Pineal glandThe pineal gland (also known as the pineal body, conarium, or epiphysis cerebri) is a small endocrine gland in the brain of most vertebrates. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles. The shape of the gland resembles a pine cone, which gives it its name. The pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join.
Sleep state misperceptionSleep state misperception (SSM) is a term in the International Classification of Sleep Disorders (ICSD) most commonly used for people who mistakenly perceive their sleep as wakefulness, though it has been proposed that it be applied to those who severely overestimate their sleep time as well ("positive" sleep state misperception). While most sleepers with this condition will report not having slept in the previous night at all or having slept very little, clinical recordings generally show normal sleep patterns.
Retinal ganglion cellA retinal ganglion cell (RGC) is a type of neuron located near the inner surface (the ganglion cell layer) of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and retina amacrine cells. Retina amacrine cells, particularly narrow field cells, are important for creating functional subunits within the ganglion cell layer and making it so that ganglion cells can observe a small dot moving a small distance.
Circadian rhythm sleep disorderCircadian rhythm sleep disorders (CRSD), also known as circadian rhythm sleep-wake disorders (CRSWD), are a family of sleep disorders which affect the timing of sleep. CRSDs arise from a persistent pattern of sleep/wake disturbances that can be caused either by dysfunction in one's biological clock system, or by misalignment between one's endogenous oscillator and externally imposed cues. As a result of this mismatch, those affected by circadian rhythm sleep disorders have a tendency to fall asleep at unconventional time points in the day.
Idiopathic hypersomniaIdiopathic hypersomnia (IH) is a neurological disorder which is characterized primarily by excessive sleep and excessive daytime sleepiness (EDS). The condition typically becomes evident in early adulthood and most patients diagnosed with IH will have had the disorder for many years prior to their diagnosis. , an FDA-approved medication exists for IH called Xywav, which is oral solution of calcium, magnesium, potassium, and sodium oxybates; in addition to several off-label treatments (primarily FDA-approved narcolepsy medications).
HypersomniaHypersomnia is a neurological disorder of excessive time spent sleeping or excessive sleepiness. It can have many possible causes (such as seasonal affective disorder) and can cause distress and problems with functioning. In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), hypersomnolence, of which there are several subtypes, appears under sleep-wake disorders. Hypersomnia is a pathological state characterized by a lack of alertness during the waking episodes of the day.
Cone cellCone cells, or cones, are photoreceptor cells in the retinas of vertebrates' eyes, including the human eye. They respond differently to light of different wavelengths, and the combination of their responses is responsible for color vision. Cones function best in relatively bright light, called the photopic region, as opposed to rod cells, which work better in dim light, or the scotopic region. Cone cells are densely packed in the fovea centralis, a 0.
Ocular hypertensionOcular hypertension is the presence of elevated fluid pressure inside the eye (intraocular pressure), usually with no optic nerve damage or visual field loss. For most individuals, the normal range of intraocular pressure is between 10 mmHg and 21 mmHg. Elevated intraocular pressure is an important risk factor and symptom of glaucoma. One study found that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma.
Near-sightednessNear-sightedness, also known as myopia and short-sightedness, is an eye disease where light focuses in front of, instead of on, the retina. As a result, distant objects appear blurry while close objects appear normal. Other symptoms may include headaches and eye strain. Severe near-sightedness is associated with an increased risk of retinal detachment, cataracts, and glaucoma. Myopia results from the length of the eyeball growing too long or less commonly the lens being too strong. It is a type of refractive error.
Free-running sleepFree-running sleep is a rare sleep pattern whereby the sleep schedule of a person shifts later every day. It occurs as the sleep disorder non-24-hour sleep–wake disorder or artificially as part of experiments used in the study of circadian and other rhythms in biology. Study subjects are shielded from all time cues, often by a constant light protocol, by a constant dark protocol or by the use of light/dark conditions to which the organism cannot entrain such as the ultrashort protocol of one hour dark and two hours light.
Visual fieldThe visual field is "that portion of space in which objects are visible at the same moment during steady fixation of the gaze in one direction"; in ophthalmology and neurology the emphasis is on the structure inside the visual field and it is then considered “the field of functional capacity obtained and recorded by means of perimetry”. However, the visual field can also be understood as a predominantly perceptual concept and its definition then becomes that of the "spatial array of visual sensations available to observation in introspectionist psychological experiments" (for example in van Doorn et al.
Sleep disorderA sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are tests commonly ordered for diagnosing sleep disorders. Sleep disorders are broadly classified into dyssomnias, parasomnias, circadian rhythm sleep disorders involving the timing of sleep, and other disorders including ones caused by medical or psychological conditions.
