Directional coupling of slow and fast hippocampal gamma with neocortical alpha/beta oscillations in human episodic memory.

Episodic memories hinge upon our ability to process a wide range of multisensory information and bind this information into a coherent, memorable representation. On a neural level, these 2 processes are thought to be supported by neocortical alpha/beta desynchronization and hippocampal theta/gamma synchronization, respectively. Intuitively, these 2 processes should couple to successfully create and retrieve episodic memories, yet this hypothesis has not been tested empirically. We address this by analyzing human intracranial electroencephalogram data recorded during 2 associative memory tasks. We find that neocortical alpha/beta (8 to 20 Hz) power decreases reliably precede and predict hippocampal "fast" gamma (60 to 80 Hz) power increases during episodic memory formation; during episodic memory retrieval, however, hippocampal "slow" gamma (40 to 50 Hz) power increases reliably precede and predict later neocortical alpha/beta power decreases. We speculate that this coupling reflects the flow of information from the neocortex to the hippocampus during memory formation, and hippocampal pattern completion inducing information reinstatement in the neocortex during memory retrieval.

Measuring Foot Abduction Brace Wear Time Using a Single 3-Axis Accelerometer.

The recommended treatment for idiopathic congenital clubfoot deformity involves a series of weekly castings, surgery, and a period of bracing using a foot abduction brace (FAB). Depending on the age of the child, the orthotic should be worn for periods that reduce in duration as the child develops. Compliance is vital to achieve optimal functional outcomes and reduce the likelihood of reoccurrence, deformity, or the need for future surgery. However, compliance is typically monitored by self-reporting, which is time-consuming to implement and lacks accuracy. This study presents a novel method for objectively monitoring FAB wear using a single 3-axis accelerometer. Eleven families mounted an accelerometer on their infant's FAB for up to seven days. Parents were also given a physical diary that was used to record the daily application and removal of the orthotic in line with their treatment. Both methods produced very similar measurements of wear that visually aligned with the movement measured by the accelerometer. Bland Altman plots showed a -0.55-h bias in the diary measurements and the limits of agreement ranging from -2.96 h to 1.96 h. Furthermore, the Cohens Kappa coefficient for the entire dataset was 0.88, showing a very high level of agreement. The method provides an advantage over existing objective monitoring solutions as it can be easily applied to existing FABs, preventing the need for bespoke monitoring devices. The novel method can facilitate increased research into FAB compliance and help enable FAB monitoring in clinical practice.

Defining Continuous Walking Events in Free-Living Environments: Mind the Gap.

In free-living environments, continuous walking can be challenging to achieve without encountering interruptions, making it difficult to define a continuous walking event. While limited research has been conducted to define a continuous walking event that accounts for interruptions, no method has considered the intensity change caused by these interruptions, which is crucial for achieving the associated health outcomes. A sample of 24 staff members at the University of Salford were recruited. The participants wore an accelerometer-based device (activPAL™) for seven days continuously and completed an activity diary, to explore a novel methodological approach of combining short interruptions of time between walking events based on an average walking cadence. The definition of moderate-to-vigorous physical activity (MVPA) used was a minimum walking cadence of either 76, 100, or 109 steps/min. The average daily time spent in MVPA increased from 75.2 ± 32.6 min to 86.5 ± 37.4 min using the 76 steps/min, 48.3 ± 29.5 min to 53.0 ± 33.3 min using the 100 steps/min threshold, and 31.4 ± 20.5 min to 33.9 ± 22.6 min using the 109 steps/min threshold; the difference before grouping and after grouping was statistically significant (p < 0.001). This novel method will enable future analyses of the associations between continuous walking and health-related outcomes.

Disentangling neocortical alpha/beta and hippocampal theta/gamma oscillations in human episodic memory formation.

To form an episodic memory, we must first process a vast amount of sensory information about the to-be-encoded event and then bind these sensory representations together to form a coherent memory trace. While these two cognitive capabilities are thought to have two distinct neural origins, with neocortical alpha/beta oscillations supporting information representation and hippocampal theta-gamma phase-amplitude coupling supporting mnemonic binding, evidence for a dissociation between these two neural markers is conspicuously absent. To address this, seventeen human participants completed an associative memory task that first involved processing information about three sequentially-presented stimuli, and then binding these stimuli together into a coherent memory trace, all the while undergoing MEG recordings. We found that decreases in neocortical alpha/beta power during sequence perception, but not mnemonic binding, correlated with enhanced memory performance. Hippocampal theta/gamma phase-amplitude coupling, however, showed the opposite pattern; increases during mnemonic binding (but not sequence perception) correlated with enhanced memory performance. These results demonstrate that memory-related decreases in neocortical alpha/beta power and memory-related increases in hippocampal theta/gamma phase-amplitude coupling arise at distinct stages of the memory formation process. We speculate that this temporal dissociation reflects a functional dissociation in which neocortical alpha/beta oscillations could support the processing of incoming information relevant to the memory, while hippocampal theta-gamma phase-amplitude coupling could support the binding of this information into a coherent memory trace.

A Machine Learning Classification Model for Monitoring the Daily Physical Behaviour of Lower-Limb Amputees.

There are currently limited data on how prosthetic devices are used to support lower-limb prosthesis users in their free-living environment. Possessing the ability to monitor a patient's physical behaviour while using these devices would enhance our understanding of the impact of different prosthetic products. The current approaches for monitoring human physical behaviour use a single thigh or wrist-worn accelerometer, but in a lower-limb amputee population, we have the unique opportunity to embed a device within the prosthesis, eliminating compliance issues. This study aimed to develop a model capable of accurately classifying postures (sitting, standing, stepping, and lying) by using data from a single shank-worn accelerometer. Free-living posture data were collected from 14 anatomically intact participants and one amputee over three days. A thigh worn activity monitor collected labelled posture data, while a shank worn accelerometer collected 3-axis acceleration data. Postures and the corresponding shank accelerations were extracted in window lengths of 5-180 s and used to train several machine learning classifiers which were assessed by using stratified cross-validation. A random forest classifier with a 15 s window length provided the highest classification accuracy of 93% weighted average F-score and between 88 and 98% classification accuracy across all four posture classes, which is the best performance achieved to date with a shank-worn device. The results of this study show that data from a single shank-worn accelerometer with a machine learning classification model can be used to accurately identify postures that make up an individual's daily physical behaviour. This opens up the possibility of embedding an accelerometer-based activity monitor into the shank component of a prosthesis to capture physical behaviour information in both above and below-knee amputees. The models and software used in this study have been made open source in order to overcome the current restrictions of applying activity monitoring methods to lower-limb prosthesis users.

Event conjunction: How the hippocampus integrates episodic memories across event boundaries.

Our lives are a continuous stream of experience. Our episodic memories on the other hand have a definitive beginning, middle, and end. Theories of event segmentation suggest that salient changes in our environment produce event boundaries which partition the past from the present and, as a result, produce discretized memories. However, event boundaries cannot completely discretize two memories; any shared conceptual link will lead to the rapid integration of these memories. Here, we present a new framework inspired by electrophysiological research that resolves this apparent contradiction. At its heart, the framework proposes that hippocampal theta-gamma coupling maintains a highly abstract model of an ongoing event and serves to encode this model as an episodic memory. When a second but related event begins, this theta-gamma model is rapidly reconstructed within the hippocampus where new details of the second event can be appended to the existing event model. The event conjunction framework is the first electrophysiological explanation of how event memories can be formed at, and integrated across, event boundaries.

Music festival attendees' illicit drug use, knowledge and practices regarding drug content and purity: a cross-sectional survey.

BACKGROUND: Drug checking is a harm reduction strategy which allows users to check the content and purity of illicit drugs. Although drug checking has been trialled internationally, with demonstrated value as a harm reduction and health promotion strategy, the use of such services in Australia remains a contentious issue. This study aimed to investigate the proportion and patterns of illicit drug use among young people, their attitudes towards drug checking at festivals and the potential impact of drug checking on intended drug use behaviour. METHODS: The survey was conducted at a major Australian music festival in 2016. Data was collected from a sample of festival attendees (n = 642) aged between 18 and 30 years. A descriptive analysis of the data was performed. RESULTS: Nearly three-quarters (73.4%) of participants reported that they had used illicit drugs in the past 12 months, most commonly cannabis (63.9%) and ecstasy (59.8%). A large proportion of participants believed 'somewhat' or 'a lot' that drug checking services could help users seek help to reduce harm (86.5%) and that drug checking services should be combined with harm reduction advice (84.9%). However, two thirds of the participants agreed 'somewhat' or 'a lot' that drug sellers may use this service as a quality control mechanism (68.6%). Approximately half (54.4%) indicated they would be highly likely and a third (32.7%) would be somewhat likely to utilise free drug checking services should they be available at music festivals. When asked whether the results of drug checking would influence their drug use behaviour, participants reported that they would not take substances shown to contain methamphetamine (65.1%), ketamine (57.5%) or para-methoxyamphetamine (PMA) (58.4%). CONCLUSION: The majority of festival attendees aged 18-30 participating in this study reported a history of illicit drug use and were in favour of the provision of free drug checking at festivals. A considerable proportion reported that the results of drug checking would influence their drug use behaviour. The findings of this study can contribute to the debate regarding whether drug checking services could potentially play a major role in harm reduction and health promotion programming for young people attending festivals.

Brain oscillations track the formation of episodic memories in the real world.

Despite the well-known influence of environmental context on episodic memory, little has been done to increase contextual richness within the lab. This leaves a blind spot lingering over the neuronal correlates of episodic memory formation in day-to-day life. To address this, we presented participants with a series of words to memorise along a pre-designated route across campus while a mobile EEG system acquired ongoing neural activity. Replicating lab-based subsequent memory effects (SMEs), we identified significant low to mid frequency power decreases (<30Hz), including beta power decreases over the left inferior frontal gyrus. When investigating the oscillatory correlates of temporal and spatial context binding, we found that items strongly bound to spatial context exhibited significantly greater theta power decreases than items strongly bound to temporal context. These findings expand upon lab-based studies by demonstrating the influence of real world contextual factors that underpin memory formation.

A reduction in self-reported confidence accompanies the recall of memories distorted by prototypes.

When we recall a past event, we reconstruct the event based on a combination of episodic details and semantic knowledge (e.g., prototypes). Though prototypes can impair the veracity of recall, it remains unclear whether we are metacognitively aware of the distortions they introduce. To address this, we conducted six experiments in which participants learned object-colour/object-location pairs and subsequently recalled the colour/location when cued with the object. Leveraging unsupervised machine learning algorithms, we extracted participant-specific prototypes and embedded responses in two-dimensional space to quantify prototype-based distortions in individual memory traces. Our findings reveal robust and conceptually replicable evidence to suggest that prototype-based distortion is accompanied by a reduction in self-reported confidence - an implicit measure of metacognitive awareness. Critically, we find evidence to suggest that it is prototype-based distortion of a memory trace that undermines confidence, rather than a lack of confidence biasing reconstruction towards the use of prototypes. Collectively, these findings suggest that we possess metacognitive awareness of distortions embedded in our memories.

Impact of environmental air pollution on respiratory health and function.

Environmental air pollution presents a considerable risk to global respiratory health. If critical levels are exceeded, inhaled pollutants can lead to the development of respiratory dysfunction and provoke exacerbation in those with pre-existing chronic respiratory disease. Over 90% of the global population currently reside in areas where environmental air pollution is considered excessive-with adverse effects ranging from acute airway irritation to complex immunomodulatory alterations. This narrative review provides an up-to-date perspective concerning the impact of environmental air pollution on respiratory health and function and describes the underpinning mechanisms that contribute to the development and progression of chronic respiratory disease.