Task Periods Research Articles

A Functional Near Infrared Spectroscopy Investigation of the Physiological Underpinnings of Visual Cognitive Workload After Concussion

Background:In concussion, functional near infrared spectroscopy (fNIRS) has been shown to detect differences in cortical oxygenation during neurocognitive testing, with concussed adults manifesting less task-based cortical activation compared to controls. In addition, fNIRS has identified significantly reduced interhemispheric coherence in adult concussions relative to controls. In addition, adults with greater post-concussive symptom burden demonstrate lower task-related oxygenation in the frontal and dorsolateral prefrontal cortex (DLPFC) and reduced connectivity compared to controls.Hypothesis:The goal of this study was to use fNIRS to identify any differences in visual task-related cortical activation between concussed adolescents and healthy controls while performing a the King-Devick (KD) test.Methods:We enrolled 112 adolescents, ages 12-18 years, with recent concussion and 165 healthy controls as part of a large observational prospective cohort. Participants were provided standardized instructions to read the KD cards while wearing the fNIRS sensor pad. The relative changes in the difference of oxy-and deoxy-hemoglobin concentrations over each task condition for each optode were calculated via the Modified Beer-Lambert Law using local baselines for each task condition period as its beginning. The averaged oxy-hemoglobin concentration changes for each task period were used for statistical analysis of group (e.g., concussed vs healthy) effect.Results:The concussed adolescents (n=112) and healthy controls (n=165) were demographically comparable with respect to age, sex, and race/ethnicity. The concussed group was more likely to have a history of prior concussion (p = <.0001) and migraine (p = .0001) compared to the healthy control group (Table 1). The concussed adolescents were assessed with fNIRS while performing a visual task a median of 10 days after injury (IQR 4-16). The concussed group had significantly lower oxygenation changes that are the difference between oxygenated and deoxygenated hemoglobin as an indicator of task-evoked response, on left lateral prefrontal area (p<.005, FDR q<.005). As expected, there was also a main effect for task condition (cards) at right lateral prefrontal cortex (p<.001, FDR q<.005).Conclusions:fNIRS is able to distinguish concussed adolescents from healthy controls while performing a visual-cognitive task, the K-D test. Injured adolescents with concussion demonstrated a compensatory pattern of cortical activation, suggesting localized brain dysfunction, recruiting from both hemispheres, distinguishing it from the pattern of cortical activation in healthy controls. fNIRS, as a modality, is not only able to differentiate concussion from healthy controls, but also captures the compensatory mechanisms of cortical activation that underlie visual cognitive function after injury.

GAT-FD: An integrated MATLAB toolbox for graph theoretical analysis of task-related functional dynamics.

Functional connectivity has been demonstrated to be varying over time during sensory and cognitive processes. Quantitative examinations of such variations can significantly advance our understanding on large-scale functional organizations and their topological dynamics that support normal brain functional connectome and can be altered in individuals with brain disorders. However, toolboxes that integrate the complete functions for analyzing task-related brain functional connectivity, functional network topological properties, and their dynamics, are still lacking. The current study has developed a MATLAB toolbox, the Graph Theoretical Analysis of Task-Related Functional Dynamics (GAT-FD), which consists of four modules for sliding-window analyses, temporal mask generation, estimations of network properties and dynamics, and result display, respectively. All the involved functions have been tested and validated using functional magnetic resonance imaging data collected from human subjects when performing a block-designed task. The results demonstrated that the GAT-FD allows for effective and quantitative evaluations of the functional network properties and their dynamics during the task period. As an open-source and user-friendly package, the GAT-FD and its detailed user manual are freely available at https://www.nitrc.org/projects/gat_fd and https://centers.njit.edu/cnnl/gat_fd/.

Phase-amplitude coupling between low-frequency scalp EEG and high-frequency intracranial EEG during working memory task

Objective. Revealing the relationship between simultaneous scalp electroencephalography (EEG) and intracranial electroencephalography (iEEG) is of great importance for both neuroscientific research and translational applications. However, whether prominent iEEG features in the high-gamma band can be reflected by scalp EEG is largely unknown. To address this, we investigated the phase-amplitude coupling (PAC) phenomenon between the low-frequency band of scalp EEG and the high-gamma band of iEEG. Approach. We analyzed a simultaneous iEEG and scalp EEG dataset acquired under a verbal working memory paradigm from nine epilepsy subjects. The PAC values between pairs of scalp EEG channel and identified iEEG channel were explored. After identifying the frequency combinations and electrode locations that generated the most significant PAC values, we compared the PAC values of different task periods (encoding, maintenance, and retrieval) and memory loads. Main results. We demonstrated that the amplitude of high-gamma activities in the entorhinal cortex, hippocampus, and amygdala was correlated to the delta or theta phase at scalp locations such as Cz and Pz. In particular, the frequency bin that generated the maximum PAC value centered at 3.16–3.84 Hz for the phase and 50–85 Hz for the amplitude. Moreover, our results showed that PAC values for the retrieval period were significantly higher than those of the encoding and maintenance periods, and the PAC was also influenced by the memory load. Significance. This is the first human simultaneous iEEG and scalp EEG study demonstrating that the amplitude of iEEG high-gamma components is associated with the phase of low-frequency components in scalp EEG. These findings enhance our understanding of multiscale neural interactions during working memory, and meanwhile, provide a new perspective to estimate intracranial high-frequency features with non-invasive neural recordings.

147 Transition Across Care Boundaries: Opportunities to Improve Medication Safety for Children with Medical Complexity

OBJECTIVES/GOALS: Children with medical complexity (CMC) experience frequent transitions of care (e.g., hospital to home) and are at increased risk for medication-related harm. This study aimed to identify transition-related medication safety barriers experienced by family caregivers, as they shoulder most of the caregiving responsibility following discharge. METHODS/STUDY POPULATION: We conducted semi-structured qualitative research interviews of 6 family caregivers and 10 healthcare professionals with roles assisting families during hospital discharge. Interviews focused on identifying key stages of the hospital-to-home transition period as well as medication-related tasks, decisions, and contexts. Transcribed audio interviews and research meeting notes were content analyzed to develop journey maps visually depicting key phases of the families experiences managing medication at home and their decision points and unmet needs. RESULTS/ANTICIPATED RESULTS: Journey mapping identified key decision points, medication management needs, and way points navigated by family caregivers during the hospital-to-home transition. Findings were salient for each phase of the family journey: 1) initial admission/intra-unit transfer; 2) in-patient care; 3) peri-discharge planning; 4) discharge; 5) immediate post discharge period (we termed post-discharge configuration); and 6) period of ongoing tasks and needs. Illustrative examples will be presented and discussed. DISCUSSION/SIGNIFICANCE: Family caregivers of CMC have needs that evolve throughout the medication use journey, suggesting a need for interventions that account for the time variant nature of this work. Findings lay a foundation for the next step of our study which aims to develop a prototype medication safety intervention that will be evaluated with family caregivers.

Replicable patterns of causal information flow between hippocampus and prefrontal cortex during spatial navigation and spatial-verbal memory formation.

Interactions between the hippocampus and prefrontal cortex (PFC) play an essential role in both human spatial navigation and episodic memory, but the underlying causal flow of information between these regions across task domains is poorly understood. Here we use intracranial EEG recordings and spectrally resolved phase transfer entropy to investigate information flow during two different virtual spatial navigation and memory encoding/recall tasks and examine replicability of information flow patterns across spatial and verbal memory domains. Information theoretic analysis revealed a higher causal information flow from hippocampus to lateral PFC than in the reverse direction. Crucially, an asymmetric pattern of information flow was observed during memory encoding and recall periods of both spatial navigation tasks. Further analyses revealed frequency specificity of interactions characterized by greater bottom-up information flow from hippocampus to PFC in delta-theta band (0.5-8Hz); in contrast, top-down information flow from PFC to hippocampus was stronger in beta band (12-30Hz). Bayesian analysis revealed a high degree of replicability between the two spatial navigation tasks (Bayes factor > 5.46e+3) and across tasks spanning the spatial and verbal memory domains (Bayes factor > 7.32e+8). Our findings identify a domain-independent and replicable frequency-dependent feedback loop engaged during memory formation in the human brain.

Cortical activation and functional connectivity during the verbal fluency task for adolescent-onset depression: A multi-channel NIRS study

ObjectiveDepression disorder is accompanied by cognitive impairments. However, there is limited research focused on cognitive impairments and their neurological mechanism in adolescents with depression. The purpose of the current study is to illustrate the differences in brain activity patterns between depressed adolescents and healthy controls (HCs). MethodA total of 72 adolescents with depression, as well as 74 HCs, were recruited. We utilized functional near-infrared spectroscopy (fNIRS) to monitor the concentrations of oxyhemoglobin (Oxy-Hb) in the brains of participants while they performed the verbal fluency task (VFT) to examine cognitive impairment in adolescents with depression. ResultsOur study demonstrated that adolescents with depression had significantly less cortical activation in the hemodynamic responses of Oxy-Hb at channels mainly located in the prefrontal cortex (PFC) than HCs during the 60-s task period (false discovery rate (FDR)-corrected p < 0.05). The mean channel-to-channel connectivity was 0.400 for HCs (SD = 0.149) and 0.303 (SD = 0.138) for adolescents with depression, and the HC group had a higher mean channel-to-channel connectivity strength than the depression group (t = −15.586, p < 0.001). For the patient group, we found significant negative correlations between HAMD scores and mean Oxy-Hb changes in Channel 38 (r = −0.33, p < 0.01), Channel 39 (r = −0.34, p < 0.01), Channel 41 (r = −0.25, p < 0.05), Channel 42 (r = −0.28, p < 0.05), and Channel 44 (r = −0.27, p < 0.05), and these channels were mainly located in areas with little difference between groups. ConclusionsOur study provides neurological evidence about the executive function (EF) in depressed adolescents. Adolescents with depression exhibited an abnormal activation pattern and decreased task-related functional connectivity compared to HCs. The changed Oxy-Hb concentration of PFC during VFT was not sensitive to depression symptoms.

Cognitive Networks (Cognits) Process and Maintain Working Memory.

Ever since it was discovered in the monkey’s prefrontal cortex, persistent neuronal activity during the delay period of delay tasks has been considered a phenomenon of working memory. Operationally, this interpretation is correct, because during that delay those tasks require the memorization of a sensory cue, commonly visual. What is incorrect is the assumption that the persistent activity during the delay is caused exclusively by the retention of the sensory cue. In this brief review, the author takes the position that the neural substrate of working memory is an array of long-term memory networks, that is, of cognitive networks (cognits), updated and orderly activated for the attainment of a behavioral goal. In the case of a behavioral task, that activated array of cognits has been previously formed in long-term memory (throughout this text, the expression “long-term memory” refers to all experiences acquired after birth, including habits and so-called procedural memory, such as the learning of a behavioral task). The learning of a task is the forming of synaptic associations between neural representations of three cognitive components of the task: perceptual, motor, and reward-related. Thereafter, when needed, the composite cognit of the task is activated in an orderly fashion to serve working memory in the perception-action cycle. To make his points on a complex issue, which has been the focus of his work, and to delineate a frontier for future research, the author refers to several of his own publications and previously published reviews.

Basic Examination of Haemoglobin Phase of Oxygenation and Deoxygenation in Resting State and Task Periods in Adults Using fNIRS.

Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique used to measure the relative changes in concentrations of oxygenated haemoglobin (oxy-Hb) and deoxygenated haemoglobin (deoxy-Hb) in the cerebral cortex. While most previous studies using fNIRS have relied only on a single oxy-Hb or deoxy-Hb parameter to infer about neural activation, the phase difference between the oxy- and deoxy-Hb signals (haemoglobin phase of oxygenation and deoxygenation: hPod) has been reported to be an important biomarker for analysing haemodynamic characteristics of the brain in infants. In this study, we examined the basic characteristics of adult hPod to develop a new analysis method to detect more sensitive signals that reflect neural activation in adults using fNIRS. We measured the hPod of 12 healthy adults in the frontal and occipital cortex during rest and upon exposure to visual stimuli and the verbal working memory (WM) task. We found that the average hPod values during the entire measurement period ranged between π and 1.5π rad in all conditions. This result indicates that the phase differences in adults were generally close to a stable antiphase pattern (hPod values around π), regardless of the presence or absence of tasks and stimuli. However, when dynamic changes in hPod values were analysed, significant differences between the resting state and WM tasks were observed during activation period in the frontal and occipital regions. These results suggest that the analysis of dynamic hPod change is useful for detecting a subtle activation for cognitive tasks.

Правові аспекти легалізації обігу та застосування цивільними особами вогнепальної зброї для відсічі збройної агресії Російської Федерації

The current aggression of the Russian Federation (RF) against Ukraine has highlighted various actual socio-political and criminal issues. It was established that the problem of legalization of circulation and use of firearms by civilians to repel the armed aggression of the Russian Federation arouses the greatest interest in society. The analysis of normative acts allows determining two levels of civilians’ accessing to firearms to repel the armed aggression of the Russian Federation: general and special. The general level is determined by the laws of Ukraine «On Ensuring the Participation of Civilians in the Defense of Ukraine» from 03.03.2022 № 2114-IX and «On Amendments to the Criminal Code of Ukraine and other Laws of Ukraine to Determine the Circumstances that Exclude Criminal Misconduct and Provide Combat Immunity Actions in the conditions of martial law» from 15.03.2022 № 2124-IX. Special one is defined by the Law of Ukraine «On Fundamentals of National Resistance» of 16.07.2021 № 1702-IX and the Procedure for the use of personal hunting weapons and ammunition by members of voluntary formations of territorial communities in the performance of territorial defense tasks, approved by the Resolution of the Cabinet of Ministers of Ukraine of December 29, 2021 № 1448. The analysis of normative acts at the general level allows to determine the gaps in the Law of Ukraine № 2114-IX, such as: the lack of clear correspondence with the Law of Ukraine № 1702-IX; incorrect reference to the resolution of the Cabinet of Ministers of Ukraine № 828; lack of clear conditions for the use of weapons. The positive aspects are: expanding opportunities not only for the citizens of Ukraine, but also for foreigners and stateless persons to obtain and use firearms; de facto exclusion of criminal liability for the use of firearms. It is established that the Law of Ukraine № 2124-IX provides for a new circumstance that excludes the criminal illegality of the act, that is «Fulfillment of the Duty to Protect the Fatherland, Independence and Territorial Integrity of Ukraine» (Article 43–1 of the Criminal Code), which determines, on the one hand, rather wide opportunities for Ukraine protection; on the other hand, it provides a number of conditions for the legality of the act, which significantly complicate such activities. It is proved that regulations at the special level are designed more for the peaceful period of life (it is complicated by conditions that are difficult to comply with in a particular period), subjects and means of protection are clearly defined, time limits are defined, and that is the period of territorial defense tasks performing. A discrepancy was established between the list of remedies defined by the Law of Ukraine № 1702-IX and the Cabinet of Ministers of Ukraine Resolution № 1448. It was stated that these regulations do not apply to all civilians and do not provide more opportunities for defense.

Targeting Frontal Gamma Activity with Neurofeedback to Improve Working Memory in Schizophrenia.

Optimal working memory (WM), the mental ability to internally maintain and manipulate task-relevant information, requires coordinated activity of dorsal-lateral prefrontal cortical (DLPFC) neurons. More specifically, during delay periods of tasks with WM features, DLPFC microcircuits generate persistent, stimulus-specific higher-frequency (e.g., gamma) activity. This activity largely depends on recurrent connections between parvalbumin positive inhibitory interneurons and pyramidal neurons in more superficial DLPFC layers. Due to the size and organization of pyramidal neurons (especially apical dendrites), local field potentials generated by DLPFC microcircuits are strong enough to pass outside the skull and can be detected using electroencephalography (EEG). Since patients with schizophrenia (SCZ) exhibit both DLPFC and WM abnormalities, EEG markers of DLPFC microcircuit activity during WM may serve as effective biomarkers or treatment targets. In this review, we summarize converging evidence from primate and human studies for a critical role of DLPFC microcircuit activity during WM and in the pathophysiology of SCZ. We also present a meta-analysis of studies available in PubMed specifically comparing frontal gamma activity between participants with SCZ and healthy controls, to determine whether frontal gamma activity may be a valid biomarker or treatment target for patients with SCZ. We summarize the complex cognitive and neurophysiologic processes contributing to neural oscillations during tasks with WM features, and how such complexity has stalled the development of neurophysiologic biomarkers and treatment targets. Finally, we summarize promising results from early reports using neuromodulation to target DLPFC neural activity and improve cognitive function in participants with SCZ, including a study from our team demonstrating that gamma-EEG neurofeedback increases frontal gamma power and WM performance in participants with SCZ. From the evidence discussed in this review, we believe the emerging field of neuromodulation, which includes extrinsic (electrical or magnetic stimulation) and intrinsic (EEG neurofeedback) modalities, will, in the coming decade, provide promising treatment options targeting specific neurophysiologic properties of specific brain areas to improve cognitive and behavioral health for patients with SCZ.

Measuring the Performance of FreeRTOS on ESP32 Multi-Core

Real-Time Operating System (RTOS) executing on multi-core architectures still links to a lot of unresolved issues. The article presents potential problems and discusses measurement techniques indicating the performance and determinism. The advantages and disadvantages of individual measurement approaches are discussed, which cover a range from non-invasive techniques to techniques that require the cooperation of a monitored application. On top of that, the parameters indicating the performance and properties of RTOS running on multi-core are defined. Among them, the measuring of the semaphore taking, and task period jitter are described deeply. The operations are measured on ESP32-WROOM-32 development kit equipped with XTENSA dual-core processor running FreeRTOS. The results show unexpectedly high values of the switching context time and jitter when the rescheduling to another core was forced compared to time values measured on single core. Consequently, the unexpected rescheduling to other core increases the execution time of FreeRTOS operations. The work should facilitate the improvement of FreeRTOS implementation when running on multi-core architecture.

Delayed reinforcement hinders subsequent extinction

In operant conditioning, animals associate their own behavior with a reinforcer, and the probability of the behavioral responses is increased. This form of learning is called reinforcement. In contrast, when the previously reinforced responses are no longer paired with a reinforcer, these responses are eventually extinguished. The effectiveness of reinforcement depends primarily on time intervals between reinforcers and responses, but it is not fully understood how the intervals affect subsequent extinction. To address this question, we performed electrical stimulation of the rat medial forebrain bundle (MFB), a part of the brain reward system, and an operant task in which the MFB was electrically stimulated 0.1 s (immediate condition) or 1 s (delayed condition) after the rat's nose was poked. During the first half of the task period (a reinforcement period), nose pokes were associated with MFB stimulation. In contrast, during the second half (an extinction period), we did not stimulate the MFB irrespective of nose pokes. We found that rats exhibited increased nose-poke behaviors during the reinforcement period under both conditions, whereas during the extinction period, nose pokes were more persistent in the delayed condition than in the immediate condition. The persistent responses in the extinction period were independent of responses in the reinforcement period. Therefore, reinforcement and extinction are driven by independent neural mechanisms.

The Effect of a Verbal Cognitive Task on Postural Sway Does Not Persist When the Task Is Over.

Dual-task balance studies explore interference between balance and cognitive tasks. This study is a descriptive analysis of accelerometry balance metrics to determine if a verbal cognitive task influences postural control after the task ends. Fifty-two healthy older adults (75 ± 6 years old, 30 female) performed standing balance and cognitive dual-tasks. An accelerometer recorded movement from before, during, and after the task (reciting every other letter of the alphabet). Thirty-six balance metrics were calculated for each task condition. The effect of the cognitive task on postural control was determined by a generalized linear model. Twelve variables, including anterior–posterior centroid frequency, peak frequency and entropy rate, medial-later entropy rate and wavelet entropy, and bandwidth in all directions, exhibited significant differences between baseline and cognitive task periods, but not between baseline and post-task periods. These results indicate that the verbal cognitive task did alter balance, but did not bring about persistent effects after the task had ended. Traditional balance measurements, i.e., root mean square and normalized path length, notably lacked significance, highlighting the potential to use other accelerometer metrics for the early detection of balance problems. These novel insights into the temporal dynamics of dual-task balance support current dual-task paradigms to reduce fall risk in older adults.

Age Group Differences in Response to Repeated Exposure to Laboratory Stress Tasks

Research examining age differences in affect reactivity (i.e. how much affective experiences change in response to stressors) has produced mixed results, suggesting that there are areas of relative strength and weakness in regulatory processes across age-groups. The present study’s goals were to examine potential age-group differences in affect reactivity and subjective task-appraisals across repeated exposures to a psychosocial laboratory stressor. In the Health and Daily Experiences (HEADE) study, younger (18-35 years old; n=107) and older adults (60-90 years old; n=90) were exposed to the Trier Social Stress Test on three occasions in a laboratory setting over a five-day period. Current affective experiences and task-appraisals were assessed at each session using validated self-report scales, with current affective experiences measured at baseline and task periods to determine affect reactivity. Repeated measures ANOVA analyses were conducted to examine age-group differences in affect reactivity and task-appraisals across sessions. In support of our hypotheses, younger adults showed greater reductions in their negative affect reactivity over time compared to older adults [F(2, 390)= 8.18, p<.001]. Additionally, younger adults’ appraisals of task-difficulty decreased [F(2, 384)= 14.79, p<.001] and appraisals of task-performance increased [F(2,384)= 13.39, p<.001] across sessions, while older adults’ task-appraisals remained stable. Age-group differences in negative affect reactivity and task-difficulty appraisals were not evident for the first session and only emerged after repeated exposure to the stressors. These results highlight the importance of identifying age-related vulnerabilities in adapting to repeated stressors, with implications for designing effective interventions aimed at improving health and well-being for older adults.

Hippocampal–prefrontal interactions during spatial decision‐making

AbstractThe hippocampus has been linked to memory encoding and spatial navigation, while the prefrontal cortex is associated with cognitive functions such as decision‐making. These regions are hypothesized to communicate in tasks that demand both spatial navigation and decision‐making processes. However, the electrophysiological signatures underlying this communication remain to be better elucidated. To investigate the dynamics of the hippocampal–prefrontal interactions, we have analyzed their local field potentials and spiking activity recorded from rats performing a spatial alternation task on a figure eight‐shaped maze. We found that the phase coherence of theta peaked around the choice point area of the maze. Moreover, Granger causality revealed a hippocampus → prefrontal cortex directionality of information flow at theta frequency, peaking at starting areas of the maze, and on the reverse direction at delta frequency, peaking near the turn onset. Additionally, the patterns of phase‐amplitude cross‐frequency coupling within and between the regions also showed spatial selectivity, and hippocampal theta and prefrontal delta modulated not only gamma amplitude but also inter‐regional gamma synchrony. Finally, we found that the theta rhythm dynamically modulated neurons in both regions, with the highest modulation at the choice area; interestingly, prefrontal cortex neurons were more strongly modulated by the hippocampal theta rhythm than by their local field rhythm. In all, our results reveal maximum electrophysiological interactions between the hippocampus and the prefrontal cortex near the decision‐making period of the spatial alternation task, corroborating the hypothesis that a dynamic interplay between these regions takes place during spatial decisions.

Self-reported emotional eaters consume more food under stress if they experience heightened stress reactivity and emotional relief from stress upon eating

Group data means from individuals who self-assess as emotional eaters do not reliably show increased food intake in response to stress or negative emotions. This inconsistency in predictive validity of self-reported emotional eating (EE) could be attributable to unconsidered moderation of the relationship between self-reported EE and behavioral measures of EE. Greater emotional relief from stress by eating may provide enhanced negative reinforcement and promote future EE in response to stress as a form of self-medication. Thus, we predicted that greater emotional relief from stress by eating (decrease in negative affect from stress to post-eating) would moderate the extent to which heightened stress reactivity (measured by systolic blood pressure, SBP) moderates the relationship between self-reported EE and food intake post-stress. We also hypothesized that self-reported EE would not predict greater food consumption on the rest day. 43 undergraduate women completed online assessments of eating behaviors. Participants were given snacks to eat after a mental stress task (TSST) or rest period on separate days in counterbalanced order. Our prediction was supported, as the moderated moderation model (PROCESS model 3) was highly significant on the stress day. Self-reported EE predicted increased food intake post-stress only under conditions of high stress reactivity and high emotional relief. On the rest day, self-reported EE predicted greater snack food intake only when SBP was high. This conditional increased intake substantiates stress as a promoter of snack food consumption for women with greater EE. Overall, our findings identified factors that may distinguish the subset of self-reported emotional eaters who are more likely to display EE behaviors in a laboratory setting, yet further studies are needed to directly test whether negative reinforcement via emotional relief from stress by eating drives enhanced EE following stress.

Intrinsic timescales across the basal ganglia

Recent studies have shown that temporal stability of the neuronal activity over time can be estimated by the structure of the spike-count autocorrelation of neuronal populations. This estimation, called the intrinsic timescale, has been computed for several cortical areas and can be used to propose a cortical hierarchy reflecting a scale of temporal receptive windows between areas. In this study, we performed an autocorrelation analysis on neuronal populations of three basal ganglia (BG) nuclei, including the striatum and the subthalamic nucleus (STN), the input structures of the BG, and the external globus pallidus (GPe). The analysis was performed during the baseline period of a motivational visuomotor task in which monkeys had to apply different amounts of force to receive different amounts of reward. We found that the striatum and the STN have longer intrinsic timescales than the GPe. Moreover, our results allow for the placement of these subcortical structures within the already-defined scale of cortical temporal receptive windows. Estimates of intrinsic timescales are important in adding further constraints in the development of computational models of the complex dynamics among these nuclei and throughout cortico-BG-thalamo-cortical loops.

Shielding working-memory representations from temporally predictable external interference

Protecting working-memory content from distracting external sensory inputs and intervening tasks is an ubiquitous demand in daily life. Here, we ask whether and how temporal expectations about external events can help mitigate effects of such interference during working-memory retention. We manipulated the temporal predictability of interfering items that occurred during the retention period of a visual working-memory task and report that temporal expectations reduce the detrimental influence of external interference on subsequent memory performance. Moreover, to determine if the protective effects of temporal expectations rely on distractor suppression or involve shielding of internal representations, we compared effects after irrelevant distractors that could be ignored vs. interrupters that required a response. Whereas distractor suppression may be sufficient to confer protection from predictable distractors, any benefits after interruption are likely to involve memory shielding. We found similar benefits of temporal expectations after both types of interference. We conclude that temporal expectations may play an important role in safeguarding behaviour based on working memory – acting through mechanisms that include the shielding of internal content from external interference.

Guaranteeing Timely Response to Changes of Monitored Objects by Assigning Deadlines and Periods to Tasks

Timely response to changes of monitored objects is the key to ensuring the safety and reliability of cyber-physical systems (CPSs). There are two kinds of tasks in CPSs: update tasks and control tasks. Update tasks are responsible for updating the data in the system based on the state of the objects they monitor. Control tasks are responsible for making decisions based on the data in the system. The response time of the system to the change of a monitored object consists of two parts: the time taken by update tasks to reflect the change to the system, and the time taken by control tasks to make decisions according to the data in the system. Deadlines and periods of update tasks and control tasks directly affect the response time. Reasonable deadline and period assignment is the key to ensuring timely response to the changes of monitored objects. In this paper, we study the deadline and period assignment in CPSs. To the best of our knowledge, all existing work only focuses on the deadline and period assignment for update tasks with the goal of ensuring the freshness of the data in CPSs, and this is the first study focusing on the deadline and period assignment for both update tasks and control tasks with the goal of ensuring timely response to the changes of monitored objects. A new problem about response time control and system workload control is defined in this paper. Two deadline and period assignment methods are proposed to solve the defined problem. All the proposed methods can be used in the CPSs adopting the earliest deadline first (EDF) scheduling method. Experiments with randomly generated tasks are conducted to evaluate the performance of the proposed methods in terms of acceptance ratio and execution efficiency.

Thermal-aware Adaptive Platform Management for Heterogeneous Embedded Systems

Recent trends in real-time applications have raised the demand for high-throughput embedded platforms with integrated CPU-GPU based Systems-On-Chip (SoCs). The enhanced performance of such SoCs, however, comes at the cost of increased power consumption, resulting in significant heat dissipation and high on-chip temperatures. The prolonged occurrences of high on-chip temperature can cause accelerated in-circuit ageing, which severely degrades the long-term performance and reliability of the chip. Violation of thermal constraints leads to on-board dynamic thermal management kicking-in, which may result in timing unpredictability for real-time tasks due to transient performance degradation. Recent work in adaptive software design have explored this issue from a control theoretic stand-point, striving for smooth thermal envelopes by tuning the core frequency. Existing techniques do not handle thermal violations for periodic real-time task sets in the presence of dynamic events like change of task periodicity, more so in the context of heterogeneous SoCs with integrated CPU-GPUs. This work presents an OpenCL runtime extension for thermal-aware scheduling of periodic, real-time tasks on heterogeneous multi-core platforms. Our framework mitigates dynamic thermal violations by adaptively tuning task mapping parameters, with the eventual control objective of satisfying both platform-level thermal constraints and task-level deadline constraints. We consider multiple platform-level control actions like task migration, frequency tuning and idle slot insertion as the task mapping parameters. To the best of our knowledge, this is the first work that considers such a variety of task mapping control actions in the context of heterogeneous embedded platforms. We evaluate the proposed framework on an Odroid-XU4 board using OpenCL benchmarks and demonstrate its effectiveness in reducing thermal violations.