Numerosity estimation of virtual humans as a digital-robotic marker for hallucinations in Parkinson's disease

Hallucinations are frequent non-motor symptoms in Parkinson's disease (PD) associated with dementia and higher mortality. Despite their high clinical relevance, current assessments of hallucinations are based on verbal self-reports and interviews that are limited by important biases. Here, we used virtual reality (VR), robotics, and digital online technology to quantify presence hallucination (vivid sensations that another person is nearby when no one is actually present and can neither be seen nor heard) in laboratory and home-based settings. We establish that elevated numerosity estimation of virtual human agents in VR is a digital marker for experimentally induced presence hallucinations in healthy participants, as confirmed across several control conditions and analyses. We translated the digital marker (numerosity estimation) to an online procedure that 170 PD patients carried out remotely at their homes, revealing that PD patients with disease-related presence hallucinations (but not control PD patients) showed higher numerosity estimation. Numerosity estimation enables quantitative monitoring of hallucinations, is an easy-to-use unobtrusive online method, reaching people far away from medical centers, translating neuroscientific findings using robotics and VR, to patients' homes without specific equipment or trained staff.

The diagnostic performance of functional dopaminergic scintigraphic imaging in the diagnosis of dementia with Lewy bodies: an updated systematic review

INTRODUCTION

Dopaminergic scintigraphic imaging is a cornerstone to support the diagnosis in dementia with Lewy bodies. To clarify the current state of knowledge on this imaging modality and its impact on clinical diagnosis, we performed an updated systematic review of the literature.

METHODS

This systematic review was carried out according to PRISMA guidelines. A comprehensive computer literature search of PubMed/MEDLINE, EMBASE, and Cochrane Library databases for studies published through June 2022 was performed using the following search algorithm: (a) "Lewy body" [TI] OR "Lewy bodies" [TI] and (b) ("DaTscan" OR "ioflupane" OR "123ip" OR "123?ip" OR "123 ip" OR "123i-FP-CIT" OR "FPCIT" OR "FP-CIT" OR "beta?CIT" OR "beta CIT" OR "CIT?SPECT" OR "CIT SPECT" OR "Dat?scan*" OR "dat scan*" OR "dat?spect*" OR "SPECT"). Risk of bias and applicability concerns of the studies were evaluated using the QUADAS-2 tool.

RESULTS

We performed a qualitative analysis of 59 studies. Of the 59 studies, 19 (32%) addressed the diagnostic performance of dopamine transporter imaging, 15 (25%) assessed the identification of dementia with Lewy bodies in the spectrum of Lewy body disease and 18 (31%) investigated the role of functional dopaminergic imaging in distinguishing dementia with Lewy bodies from other dementias. Dopamine transporter loss was correlated with clinical outcomes in 19 studies (32%) and with other functional imaging modalities in 15 studies (25%). Heterogeneous technical aspects were found among the studies through the use of various radioligands, the more prevalent being the [123I]N‑ω‑fluoropropyl‑2β‑carbomethoxy‑3β‑(4‑iodophenyl) nortropane (123I-FP-CIT) in 54 studies (91.5%). Image analysis used visual analysis (9 studies, 15%), semi-quantitative analysis (29 studies, 49%), or a combination of both (16 studies, 27%).

CONCLUSION

Our systematic review confirms the major role of dopaminergic scintigraphic imaging in the assessment of dementia with Lewy bodies. Early diagnosis could be facilitated by identifying the prodromes of dementia with Lewy bodies using dopaminergic scintigraphic imaging coupled with emphasis on clinical neuropsychiatric symptoms. Most published studies use a semi-quantitative analytical assessment of tracer uptake, while there are no studies using quantitative analytical methods to measure dopamine transporter loss. The superiority of a purely quantitative approach to assess dopaminergic transmission more accurately needs to be further clarified.

Phantom boarder relates to experimentally‐induced presence hallucinations in Parkinson's disease

Background

Phantom boarder (PB) is the sensation that someone uninvited is in the patient's home despite evidence to the contrary. It is mostly reported by patients with neurodegenerative disorders such as Alzheimer's disease, dementia with Lewy bodies or Parkinson's disease (PD). Presence hallucination (PH) is frequent in neurodegenerative disease, shares several aspects with PB, and is the sensation that someone is nearby, behind or next to the patient (when nobody is actually there). Recent work developed a sensorimotor method to robotically induce PH (robot-induced PH, riPH) and demonstrated that a subgroup of PD patients showed abnormal sensitivity for riPH.

Objective

We investigated if PD patients with PB (PD-PB) would (1) show elevated sensitivity for riPH that (2) is comparable to that of patients reporting PH, but not PB (PD-PH).

Methods

We studied the sensitivity of non-demented PD patients in a sensorimotor stimulation paradigm, during which three groups of patients (PD-PB; PD-PH; PD patients without hallucinations, PD-nPH) were exposed to different conditions of conflicting sensorimotor stimulation.

Results

We show that PD-PB and PD-PH groups had a higher sensitivity to riPH (compared to PD-nPH). PD-PB and PD-PH groups did not differ in riPH sensitivity. Together with interview data, these behavioral data on riPH show that PB is associated with PH, suggesting that both share some underlying brain mechanisms, although interview data also revealed phenomenological differences.

Conclusions

Because PD-PB patients did not suffer from dementia nor delusions, we argue that these shared mechanisms are of perceptual-hallucinatory nature, involving sensorimotor signals and their integration.

Neuroscience robotics for controlled induction and real-time assessment of hallucinations

Although hallucinations are important and frequent symptoms in major psychiatric and neurological diseases, little is known about their brain mechanisms. Hallucinations are unpredictable and private experiences, making their investigation, quantification and assessment highly challenging. A major shortcoming in hallucination research is the absence of methods able to induce specific and short-lasting hallucinations, which resemble clinical hallucinations, can be elicited repeatedly and vary across experimental conditions. By integrating clinical observations and recent advances in cognitive neuroscience with robotics, we have designed a novel device and sensorimotor method able to repeatedly induce a specific, clinically relevant hallucination: presence hallucination. Presence hallucinations are induced by applying specific conflicting (spatiotemporal) sensorimotor stimulation including an upper extremity and the torso of the participant. Another, MRI-compatible, robotic device using similar sensorimotor stimulation permitted the identification of the brain mechanisms of these hallucinations. Enabling the identification of behavioral and a frontotemporal neural biomarkers of hallucinations, under fully controlled experimental conditions and in real-time, this method can be applied in healthy participants as well as patients with schizophrenia, neurodegenerative disease or other hallucinations. The execution of these protocols requires intermediate-level skills in cognitive neuroscience and MRI processing, as well as minimal coding experience to control the robotic device. These protocols take ~3 h to be completed.

Increased Functional Connectivity of the Intraparietal Sulcus Underlies the Attenuation of Numerosity Estimations for Self-Generated Words

Previous studies have shown that self-generated stimuli in auditory, visual, and somatosensory domains are attenuated, producing decreased behavioral and neural responses compared with the same stimuli that are externally generated. Yet, whether such attenuation also occurs for higher-level cognitive functions beyond sensorimotor processing remains unknown. In this study, we assessed whether cognitive functions such as numerosity estimations are subject to attenuation in 56 healthy participants (32 women). We designed a task allowing the controlled comparison of numerosity estimations for self-generated (active condition) and externally generated (passive condition) words. Our behavioral results showed a larger underestimation of self-generated compared with externally generated words, suggesting that numerosity estimations for self-generated words are attenuated. Moreover, the linear relationship between the reported and actual number of words was stronger for self-generated words, although the ability to track errors about numerosity estimations was similar across conditions. Neuroimaging results revealed that numerosity underestimation involved increased functional connectivity between the right intraparietal sulcus and an extended network (bilateral supplementary motor area, left inferior parietal lobule, and left superior temporal gyrus) when estimating the number of self-generated versus externally generated words. We interpret our results in light of two models of attenuation and discuss their perceptual versus cognitive origins.SIGNIFICANCE STATEMENT We perceive sensory events as less intense when they are self-generated compared with when they are externally generated. This phenomenon, called attenuation, enables us to distinguish sensory events from self and external origins. Here, we designed a novel fMRI paradigm to assess whether cognitive processes such as numerosity estimations are also subject to attenuation. When asking participants to estimate the number of words they had generated or passively heard, we found bigger underestimation in the former case, providing behavioral evidence of attenuation. Attenuation was associated with increased functional connectivity of the intraparietal sulcus, a region involved in numerosity processing. Together, our results indicate that the attenuation of self-generated stimuli is not limited to sensory consequences but is also impact cognitive processes such as numerosity estimations.

Fronto-Temporal Disconnection Within the Presence Hallucination Network in Psychotic Patients With Passivity Experiences

Psychosis, characterized by hallucinations and delusions, is a common feature of psychiatric disease, especially schizophrenia. One prominent theory posits that psychosis is driven by abnormal sensorimotor predictions leading to the misattribution of self-related events. This misattribution has been linked to passivity experiences (PE), such as loss of agency and, more recently, to presence hallucinations (PH), defined as the conscious experience of the presence of an alien agent while no person is actually present. PH has been observed in schizophrenia, Parkinson's disease, and neurological patients with brain lesions and, recently, the brain mechanisms of PH (PH-network) have been determined comprising bilateral posterior middle temporal gyrus (pMTG), inferior frontal gyrus (IFG), and ventral premotor cortex (vPMC). Given that the experience of an alien agent is a common feature of PE, we here analyzed the functional connectivity within the PH-network in psychotic patients with (N = 39) vs without PE (N = 26). We observed reduced fronto-temporal functional connectivity in patients with PE compared to patients without PE between the right pMTG and the right and left IFG of the PH-network. Moreover, when seeding from these altered regions, we observed specific alterations with brain regions commonly linked to auditory-verbal hallucinations (such as Heschl's gyrus). The present connectivity findings within the PH-network extend the disconnection hypothesis for hallucinations to the specific case of PH and associates the PH-network with key brain regions for frequent psychotic symptoms such as auditory-verbal hallucinations, showing that PH are relevant to the study of the brain mechanisms of psychosis and PE.

Robot-induced hallucinations in Parkinson's disease depend on altered sensorimotor processing in fronto-temporal network

Hallucinations in Parkinson's disease (PD) are disturbing and frequent non-motor symptoms and constitute a major risk factor for psychosis and dementia. We report a robotics-based approach applying conflicting sensorimotor stimulation, enabling the induction of presence hallucinations (PHs) and the characterization of a subgroup of patients with PD with enhanced sensitivity for conflicting sensorimotor stimulation and robot-induced PH. We next identify the fronto-temporal network of PH by combining MR-compatible robotics (and sensorimotor stimulation in healthy participants) and lesion network mapping (neurological patients without PD). This PH-network was selectively disrupted in an additional and independent cohort of patients with PD, predicted the presence of symptomatic PH, and associated with cognitive decline. These robotics-neuroimaging findings extend existing sensorimotor hallucination models to PD and reveal the pathological cortical sensorimotor processes of PH in PD, potentially indicating a more severe form of PD that has been associated with psychosis and cognitive decline.

Self-continuity across time in schizophrenia: An exploration of phenomenological and narrative continuity in the past and future

Disorders of the self, such as the “loss of continuity” of the self in time, are a core symptom of schizophrenia, but one, which is still poorly understood. In the present study, we investigated two complementary aspects of self-continuity, namely phenomenological and narrative continuity, in 27 patients with schizophrenia, and compared them with 27 control participants. Participants were asked to identify 7 important past events and to narrate a story taken from their life that included these events. They were then asked to imagine 3 important events that might happen in their personal future and to build a narrative of their future life. The memory vividness of these important life-events and the proportion of self-event connections in the narratives were used as a measure of phenomenological and narrative continuity, respectively. Our results showed that the difficulty for patients to construct vivid representations of personally significant events was observed in both temporal directions, past and future. Patients’ ability to establish explicit connections between personal events and attributes of self in life narratives was also impaired, but only in the case of past narratives. Our results yield a fresh understanding of the cognitive mechanisms of self-disorders in schizophrenia. The clinical and therapeutic implications of these findings are discussed.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

From a Lived Event to Its Autobiographical Memory: An Ecological Study Using Wearable Camera in Schizophrenia

Cognitive disorders are considered as a core symptom of schizophrenia. Importantly, episodic autobiographical memory deficits are strongly related to patients' social dysfunction. Although the cognitive mechanisms underlying autobiographical memory deficit are highly important to open the door for specific cognitive remediation, they are yet to be understood. The present study focused on event segmentation to check to which extent possible impairments in temporal ordering and segmenting in patients hinder memories construction. Twenty-seven patients with schizophrenia and 27 matched controls took part in an outdoor circuit while wearing a wearable camera. A week later, their memory and the temporal organization of this event have been assessed. Results showed that patients, compared with control participants, reported a reduced amount of details, especially less actions with interaction related to the event. Contrary to our initial hypotheses, event segmentation abilities in patients were not affected. The relationship between event segmentation and memory is discussed.

Self-continuity across time in schizophrenia: An exploration of phenomenological and narrative continuity in the past and future

BACKGROUND

Disorders of the self, such as a reduced sense of personal continuity in time, are a core symptom of schizophrenia, but one that is still poorly understood. In the present study, we investigated two complementary aspects of self-continuity, namely phenomenological and narrative continuity, in 27 patients with schizophrenia, and compared them with 27 control participants.

METHODS

Participants were asked to identify important past events and to narrate a story from their life that included these events. They were also asked to imagine important events that might happen in their personal future and to build a narrative of their future life. The vividness of these important life events and the proportion of self-event connections in the narratives were used as a measure of phenomenological and narrative continuity, respectively.

RESULTS

Our study showed patients with schizophrenia experienced less vivid representations of personally significant events (p = .02) for both temporal directions (past and future) (p < .001). In addition, their ability to make explicit connections between personal events and self-attributes in life narratives was also impaired (p = .03), but only in the case of past narratives (p < .001).

CONCLUSIONS

These results shed new light on the cognitive mechanisms underlying self-disorders in schizophrenia. The clinical and therapeutic implications of these findings are discussed.

Grasping the mechanisms of narratives' incoherence in schizophrenia: an analysis of the temporal structure of patients' life story

OBJECTIVE

Life narratives of patients with schizophrenia are characterized by impaired coherence so that the listener has often difficulties to grasp the life trajectory of the patients. In order to better understand what causes this reduced temporal coherence, we investigated the temporal structure of patients' life narratives through different temporal narrative elements (elaboration of beginnings and endings, local temporal indicators and temporal deviations from a linear order), across two complementary studies.

METHODS

Life narratives were collected by means of two different methods; a free recall in study 1 and a more structured protocol, aiming at reducing the cognitive task demands in study 2. All narratives from the two studies were analyzed using the same validated method.

RESULTS

Both studies showed that global temporal coherence is significantly reduced in patients with schizophrenia (ps.02). This is mainly due to their stronger tendency to temporally deviate from a linear temporal order without marking the deviation as such. We also observed significant correlations in the patient groups between global temporal coherence and executive dysfunction (p=.008) or their higher tendency to temporally deviate from a linear temporal order in their life narratives (p<.001).

CONCLUSIONS

These results shed light on narrative correlates of temporal narrative incoherence in schizophrenia and highlight the central role of executive dysfunction in this incoherence.

A Meta-Analysis of Autobiographical Memory Studies in Schizophrenia Spectrum Disorder

Meta-analyses and reviews on cognitive disorders in schizophrenia have shown that the most robust and common cognitive deficits are found in episodic memory and executive functions. More complex memory domains, such as autobiographical memory (AM), are also impaired in schizophrenia, but such impairments are reported less often despite their negative impact on patients' outcome. In contrast to episodic memory, assessed in laboratory tasks, memories of past personal events are much more complex and directly relate to the self. The meta-analysis included 20 studies, 571 patients with schizophrenia spectrum disorder, and 503 comparison subjects. It found moderate-to-large effect sizes with regard to the 3 parameters commonly used to assess AM: memory specificity (g = -0.97), richness of detail (g = -1.40), and conscious recollection (g = -0.62). These effect sizes were in the same range as those found in other memory domains in schizophrenia; for this reason, we propose that defective memories of personal past events should be regarded as a major cognitive impairment in this illness.

Self-recovery in schizophrenia: Insight from autobiographical narratives of patients

The self or identity is often seriously challenged by the emergence of psychotic symptoms. A first reason for that is most likely due to the traumatic experience caused by the sudden emergence of hallucinations or persecutory ideas that challenge both the representation of oneself and that of the world and others. A second reason is linked to the social consequences of having a mental illness and of being assigned with the label of “mentally ill or disabled person”. A third relates to the patients’ cognitive impairment that alters their ability to take distance from these self-challenging events, to give a meaning to these experiences and to build coherent narratives of their life that integrate a great variety of personal experiences such as turning points or unpleasant events. For these reasons, recovering from a severe mental illness is a process through which the self evolves by integrating the lessons of past personal events, building new representations of oneself and looking to new directions for future projects. Excerpts of patients’ narratives collected in experimental setting will be presented in order to illustrate how indexes of recovery can be measured in self-narratives and how they help identifying the steps of self-recovery that have been identified in qualitative research on patients with schizophrenia .

Effectiveness of a specific cueing method for improving autobiographical memory recall in patients with schizophrenia

Autobiographical memory deficits in schizophrenia have a significant impact on patients' daily life. Our study was aimed at testing the effectiveness of a specific cueing (SC) method for improving autobiographical memory recall in patients with schizophrenia, particularly the phenomenological details of their memories. Twenty-five patients with schizophrenia and 25 comparison participants took part in the study. They recalled 6 specific autobiographical events which occurred during 3 different life periods. After each memory recall, participants were given a general cue which allowed them to add further information to their narration. The SC was then applied by means of a series of specific questions to elicit more precise memory detail. The overall memory specificity as well as the number and richness of 5 categories of memory detail (perceptual/sensory, temporal, contextual, emotional, and cognitive) were assessed before and after the SC phase. Before SC, patients' memories were less specific and less detailed. SC had a beneficial effect on patients' memory recall. The overall memory specificity of patients improved. The gain in the number and richness of memory details was comparable between patients and comparison participants. The difference between groups in terms of the number of memory details was not significant. Richness of details was still lower in patients, except for emotional and cognitive details, which were similarly rich in both groups. The cueing method reduces the autobiographical memory impairment of patients with schizophrenia and paves the way for developing specific cognitive remediation therapies to help patients in their daily life.