SCIENTIFIC GLOSSARY

Prescription Artwork, Module 1

Neural Processing of Light and Visual Information

Amygdala

• Location: The amygdala is located in the medial temporal lobe and consists of several nuclei.

• Function: It contributes to the processing of emotional significance, potential threats, salience, and arousal.

• Autonomic connection: The amygdala interacts with the hypothalamus, brainstem, and prefrontal regions and may contribute to the regulation of autonomic and hormonal responses.

• Relationship with light: Light intensity may influence amygdala activity. In one study, dim-to-moderate white light reduced amygdala activity compared with darkness and strengthened functional connectivity between the amygdala and the ventromedial prefrontal cortex. However, the study did not establish that “soft light” generally calms the amygdala in every individual.

Retina

• Function: The retina receives light and converts it into neural signals.

• Principal light-sensitive cells: Rods, cones, and melanopsin-expressing intrinsically photosensitive retinal ganglion cells, known as ipRGCs.

• Visual processing: Rods and cones contribute to the perception of luminance, color, form, and movement.

• Non-visual processing: ipRGCs combine their intrinsic melanopsin-mediated light sensitivity with information received from rods and cones. They transmit this information to several areas of the brain.

• Response timing: Light processing begins rapidly. However, an exact response time of approximately 20 milliseconds should not be presented as a general fact without a research source directly related to the specific stimulus and measurement method.

Retina–LGN–Visual Cortex Pathway

The heading “Retina–LGN–Thalamus” should be replaced with:

Retina–LGN–Visual Cortex

The LGN is already part of the thalamus. Presenting the LGN and thalamus as two separate structures within a simple linear sequence would therefore be anatomically misleading.

LGN, or Lateral Geniculate Nucleus

• Location: The LGN is part of the thalamus.

• Function: It relays and modifies visual information received from the retina before transmitting it to the primary visual cortex.

• Information processed: It contributes to the processing of information related to luminance, contrast, color, spatial properties, and temporal changes.

• Clarification: The LGN does not independently determine the final neural interpretation of light and contrast. Visual perception emerges through the coordinated activity of retinal, thalamic, and cortical networks.

Thalamus

• Location: The thalamus is located in the diencephalon.

• Function: It contributes to the relay and modulation of several types of sensory information, as well as to the regulation of attention, arousal, and cortical functioning.

• Visual connection: The LGN of the thalamus receives visual information from the retina and transmits it to the visual cortex.

• Clarification: In educational contexts, the thalamus may be described as a selective relay and regulatory system. However, the expression “stabilizes the receptive state of the nervous system” is not a sufficiently precise scientific description of its function.

Visual Cortex

• Location: Primarily in the occipital lobe and in related visual networks extending into the temporal and parietal lobes.

• Principal areas: The primary visual cortex, or V1, and several extrastriate visual areas.

• Function: It contributes to the processing of edges, orientation, contrast, color, movement, form, and spatial relationships.

• Conscious perception: Visual information processing begins before detailed conscious interpretation. However, conscious visual experience arises through the coordinated activity of extensive brain networks.

• Relationship with light: Spectrum, luminance, contrast, exposure duration, visual-field location, and surrounding stimuli can all influence visual cortical responses. A single general level of “cortical activation” cannot be inferred from color alone.

Limbic and Emotion-Processing Networks

• Principal structures: The amygdala, hippocampus, hypothalamus, and regions of the cingulate cortex.

• Function: These structures contribute to the processing of emotion, memory, motivation, salience, and physiological states.

• Visual connection: Visual stimuli may acquire different emotional meanings depending on their content, context, previous experiences, and the individual characteristics of the viewer.

• Clarification: The limbic system does not classify light according to a simple and fixed distinction between “calming” and “activating.”

The vmPFC should not be listed directly as an anatomical component of the limbic system. It is a prefrontal cortical region that interacts with limbic networks and systems involved in autonomic regulation.

Hippocampus

• Location: The medial temporal lobe.

• Function: The hippocampus contributes particularly to memory formation, learning, contextual processing of events and environments, and spatial memory.

• Emotional connection: It interacts with the amygdala, hypothalamus, and prefrontal regions.

• Clarification: The primary function of the hippocampus should not be defined as producing a calming or homeostatic effect.

• Relationship with light: There is insufficient research evidence for the general claim that soft light strengthens an inhibitory effect of the hippocampus on the amygdala.

vmPFC, or Ventromedial Prefrontal Cortex

• Function: The vmPFC contributes to emotion regulation, valuation, decision-making, safety learning, and the regulation of autonomic responses.

• Connection with the amygdala: The vmPFC and amygdala operate within wider networks involved in emotional processing and regulation.

• Relationship with light: In one study, white light strengthened functional connectivity between the amygdala and vmPFC compared with darkness. This does not establish that blue-green light or a “calming spectrum” generally activates a calming function of the vmPFC.

Vagus Nerve

• Location: The tenth cranial nerve, or cranial nerve X.

• Function: The vagus nerve transmits sensory information from internal organs to the central nervous system and carries parasympathetic motor signals to several organs.

• Cardiac regulation: Vagal activity contributes to slowing the heart rate.

• Breathing: The vagus nerve contributes to respiratory and internal-organ regulation. However, “deepens breathing” is not a universal or unambiguous description of its effect.

• Relationship with light: Current research does not demonstrate that viewing a blue or turquoise color surface directly activates the vagus nerve through the nucleus tractus solitarius.

Research has examined the combined effects of blue-enriched light and transcutaneous vagus-nerve stimulation through pupillary measurements. In this research, the vagus nerve was stimulated using a separate electrical method. The findings did not demonstrate that blue light itself activates the vagus nerve.

Nucleus Tractus Solitarius, or NTS

• Location: The medulla oblongata in the brainstem.

• Function: The NTS receives extensive sensory information through the vagus nerve and other cranial nerves.

• Autonomic connection: It contributes to reflexive regulation of cardiovascular, respiratory, and digestive functions.

• Relationship with light: There is insufficient evidence to claim that the NTS mediates a general calming effect of light or that the blue-turquoise spectrum directly increases NTS activity and parasympathetic tone.

Ascending Reticular Activating System, or ARAS

• Location: A functional system formed by networks in the brainstem and related thalamic, hypothalamic, and forebrain regions.

• Function: It contributes to the maintenance of wakefulness, arousal, consciousness, and cortical activation.

• Clarification: The ARAS is not a single anatomical structure or exclusively a dopaminergic system. It involves several neurotransmitter systems and brain regions.

• Relationship with light: Yellow light has not been shown to activate the ARAS universally or to improve attention in every context.

The term RAS should be replaced with the more precise term ARAS when referring to the ascending system involved in maintaining wakefulness.

Cortical Arousal

• Definition: The functional readiness of the cerebral cortex, related to alertness, attention, and the ability to process stimuli.

• Regulation: Cortical arousal involves the ARAS, thalamus, hypothalamus, basal ganglia, and several neurotransmitter systems.

• Relationship with light: Light intensity, spectrum, exposure duration, and time of day may influence perceived alertness and brain activity.

• Relationship with color: Yellow, orange, and red should not be presented as a direct biological scale in which yellow increases alertness, orange produces controlled sympathetic activation, and red creates physiological readiness for action.

Melanopsin-Expressing Retinal Ganglion Cells

The scientifically more precise heading is “Melanopsin-Expressing Retinal Ganglion Cells”, rather than “melanopsin receptors.”

• Location: Intrinsically photosensitive retinal ganglion cells, or ipRGCs, in the retina.

• Light sensitivity: These cells contain melanopsin and respond to light. They also receive information from rods and cones.

• Function: They contribute to the transmission of information about environmental illumination, pupillary responses, circadian regulation, and other non-visual effects of light.

• Stimulus characteristics: ipRGCs are particularly suited to processing ambient light intensity and sustained illumination. However, their function is not completely independent of the visual systems involved in processing form and other visual properties.

• Clarification: Bright light does not automatically mean sympathetic activation, and soft light does not automatically mean parasympathetic activation. Effects depend on factors such as spectrum, intensity, timing, exposure duration, and the individual’s current state. The non-visual effects of light and their central neural mechanisms remain active areas of research.

Sympathetic Nervous System

• Function: The sympathetic nervous system contributes to physiological readiness for action, cardiovascular regulation, the use of energy resources, and adaptation to changing circumstances.

• Possible effects: Depending on the situation and target organ, sympathetic activity may increase heart rate, modify blood pressure, and influence metabolism.

• Relationship with light and color: Orange or red has not been shown to activate the sympathetic nervous system universally or in every individual.

Studies of colored light have found changes in autonomic measurements. However, the results do not support a simple model in which red is always a sympathetic stimulus and blue is always a parasympathetic stimulus.

Parasympathetic Nervous System

• Function: The parasympathetic nervous system contributes to the regulation of the heart, digestion, secretory functions, and the management of internal physiological resources.

• Possible effects: Vagal parasympathetic activity may slow the heart rate and support resting and digestive functions.

• Clarification: Parasympathetic activity is not simply equivalent to calmness or recovery across all organs and situations.

• Relationship with light and color: Blue, turquoise, or green has not been shown to activate the parasympathetic nervous system universally.

In a small clinical study, blue lighting was associated with lower anxiety ratings and higher RMSSD values in a group of 30 patients awaiting cataract surgery. This result does not establish a general rule concerning the effects of blue light on all individuals or all blue color surfaces.

Homeostatic Regulation

• Definition: The processes through which the body maintains internal physiological variables within ranges that support effective functioning.

• Systems involved: The autonomic nervous system, endocrine system, immune system, regulatory networks of the brainstem and hypothalamus, and behavior.

• Clarification: Homeostasis is not a single, permanent “state of nervous-system balance.” It is a continuous and adaptive process of regulation.

• Relationship with light and color: Green light or a green color surface has not been shown to stabilize the autonomic nervous system universally.

Research Notice for the Module

Research notice: The visual and non-visual effects of light involve multiple systems in the retina, brainstem, hypothalamus, thalamus, and cerebral cortex. These effects depend on the light spectrum, intensity, exposure duration, time of day, viewing environment, and individual factors. A single color should not be defined as a direct activator of the sympathetic or parasympathetic nervous system. The color classifications used in the TERRY–NORA® Method are treated as pedagogical models and research hypotheses to be evaluated, rather than as universally established biological rules.

Main translation choices: The anatomical structures and their established functions have been retained, while unsupported color-specific and light-specific causal claims have been replaced with scientifically cautious descriptions.