Hallucinations Associated with Neurological Disorders and Sensory Loss

Abstract

Hallucinations occur in a great variety of neurological conditions and are facilitated by sensory loss. The common end pathway of their pathophysiology involves the activation of cortical sensory areas implicated in normal sensory processing. Based on the presumed pathophysiology, we here classify the hallucinations in four main groups. In migraine aura and epilepsy, hallucinations result from spontaneous intrinsic overactivity in hyperexcitable sensory cortical areas. Deafferentation, i.e. the loss or impairment of sensory input, facilitates hallucinations in the corresponding sensory modality, probably by leading to chronic hyperexcitability of the corresponding cortical areas. The archetypal example of this mechanism is the Charles Bonnet syndrome, where hallucinations are associated with visual impairment. A third mechanism relies on the dissociation of dream and sleep mechanism, as illustrated by hypnagogic and hypnopompic hallucinations. Finally, in the course of neurodegenerative diseases such as Parkinson's disease and dementia with Lewy bodies, hallucinations are frequent and probably result from a combination of factors, including dysfunction of both bottomup sensory processing and top-down modulatory mechanisms, as well as dream intrusion phenomena and facilitating pharmacological factors.

A phenomenology of meditation-induced light experiences: traditional buddhist and neurobiological perspectives

“…Second, Buddhist meditation practice, especially among more-experienced practitioners, is associated with an increased alertness that is neurologically distinct from and resistant to sleepiness ( Britton et al, 2013 ). Third, as described previously, hypnagogic hallucinations are phenomenologically and neurologically different from waking hallucinations that arise in the context of sensory deprivation or perceptual isolation ( Cheyne et al, 1999a , b ; Ohayon, 2000 ; Wackermann et al, 2002 ; Collerton and Perry, 2011 ; Fenelon, 2013 ). Finally, several of our subjects reported that their eyes were open during these experiences, and mentioned them in conjunction with concentration, never drowsiness or sleep.…”

“…While the sensory loss that occurs at sleep onset may also result in hallucinations, these “hypnagogic” hallucinations are more similar – both neurologically and phenomenologically – to dreams that occur during REM sleep than to visual hallucinations that occur during wake ( Wackermann et al, 2002 ; Collerton and Perry, 2011 ; Fenelon, 2013 ). Like dreams, hypnagogic hallucinations tend to occur in multiple sensory modalities at once, are panoramic or “full screen” rather than circumscribed, and are associated with lack of insight and strong, often negative affect ( Cheyne et al, 1999a , b ; Ohayon, 2000 ; Collerton and Perry, 2011 ).…”

The effects of virtual reality training in stroke and Parkinson’s disease rehabilitation: a systematic review and a perspective on usability

“…This however might provoke hallucinations in neurological patients. Hallucinations can occur in different neurological conditions due to affected sensory processing but is particularly frequent among Parkinson’s disease patients [ 63 ]. In such neurodegenerative disease like PD, the hallucinations might be explained by a combination of factors – sensory loss and dysfunction in modulatory mechanisms, dream intrusion phenomena and pharmacological side effect of the dopaminergic treatment [ 62 , 63 ].…”

“…Hallucinations can occur in different neurological conditions due to affected sensory processing but is particularly frequent among Parkinson’s disease patients [ 63 ]. In such neurodegenerative disease like PD, the hallucinations might be explained by a combination of factors – sensory loss and dysfunction in modulatory mechanisms, dream intrusion phenomena and pharmacological side effect of the dopaminergic treatment [ 62 , 63 ]. The hallucinations and impaired adaptation to visuomotor perturbations typically occur in an off-medication state during or after the VR session [ 4 , 62 ].…”

Felt Reality and the Opacity of Perception

“…Diederich et al 2009), migraine or epilepsy (e.g. Russell and Olesen 1996); sensory deprivations (Pascual-Leone and Hamilton 2001) or sensory impairments including Charles Bonnet syndrome (Fénelon 2013); substance abuse, for example lysergic acid diethylamide (LSD), peyote (a cactus from Mexico) or mescaline (peyote alkaloid); transitional states to and from sleep (i.e. hypnagogic and hypnopompic hallucinations, respectively) and, finally, psychiatric conditions like schizophrenia (Esquirol 1838).…”