we know is the sleep-wake cycle.

Lighting in your sleep environment then becomes important as the idea is to synchronize your lighting options to best maintain a true 24-hour cycle that mimics nature. While the sleep-wake cycle is the most known, what is not as obvious is that our internal clock controls the majority of our physiology. Interrupting the 24-hour cycle impacts a lot of our biological processes, like hormone secretions and enzyme activities. Managing light stimulants in our environment can then synchronize our systems, and mitigate the issues caused by our artificially illuminated environment.




There are many light stimulants in your sleep environment that can interrupt your natural circadian rhythm. This is particularly the case in the evening hours when the circadian system is most sensitive to light-induced phase delays. The most common of these light stimulants include:

  • LED Lighting
  • Television Screens 
  • Cellular Phones 
  • Tablets 
  • eReaders

Input and output pathways to/from the suprachiasmatic nuclei (SCN). The photic input pathways that relay information about the intensity and spectral composition of ambient light are the retinohypothalamic tract (RHT) and the geniculohypothalamic tract (GHT), which connects retina and SCN via the intergeniculate leaflet (IGL) in the thalamus. Additionally, the SCN also receive non-photic information from the raphe nuclei (RN) via the raphe-hypothalamic tract (raphe-HT) and from the pineal gland. The main output is from the SCN to the serotonergic raphe nuclei (RN, receive information about the phase of the circadian clock and regulate vigilance state of the body) and the pineal gland, where melatonin is produced. Input and output pathways form reciprocal loops. source.

When addressing the circadian rhythms, you fall short if you only focus on sleep time light. Assuring heightened daytime signals in your daytime environments at home or office, and managing lighting color will play a part in assuring the proper function of your internal clock throughout your sleep cycle. Creating habits and managing timers that can change the intensity of lighting to align with your social requirements such as wake-up times can be great tools in maintaining your natural rhythms and assuring a proper sleep schedule. Behavior also plays a role in circadian alignment, aside from lighting, late-night activities, training, and also olfactory stimulants that can impact the natural rhythms.


During slow-wave sleep, the piriform cortex becomes hypo-responsive to odor stimulation and instead displays sharp-wave activity similar to that observed within the hippocampal formation. Data suggest that both the strength and precision of odor memories are sleep-dependent.

Knowing that olfactory stimulants also have an effect on your circadian rhythm and quality of sleep means you must also be aware of the stimulants in your bedroom at night including volatile organic compounds and toxins. These can trigger the central nervous system and result in the body not experiencing slow wave or REM sleep patterns. 


A schematic representation of changes in olfactory system activity between waking and slow-wave sleep. Odor stimulation during waking (symbolized by the rose) evokes odor-specific patterns of activity in the OB and mitral/tufted cell output to the piriform cortex. This afferent activity is respiration entrained and evokes intra-cortical association fiber activity linking co-active piriform cortical neurons. It also results in piriform cortical output, including feedback to OB granule cells (red dots) as well as to other regions of olfactory cortex and non-olfactory regions. During slow-wave sleep, the balance of afferent and intracortical activity shifts, with decreases in sensory-evoked input to piriform cortex and enhanced intra-cortical mediated activity, primarily during sharp-wave events. The sharp-wave associated activity replays cortical ensemble activity evoked by odors during waking. These strong, synchronous sharp-wave events help strengthen synaptic connections within odor-coding ensembles, as well as help shape OB granule cell survival in an odor-specific manner. Abbreviations: GL = glomerular layer, M = mitral cell layer, G = granule cell layer.

While you take steps to address the lighting stimulants in your sleep environment, here at Essentia we ensure that you won't encounter olfactory stimulants such as chemical fumes, toxins, or allergens. We deep dive in Part 2 managing stimulants in the indoor air environment, and in Part 3 managing allergen stimulants

Be Well.