Simulated monotonous driving performance in two studies revealed a deterioration in the ability to detect stimuli presented in the periphery, compared to central presentations, as driving time increased 15 , This indicates that conditions that lower alertness, such as time-on-task, can narrow attention to the centre of the visuospatial field.

A growing body of literature link lower levels of alertness with a spatial shift of attention towards the right side This rightward shift in attention is characterised by slowed reaction times to left-sided stimuli 18 , left-sided stimuli misidentified as being on the right 19 , and omission of left-sided objects A study 20 examined spatial attentional performance in hospital staff at two testing periods: one during a well-rested state i.

The authors found a rightward shift in attention, indicating a neglect of the left side in the reduced alertness condition compared to the well-rested condition. Hence, these findings have safety implications for shiftworkers.

For example, highway driving under high-speed conditions whilst operating a large vehicle, such as a truck, requires skilled motor and visuospatial ability 21 , and as truck drivers commonly commute during the night and early hours, this places them under monotonous driving conditions which can lower alertness Previous research suggests impaired performance resulting from lowered alertness is linked with vehicular accidents 23 , Currently, the literature examining the spatial attention and alertness relationship is limited, highlighting the need for future research to explore the relationship between lowered alertness and spatial attention under shiftworking conditions, particularly whilst working the nightshift, when alertness is already reduced due to working at a time when the drive for sleepiness is at its greatest 3.

Alertness can be separated into tonic alertness referring to general alertness and phasic alertness referring to moment to moment alertness and these can differentially influence spatial attention Tonic alertness can be measured via simple reaction time tasks which involve maintaining a state of preparedness to respond to stimuli, for a period of time Phasic alertness can be measured via cued-response tasks and can accelerate and enhance orienting towards a cued stimulus in healthy adults In neglect patients experiencing left-sided neglect, a reduction in this neglect under phasic alerting conditions is found A dominant theoretical framework postulates a rightward shift in attention with declining alertness This is due to decreasing alertness resulting in an activation advantage in the left hemisphere, which directs attention to the right visuospatial field, and consequently leads to an attentional bias towards the right.

Under alert conditions, the right hemisphere is slightly more activated, biasing attention towards the left due to contralateral attentional allocation. Therefore, changes in alertness should demonstrate corresponding changes in attentional biases, where high and low levels of alertness show a leftward bias and rightward bias, respectively.

The current study aimed to investigate the relationship between alertness and spatial attention under simulated shiftwork conditions. The main hypotheses were that 1 lowered alertness will correspond with a rightward bias in attention and high alertness will correspond with a leftward bias in attention, and 2 lowered alertness will be associated with a narrowing of attention.

If deemed eligible, following written informed consent to participate in the study, participants attended two further screening sessions in person to complete questionnaires regarding psychological and physical health, had a blood test completed, and wore an activity monitor for 7 consecutive days prior to the study commencing Phillips Respironics Actiwatch, Murrysville, PA, USA.

Participants also completed a 7-day sleep diary and a 4-day food diary to assess habitual sleeping and eating patterns, respectively.

Female participants were only scheduled to participate in the luteal phase of their menstrual cycle, as confirmed by self-report, to control for changes in sleep quality, hormonal factors, and basal metabolism during the menstrual cycle Participants refrained from over-the-counter medications, caffeine, alcohol, napping, and were instructed to keep a strict habitual sleep schedule — to — , which was verified by actigraphy and a subjective sleep diary during the 7 days prior to study commencement.

Urine toxicology was performed to verify the absence of any illicit substances immediately prior to study commencement. Handedness was assessed using the Flinders Handedness Survey FLANDERS 32 and was not used as inclusion or exclusion criteria.

Data collection for the present study took place within a wider study, which received approval by the University of South Australia Human Research Ethics Committee and is registered with the Australian New Zealand Clinical Trials Registry ANZCTR All procedures were in accordance with the National Statement on Ethical Conduct in Human Research.

The study was conducted at the Sleep and Chronobiology Laboratory at the University of South Australia. Participants spent six nights and seven days consecutively in a laboratory-controlled environment. On the first night, participants had an 8-h sleep opportunity, which followed a baseline day.

Prior to the first night shift, participants were awake for 28 h to simulate the common pattern observed in shiftworkers prior to their first shift 4. From days three to six, during the simulated night shifts, participants were given a 7-h daytime sleep opportunity on each day between to h.

Further information on the protocol can be found from a previously published study Data for the current study was collected at six different time points across six days. Refer to Fig. Simulated shiftwork protocol with the timepoints of the alertness Psychomotor Vigilance Task [PVT], Stanford Sleepiness Scale [SSS] and spatial attention Landmark Task, Detection Task measures outlined.

The numbers correspond to the order of the tests. Two measures of alertness were employed in the current study, one assessing objective behavioural alertness, and the other assessing subjective self-reported alertness.

A min hand-held PVT device, which is highly sensitive to sleep loss was used to measure alertness in the current study. The PVT is regarded as a reliable and valid assay of alertness 34 , The PVT required participants to respond as quickly as possible to the presentation of a visual stimulus i.

PVT performance at six time points were obtained in the current study: days two and seven at h, days four and five at h, and days four and five at h were examined. The PVT reciprocal of the mean reaction time mean RRT and lapses were used for analysis.

A lapse was counted when reaction time was greater than ms Lower mean RRT scores and higher lapses indicate poorer performance and lowered alertness.

The SSS has been found to predict performance on tasks that assess alertness, such as reaction time and vigilance tests 38 , The SSS was used to assess subjective sleepiness throughout the protocol at the same six time points as the PVT i.

Higher SSS scores indicate higher levels of sleepiness. Two measures assessing spatial attention, more specifically, one assessing judgement and the other assessing detection, were used in the present study.

The judgment task entailed judgment of the spatial properties of lines, whilst the detection task required speeded responses to presented stimuli.

Stimulus presentation for both tasks were presented using E-prime 2. A commonly used spatial attention task, the Landmark task 18 , 20 , 40 was employed in the current study. One hundred and eight vertically pre-bisected horizontal lines were presented against a grey background.

Each pre-bisected horizontal line contained diagonally opposite pairs of black and white segments on each side of the vertical divider.

The top segment on one side was white whilst the bottom segment of the same side was black, and vice versa for the opposite side. Half the total number of stimuli were pre-bisected towards the left, and half the stimuli contained upper left black polarity.

The factors side, polarity and deviation were counterbalanced between the stimuli, such that each factorial combination was presented on nine occasions.

Each trial started with a blank screen for ms followed by a stimulus presentation for ms and a blank response window for a maximum of ms see Fig. If the participants responded within ms, the following trial was presented. However, if participants did not respond within the allocated response time window, the trial was presented again at a later stage, so each participant responded to stimuli before task termination.

The task lasted approximately eight minutes. Bisection bias on the Landmark Task was calculated as the number of right responses minus the number of left responses divided by the total number of trials for each participant Hence, negative and positive bias scores indicate a bias towards the left and right side, respectively.

Landmark Task spatial bias on days two and seven at h, and days four and five at h were analysed. Landmark Task stimulus train. Prior to stimulus presentation, a blank screen was presented for ms. Stimulus presentation was ms and the maximum response window was ms. Participants were presented with 5 mm circular dark grey stimuli at varying eccentricities on a light grey screen.

Each circular stimulus was presented randomly at one of four eccentricities on each side of the fixation point at 2, 7, 12, and 17 cm from the centre of the screen with a height of 28 cm and width of 51 cm.

A total of stimuli were presented, with 15 stimuli at each of the eight screen positions. A fixation cross was presented throughout the trials. Each trial started with the presentation of the central fixation cross for a randomized presentation time ranging between to ms, followed by the stimulus presentation for ms.

The response window was set to a maximum of ms see Fig. The trial terminated once the participant responded or if no response was made after ms. If participants did not respond to a stimulus, that trial was considered an omission of response.

If participants responded within ms of stimulus presentation, this response was deemed an anticipatory response and removed from analysis.

The task lasted approximately 12 min. Detection Task performance was assessed on days two and seven at h, and days four and five at h. The number of omissions i. Detection Task stimulus train.

Prior to stimulus presentation, a blank screen was displayed for a duration between to ms. Stimulus presentation was ms with a maximum response window of ms. Data was analysed using jamovi version 1. Missing data was not imputed or corrected for in the analyses as mixed effects models allow for parameters to be estimated using available data Three mixed effects models with ID as a random intercept were run to determine whether alertness changed across the different time points of the simulated shiftwork protocol.

All three models included the categorical variable of time D2 h, D4 h, D4 h, D5 h, D5 h, D7 h as a fixed effect. The continuous variables PVT lapses, PVT mean reciprocal reaction time mean RRT , or SSS were entered as the outcome variable for each model.

F-values from fixed effects, degrees of freedom, and post hoc analyses are reported in Table 1. Holm corrections were used to account for multiple post hoc comparisons. Partial eta 2 effect sizes were also calculated independently from the mixed effects modelling.

Three mixed effects models with ID as a random intercept were run to investigate whether the Landmark Task bisection bias, and Detection Task reaction time and omissions related to time. All models had time as a fixed effect, and the continuous variables bisection bias, reaction time or omissions as the outcome variable for each model.

Side and location were further predictors in the Detection Task models. F values, degrees of freedom, and post hocs comparisons with Holm corrections are reported in Table 1. A series of mixed effect models were conducted to investigate the relationship between alertness and spatial attention during the simulated shiftwork protocol.

For the Landmark Task, two linear mixed effects models with fixed effects of objective alertness, as measured by PVT lapses and PVT mean RRT, were conducted.

PVT lapses and PVT mean RRT were predictors in separate models. Bisection bias was the outcome variable in these models.

Another mixed effects model, with subjective alertness, as measured by the SSS, with the same time points as the previous model was conducted, and bisection bias as the outcome variable was run.

ID was entered as a random intercept in all models. For the Detection Task, six linear mixed effects models with fixed effects of objective alertness i.

The outcome variable was reaction time for three models and omissions for the remaining three models. Post hoc comparisons with Holm corrections were also conducted. The calculated partial eta 2 effect sizes were moderate for PVT lapses 0.

Figure 4 illustrates these changes in alertness over time, with alertness generally higher during the afternoon testing time points compared to the early morning testing time points.

Alertness and spatial bias performance indicators change with day and time. High PVT lapses suggest poor performance. Low PVT mean RRT reflects poor performance. High scores on the SSS reflect high levels of sleepiness. Negative and positive scores on the Landmark Task bisection bias suggests a leftward and rightward bias, respectively.

High Detection Task reaction times represent poor performance. High Detection Task omissions represent poor perfomance. There was also a significant effect of location, such that performance was better when responding to stimuli closer to the centre compared to the periphery Table 1.

Figure 4 depicts the pattern of spatial attention performance with time of testing and Fig. Performance in the periphery is worse than in the centre. Detection Task changes in reaction time A , and omissions B with time, relative to stimulus location.

Refer to Table 2. That is, for every increase in a PVT lapse, there was a corresponding average increase in reaction time by 2. Figure 6 Panel A portrays this interaction pattern.

That is, every increase in mean RRT corresponded with a decrease in reaction time by Mixed models data show Detection Task performance decreases with a decrease in alertness. Reaction time increases more strongly for left-sided stimuli with an increase in PVT lapses.

Reaction time decreases more strongly for left-sided stimuli with an increase in PVT mean RRT higher mean RRT scores reflect better performance. The further away the stimulus, the stronger the effect of PVT mean RRT on omissions.

Shaded areas indicate standard error. That is, every increase in lapses related to a 0. The negative association shows every increase in PVT mean RRT to correspond with a reduction in 2 omissions. Refer to Panel C Fig.

We observed changes in PVT, subjective sleepiness, and response times and omissions on the spatial attention tasks over time that reflect typical circadian modulation. There were also more omissions occurring in the periphery than the centre.

However, while there were no significant spatial attentional shifts found in relation to time of testing, there was a relationship between shifts in spatial attention and PVT response times and lapses, which was our assay of behavioural alertness. As PVT response times and number of lapses increased, so did detection task response times, and this relationship was stronger for stimuli presented on the left side consistent with the current model 28 , and for those in the periphery illustrated in Fig.

Put differently, alertness is not reduced uniformly across the whole hemifield, rather a larger reduction is observed in the periphery especially in the left hemifield.

In contrast to the Detection Task, there were no associations between the spatial performances in the Landmark Task and the objective and subjective assays of alertness see Table 2. The lack of associations stands in contrast to the findings from a previous study The authors examined Landmark Task performance in shiftworkers and reported a leftward bias with high alertness and a rightward bias with low alertness.

The objective assays of alertness were only associated with the Detection task, but not the Landmark task. The reason for this observed dissociation is not clear. It cannot be ruled out that we were underpowered to detect subtle spatial shifts in the Landmark Task.

The effect sizes for the Landmark Task and PVT assays of behavioural alertness suggests that the effects, although non-statistically significant and very small, were in the expected direction. It is also possible that the lack of association in the Landmark Task is due to the fact that the two spatial tasks tap into different underlying mechanisms.

A principal component analysis identified the Landmark and Detection tasks as distinct factors contributing to observed variances in spatial tasks They also differ in their cognitive processing demands with one task being a simple detection task and the other task requiring a judgment on spatial properties.

However, the degree to which different tasks tap into different underlying spatial mechanisms is a matter of debate 45 and our study was not designed to disentangle these mechanisms. Also, a recent meta-analysis did not find evidence that effect sizes for associations between alertness and spatial attention differ between tasks requiring speeded responses to stimuli i.

The findings from the Detection Task revealed that there is a narrowing of attention to the centre from the periphery with slower responses and more omissions to stimuli in the periphery consistent with studies that generated alertness reductions through extended time-on-task and sleep restriction 15 , The current study suggests that even under conditions of relatively common amounts of sleep, attention narrowing may be observed across circadian fluctuations in alertness, particularly as assessed by behavioural assay.

The relationship between spatial attention and alertness measures was stronger for PVT than for subjective alertness. In particular, PVT responses corresponded more strongly to performance decrements to left-sided stimuli Table 2. This was not the case for subjective alertness, suggesting that behaviourally-assessed alertness is a closer reflection of shifts in spatial attention than self-reports.

PVT responses, but not time of the day, were associated with spatial biases. Individual levels of alertness at specific times can vary considerably between participants Overall, our findings highlight potential safety risks for occupations requiring a high level of visuospatial ability.

If we are working on a project or a goal and are unaware of the thoughts and opinions of those around us, we may be missing out on an opportunity to either gain ideas from others or to overcome their objections and bring them on board. Alertness demands awareness of details and groups or individuals that can influence outcomes.

The soldiers practiced entering the building and classrooms numerous times, while actually just walking between lines of tape. Watching this made me reflect, and ask myself, do I prepare myself to be alert to every possible outcome and every possible variable, no matter the circumstances?

Do I think things through not just once, but multiple times to consider all options and all angles, in order to recognize threats and opportunities? But attentiveness needs alertness to be truly effective. In the end, we can focus on the things that are really important only by honing our ability to see the whole picture.

The Owasso Character Council is committed to providing a forum for users to share their thoughts and opinions about articles and stories of their own experiences.

We are dedicated to inspiring thought-provoking conversation and an engaging atmosphere. Please be polite and civil while posting. Decorrelation — neurons firing in an unsynchronized manner — can enhance and even optimize information processing.

The Picower study pinpoints, for the first time, a specific subtype of inhibitory neuron that contributes to decorrelation in a major brain circuit tied to attention and arousal. The mechanisms underlying ACh-modulated brain functions are complex due to the sheer number of types of brain cells that ACh modulates, says former MIT graduate student Naiyan Chen, co-author of the paper.

Naiyan and research scientist Hiroki Sugihara demonstrated these circuits and their function in genetically modified mice by recording the actions of specific neurons and activating and inactivating different neuron classes to deconstruct their roles.

Chen anticipates that these findings will motivate future research in other brain functions — such as learning and plasticity — modulated by the neurotransmitter acetylcholine. This work is supported by the National Institutes of Health, the National Science Foundation, and the Simons Foundation.

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