Functional magnetic resonance imaging (fMRI) of Charles Bonnet Syndrome patients displays a relationship between visual hallucinations and activity in the ventral occipital lobe. A connection between age-related macular degeneration (AMD) and colored visual hallucinations has been presented. Color vision signals travel through the parvocellular layers of the lateral geniculate nucleus (LGN), later transmitting down the color regions of the ventral visual pathway. Due to cone photoreceptor damage located in the macula, there is a significant reduction of visual input to the visual association cortex, stirring endogenous activation in the color areas and thus leading to colored hallucinations. Patients with CBS alongside macular degeneration exhibit hyperactivity in the color areas of the visual association cortex (as shown in fMRIs). Those who have significant ocular disease yet maintain visual acuity may still be susceptible to CBS.The Deep Boltzmann Machine (DBM) is a way of utilizing an undirected probabilistic process in a neural framework. Researchers argue that the DBM has the ability to model features of cortical learning, perception, and the visual cortex (the locus of visual hallucinations). Compelling evidence details the role homeostatic operations in the cortex play in regards to stabilizing neuronal activity. By using the DBM, researchers show that when sensory input is absent, neuron excitability is influenced, thus potentially triggering complex hallucinations. A short-term change in the levels of feedforward and feedback flows of information may intensely affect the presence of hallucinations. In periods of drowsiness, CBS related hallucinations are more prone to arise.
Visual release hallucinations, also known as Charles Bonnet syndrome or CBS, are a type of psychophysical visual disturbance in which a person with partial or severe blindness experiences visual hallucinations. First described by Charles Bonnet in 1760, the term Charles Bonnet syndrome was first introduced into English-speaking psychiatry in 1982. A related type of hallucination that also occurs with lack of visual input is the closed-eye hallucination. Signs and symptoms
People with significant vision loss may have vivid recurrent visual hallucinations (fictive visual percepts). One characteristic of these hallucinations is that they usually are "lilliputian" (hallucinations in which the characters or objects are smaller than normal). Depending on the content, visual hallucinations can be classified as either simple or complex. Simple visual hallucinations are commonly characterized by shapes, photopsias, and grid-like patterns. Complex visual hallucinations consist of highly detailed representations of people and objects. The most common hallucination is of faces or cartoons. Sufferers understand that the hallucinations are not real, and the hallucinations are only visual, that is, they do not occur in any other senses (such as hearing, smell or taste). Visual hallucinations generally appear when the eyes are open, fading once the visual gaze shifts. It is widely claimed that sensory deprivation is instrumental in the progression of CBS. During episodes of inactivity, hallucinations are more likely to occur.