Mental Image

A mental image is an experience that, on most occasions, significantly resembles the experience of 'perceiving' some object, event, or scene, but occurs when the relevant object, event, or scene is not actually present to the senses. There are sometimes episodes, particularly on falling asleep (hypnagogic imagery) and waking up ( hypnopompic imagery), when the mental imagery may be dynamic, phantasmagoric and involuntary in character, repeatedly presenting identifiable objects or actions, spilling over from waking events, or defying perception, presenting a kaleidoscopic field, in which no distinct object can be discerned. Mental imagery can sometimes produce the same effects as would be produced by the behavior or experience imagined.

The nature of these experiences, what makes them possible, and their function (if any) have long been subjects of research and controversy in philosophy, psychology, cognitive science, and, more recently, neuroscience. As contemporary researchers use the expression, mental images or imagery can comprise information from any source of sensory input; one may experience auditory images, olfactory images, and so forth. However, the majority of philosophical and scientific investigations of the topic focus upon ''visual'' mental imagery. It has sometimes been assumed that, like humans, some types of animals are capable of experiencing mental images. Due to the fundamentally introspective nature of the phenomenon, it has been difficult to assess whether or not non-human animals experience mental imagery.

Philosophers such as George Berkeley and David Hume, and early experimental psychologists such as Wilhelm Wundt and William James, understood ideas in general to be mental images. Today it is very widely believed that much imagery functions as mental representations (or mental models), playing an important role in memory and thinking. William Brant (2013, p. 12) traces the scientific use of the phrase "mental images" back to John Tyndall's 1870 speech called the "Scientific Use of the Imagination". Some have suggested that images are best understood to be, by definition, a form of inner, mental or neural representation. Others reject the view that the image experience may be identical with (or directly caused by) any such representation in the mind or the brain, but do not take account of the non-representational forms of imagery.

Mind's eye

The notion of a "mind's eye" goes back at least to Cicero's reference to ''mentis oculi'' during his discussion of the orator's appropriate use of simile.

In this discussion, Cicero observed that allusions to "the Syrtis of his patrimony" and "the Charybdis of his possessions" involved similes that were "too far-fetched"; and he advised the orator to, instead, just speak of "the rock" and "the gulf" (respectively)—on the grounds that "the eyes of the mind are more easily directed to those objects which we have seen, than to those which we have only heard".

The concept of "the mind's eye" first appeared in English in Chaucer's (c. 1387) Man of Law's Tale in his '' Canterbury Tales'', where he tells us that one of the three men dwelling in a castle was blind, and could only see with "the eyes of his mind"; namely, those eyes "with which all men see after they have become blind".

Physical basis

The biological foundation of mental imagery is not fully understood. Studies using fMRI have shown that the lateral geniculate nucleus and the V1 area of the visual cortex are activated during mental imagery tasks. Ratey writes:

The visual pathway is not a one-way street. Higher areas of the brain can also send visual input back to neurons in lower areas of the visual cortex. ..As humans, we have the ability to see with the mind's eye—to have a perceptual experience in the absence of visual input. For example, PET scans have shown that when subjects, seated in a room, imagine they are at their front door starting to walk either to the left or right, activation begins in the visual association cortex, the parietal cortex, and the prefrontal cortex—all higher cognitive processing centers of the brain.

A biological basis for mental imagery is found in the deeper portions of the brain below the neocortex. In a large study with 285 participants, Tabi, Maio, Attaallah, et al. (2022) investigated the association between an established measure of visual mental imagery, Vividness of Visual Imagery Questionnaire (VVIQ) scores, and volumes of brain structures including the hippocampus, amygdala, primary motor cortex, primary visual cortex and the fusiform gyrus. Tabi et al. (2022) found significant positive correlations between visual imagery vividness and the volumes of the hippocampus and primary visual cortex.

Significant positive correlations were also obtained between VVIQ scores and hippocampal structures including Bilateral CA1, CA3, CA4 and Granule Cell (GC) and Molecular Layer (ML) of the Dentate Gyrus (DG). Follow-up analysis revealed that visual imagery was in particular correlated with the four subfields presented in the above illustration (Tabi et al., 2022).

The thalamus has been found to be discrete to other components in that it processes all forms of perceptional data relayed from both lower and higher components of the brain. Damage to this component can produce permanent perceptual damage, however when damage is inflicted upon the cerebral cortex, the brain adapts to neuroplasticity to amend any occlusions for perception . It can be thought that the neocortex is a sophisticated memory storage warehouse in which data received as an input from sensory systems are compartmentalized via the cerebral cortex. This would essentially allow for shapes to be identified, although given the lack of filtering input produced internally, one may as a consequence, hallucinate—essentially seeing something that isn't received as an input externally but rather internal (i.e. an error in the filtering of segmented sensory data from the cerebral cortex may result in one seeing, feeling, hearing or experiencing something that is inconsistent with reality).

Not all people have the same mental imagery ability. For many, when the eyes are closed, the perception of darkness prevails. However, some people are able to perceive colorful, dynamic imagery (McKellar, 1957). The use of hallucinogenic drugs increases the subject's ability to consciously access mental imagery including synaestesia (McKellar, 1957).

Furthermore, the pineal gland is a hypothetical candidate for producing a mind's eye. Rick Strassman and others have postulated that during near-death experiences (NDEs) and dreaming, the gland might secrete a hallucinogenic chemical ''N'',''N''-Dimethyltryptamine (DMT) to produce internal visuals when external sensory data is occluded. However, this hypothesis has yet to be fully supported with neurochemical evidence and plausible mechanism for DMT production.

The condition where a person lacks mental imagery is called aphantasia. The term was first suggested in a 2015 study.

Common examples of mental images include daydreaming