The role of environmental contextual cues in sequence learning: evidence from a virtual maze context.

Studies on sequence learning usually focus on single, isolated stimuli that are presented sequentially. For example, in the serial reaction time (RT) task, stimuli are either presented in a predictable sequence or in a random sequence, and better performance with the predictable sequence is taken as evidence for sequence-specific learning. Yet, little is known about the role of environmental context cues in sequence learning. If the target stimuli are embedded in a meaningful context, would this facilitate learning by providing helpful contextual associations or would it hinder learning by adding distracting stimuli? This question was examined in two studies. A pilot study compared sequence learning in a virtual maze with a horizontal vs. vertical maze context, in which arrow stimuli guide spatial lever movement responses that resulted in a corresponding virtual transport on the screen. The results showed only overall somewhat better performance with the vertical maze compared to the horizontal maze, but general practice effects and sequence-specific learning effects were the same for both contexts. The main study compared sequence learning with a maze context to sequence learning of arrows without a maze context. The results showed significantly better learning with maze context than without context. These data suggest that the maze context facilitated sequence learning by inducing a meaningful spatial representation ("mental map") similar to that formed in wayfinding.

Effect of additional tasks on the reaction time of braking responses in simulated car driving: beyond the PRP effect.

The presentation of one task increases the reaction time on a subsequent task, if stimulus onset asynchrony (SOA) between tasks is short. This psychological refractory period (PRP) effect is typically leveling off as SOA approaches 1 s, which has been documented both in classical laboratory paradigms and in simulated car driving. Here we report a more persistent effect on the subsequent task that goes well beyond the typical duration of the PRP effect. In a driving simulator, 120 healthy older participants followed a lead car that mostly drove at a constant speed. They had to maintain a regular distance from the lead car and had to brake when the lead car braked. Participants also engaged in several additional tasks during driving (two types of tasks: typing three-digit numbers, stating arguments on public issues). SOA between the braking task and the last preceding additional task was 11.49 s ± 1.99 (mean and standard deviation). In a control condition, the braking task was administered without additional tasks. Main performance outcome was Braking Reaction Time (RT, in s), as the interval between onset of brake lights of the lead car and the moment participants released the gas pedal. Additionally, foot movement time (MT, in s), i.e., the difference between gas pedal release and brake pedal onset, was considered for possible compensation behavior. Inter-vehicle distance to the lead car (in m) was taken into account as a moderator. We found that RT averaged 0.77 s without additional tasks, but averaged 1.45 s with additional tasks. This RT difference was less pronounced at smaller inter-vehicle distances, and was not compensated for by faster MT from the gas pedal to the brake pedal. We conclude that detrimental effects of additional tasks on subsequent braking responses can be more persistent than suggested by the PRP effect, possibly because of maintaining multiple task sets, requiring increased executive control. We further conclude that potential detrimental effects can be ameliorated at small inter-vehicle distances by mobilizing extra cognitive resources when response urgency is higher. As a practical implication of our study, distracting stimuli can have persisting detrimental effects on traffic safety.

The structure of cognitive strategies for wayfinding decisions.

Literature proposes five distinct cognitive strategies for wayfinding decisions at intersections. Our study investigates whether those strategies rely on a generalized decision-making process, on two frame-specific processes-one in an egocentric and the other in an allocentric spatial reference frame, and/or on five strategy-specific processes. Participants took six trips along a prescribed route through five virtual mazes, each designed for decision-making by a particular strategy. We found that wayfinding accuracy on trips through a given maze correlated significantly with the accuracy on trips through another maze that was designed for a different reference frame (rbetween-frames = 0.20). Correlations were not significantly higher if the other maze was designed for the same reference frame (rwithin-frames = 0.19). However, correlations between trips through the same maze were significantly higher than those between trips through different mazes that were designed for the same reference frame (rwithin-maze = 0.52). We conclude that wayfinding decisions were based on a generalized cognitive process, as well as on strategy-specific processes, while the role of frame-specific processes-if any-was relatively smaller. Thus, the well-established dichotomy of egocentric versus allocentric spatial representations did not translate into a similar, observable dichotomy of decision-making.

Inefficient frontal and parietal brain activation during dual-task walking in a virtual environment in older adults.

Walking while performing an additional cognitive task (dual-task walking; DT walking) is a common yet highly demanding behavior in daily life. Previous neuroimaging studies have shown that performance declines from single-task (ST) to DT conditions are accompanied by increased prefrontal cortex (PFC) activity. This increment is particularly pronounced in older adults and has been explained either by compensation, dedifferentiation, or inefficient task processing in fronto-parietal circuits. However, there is only limited evidence for the hypothesized fronto-parietal activity changes measured under real-life conditions such as walking. In this study, we therefore assessed brain activity in PFC and parietal lobe (PL), to investigate whether higher PFC activation during DT walking in older adults is related to compensation, dedifferentiation, or neural inefficiency. Fifty-six healthy older adults (69.11 ± 4.19 years, 30 female) completed three tasks (treadmill walking at 1 m/s, Stroop task, Serial 3's task) under ST and DT conditions (Walking + Stroop, Walking + Serial 3's), and a baseline standing task. Behavioral outcomes were step time variability (Walking), Balance Integration Score BIS (Stroop), and number of correct calculations S3corr (Serial 3's). Brain activity was measured using functional near-infrared spectroscopy (fNIRS) over ventrolateral and dorsolateral PFC (vlPFC, dlPFC) and inferior and superior PL (iPL, sPL). Neurophysiological outcome measures were oxygenated (HbO2) and deoxygenated hemoglobin (HbR). Linear mixed models with follow-up estimated marginal means contrasts were applied to investigate region-specific upregulations of brain activation from ST to DT conditions. Furthermore, the relationships of DT-specific activations across all brain regions was analyzed as well as the relationship between changes in brain activation and changes in behavioral performance from ST to DT. Data indicated the expected upregulation from ST to DT and that DT-related upregulation was more pronounced in PFC (particularly in vlPFC) than in PL regions. Activation increases from ST to DT were positively correlated between all brain regions, and higher brain activation changes predicted higher declines in behavioral performance from ST to DT. Results were largely consistent for both DTs (Stroop and Serial 3's). These findings more likely suggest neural inefficiency and dedifferentiation in PFC and PL rather than fronto-parietal compensation during DT walking in older adults. Findings have implications for interpreting and promoting efficacy of long-term interventions to improve DT walking in older persons.

Choice between decision-making strategies in human route-following.

To follow a prescribed route, we must decide which way to turn at intersections. To do so, we can memorize either the serial order of directions or the associations between spatial cues and directions ("at the drug store, turn left"). Here, we investigate which of these two strategies is used if both are available. In Task S, all intersections looked exactly alike, and participants therefore had to use the serial order strategy to decide which way their route continued. In Task SA, each intersection displayed a unique spatial cue, and participants therefore could use either strategy. In Task A, each intersection displayed a unique cue, but the serial order of cues varied between trips, and participants therefore had to use the associative cue strategy. We found that route-following accuracy increased from trip to trip, was higher on routes with 12 rather than 18 intersections, and was higher on Task SA than on the other two tasks, both with 12 and with 18 intersections. Furthermore, participants on Task SA acquired substantial knowledge about the serial order of directions as well as about cue-direction associations, both with 12 and with 18 intersections. From this we conclude that, when both strategies were available, participants did not pick the better one but rather used both. This represents dual encoding, a phenomenon previously described for more elementary memory tasks. We further conclude that dual encoding may be implemented even if the memory load is not very high (i.e., even with only 12 intersections).

Cognitive-motor multitasking in older adults: a randomized controlled study on the effects of individual differences on training success.

BACKGROUND: Multitasking is an essential part of our everyday life, but performance declines typically in older age. Many studies have investigated the beneficial effects of cognitive, motor and combined cognitive-motor training on multitasking performance in older adults. Previous work, however, has not regarded interindividual differences in cognitive functioning and motor fitness that may affect training benefits. The current study aims to identify whether different training programs may have differential effects on multitasking performance depending on the initial level of cognitive functioning and motor fitness. METHODS: We conduct a 12-week single-blinded randomized controlled trial. A total of N = 150 healthy older adults are assigned to either a single cognitive, a single motor, or a simultaneous cognitive-motor training. Participants are trained twice per week for 45 min. A comprehensive test battery assesses cognitive functions, motor and cardiovascular fitness, and realistic multitasking during walking and driving in two virtual environments. We evaluate how multitasking performance is related not only to the training program, but also to participants' initial levels of cognitive functioning and motor fitness. DISCUSSION: We expect that multitasking performance in participants with lower initial competence in either one or both domains (cognitive functioning, motor fitness) benefits more from single-task training (cognitive training and/or motor training). In contrast, multitasking performance in participants with higher competence in both domains should benefit more from multitask training (simultaneous cognitive-motor training). The results may help to identify whether tailored training is favorable over standardized one-size-fits all training approaches to improve multitasking in older adults. In addition, our findings will advance the understanding of factors that influence training effects on multitasking. TRIAL REGISTRATION: DRKS (German Clinical Trials Register), DRKS00022407. Registered 26/08/2020 - Retrospectively registered at https://www.drks.de/drks_web/setLocale_EN.do.

Acquisition of landmark, route, and survey knowledge in a wayfinding task: in stages or in parallel?

According to an influential concept, humans acquire spatial knowledge about their environment in three distinct stages: landmark knowledge is acquired first, then route knowledge, and finally survey knowledge. The stage concept has been challenged by studies which observed that in a wayfinding paradigm, route, and survey knowledge emerge at the same time and; therefore, were seemingly acquired in parallel. However, this experimental evidence is not conclusive because the above studies suffered from a ceiling effect. The present study was designed to overcome the ceiling effect by increasing the complexity of the wayfinding task. We asked 60 young participants to find their way through an urban environment rendered in virtual reality, and assessed their landmark, route, and survey knowledge after each of ten trials. We found that all three types of knowledge gradually increased from the first to the last trial. We further found that correlations between the three types of knowledge increased from trial to trial. This outcome disagrees profoundly with the stage concept, but is compatible with the parallel concept. Specifically, it is in accordance with the view that landmark, route, and survey knowledge are acquired by multiple overlapping and interacting processes: those processes may start out more or less independently in the first trial but, due to common constraints or synergies, may gradually increase their cooperation during subsequent trials.

Dual-task interference and response strategies in simulated car driving: impact of first-task characteristics on the psychological refractory period effect.

Presentation of a task T1 typically delays the response to a subsequent task T2, more so with high temporal task overlap than with low temporal overlap. This so-called "psychological refractory period effect" (PRP effect) has been observed even if T1 required not a choice between distinct stimulus-response pairs, but rather between a given stimulus-response pair occurring once or twice. We explored which response strategy participants use for responding to such an unusual type of T1 and how such a T1 interacts with T2 performance. In a driving simulator, participants followed a lead car and had to honk when that car's rear window changed color (T1). In condition "pure", the color always changed once and required a single honk; in condition "mixed", the color changed once and required a single honk on some trials, but on other trials, it changed twice 200 ms apart and required a double honk. Participants also had to brake when the lead car braked (T2). On dual-task trials, T1 preceded T2 with a varying stimulus onset asynchrony (SOA) of 50-1200 ms. Reaction time to the first T1 stimulus was similar in "pure" and "mixed" and it was comparable with the reaction time to the second T1 stimulus. Reaction time to the T2 stimulus increased as SOA decreased from 350 to 50 ms, confirming the existence of a PRP effect. Furthermore, reaction time to the T2 stimulus was similar in "pure" and in "mixed" with one T1 stimulus, but was higher in "mixed" with two T1 stimuli. This pattern of findings is compatible with the view that presentation of the first T1 stimulus triggers a single response, which is amended into a double response, if a second T1 stimulus is displayed. The amendment does not need to wait until central processing of the original response is completed, and it therefore begins with no delay beyond the regular reaction time. Our findings further suggest that the mere possibility of a second T1 stimulus being presented does not increase the PRP effect on T2, probably because response amendments are not equivalent to classical response choices. However, the actual presentation of a second T1 stimulus indeed does increase the PRP effect on T2, probably because amendments start 200 ms later than the original response, and therefore prolong central processing of T1.

Effects of practice on visuo-spatial attention in a wayfinding task.

Several studies have evaluated the distribution of visuo-spatial attention in a wayfinding task, using gaze direction as an indicator for the locus of attention. We extended that work by evaluating how visuo-spatial attention is modified by wayfinding practice. Young and older participants followed prescribed routes through a virtual city on six trials. Each trial was followed by a route recall test, where participants saw screenshots of intersections encountered, and had to indicate which way to proceed. Behavioral and gaze data were registered in those tests. Wayfinding accuracy increased from trial to trial, more so in young than in older persons. Total gaze time, mean fixation time, and the vertical scatter of fixations decreased from trial to trial, similarly in young and older persons. The horizontal scatter of fixations did not differ between trials and age groups. The incidence of fixations on the subsequently chosen side also did not differ between trials, but it increased in older age. We interpret these findings as evidence that as wayfinding practice increased, participants gradually narrowed their attentional focus to the most relevant screenshot area, processed information within this focus more efficiently, reduced the total time in which attention dwelled on the rejected side of the screenshot, but maintained the total time on the chosen side. These dynamic changes of visuo-spatial attention were comparable in young and older participants. However, it appears that decision-making differed between age groups: older persons' attention dwelled longer on the chosen side before they made their choice.

[Smartphone-based health promotion in old age : An explorative multi-component approach to improving health in old age]. / Smartphone-basierte Gesundheitsförderung im Alter : Ein explorativer, mehrkomponentiger Ansatz zur Verbesserung der Gesundheit im höheren Alter.

BACKGROUND: As age-related health problems are often related to a combination of physiological, psychological and social aspects, it has been proposed that multi-component interventions might be particularly effective to improve older peoples' health. The present study used a smartphone-based approach to promote health through activities including physical as well as cognitive components performed in a daily life context. METHODS: This study investigated the effects of different health-related variables (e.g. gait and cognition) as well as the individual motivation for physical activity. The study included 34 community-dwelling older adults (mean age 75.0 ± 3.7 years, 15 women) who took part either in smartphone-based activities (intervention group) or attended lectures (control group). The smartphone-based interventions were undertaken semiweekly. RESULTS: Baseline tests showed that participants in both groups already had a high motivation for physical activities. Analyses indicated that the smartphone application was considered to be user-friendly. CONCLUSION: There were no substantial health-related benefits from the activities, probably due to moderate to good health status and activity levels at baseline and too little additional activity intensity during the intervention. Hence, it is recommended that for future research the subjects included should be less active or have health restrictions.

How visual information influences dual-task driving and tracking.

The study examined the impact of visual predictability on dual-task performance in driving and tracking tasks. Participants (N = 27) performed a simulated driving task and a pursuit tracking task. In either task, visual predictability was manipulated by systematically varying the amount of advance visual information: in the driving task, participants drove at night with low beam, at night with high beam, or in daylight; in the tracking task, participants saw a white line that specified the future target trajectory for 200, 400 or 800 ms. Concurrently with driving or tracking, participants performed an auditory task. They had to discriminate between two sounds and press a pedal upon hearing the higher sound. Results show that in general, visual predictability benefited driving and tracking; however, dual-task driving performance was best with highest visual predictability (daylight), dual-task tracking performance was best with medium visual predictability (400 ms). Braking/reaction times were higher in dual tasks compared to single tasks, but were unaffected by visual predictability, showing that its beneficial effects did not transfer to the auditory task. In both tasks, manual accuracy decreased around the moment the foot pressed the pedal, indicating interference between tasks. We, therefore, conclude that despite a general beneficial impact of predictability, the integration of visual information seems to be rather task specific, and that interference between driving and audiomotor tasks, and tracking and audiomotor tasks, seems comparable.

Ecological validity of manual grasping movements in an everyday-like grocery shopping task.

In our earlier research, kinematic and kinetic parameters of grasping differed significantly when participants grasped the same object once in a traditional laboratory paradigm, and once as part of a captivating computer game. We attributed this finding to the fact that grasping movements in the laboratory were repetitive and meaningless, while those in the computer game were embedded in complex behavior and served a meaningful purpose. In that work, we argued that grasping in the computer game is more characteristic of everyday life behavior; however, this conclusion has been criticized on the grounds that a computer game is not a typical everyday activity. The present study therefore compares grasping in a traditional laboratory paradigm to that in an indisputably everyday context: grocery shopping. Thirty-three young adults executed externally triggered arm movements to grasp nondescript objects (laboratory task, L) and place them on a tablet, or they walked through a fictitious grocery store towards a shelf to grasp grocery products and placed them into a shopping basket (everyday-like task, E). Size, shape, weight and location of to-be-grasped objects were identical in both tasks. We found that of the analyzed 16 kinematic parameters, 13 differed significantly between tasks. Specifically, grip apertures were larger, movements were slower and grip-transport coupling was more variable in E compared to L. We conclude that kinematic differences between both persist even if task is more realistic than in our earlier research. Our findings are compatible with the notion that movement planning is less stringent in E than in L.

The habitual motor vertical of humans depends on gravicentric and egocentric cues, but only little on visual cues.

Many studies have evaluated the interplay of gravicentric, egocentric, and visual cues for our perception of the vertical, but little is known about their interplay for motor control. Thirty-five participants flipped a switch "down" in experimental conditions which systematically varied body posture (upright; tilted 45° left-ear-down), visually indicated vertical (absent; aligned with the long body axis; rotated 45° counterclockwise with respect to the long body axis), and egocentric tactile information provided by a handhold (absent; present). Since we were interested in the participants' habitual rather than an instructed motor vertical, we did not specify which cues they should rely on. Our data revealed two response categories. Type-1 responses depended moderately on switch position; they relied mainly on gravicentric and egocentric cues, but only marginally on visual cues. Type-2 responses depended strongly on switch position; they relied on egocentric, but not on gravicentric or visual cues. We interpret the dependence on switch position as evidence that egocentric cues for type-2 responses may be anchored in the participants' arm rather than in their long body axis. In conclusion, the habitual motor vertical can vary when available cues are not aligned, and this variability can compromise manual performance of human operators.

Interplay of Gravicentric, Egocentric, and Visual Cues About the Vertical in the Control of Arm Movement Direction.

Our perception of the vertical corresponds to the weighted sum of gravicentric, egocentric, and visual cues. Here we evaluate the interplay of those cues not for the perceived but rather for the motor vertical. Participants were asked to flip an omnidirectional switch down while their egocentric vertical was dissociated from their visual-gravicentric vertical. Responses were directed mid-between the two verticals; specifically, the data suggest that the relative weight of congruent visual-gravicentric cues averages 0.62, and correspondingly, the relative weight of egocentric cues averages 0.38. We conclude that the interplay of visual-gravicentric cues with egocentric cues is similar for the motor and for the perceived vertical. Unexpectedly, we observed a consistent dependence of the motor vertical on hand position, possibly mediated by hand orientation or by spatial selective attention.

The effects of priming with age stereotypes on a PC-based mail-sorting task.

OBJECTIVE: This study examines whether unconscious priming of attitudes towards older age might change the self-efficacy of older employees, and thus modify their performance at work. METHODS: Three age- and gender-matched groups of 20 participants were primed with positive, negative or no age stereotypes by means of the scrambled sentence task, and were then transferred to a cognitively demanding PC-based mail-sorting task. RESULTS: Participants' accuracy on the latter task was significantly higher in the positively primed group than in the unprimed group, and was significantly lower in the negatively primed group than in the unprimed group, except for one parameter. CONCLUSIONS: These findings indicate that the performance of older workers may indeed be modifiable by unconscious priming. Practitioner Summary: This study analyses whether unconscious priming attitudes towards older age might modify work performance. Participants were primed with the scrambled sentence task and then conducted a cognitive mail-sorting task. The findings indicate that the performance of older workers may indeed be modifiable by unconscious negative as well as positive priming.

Role of gravitational versus egocentric cues for human spatial orientation.

Our perception of the vertical depends on allocentric information about the visual surrounds, egocentric information about the own body axis and gravicentric information about the pull of gravity. Previous work has documented that some individuals rely strongly on allocentric information, while others do not, and the present work scrutinizes the existence of yet another dichotomy: We hypothesize that in the absence of allocentric cues, some individuals rely strongly on gravicentric information, while others do not. Twenty-four participants were tested at three angles of body pitch (0° = upright, -90° = supine, -110° = head down) after eliminating visual orientation cues. When asked to adjust a rotating tree '…such that the tree looks right,' nine persons set the tree consistently parallel to gravity, eight consistently parallel to their longitudinal axis and seven switched between these two references; responses mid-between gravity and body axis were rare. The outcome was similar when tactile cues were masked by body vibration, as well as when participants were asked to adjust the tree '… such that leaves are at the top and roots are at the bottom'; the incidence of gravicentric responses increased with the instruction to set the tree '… such that leaves are at the top and roots are at the bottom in space, irrespective of your own position.' We conclude that the perceived vertical can be anchored in gravicentric or in egocentric space, depending on instructions and individual preference.

Influence of movement kinematics on visuomotor adaptation.

It is still unknown whether visuomotor adaptation depends on the time during which a person is exposed to distorted vision, or rather on the number of movements executed under the distortion. To find out, we analysed the pointing errors and movement kinematics of 52 participants adapting with online visual feedback to a 60° visual rotation and 39 participants adapting to a 75° visual rotation without time constraints. We found that movement time was not related with participants' success during adaptation, whereas peak velocity was inversely associated to adaptive success. However, peak velocity lost its association to adaptation when other parameters were taken into account. Movement kinematics during adaptation had little influence on participants' performance during de-adaptation. Our data suggest that adaptation does not depend primarily on the duration but rather on the number of movements executed under distorted vision. It further suggests that the measured kinematic parameters are consequences of error corrections rather than determinants of the adaptive success. We further have evidence for the view that adaptive recalibration is independent of movement kinematics during adaptation. This outcome generalizes across different visual rotations and is in accordance with earlier work where online visual feedback of the hand was unavailable.

On the relationship between subjective and objective measures of fatigue.

OBJECTIVE: Objective and subjective methods have been used in the past to assess workplace fatigue, but little is known about correlations between them. We examine correlations between subjective and objective measures, including measures collected in a workplace scenario. METHODS: 15 young and 17 older participants were assessed before and after work with four types of fatigue measure: objective physical (posturography), objective mental (psychomotor vigilance task), subjective physical and mental (self-assessment), objective and subjective realistic (oculomotor behaviour, observer-rated facial expression, typing performance). RESULTS: Pre- and post-test scores were analysed with an ANOVA, significant differences were submitted to a factor analysis. It yielded three factors: one representing posturography, the second self-rated mental and physical fatigue and the third observer-rated facial expression. CONCLUSIONS: Results advocate the existence of three independent fatigue components: Objective physical fatigue, introspective and extrospective fatigue. Practitioner Summary: This study analyses correlations between different subjective and objective fatigue markers to better understand the complex nature of workplace fatigue. Measurements were conducted directly at the workplace. Results reveal that fatigue comprises three independent fatigue components: Objective physical fatigue, introspective and extrospective fatigue.

Motor imagery: effects of age, task complexity, and task setting.

UNLABELLED: BACKGROUND/STUDY CONTEXT: Mental training may potentially enhance motor performance and self-efficacy in older adults. However, several studies revealed an age-related decay of motor imagery (MI), which suggests that mental training might be too challenging for older adults. Recognizing that laboratory results are often not transferable to real-life situations, the purpose of the present study was to evaluate imagery performance in the elderly with a more real-life-like approach. METHODS: MI performance of 21 older (70.28 ± 4.65 years) and 19 younger adults (24.89 ± 3.16 years) was estimated by mental chronometry from the first-person perspective. Subjects were asked to walk in a supermarket scenario straight ahead (A), or with two changes of direction (B), or with two changes of direction while retrieving products (C). The three tasks were completed first in the subjects' imagination and then in reality, with time required as the dependent measure. MI ability was also assessed by the Controllability of Motor Imagery (CMI) test, in which subjects are required to mentally assume a sequence of body postures. RESULTS: Age-related alterations of MI were observed for walking only in Tasks B and C, and only in terms of intersubject variability, not in terms of across-subject means. This is in contrast to earlier studies that used a less realistic walking scenario and found an age-related decay even for MI means. Age-related alterations of CMI were observed as well, but they correlated little with those of walking. CONCLUSION: These findings suggest that MI is not a global phenomenon, as it decays in old age independently in the temporal and in the spatial domain, decays less with simple than with complex tasks, and less in an everyday-like than in a typical laboratory setting. These characteristics of MI should be taken into account when assessing its decay in old age, and when designing mental training for the elderly.