Acceptability, Feasibility, and Effectiveness of Immersive Virtual Technologies to Promote Exercise in Older Adults: A Systematic Review and Meta-Analysis.

CONTEXT: This review aimed to synthesize the literature on the acceptability, feasibility, and effectiveness of immersive virtual technologies to promote physical exercise in older people. METHOD: We performed a literature review, based on four databases (PubMed, CINAHL, Embase, and Scopus; last search: 30 January 2023). Eligible studies had to use immersive technology with participants aged 60 years and over. The results regarding acceptability, feasibility, and effectiveness of immersive technology-based interventions in older people were extracted. The standardized mean differences were then computed using a random model effect. RESULTS: In total, 54 relevant studies (1853 participants) were identified through search strategies. Concerning the acceptability, most participants reported a pleasant experience and a desire to use the technology again. The average increase in the pre/post Simulator Sickness Questionnaire score was 0.43 in healthy subjects and 3.23 in subjects with neurological disorders, demonstrating this technology's feasibility. Regarding the effectiveness, our meta-analysis showed a positive effect of the use of virtual reality technology on balance (SMD = 1.05; 95% CI: 0.75-1.36; p < 0.001) and gait outcomes (SMD = 0.7; 95% CI: 0.14-0.80; p < 0.001). However, these results suffered from inconsistency and the number of trials dealing with these outcomes remains low, calling for further studies. CONCLUSIONS: Virtual reality seems to be well accepted by older people and its use with this population is feasible. However, more studies are needed to conclude its effectiveness in promoting exercise in older people.

Attending to pitch information inhibits processing of pitch information: the curious case of amusia.

In normal listeners, the tonal rules of music guide musical expectancy. In a minority of individuals, known as amusics, the processing of tonality is disordered, which results in severe musical deficits. It has been shown that the tonal rules of music are neurally encoded, but not consciously available in amusics. Previous neurophysiological studies have not explicitly controlled the level of attention in tasks where participants ignored the tonal structure of the stimuli. Here, we test whether access to tonal knowledge can be demonstrated in congenital amusia when attention is controlled. Electric brain responses were recorded while asking participants to detect an individually adjusted near-threshold click in a melody. In half the melodies, a note was inserted that violated the tonal rules of music. In a second task, participants were presented with the same melodies but were required to detect the tonal deviation. Both tasks required sustained attention, thus conscious access to the rules of tonality was manipulated. In the click-detection task, the pitch deviants evoked an early right anterior negativity (ERAN) in both groups. In the pitch-detection task, the pitch deviants evoked an ERAN and P600 in controls but not in amusics. These results indicate that pitch regularities are represented in the cortex of amusics, but are not consciously available. Moreover, performing a pitch-judgment task eliminated the ERAN in amusics, suggesting that attending to pitch information interferes with perception of pitch. We propose that an impaired top-down frontotemporal projection is responsible for this disorder.

Real-time modulation of visual feedback on human full-body movements in a virtual mirror: development and proof-of-concept.

BACKGROUND: Virtual reality (VR) provides interactive multimodal sensory stimuli and biofeedback, and can be a powerful tool for physical and cognitive rehabilitation. However, existing systems have generally not implemented realistic full-body avatars and/or a scaling of visual movement feedback. We developed a "virtual mirror" that displays a realistic full-body avatar that responds to full-body movements in all movement planes in real-time, and that allows for the scaling of visual feedback on movements in real-time. The primary objective of this proof-of-concept study was to assess the ability of healthy subjects to detect scaled feedback on trunk flexion movements. METHODS: The "virtual mirror" was developed by integrating motion capture, virtual reality and projection systems. A protocol was developed to provide both augmented and reduced feedback on trunk flexion movements while sitting and standing. The task required reliance on both visual and proprioceptive feedback. The ability to detect scaled feedback was assessed in healthy subjects (n = 10) using a two-alternative forced choice paradigm. Additionally, immersion in the VR environment and task adherence (flexion angles, velocity, and fluency) were assessed. RESULTS: The ability to detect scaled feedback could be modelled using a sigmoid curve with a high goodness of fit (R2 range 89-98%). The point of subjective equivalence was not significantly different from 0 (i.e. not shifted), indicating an unbiased perception. The just noticeable difference was 0.035 ± 0.007, indicating that subjects were able to discriminate different scaling levels consistently. VR immersion was reported to be good, despite some perceived delays between movements and VR projections. Movement kinematic analysis confirmed task adherence. CONCLUSIONS: The new "virtual mirror" extends existing VR systems for motor and pain rehabilitation by enabling the use of realistic full-body avatars and scaled feedback. Proof-of-concept was demonstrated for the assessment of body perception during active movement in healthy controls. The next step will be to apply this system to assessment of body perception disturbances in patients with chronic pain.

Operationalizing protocol differences for EADC-ADNI manual hippocampal segmentation.

BACKGROUND: Hippocampal volumetry on magnetic resonance imaging is recognized as an Alzheimer's disease (AD) biomarker, and manual segmentation is the gold standard for measurement. However, a standard procedure is lacking. We operationalize and quantitate landmark differences to help a Delphi panel converge on a set of landmarks. METHODS: One hundred percent of anatomic landmark variability across 12 different protocols for manual segmentation was reduced into four segmentation units (the minimum hippocampus, the alveus/fimbria, the tail, and the subiculum), which were segmented on magnetic resonance images by expert raters to estimate reliability and AD-related atrophy. RESULTS: Intra- and interrater reliability were more than 0.96 and 0.92, respectively, except for the alveus/fimbria, which were 0.86 and 0.77, respectively. Of all AD-related atrophy, the minimum hippocampus contributed to 67%; tail, 24%; alveus/fimbria, 4%; and the subiculum, 5%. CONCLUSIONS: Anatomic landmark variability in available protocols can be reduced to four discrete and measurable segmentation units. Their quantitative assessment will help a Delphi panel to define a set of landmarks for a harmonized protocol.

Manual segmentation qualification platform for the EADC-ADNI harmonized protocol for hippocampal segmentation project.

BACKGROUND: The use of hippocampal volumetry as a biomarker for Alzheimer's disease (AD) requires that tracers from different laboratories comply with the same segmentation method. Here we present a platform for training and qualifying new tracers to perform the manual segmentation of the hippocampus on magnetic resonance images (MRI) following the European Alzheimer's Disease Consortium and Alzheimer's Disease Neuroimaging Initiative (EADC-ADNI) Harmonized Protocol (HarP). Our objective was to demonstrate that the training process embedded in the platform leads to increased compliance and qualification with the HarP. METHOD: Thirteen new tracers' segmentations were compared with benchmark images with respect to: (a) absolute segmentation volume; (b) spatial overlap of contour with the reference using the Jaccard similarity index; and (c) spatial distance of contour with the reference. Point by point visual feedback was provided through three training phases on 10 MRI. Tracers were then tested on 10 different MRIs in the qualification phase. RESULTS: Statistical testing of training over three phases showed a significant increase of Jaccard (i.e. mean Jaccard overlap P < .001) between phases on average for all raters, demonstrating that training positively increased compliance with the HarP. Based on these results we defined qualification thresholds which all tracers were able to meet. CONCLUSIONS: This platform is an adequate infrastructure allowing standardized training and evaluation of tracers' compliance with the HarP. This is a necessary step allowing the use of hippocampal volumetry as a biomarker for AD in clinical and research centers.

Harmonized benchmark labels of the hippocampus on magnetic resonance: the EADC-ADNI project.

BACKGROUND: A globally harmonized protocol (HarP) for manual hippocampal segmentation based on magnetic resonance has been recently developed by a task force from European Alzheimer's Disease Consortium (EADC) and Alzheimer's Disease Neuroimaging Initiative (ADNI). Our aim was to produce benchmark labels based on the HarP for manual segmentation. METHODS: Five experts of manual hippocampal segmentation underwent specific training on the HarP and segmented 40 right and left hippocampi from 10 ADNI subjects on both 1.5 T and 3 T scans. An independent expert visually checked segmentations for compliance with the HarP. Descriptive measures of agreement between tracers were intraclass correlation coefficients (ICCs) of crude volumes and similarity coefficients of three-dimensional volumes. RESULTS: Two hundred labels have been provided for the 20 magnetic resonance images. Intra- and interrater ICCs were >0.94, and mean similarity coefficients were 1.5 T, 0.73 (95% confidence interval [CI], 0.71-0.75); 3 T, 0.75 (95% CI, 0.74-0.76). CONCLUSION: Certified benchmark labels have been produced based on the HarP to be used for tracers' training and qualification.

Delphi definition of the EADC-ADNI Harmonized Protocol for hippocampal segmentation on magnetic resonance.

BACKGROUND: This study aimed to have international experts converge on a harmonized definition of whole hippocampus boundaries and segmentation procedures, to define standard operating procedures for magnetic resonance (MR)-based manual hippocampal segmentation. METHODS: The panel received a questionnaire regarding whole hippocampus boundaries and segmentation procedures. Quantitative information was supplied to allow evidence-based answers. A recursive and anonymous Delphi procedure was used to achieve convergence. Significance of agreement among panelists was assessed by exact probability on Fisher's and binomial tests. RESULTS: Agreement was significant on the inclusion of alveus/fimbria (P = .021), whole hippocampal tail (P = .013), medial border of the body according to visible morphology (P = .0006), and on this combined set of features (P = .001). This definition captures 100% of hippocampal tissue, 100% of Alzheimer's disease-related atrophy, and demonstrated good reliability on preliminary intrarater (0.98) and inter-rater (0.94) estimates. DISCUSSION: Consensus was achieved among international experts with respect to hippocampal segmentation using MR resulting in a harmonized segmentation protocol.

Brain activity is related to individual differences in the number of items stored in auditory short-term memory for pitch: evidence from magnetoencephalography.

We used magnetoencephalography (MEG) to examine brain activity related to the maintenance of non-verbal pitch information in auditory short-term memory (ASTM). We focused on brain activity that increased with the number of items effectively held in memory by the participants during the retention interval of an auditory memory task. We used very simple acoustic materials (i.e., pure tones that varied in pitch) that minimized activation from non-ASTM related systems. MEG revealed neural activity in frontal, temporal, and parietal cortices that increased with a greater number of items effectively held in memory by the participants during the maintenance of pitch representations in ASTM. The present results reinforce the functional role of frontal and temporal cortices in the retention of pitch information in ASTM. This is the first MEG study to provide both fine spatial localization and temporal resolution on the neural mechanisms of non-verbal ASTM for pitch in relation to individual differences in the capacity of ASTM. This research contributes to a comprehensive understanding of the mechanisms mediating the representation and maintenance of basic non-verbal auditory features in the human brain.

When more is less: extraction of summary statistics benefits from larger sets.

Despite several processing limitations that have been identified in the visual system, research shows that statistical information about a set of objects could be perceived as accurately as the information about a single object. It has been suggested that extraction of summary statistics represents a different mode of visual processing, which employs a parallel mechanism free of capacity limitations. Here, we demonstrate, using reaction time measures, that increasing the number of stimuli in the set results in faster reaction times and better accuracy for estimating the mean tendency of a set. These results provide clear evidence that extraction of summary statistics relies on a distributed attention mode that operates across the whole display at once and that this process benefits from larger samples across which the summary statistics are calculated.

Distinguishing between lateralized and nonlateralized brain activity associated with visual short-term memory: fMRI, MEG, and EEG evidence from the same observers.

Previous functional neuroimaging studies have shown that maintenance of centrally presented objects in visual short-term memory (VSTM) leads to bilateral increases of BOLD activations in IPS/IOS cortex, while prior electrophysiological work suggests that maintaining stimuli encoded from a single hemifield leads to a sustained posterior contralateral negativity (SPCN) in electrophysiology and magnetoencephalography. These two findings have never been investigated using the same physiological measures. We recorded the BOLD response using fMRI, magnetoencephalography (MEG), and electrophysiology (EEG), while subjects encoded visual stimuli from a single hemifield of a balanced display. The EEG showed an SPCN. However, no SPCN-like activation was observed in the BOLD signals. The BOLD response in parietal cortex remained bilateral, even after unilateral encoding of the stimuli, but MEG showed both bilateral and contralateral activations, each likely reflecting a sub portion of the neuronal populations participating in the maintenance of information in VSTM. Contrary to the assumption that BOLD, EEG, and MEG responses - that were each linked to the maintenance of information in VSTM - are markers of the same neuronal processes, our findings suggest that each technique reveals a somewhat distinct but overlapping neural signature of the mechanisms supporting visual short-term memory.

Adding Haptic Feedback to Virtual Environments With a Cable-Driven Robot Improves Upper Limb Spatio-Temporal Parameters During a Manual Handling Task.

Physical interactions within virtual environments are often limited to visual information within a restricted workspace. A new system exploiting a cable-driven parallel robot to combine visual and haptic information related to environmental physical constraints (e.g. shelving, object weight) was developed. The aim of this study was to evaluate the impact on user movement patterns of adding haptic feedback in a virtual environment with this robot. Twelve healthy participants executed a manual handling task under three conditions: 1) in a virtual environment with haptic feedback; 2) in a virtual environment without haptic feedback; 3) in a real physical environment. Temporal parameters (movement time, peak velocity, movement smoothness, time to maximum flexion, time to peak wrist velocity) and spatial parameters of movement (maximum trunk flexion, range of motion of the trunk, length of the trajectory, index of curvature and maximum clearance from the shelf) were analysed during the reaching, lowering and lifting phases. Our results suggest that adding haptic feedback improves spatial parameters of movement to better respect the environmental constraints. However, the visual information presented in the virtual environment through the head mounted display appears to have an impact on temporal parameters of movement leading to greater movement time. Taken together, our results suggest that a cable-driven robot can be a promising device to provide a more ecological context during complex tasks in virtual reality.

Oscillatory activity in parietal and dorsolateral prefrontal cortex during retention in visual short-term memory: additive effects of spatial attention and memory load.

We used whole-head magnetoencephalography to study the representation of objects in visual short-term memory (VSTM) in the human brain. Subjects remembered the location and color of either two or four colored disks that were encoded from the left or right visual field (equal number of distractors in the other visual hemifield). The data were analyzed using time-frequency methods, which enabled us to discover a strong oscillatory activity in the 8-15 Hz band during the retention interval. The study of the alpha power variation revealed two types of responses, in different brain regions. The first was a decrease in alpha power in parietal cortex, contralateral to the stimuli, with no load effect. The second was an increase of alpha power in parietal and lateral prefrontal cortex, as memory load increased, but without interaction with the hemifield of the encoded stimuli. The absence of interaction between side of encoded stimuli and memory load suggests that these effects reflect distinct underlying mechanisms. A novel method to localize the neural generators of load-related oscillatory activity was devised, using cortically-constrained distributed source-localization methods. Some activations were found in the inferior intraparietal sulcus (IPS) and intraoccipital sulcus (IOS). Importantly, strong oscillatory activity was also found in dorsolateral prefrontal cortex (DLPFC). Alpha oscillatory activity in DLPFC was synchronized with the activity in parietal regions, suggesting that VSTM functions in the human brain may be implemented via a network that includes bilateral DLPFC and bilateral IOS/IPS as key nodes.

Attentional and anatomical considerations for the representation of simple stimuli in visual short-term memory: evidence from human electrophysiology.

Observers encoded the spatial arrangement of two or three horizontal line segments relative to a square frame presented for 150 ms either in left or right visual field and either above or below the horizontal midline. The target pattern was selected on the basis of colour (red vs. green) from an equivalent distractor pattern in the opposite left-right visual hemifield. After a retention interval of 450 or 650 ms a test pattern was presented at fixation. The task was to decide whether the test was the same as the encoded pattern or different. Selection of the to-be-memorized pattern produced an N2pc response that was not influenced by the number of line segments nor by the length of the retention interval, but that was smaller in amplitude for patterns presented in the upper visual field compared with patterns presented in the lower visual field. A sustained posterior contralateral negativity (SPCN) followed the N2pc. The SPCN was larger for patterns with three line segments than for two, was larger for patterns encoded from lower visual field than from upper visual field, and returned to baseline sooner for the shorter retention interval than for the longer interval. These results, and others, provide an interesting and complex pattern of similarities and differences between the N2pc and SPCN, consistent with the view that N2pc reflects mechanisms of attentional selection whereas the SPCN reflects maintenance in visual short-term memory.

A multi-frequency EIT system design based on telecommunication signal processors.

A multi-frequency electrical impedance tomography system for cardiopulmonary monitoring has been designed with specialized digital signal processors developed primarily for the telecommunications sector. The system consists of two modules: a scan-head and a base-station. The scan-head, located close to the patient's torso, contains front-end circuits for measuring transfer impedance with a 16-electrode array. The base-station, placed at the bedside, comprises 16 direct digital synthesizers, 32 digital down-converters, digital circuits to control the data acquisition sequence and a USB-2.0 microcontroller. At every step of the scan sequence, the system simultaneously measures four complex variables at eight frequencies. These variables are the potential difference between the selected pair of sense electrodes, the currents applied by the source and sink electrodes, and the current flowing through the ground electrode. Frequencies are programmable from 10 kHz to 2 MHz with a resolution of 2 mHz. Characterization tests were performed with a precision mesh phantom connected to the scan-head. For a 5 Hz frame rate, the mean signal-to-noise ratio and accuracy are, respectively, 43 dB and 95.4% for eight frequencies logarithmically spaced from 70 to 950 kHz. In vitro and in vivo time-difference images have been reconstructed.

Dissociation of the N2pc and sustained posterior contralateral negativity in a choice response task.

The N2pc, a greater negativity at posterior electrodes on the side contralateral to an attended visual stimulus, usually between 180 and 280 ms, is thought to reflect the moment-to-moment deployment of visual-spatial attention. In tasks that require the retention of information in visual short-term memory, there is also a sustained posterior contralateral negativity (SPCN) that often begins about 300-400 ms after stimulus onset and that persists for the duration of the retention interval. A positive-going deflection at around 300 ms often separates the N2pc and the SPCN. An SPCN is also observed in tasks that are not defined as memory tasks, but that presumably engage visual short-term memory as an intermediate processing buffer (e.g., in order to make a choice response to a briefly-presented visual stimulus). The SPCN in memory tasks has been shown to increase in amplitude as the memory load is increased. We used this property of the SPCN to verify that the SPCN observed during the performance of a choice task with a response following each stimulus display is related to the SPCN observed in tasks that are structured as memory tasks. Using identical physical stimuli, we manipulated the hypothesized memory load across trial blocks by instructions either to encode only one stimulus or two stimuli. We observed an increase of the amplitude of the SPCN as memory load increased, with no concomitant increase in the amplitude of the N2pc that immediately preceded it. The results provide a clear dissociation between the N2pc (spatial attention, not affected by memory load) and the SPCN (visual short-term memory, sharply sensitive to memory load).

Modulation of electric brain responses evoked by pitch deviants through transcranial direct current stimulation.

Congenital amusia is a neurodevelopmental disorder, characterized by a difficulty detecting pitch deviation that is related to abnormal electrical brain responses. Abnormalities found along the right fronto-temporal pathway between the inferior frontal gyrus (IFG) and the auditory cortex (AC) are the likely neural mechanism responsible for amusia. To investigate the causal role of these regions during the detection of pitch deviants, we applied cathodal (inhibitory) transcranial direct current stimulation (tDCS) over right frontal and right temporal regions during separate testing sessions. We recorded participants' electrical brain activity (EEG) before and after tDCS stimulation while they performed a pitch change detection task. Relative to a sham condition, there was a decrease in P3 amplitude after cathodal stimulation over both frontal and temporal regions compared to pre-stimulation baseline. This decrease was associated with small pitch deviations (6.25 cents), but not large pitch deviations (200 cents). Overall, this demonstrates that using tDCS to disrupt regions around the IFG and AC can induce temporary changes in evoked brain activity when processing pitch deviants. These electrophysiological changes are similar to those observed in amusia and provide causal support for the connection between P3 and fronto-temporal brain regions.

Stimulus intensity affects the latency but not the amplitude of the N2pc.

The N2pc component of the event-related potential (ERP) is an index of visual-spatial attention. It is not clear whether the N2pc reflects pure top-down attentional activity or an interaction of top-down activity with bottom-up sensory activity. Here, we manipulated stimulus intensity of the items composing the target display. Although the amplitude of the P1 component increased monotonically with increasing stimulus intensity, the amplitude of the N2pc did not vary with stimulus intensity. Instead, the onset latency of the N2pc was delayed for weaker stimuli, suggesting that the strength of the selection cue (target color) influenced the moment at which attention was deployed. The results reveal one way in which early sensory ERP amplitude differences are converted into later latency differences.

Short-term consolidation of visual patterns interferes with visuo-spatial attention: converging evidence from human electrophysiology.

In order to investigate the interplay between visuo-spatial attention and central attention, we varied the relative probability (25% vs. 75%) of the responses to lateralized targets in an attentional blink paradigm. When the first target was associated with a less probable response, we observed a larger attentional blink, that is, a general reduction in accuracy for the second target. The efficiency of deployment of spatial attention to the second target was also reduced as a function of the response frequency for the first target. Both the N2pc, an event-related potential (ERP) associated with the deployment of attention in visual space, and the SPCN (sustained posterior contralateral negativity), an ERP associated with the maintenance of information in visual short-term memory, time-locked to T2 were significantly reduced when the first target was associated with a less frequent response. Furthermore, the P3 ERP to T2 was abolished when the response to T1 was rare but not when it was frequent. The results show that the association of T1 to either a rare or frequent response causes significant interference with the deployment of visual spatial attention to T2, and with the short-term consolidation of T2 into visual short-term memory.

A Virtual Reality avatar interaction (VRai) platform to assess residual executive dysfunction in active military personnel with previous mild traumatic brain injury: proof of concept.

PURPOSE: This proof of concept study tested the ability of a dual task walking protocol using a recently developed avatar-based virtual reality (VR) platform to detect differences between military personnel post mild traumatic brain injury (mTBI) and healthy controls. METHODS: The VR platform coordinated motion capture, an interaction and rendering system, and a projection system to present first (participant-controlled) and third person avatars within the context of a specific military patrol scene. A divided attention task was also added. A healthy control group was compared to a group with previous mTBI (both groups comprised of six military personnel) and a repeated measures ANOVA tested for differences between conditions and groups based on recognition errors, walking speed and fluidity and obstacle clearance. RESULTS: The VR platform was well tolerated by both groups. Walking fluidity was degraded for the control group within the more complex navigational dual tasking involving avatars, and appeared greatest in the dual tasking with the interacting avatar. This navigational behaviour was not seen in the mTBI group. CONCLUSIONS: The present findings show proof of concept for using avatars, particularly more interactive avatars, to expose differences in executive functioning when applying context-specific protocols (here for the military). Implications for rehabilitation Virtual reality provides a means to control context-specific factors for assessment and intervention. Adding human interaction and agency through avatars increases the ecologic nature of the virtual environment. Avatars in the present application of the Virtual Reality avatar interaction platform appear to provide a better ability to reveal differences between trained, military personal with and without mTBI.

Effect of cue-target interval on the N2pc.

The N2pc component of the event-related potential occurs when participants must select and process a lateralized visual target, often in the presence of one or more distractors. The goal of this research was to determine whether the N2pc reflects unique processing related to the treatment of the target or whether it reflects processing related to the presence of a distractor. The selection cue for the target was presented 100 ms earlier, at the same time as, or 100 ms later than the target itself. An earlier cue allowed earlier spatial selection, leading to less interference from the distractor. The results indicated that the offset of the N2pc was delayed when more interference from the distractor was expected.