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Fixation (German: Fixierung) [1] is a concept (in human psychology) that was originated by Sigmund Freud (1905) to denote the persistence of anachronistic sexual traits. [ 2 ] [ 3 ] The term subsequently came to denote object relationships with attachments to people or things in general persisting from childhood into adult life.
Traditionally, pupil measurements have been performed in a subjective manner by using a penlight or flashlight to manually evaluate pupil reactivity (sPLR, "s" stands for standard) and using a pupil gauge to estimate pupil size. However, manual pupillary assessment is subject to significant inaccuracies and inconsistencies.
According to intellectual historian Jan E. Goldstein, the initial introduction of idée fixe as a medical term occurred around 1812 in connection with monomania. [1] The French psychiatrist Jean-Étienne Dominique Esquirol considered an idée fixe – in other words an unhealthy fixation on a single object – to be the principal symptom of monomania. [2]
Fixation or visual fixation is the maintaining of the gaze on a single location. An animal can exhibit visual fixation if it possess a fovea in the anatomy of their eye. The fovea is typically located at the center of the retina and is the point of clearest vision. The species in which fixational eye movement has been verified thus far include ...
Light from a single point of a distant object and light from a single point of a near object being brought to a focus. The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape (accommodation) and pupil size.
An example of eye movement over a photograph over the span of just two seconds. Eye movement includes the voluntary or involuntary movement of the eyes. Eye movements are used by a number of organisms (e.g. primates, rodents, flies, birds, fish, cats, crabs, octopus) to fixate, inspect and track visual objects of interests.
For example, when taking part in an experiment involving the n-back task, a correlation was observed between those with higher dilation, due to pupillary response, and improved performance. Conversely, other studies show the opposite relationship, where higher pupillary dilation is associated with lower task performance. [ 4 ]
When the optic nerve is damaged, the sensory (afferent) stimulus sent to the midbrain is reduced. The pupil, responding less vigorously, dilates from its prior constricted state when the light is moved away from the unaffected eye and towards the affected eye. This response is a relative afferent pupillary defect (or Marcus Gunn pupil). [1]