Acuity enhancement is a heightening of the clearness and clarity of vision. This results in the visual details of the external environment becoming sharpened to the point where the edges of objects become perceived as extremely focused, clear, and defined. The experience of acuity enhancement can be likened to bringing a camera or projector lens that was slightly blurry into focus. At its highest level, a person may experience the ability to observe and comprehend their entire visual field simultaneously, including their peripheral vision. This is in contrast to the default sober state where a person is only able to perceive the small area of central vision in detail.  Acuity enhancement is often accompanied by other coinciding effects such as colour enhancement and pattern recognition enhancement.   It is most commonly induced under the influence of mild dosages of psychedelic compounds, such as LSD, psilocybin, and mescaline. However, it can also occur to a lesser extent under the influence of certain stimulants and dissociatives such as MDMA or 3-MeO-PCP.
It is thought that a fundamental feature of information-processing dysfunction in both hallucinogen-induced states and schizophrenia-spectrum disorders is the inability of these people to screen out, inhibit, filter, or gate irrelevant stimuli and to attend selectively to more important features of the environment.    The CSTC model of the brain posits that the thalamus plays a key role in controlling or gating external sensory information to the conscious faculties and is thereby fundamentally involved in the regulation of a person's awareness and attention.     The interruption of psychedelics to these neural pathways that inhibit the sensory gating systems   may therefore result in an enhanced availability of sensory information which is normally filtered out by these systems. This process is likely also involved in the various visual, tactile, and auditory enhancements which commonly occur when under the influence of a psychedelic experience.
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