Prefrontal Activation is Associated With Gait Quality During an Attentional Task in Older Adults

Prefrontal cortical activation varies by walking task and is a marker of attentional demand. We compared prefrontal activation by functional near-infrared spectroscopy (fNIRS) to accelerometry-derived gait quality. We hypothesized greater activation with lower gait quality (greater step-time coefficient-of-variation, decreased cadence, smoothness, regularity, and signal variability). Participants (n=114; age 74.4±6.0 years, 59.6% female) were independently ambulating individuals >64 years. Attentional (reciting every-other alphabet letter) and physical (uneven surface) challenges mimicked community mobility and provided four 15m walking conditions: even, uneven, ABC-even, and ABC-uneven. fNIRS data were referenced to quiet standing and averaged within left and right hemispheres. Gait metrics from a tri-axial accelerometer at the lower-back included cadence (steps/min), step-time coefficient-of-variation, signal variability (standard deviation), smoothness (harmonic ratio), and regularity (entropy). Associations between fNIRS and gait were quantified using Pearson correlations (α=0.05). Results were consistent across hemispheres, gait axes, and robust to adjustment for age and gait speed; we report unadjusted coefficients for left hemisphere and anterior-posterior gait direction. Greater prefrontal activation was associated with slower cadence (r=-0.220, p=0.019), lower signal variability (r=-0.228, p=0.015), and reduced smoothness (r=-0.194, p=0.039) during ABC-even. No relation was observed for step-time coefficient-of-variation or regularity. Results were similar for the ABC-uneven condition, except there was no association with gait smoothness but was with step-time coefficient-of-variation (r=0.25, p=0.007). Prefrontal activation was not correlated to gait quality in non-ABC conditions. Our findings support our hypothesis only during the ABC challenge, suggesting that older adults may rely on prefrontal activation to complete attentional but not physical challenges during gait.

The P600, but not N400, is modulated by sustained attention

The functional significance of the two prominent language-related ERP components N400 and P600 is still under debate. It has recently been suggested that one important dimension along which the two vary, is in terms of automaticity versus attentional control, with N400 amplitudes reflecting more automatic and P600 amplitudes reflecting more controlled aspects of sentence comprehension. The availability of executive resources necessary for controlled processes depends on sustained attention, which fluctuates over time. Here, we thus tested whether P600 and N400 amplitudes depend on the level of sustained attention. We re-analyzed EEG and behavioral data from a sentence processing task by Sassenhagen & Bornkessel-Schlesewsky (2015, Cortex), which included sentences with morphosyntactic and semantic violations. Participants read sentences phrase by phrase and indicated whether a sentence contained any type of anomaly as soon as they had the relevant information. To quantify periods of high versus low sustained attention, we extracted a moving reaction time coefficient of variation over the entire course of the task. We found that the P600 amplitude was significantly larger during periods of low reaction time variability (high sustained attention) than in periods of high reaction time variability (low sustained attention). In contrast, the amplitude of the N400 was not affected by reaction time variability. These results thus suggest that the P600 component is sensitive to sustained attention while the N400 component is not, which provides independent evidence for accounts suggesting that P600 amplitudes reflect more controlled and N400 amplitudes more automatic aspects of sentence comprehension.

Working beyond SPA and the trajectories of cognitive and mental health of UK pensioners: Do gender, choice, and occupational status matter?

We assessed the association between work status beyond state pension age (SPA) and the long-term trajectories of cognitive and mental health for men and women separately, and the extent to which this relationship is conditioned by their occupational status and whether the choice to retire or continue working is voluntary or involuntary. Data are pensioners (aged between SPA and SPA + 9) from the English Longitudinal Study of Ageing waves 4 (2008/09) through 9 (2018/19). The analytic sample includes 959 men and 1217 women when considering cognitive outcomes and 1131 men and 1434 women when evaluating depression. Findings based on growth curve models reveal that, compared to women who retired at SPA and without any particular reason, their peers who retired due to frailing health reported a more precipitous decline in memory over time (coefficient = −0.10). However, analysis stratified by occupation shows that this association between ill-health retirement and long-term memory decline was concentrated among older women of the highest occupational status. We also found that men who retired or worked past SPA voluntarily reported a better baseline verbal fluency and were less likely to report depression over time (coefficient for work = 0.80; coefficient for retired = 0.87). Women who worked past SPA voluntarily were less likely to report depression at baseline (OR = 0.53). Policies that extend work life should offer older people more personal control over decision surrounding retirement.

Gait Parameters Measured from Wearable Sensors Reliably Detect Freezing of Gait in a Stepping in Place Task

Freezing of gait (FOG), a debilitating symptom of Parkinson’s disease (PD), can be safely studied using the stepping in place (SIP) task. However, clinical, visual identification of FOG during SIP is subjective and time consuming, and automatic FOG detection during SIP currently requires measuring the center of pressure on dual force plates. This study examines whether FOG elicited during SIP in 10 individuals with PD could be reliably detected using kinematic data measured from wearable inertial measurement unit sensors (IMUs). A general, logistic regression model (area under the curve = 0.81) determined that three gait parameters together were overall the most robust predictors of FOG during SIP: arrhythmicity, swing time coefficient of variation, and swing angular range. Participant-specific models revealed varying sets of gait parameters that best predicted FOG for each participant, highlighting variable FOG behaviors, and demonstrated equal or better performance for 6 out of the 10 participants, suggesting the opportunity for model personalization. The results of this study demonstrated that gait parameters measured from wearable IMUs reliably detected FOG during SIP, and the general and participant-specific gait parameters allude to variable FOG behaviors that could inform more personalized approaches for treatment of FOG and gait impairment in PD.

Gait Parameters Measured From Wearable Sensors Reliably Detect Freezing of Gait in a Stepping in Place Task

Freezing of gait (FOG), a debilitating symptom of Parkinson’s disease (PD), can be safely studied using the stepping in place (SIP) task. However, clinical, visual identification of FOG during SIP is subjective and time consuming, and automatic FOG detection during SIP currently requires measuring center of pressure on dual force plates. This study examines whether FOG elicited during SIP in 10 individuals with PD could be reliably detected using kinematic data measured from wearable inertial measurement unit sensors (IMUs). A general, logistic regression model (AUC = 0.81) determined that three gait parameters together were overall the most robust predictors of FOG during SIP: arrhythmicity, swing time coefficient of variation, and swing angular range. Participant-specific models revealed varying sets of gait parameters that best predicted FOG for each participant, highlighting variable FOG behaviors, and demonstrated equal or better performance for 6 out of the 10 participants, suggesting the opportunity for model personalization. The results of this study demonstrated that gait parameters measured from wearable IMUs reliably detected FOG during SIP, and the general and participant-specific gait parameters allude to variable FOG behaviors that could inform more personalized approaches for treatment of FOG and gait impairment in PD.

Justification of the Coefficient of Use of the Working Time of the Unit Change for Harrowing Winter Crops with Simultaneous Top Dressing

The dependences of the coefficient of use of the working time of the change of the proposed multifunctional unit for harrowing winter crops with simultaneous additional fertilizing with solid mineral fertilizers are theoretically justified. In the conditions of agriculture of Krasnodar Territory, with an increase in the working speed of the unit, a significant decrease in this coefficient was found for various ruts and capacities of the fertilizer silo. For the proposed unit, all components of the cycle time spent on performing two working and two idle passes through the field with the shuttle method of movement, as well as the number of cycles per shift, the actual duration of the shift time and its utilization rate are calculated. With an increase in the working speed of the unit, all other things being equal, the value of the shift time coefficient decreases.

Influence of stand and terrain characteristics on the productivity of the Timberjack 240b tractor in pure beech stands

This paper presents the results of research of the Timberjack 240b tractor equipped with a double-drum winch (work form 1 Tractor driver + 0 Assistant) in beech stand at an average elevation of 983.73 m. The research was conducted using the time and work study method, with the help of GIS technology in certain segments of research. The achieved working hours consist of 75.44% effective time and 24.56% delay time. The delay time coefficient is 1.33. In total, 47 transport cycles were realized, with 66 stopping points, an average of 1.41 per transport cycle. The average skidding distance was 221.19 m. In total, 363 logs (204.04 m3) were collected by 79 winches. The average load volume was 4.34 m3 and consisted of 5.43 pieces. Loaded tractor skidding time is strongly influenced by skidding distance and load volume in interaction with the longitudinal slope of skidding trails. To increase tractor productivity, it was concluded that the skidding roads should be built with the smallest longitudinal slope possible. Preferably, logs should be skidded downhill.