Negative mood invites psychotic false perception in dementia

Abstract

BackgroundThere is increasing evidence for predictive coding theories of psychosis, which state that hallucinations arise from abnormal perceptual priors or biases. However, psychological processes that foster abnormal priors/biases in patients suffering hallucinations have been largely unexplored. The widely recognized relationship between affective disorders and psychosis suggests a role for mood and emotion.MethodsThirty-six patients with dementia with Lewy bodies (DLB), a representative condition associated with psychosis of neurological origin, and 12 patients with Alzheimer’s disease (AD) were enrolled. After an experimental mood induction, the participants underwent the pareidolia test, in which visual hallucination-like illusions were evoked and measured.ResultsIn DLB patients, the number of pareidolic illusions was doubled under negative mood compared to that under neutral mood. In AD patients, there was no significant difference in the number of pareidolic responses between negative and neutral mood conditions. A signal detection theory analysis demonstrated that the observed affective modulation of pareidolic illusions was mediated through heightened perceptual bias, not sensory deterioration.ConclusionsThe current findings demonstrated that abnormal perceptual priors in psychotic false perception have an affective nature, which we suggest are a type of cognitive feeling that arises in association with perception and cognition.

Prestimulus Low-Alpha Frontal Networks Are Associated with Pareidolias in Parkinson's Disease

“…In patients who demonstrate pareidolic misperceptions, we found that: (i) the pre-stimulus low-alpha power tends to be higher in Face detection on the NPT necessitates an active search-and-detect effort requiring configural face processing and a top-down integration of facial features (Revankar et al, 2020). While these images serve as sensory deprived ambiguous stimuli, a subset of PD patients consciously misperceive noisy patches as faces, likely due to abnormal perceptual biases (Watanabe et al, 2018). In our experiment during the pre-stimulus phase, this misrepresentation was observed as a near-significant increase in low-alpha spectral power in the frontal electrodes.…”

“…Participants verbally responded to each image within 30s of stimulus presentation and the experimenter recorded the responses since patients' tremor severity may have prevented reliable manual responses. Visual misperceptual phenomena are strongly influenced by time of the day ('sundowning'), age-related vision problems and mood that fluctuate during the day (Suzuki et al, 2011;Weil et al, 2016;ffytche et al, 2017;Watanabe et al, 2018). To minimize these effects, we performed the NPT (i) on a fixed time of the day (late afternoons), (ii) when vision was normal or corrected-to-normal; and…”

“…Eye-tracking metrics such as change in lowfrequency pupillary power is suggested to be crucial during stimulus anticipation in patients experiencing pareidolias (Suzuki et al, 2017). The effect of negative mood is also known to affect the outcomes of the NPT (Watanabe et al, 2018). We also avoided subclassifying the pre-stimulus responses into face, noise, pareidolias and missed images due to the skewed nature of the NPT (fewer face stimuli than noise).…”

“…Recently, in a multimodal electroencephalography (EEG) experiment, we showed that PD patients exhibited abnormal top-down modulation of visual information 'during' pareidolic manifestations (Revankar et al, 2020), suggestive of deficits in matching external sensory information with prior knowledge (Flowers and Robertson, 1995). However, considering the impact of abnormal priors in the causation of pareidolias (Watanabe et al, 2018;Corlett et al, 2019), it is yet to be determined how neural information 'preceding' stimulus onset influences perception in those susceptible to pareidolias. To that end, we investigated how pre-stimulus cortical activity affects visual processing in PD patients during the performance of the NPT.…”

Pre-stimulus low-alpha frontal networks characterize pareidolias in Parkinson’s disease

“…Face detection on the NPT necessitates an active search-and-detect effort requiring configural face processing and a top-down integration of facial features(10). While these images serve as sensory deprived ambiguous stimuli, a subset of PD patients consciously misperceive noisy patches as faces, likely due to abnormal perceptual biases(13). In our experiment during the pre-stimulus phase, this misrepresentation was observed as a near-significant increase in low-alpha spectral power in the frontal electrodes.…”