A case of persistent visual hallucinations of faces following LSD abuse: a functional Magnetic Resonance Imaging study

Visual hallucinations originating in the retinofugal pathway under clinical and psychedelic conditions

Psychedelics like LSD (Lysergic acid diethylamide) and psilocybin are known to modulate perceptual modalities due to the activation of mostly serotonin receptors in specific cortical (e.g., visual cortex) and subcortical (e.g., thalamus) regions of the brain. In the visual domain, these psychedelic modulations often result in peculiar disturbances of viewed objects and light and sometimes even in hallucinations of non-existent environments, objects, and creatures. Although the underlying processes are poorly understood, research conducted over the past twenty years on the subjective experience of psychedelics details theories that attempt to explain these perceptual alterations due to a disruption of communication between cortical and subcortical regions. However, rare medical conditions in the visual system like Charles Bonnet syndrome that cause perceptual distortions may shed new light on the additional importance of the retinofugal pathway in psychedelic subjective experiences. Interneurons in the retina called amacrine cells could be the first site of visual psychedelic modulation and aid in disrupting the hierarchical structure of how humans perceive visual information. This paper presents an understanding of how the retinofugal pathway communicates and modulates visual information in psychedelic and clinical conditions. Therefore, we elucidate a new theory of psychedelic modulation in the retinofugal pathway.

Hallucinogenic Persisting Perception Disorder: A Case Series and Review of the Literature

Background

Hallucinogen persisting perception disorder (HPPD) is characterized by the re-emergence of perceptual symptoms experienced during acute hallucinogen intoxication following drug cessation. The underlying pathophysiology is poorly understood. We report the clinical characteristics and investigation findings of a series of HPPD cases with a literature review of previous case reports. We draw parallels between the features of HPPD and Visual Snow Syndrome (VSS).

Methods

Retrospective case series of 13 patients referred from neuro-ophthalmologists. Literature review with 24 HPPD case reports were identified through database search using the terms “hallucinogenic persisting perception disorder” OR “hallucinogen persisting perception disorder.”

Results

Lysergic acid diethylamide (LSD), 3,4-Methyl enedioxy methamphetamine (MDMA) and cannabinoid use was common. Cannabinoids and MDMA were mostly used in association with classical hallucinogens. The most frequent symptoms in our patients were visual snow, floaters, palinopsia, photophobia and nyctalopia. In the literature other symptoms included visual hallucinations altered motion perception, palinopsia, tracers and color enhancement. Ophthalmic and neurologic investigations were mostly normal. The majority of patients had ongoing symptoms. Two of our patients fully recovered—one after treatment with benzodiazepine and one without treatment. Twenty-five percent of cases from the literature fully recovered.

Conclusions

HPPD presents with heterogeneous visual phenomena on a background of previous classic and non-classic hallucinogen use. Ophthalmic investigations are typically normal. The symptoms of HPPD in our case series overlap with the typical features of Visual Snow Syndrome (VSS). Patients presenting with VSS should be screened for past recreational drug use. The DSM-5 description of HPPD does not include visual snow, nyctalopia, photophobia or floaters. A revision of the diagnostic criteria to include these symptoms may better reflect the typical clinical phenotype. Increased awareness of HPPD as a secondary cause of VSS can avoid extensive investigations. Controlled trials comparing primary and secondary VSS patients are needed to understand the pathophysiology better and optimize treatment for HPPD.

Pareidolia in a Built Environment as a Complex Phenomenological Ambiguous Stimuli

Pareidolia is a kind of misperception caused by meaningless, ambiguous stimuli perceived with meaning. Pareidolia in a built environment may trigger the emotions of residents, and the most frequently observed pareidolian images are human faces. Through a pilot experiment and an in-depth questionnaire survey, this research aims to compare built environmental pareidolian phenomena at different time points (6 a.m., 12 p.m., 2 a.m.) and to determine people’s sensitivity and reactions towards pareidolia in the built environment. Our findings indicate that the differences in stress level do not influence the sensitivity and reactions towards pareidolia in the built environment; however, age does, and the age of 40 seems to be a watershed. Females are more likely to identify pareidolian faces than males. Smokers, topers, and long-term medicine users are more sensitive to pareidolian images in the built environment. An unexpected finding is that most pareidolian images in built environments are much more easily detected in the early morning and at midnight but remain much less able to be perceived at midday. The results help architects better understand people’s reactions to pareidolia in the built environment, thus allowing them to decide whether to incorporate it appropriately or avoid it consciously in building design.

Pareidolia in Schizophrenia and Bipolar Disorder

While there are many studies on pareidolia in healthy individuals and patients with schizophrenia, to our knowledge, there are no prior studies on pareidolia in patients with bipolar disorder. Accordingly, in this study, we, for the first time, measured pareidolia in patients with bipolar disorder (N = 50), and compared that to patients with schizophrenia (N = 50) and healthy controls (N = 50). We have used (a) the scene test, which consists of 10 blurred images of natural scenes that was previously found to produce illusory face responses and (b) the noise test which had 32 black and white images consisting of visual noise and 8 images depicting human faces; participants indicated whether a face was present on these images and to point to the location where they saw the face. Illusory responses were defined as answers when observers falsely identified objects that were not on the images in the scene task (maximum illusory score: 10), and the number of noise images in which they reported the presence of a face (maximum illusory score: 32). Further, we also calculated the total pareidolia score for each task (the sum number of images with illusory responses in the scene and noise tests). The responses were scored by two independent raters with an excellent congruence (kappa > 0.9). Our results show that schizophrenia patients scored higher on pareidolia measures than both healthy controls and patients with bipolar disorder. Our findings are agreement with prior findings on more impaired cognitive processes in schizophrenia than in bipolar patients.

Visual hallucinations in psychiatric, neurologic, and ophthalmologic disease

PURPOSE OF REVIEW

Recent studies have increased our understanding of the biochemical and structural bases of visual hallucinations in patients with a variety of underlying causes.

RECENT FINDINGS

Visual hallucinations may be related to disruption of functional connectivity networks, with underlying biochemical dysfunction such as decreased in cholinergic activity. Structural abnormalities in primary and higher order visual processing areas also have been found in patients with visual hallucinations. The occurrence of visual hallucinations after vision loss, the Charles Bonnet syndrome, may have more functional similarity to psychiatric and neurodegenerative causes than previously suspected despite retained insight into the unreal nature of the phenomena.

SUMMARY

Visual hallucinations are common, and patients may not report them if specific inquiries are not made. Presence or absence of hallucinations may be of diagnostic and therapeutic importance, especially in patients with neurodegenerative conditions that have overlapping features. Treatment of visual hallucinations remains challenging and must be tailored to each patient based on the underlying cause and comorbid conditions.

Serotonin and brain function: a tale of two receptors

Previous attempts to identify a unified theory of brain serotonin function have largely failed to achieve consensus. In this present synthesis, we integrate previous perspectives with new and older data to create a novel bipartite model centred on the view that serotonin neurotransmission enhances two distinct adaptive responses to adversity, mediated in large part by its two most prevalent and researched brain receptors: the 5-HT1A and 5-HT2A receptors. We propose that passive coping (i.e. tolerating a source of stress) is mediated by postsynaptic 5-HT1AR signalling and characterised by stress moderation. Conversely, we argue that active coping (i.e. actively addressing a source of stress) is mediated by 5-HT2AR signalling and characterised by enhanced plasticity (defined as capacity for change). We propose that 5-HT1AR-mediated stress moderation may be the brain's default response to adversity but that an improved ability to change one's situation and/or relationship to it via 5-HT2AR-mediated plasticity may also be important - and increasingly so as the level of adversity reaches a critical point. We propose that the 5-HT1AR pathway is enhanced by conventional 5-HT reuptake blocking antidepressants such as the selective serotonin reuptake inhibitors (SSRIs), whereas the 5-HT2AR pathway is enhanced by 5-HT2AR-agonist psychedelics. This bipartite model purports to explain how different drugs (SSRIs and psychedelics) that modulate the serotonergic system in different ways, can achieve complementary adaptive and potentially therapeutic outcomes.

Seeing Jesus in toast: neural and behavioral correlates of face pareidolia

Face pareidolia is the illusory perception of non-existent faces. The present study, for the first time, contrasted behavioral and neural responses of face pareidolia with those of letter pareidolia to explore face-specific behavioral and neural responses during illusory face processing. Participants were shown pure-noise images but were led to believe that 50% of them contained either faces or letters; they reported seeing faces or letters illusorily 34% and 38% of the time, respectively. The right fusiform face area (rFFA) showed a specific response when participants "saw" faces as opposed to letters in the pure-noise images. Behavioral responses during face pareidolia produced a classification image (CI) that resembled a face, whereas those during letter pareidolia produced a CI that was letter-like. Further, the extent to which such behavioral CIs resembled faces was directly related to the level of face-specific activations in the rFFA. This finding suggests that the rFFA plays a specific role not only in processing of real faces but also in illusory face perception, perhaps serving to facilitate the interaction between bottom-up information from the primary visual cortex and top-down signals from the prefrontal cortex (PFC). Whole brain analyses revealed a network specialized in face pareidolia, including both the frontal and occipitotemporal regions. Our findings suggest that human face processing has a strong top-down component whereby sensory input with even the slightest suggestion of a face can result in the interpretation of a face.