An ERP measure of non-conscious memory reveals dissociable implicit processes in human recognition using an open-source automated analytic pipeline.

Non-conscious processing of human memory has traditionally been difficult to objectively measure and thus understand. A prior study on a group of hippocampal amnesia (N = 3) patients and healthy controls (N = 6) used a novel procedure for capturing neural correlates of implicit memory using event-related potentials (ERPs): old and new items were equated for varying levels of memory awareness, with ERP differences observed from 400 to 800 ms in bilateral parietal regions that were hippocampal-dependent. The current investigation sought to address the limitations of that study by increasing the sample of healthy subjects (N = 54), applying new controls for construct validity, and developing an improved, open-source tool for automated analysis of the procedure used for equating levels of memory awareness.

Understanding the encoding of object locations in small-scale spaces during free exploration using eye tracking.

Navigation is instrumental to daily life and is often used to encode and locate objects, such as keys in one's house. Yet, little is known about how navigation works in more ecologically valid situations such as finding objects within a room. Specifically, it is not clear how vision vs.

Neural correlates of the Dunning-Kruger effect.

The Dunning-Kruger effect (DKE) is a metacognitive phenomenon of illusory superiority in which individuals who perform poorly on a task believe they performed better than others, yet individuals who performed very well believe they under-performed compared to others. This phenomenon has yet to be directly explored in episodic memory, nor explored for physiological correlates or reaction times. We designed a novel method to elicit the DKE via a test of item recognition while electroencephalography (EEG) was recorded.

Mind-wandering in Parkinson's disease hallucinations reflects primary visual and default network coupling.

Visual hallucinations are an underappreciated symptom affecting the majority of patients during the natural history of Parkinson's disease. Little is known about other forms of abstract and internally generated cognition - such as mind-wandering - in this population, but emerging evidence suggests that an interplay between the brain's primary visual and default networks might play a crucial role in both internally generated imagery and hallucinations. Here, we explored the association between mind-wandering and visual hallucinations in Parkinson's disease, and their relationship with brain network coupling.

Changes in structural network topology correlate with severity of hallucinatory behavior in Parkinson's disease.

Inefficient integration between bottom-up visual input and higher order visual processing regions is implicated in visual hallucinations in Parkinson's disease (PD). Here, we investigated white matter contributions to this perceptual imbalance hypothesis. Twenty-nine PD patients were assessed for hallucinatory behavior.

Informant- and Self-Appraisals on the Psychosis and Hallucinations Questionnaire (PsycH-Q) Enhances Detection of Visual Hallucinations in Parkinson's Disease.

Background: Clinicians vary in their ability to elicit and interpret hallucinatory symptoms in patients with Parkinson's disease (PD). There is limited evidence for informant-report measures of PD hallucinations as adjuncts to clinician-rated scales.

Objectives: To determine the utility of an informant version of the validated Psychosis and Hallucinations Questionnaire (PsycH-Q) for assessing the presence and severity of hallucinations in PD; and, to evaluate accuracy of clinician judgements by comparison with informant report and self-report.

Evidence for subtypes of freezing of gait in Parkinson's disease.

Background: The purpose of this study is to identify and characterize subtypes of freezing of gait by using a novel questionnaire designed to delineate freezing patterns based on self-reported and behavioral gait assessment.

Methods: A total of 41 Parkinson's patients with freezing completed the Characterizing Freezing of Gait questionnaire that identifies situations that exacerbate freezing. This instrument underwent examination for construct validity and internal consistency, after which a data-driven clustering approach was employed to identify distinct patterns amongst individual responses.

Cognitive training for freezing of gait in Parkinson's disease: a randomized controlled trial.

The pathophysiological mechanism of freezing of gait (FoG) has been linked to executive dysfunction. Cognitive training (CT) is a non-pharmacological intervention which has been shown to improve executive functioning in Parkinson's disease (PD). This study aimed to explore whether targeted CT can reduce the severity of FoG in PD.

Visual Hallucinations Are Characterized by Impaired Sensory Evidence Accumulation: Insights From Hierarchical Drift Diffusion Modeling in Parkinson's Disease.

Background: Models of hallucinations emphasize imbalance between sensory input and top-down influences over perception, as false perceptual inference can arise when top-down predictions are afforded too much precision (certainty) relative to sensory evidence. Visual hallucinations in Parkinson's disease (PD) are associated with lower-level visual and attentional impairments, accompanied by overactivity in higher-order association brain networks. PD therefore provides an attractive framework to explore contributions of bottom-up versus top-down disturbances in hallucinations.

Retrospective Neuropsychological Profile of Patients With Parkinson Disease Prior to Developing Visual Hallucinations.

Visual hallucinations (VH) are a common feature of Parkinson disease (PD); however, the cognitive profile preceding the onset of VH has not yet been established. The present study investigated longitudinal neuropsychological performance of patients with PD who developed VH during follow-up compared to a group who did not develop VH. The patient groups were matched for demographic and disease severity variables at their baseline assessments.

Dysfunction in attentional processing in patients with Parkinson's disease and visual hallucinations.

Mechanistic insights into visual hallucinations (VH) in Parkinson's disease (PD) have suggested a role for impaired attentional processes. The current study tested 25 PD patients with and 28 PD patients without VH on the attentional network test. Hallucinators had significantly lower accuracy rates compared to non-hallucinators, but no differences were found in reaction times.

Abnormal connectivity between the default mode and the visual system underlies the manifestation of visual hallucinations in Parkinson's disease: a task-based fMRI study.

Background: The neural substrates of visual hallucinations remain an enigma, due primarily to the difficulties associated with directly interrogating the brain during hallucinatory episodes.

Aims: To delineate the functional patterns of brain network activity and connectivity underlying visual hallucinations in Parkinson's disease.

Methods: In this study, we combined functional magnetic resonance imaging (MRI) with a behavioral task capable of eliciting visual misperceptions, a confirmed surrogate for visual hallucinations, in 35 patients with idiopathic Parkinson's disease.

Imagine that: elevated sensory strength of mental imagery in individuals with Parkinson's disease and visual hallucinations.

Visual hallucinations occur when our conscious experience does not accurately reflect external reality. However, these dissociations also regularly occur when we imagine the world around us in the absence of visual stimulation. We used two novel behavioural paradigms to objectively measure visual hallucinations and voluntary mental imagery in 19 individuals with Parkinson's disease (ten with visual hallucinations; nine without) and ten healthy, age-matched controls.

Visual hallucinations in Parkinson's disease: theoretical models.

One of the most challenging tasks in neuroscience is to be able to meaningfully connect information across the different levels of investigation, from molecular or structural biology to the resulting behavior and cognition. Visual hallucinations are a frequent occurrence in Parkinson's disease and significantly contribute to the burden of the disease. Because of the widespread pathological processes implicated in visual hallucinations in Parkinson's disease, a final common mechanism that explains their manifestation will require an integrative approach, in which consideration is taken across all complementary levels of analysis.