Metacognitive accuracy differences in Parkinson’s disease and REM sleep behavioral disorder relative to healthy controls

Background Metacognition is the ability to monitor and self-assess cognitive performance. It can be impaired in neurodegenerative diseases, with implications for daily function, and the ability of patients to reliably report their symptoms to health professionals. However, metacognition has not been systematically assessed in early-mid stage Parkinson’s disease (PD) and REM sleep behavioral disorder (RBD), a prodrome of PD. Objectives This study aimed to evaluate metacognitive accuracy and self-confidence in PD and RBD patients across various cognitive tasks. Methods We conducted detailed computerized cognitive assessments with 19 cognitive tasks within an established PD and RBD cohort. Participants self-rated their performance post-task. Metacognitive accuracy was calculated by comparing these ratings against objective performance and further analyzed against clinical and mental health factors. Results PD and RBD patients’ metacognitive accuracy aligned with control subjects. However, they exhibited lower confidence across cognitive domains, reflecting their reduced cognitive performance. A notable inverse correlation was observed between their confidence and MDS-UPDRS I and II scales and HADS anxiety and depression scores. Conclusion Our findings indicate that patients with early to mid-stage PD and RBD are generally aware of their cognitive status, differing from other neurological disorders. The inverse relationship between patient confidence and symptoms of depression, anxiety, and daily life challenges underscores the impact of emotional and functional difficulties on their self-perception of cognitive abilities. This insight could be significant for understanding how these conditions affect mental health, aiding clinicians in developing more effective patient care strategies.


Recognition memory (immediate and delayed)
The test measures recognition memory for words at different time delays.The participant is presented with a sequence of objects in a pseudo-random order, each presented for 1000 ms and with an interimage interval of 200 ms.The participant is then immediately presented with a sequence of 24 objects.12 of the objects are the ones they were asked to commit to memory and 12 are new words, six of which are semantically similar foils to the ones committed to memory.At the end of the battery of tests, the participant's recognition memory is probed again for the same target items alongside a different set of foils and distractors.The primary output for both immediate and delayed word memory is the sum of correct responses, with maximum score being 24.

Target detection
The Target Detection test measures spatial visual attention.The participant is presented with a target shape on the left of the screen and a probe area on the right side of the screen.After 3000ms, the probe area begins to fill with shapes, the participant must identify and click the target shape while ignoring the distractor shapes.Shapes are added every 1000ms and a subset of the shapes in the probe area are removed every 1000ms.The trial runs for a total of 120 addition/removal cycles.The target shape is included in the added shapes pseudo randomly, at a frequency of 12 in 20 cycles.The primary output is the total number of target shapes clicked.

Emotional discrimination
This test measures an individual's ability to identify and discern between emotions.Participants are presented with pictures of two people, each expressing a particular emotion (e.g.happy, neutral, angry, scared).They must decide if the emotions expressed by each person are the same or different.Trials vary based on the emotions used as well as whether individuals have congruent vs. incongruent emotional expressions.To obtain maximum points, participants must complete 50 trials as accurately as possible.For every correct answer, the total score increases by one point.The outcome measure is the total score.

2D manipulations
The 2D Mental Manipulation test measures the ability to spatially manipulate objects in mind (Silverman et al., 2000).In this version of the test, a grid with coloured squares is presented at the top of the screen, with a further four grids with coloured squares presented below (i.e.probe grids).One of the four grids is identical to the target grid above but is rotated by either 90, 180 or 270 degrees whilst the other grids differ by five squares.To obtain maximum points, the participant must indicate which of the four grids is identical to target, solving as many problems as possible within three minutes.

Digit Span
This task is a proxy for working memory.Participants must remember a string of digits that increment in length.Each time participants remember the full string, the next string displayed increments in length by one unit.The total amount of strings participants recalled fully is recorded.

Spatial Span
The Spatial Span test measures spatial short-term memory capacity.It is a variant on the classic Corsi Block Tapping Test (Corsi, 1972).The participant is presented with a 4 x 4 grid, onto which is displayed a sequence of squares in different positions in the grid.The participant must then click the squares in the order that they were highlighted.The difficulty is incremented using a ratchet system, every time a sequence is recalled correctly, the length of the subsequent sequence is incremented by one.The test is terminated when three consecutive mistakes are made on a particular sequence length.The primary output is the maximum sequence length correctly recalled.Minimum level = 2, maximum level = 16, ISI = 0ms, encoding time = 1500ms.

Blocks
Participants must remove blocks from one array until it matches a target array; blocks will fall under gravity.The Blocks task has been adapted from a common analogue neuropsychological test in which the subject has to match a shape using coloured blocks.This is thought to be a good measure of spatial visualisation skills.The current version also incorporates a measure of planning as you have to predict the shapes that will be created once a block is removed and gravity takes effect.

Tower of London
The Tower of London test measures spatial planning.It is a variant on the original Tower of London Test (Shallice, 1982).The participant is shown two sets of three prongs with coloured beads on them.The first set is the initial state and the second set is the target state.The participant must work out the lowest number of moves it would take to transition from the initial state to the target state.They must then input this number using an on-screen number pad.This differs from the original test in that the participant is not allowed to move the beads, all calculation and planning must be done in their head.This is to prevent correct answers being reached through iterative error correction.The test consists of 10 trials of variable difficulty.The difficulty is scaled using the number of beads and the convolutedness, defined as the number of moves that must be made that do not place a bead in its final target position.The outcome measure is the total number of correct trials.

Verbal Analogies
The Analogical Reasoning test measures semantic reasoning abilities.In this version of the test, participants are presented with two written relationships that they must decide have the same type of association or not (e.g."Lion is to feline as cabbage is to vegetable").Participants must indicate their decision by selecting the True or False buttons presented below the written analogies.Analogies are varied across semantic distance to modulate difficulty and association types switch throughout the sequence of trials.To obtain maximum points, participants must solve as many problems as possible within three minutes.For every correct response, the total score increases by one.For every incorrect response, the total score decreases by one.The outcome measure is the total score.

Word Definitions
In this test, individuals are assessed on their ability to identify the correct definitions of words.Participants are presented with a word accompanied by four descriptive statements.They must decide which of the four statements provides the correct definition of the word.Words vary based on their frequency of use in English written language, resulting in rare and commonly used words being presented.For each word, the participant has twenty seconds to choose a definition.To obtain maximum points, participants must answer 21 word-definitions correctly.For every correct response, the total score increases by one point.The outcome measure is the total score.

Simple reaction task
This task is the simplest task available for measuring reaction time.Participants must respond as quickly as they can to a stimulus that appears on the screen at different timepoints.What is measured is the total time it takes for the participant to press on the screen after the stimulus appeared.

Trail making
Trail Making is based on a classical pen and paper neuropsychological test.The first section, containing only numbers reflects the speed at which the participant is able to process a field of information and sort it accurately.The second section, in which there are both numbers and letters requires 'attentional switching', which is an important executive function.Subtracting the former from the latter provides a measure of the 'switching cost'.What is measured is the time required by the participant to click on all the targets in the correct order.

Pairs associate learning
This task is a measure of visual working memory.Participants must remember a series of objects and their associated locations on a grid.What is measured is the total amount of correct trials.

Switching stroop
This task is a proxy for executive function, and is a routine cognitive test that is used to classify patients suffering with conditions such as traumatic brain injury.Participants must describe the colour of a central tile by choosing between two words reading "Red" and "Blue" and coloured either red or blue.The participant must pay attention to either the text of the word or the colour of the word at any given time.What is recorded is the total number of correct trials.

Picture completion
This task is assessing the ability of the participants to identify how patterns taken out of their original context fit back within the context.This taps into visual processing and pattern recognition abilities.Participants must correctly assign missing pieces from a picture.The pieces can be rotated through 90, 180 or 270 degrees.What is recorded is the total number of errors participants make while trying to piece the pictures back together.

Card pairs
This task is a measure of working memory.Participants are shown an array of face up cards.These cards are then placed face down and the participant must remember and identify the locations of pairs of cards.What is measured is the percentage of pairs of cards the participant correctly identified.Formerly, card pairs games used to be a popular computerised entertainment game back in the 90'.

Four towers (3D Scene rotation)
Four Towers/Faulty Towers is a 3D Perspective Rotation test that measures the ability to picture a 3D scene and rotate it in the mind's eye.The participant is presented with an array comprising four perspective images each containing three tower blocks.Three of the images show the same tower blocks arranged in the same way but viewed from different perspectives.One of the images is the odd one out as it differs either by the type of tower blocks that are present or the relative locations that they are placed in.The participant must identify the odd one out as quickly and accurately as they can.A total of 12 problems are presented and the score increments or decrements by 1 dependent on whether or not the participant correctly identifies the odd one out.The primary output is total score.

Median Reaction Time
Median time to react to each block arrangement task.

Target Detection Total Correct Responses
Total number of correctly identified target shapes, reflecting spatial attention and accuracy.

Mean Reaction Time
Average time to react to each target detection stimulus.

Spatial Span Total Correct Responses
Longest sequence length correctly recalled in a spatial memory task.

Median Reaction Time
Median time to react during each spatial memory recall attempt.

Verbal Analogies Total Correct Responses
Total number of correctly solved semantic analogies, indicating semantic reasoning ability.

Median Reaction Time
Median time to react to each analogy problem.

Median Reaction Time
Median time to react to identify the unique tower.

Card Pairs Percentage of Cards Correctly Identified
Percentage of card pairs correctly identified, assessing memory and attention to detail.

Median Array Time
Median time taken to identify pairs of cards in the memory task.