Total sleep deprivation effects on the attentional blink.

The Attentional Blink (AB) is a phenomenon that reflects difficulty in detecting or identifying the second of two successive targets (T1 and T2) that are presented in rapid succession, between 200-500ms apart. The AB involves indicators of attentional and temporal integration mechanisms related to the early stages of visual processing. The aim of this study was to identify the effects of 24-h of sleep deprivation (total sleep deprivation, TSD) on the attentional and temporal integration mechanisms of the AB. Twenty-two undergraduate students were recorded during five successive days, in these three conditions: baseline (two days), TSD (one day), and recovery (two days). Each day, at around 12:00 h, participants responded to a Rapid Serial Visual Presentation task (RSVP) that presented two targets separated by random intervals from 100 to 1000ms. The attentional mechanisms were assessed by the AB presence, the AB magnitude, and the AB interval, while the temporal integration mechanisms were evaluated by lag-1 sparing and order reversal responses. TSD negatively affected the attentional mechanisms, which is expressed by an overall reduction in performance, an extended AB interval, and a reduced AB magnitude. TSD also negatively affected the temporal integration mechanisms, manifested by an absence of lag-1 sparing and an increase in order reversals. These results suggest that people are still able to respond to two successive stimuli after 24 h without sleep. However, it becomes more difficult to respond to both stimuli because the attentional and temporal integration mechanisms of the AB are impaired.

Changes during the sleep onset process on EEG activity and the components of attention.

The sleep onset process (SOP) happens every time a person falls asleep, regardless of the time of day or if they are doing an activity. Basic cognitive processes, such as attention, differ between wakefulness and sleep. The components of attention - tonic alertness, phasic alertness, selective, and sustained attention - are known to decrease during sleep, however they have not been analyzed during the sleep onset process. This study analyses the state of three of the four components of attention during the sleep onset process through electroencephalographic (EEG) activity and task performance in young people. Nine undergraduate students (18.54±1.24 years old) underwent a control session which was compared to the average of four sleep-inducing sessions. During all sessions, the EEG activity of the subjects was recorded to assess the effect of the SOP on electroencephalographic activity while they answered a continuous performance task (CPT) to assess the effect of the SOP on the components of attention. Comparisons of the EEG recordings of the control and the sleep inducing sessions demonstrated that there is lower activity in fast beta, as well as a higher theta and delta activity right before the sleep onset. There was a decrease in tonic alertness, phasic alertness, and selective attention. This study shows that there is an increase in EEG slow activity and a decrease in fast activity, as well as in attentional capacity during the SOP. This decrease can become a safety hazard since it could happen while performing daily activities.

Changes in sleep habits during the lockdown for the COVID-19 pandemic in the population and people attending a morning or an afternoon shift in Monterrey, Mexico.

To fight the Covid-19 pandemic, most countries implemented a lockdown that involved restricting the activity and confining the population to their homes. The objective of this paper is to analyze the impact of the lockdown on sleep in people from the population of Monterrey, Mexico, and people attending a morning or afternoon work or study shift after more than a month adaptation period. Participants were 861 residents from Monterrey, Mexico, who completed an anonymous 20-minute web-based survey. The survey asked for information about sleep habits both before and during the lockdown. In Mexico, a national lockdown was declared on March 23rd, 2020. Data collection began 38 days after the start of the lockdown, from April 30th to May 23rd, 2020, allowing enough time for the participants to adjust to the new conditions. The lockdown affected the sleep of the population, producing a phase delay of the sleep-wake cycle, a reduction of sleep duration, as well as an increase in sleep latency and in time awake during night sleep, resulting in a reduction of sleep efficiency. People attending an afternoon shift also showed a phase delay and a reduction in sleep quality during the lockdown. In conclusion, the lockdown produced a delay of sleep and a reduction of sleep quality of the population, even in people with an afternoon shift. It is necessary to design and implement better strategies in the fight against the pandemic, without compromising the wellbeing of the population.

Sleep deprivation effects on basic cognitive processes: which components of attention, working memory, and executive functions are more susceptible to the lack of sleep?

INTRODUCTION: Sleep deprived people have difficulties to perform daily activities. Their performance depends on three basic cognitive processes: attention, working memory, and executive functions. OBJECTIVES: The aim of this study was to identify which specific components of these cognitive processes are more susceptible to a 24-h sleep deprivation period. MATERIAL AND METHODS: Participants were 23 undergraduate students assigned to one of two groups: a control group (n=11, age=18.73±1.62 years) and a sleep deprivation group (n=12, age=18.08±1.16 years). After sleeping freely, control group participants performed a continuous performance task to evaluate the components of attention, a phonological and a visuospatial tasks to record these components of working memory, and a Stroop-like task to assess cognitive inhibition and flexibility, two components of executive functions, at noon for 3 days. Whereas, the sleep deprivation group participants performed the same tasks at noon: after sleeping freely for one night, after a 24-h sleep deprivation, and after one recovery night. RESULTS: After the sleep deprivation, participants had a significant reduction in tonic alertness, selective and sustained attention, components of attention; and in cognitive inhibition, component of executive functions. CONCLUSION: A 24-h sleep deprivation period reduces several specific components of the basic cognitive processes, which are crucial for performing many everyday activities, thus increasing the risk of errors and accidents.

Circadian and homeostatic modulation of the attentional blink.

An important property of attention is the limitation to process new information after responding to a stimulus. This property of attention can be evaluated by the Attentional Blink (AB), a phenomenon that consists of a failure to detect the second of two targets when the interval between them is 200-500 ms. The aim of the present work is to determine the possible existence of time awake (homeostatic changes) and time of day (circadian rhythm) variations in the AB. Eighteen undergraduate students, 11 men and 7 women, age = 18.06 ± 1.16 years, participated voluntarily in this research. They were recorded in a constant routine protocol during 29 h, in which rectal temperature was recorded every minute, while subjective sleepiness and responses to a Rapid Serial Visual Presentation (RSVP) task, to measure the AB, were recorded every hour. Homeostatic and circadian variations in all parameters of the RSVP task were observed, including changes in the capacity to process a new stimulus (Target 1 accuracy), a second stimulus occurring in a short interval after the first (Target 2 accuracy at lag 2, 200 ms) and to process another successive independent stimulus (Target 2 accuracy at lag 8, 800 ms). The acrophase of these parameters occurred with a phase delay of 2 h compared to the circadian rhythm of rectal temperature. The AB magnitude, an index of the AB, showed a decline with time awake, but no variations with time of day. In conclusion, there are homeostatic and circadian variations in the capacity to process any incoming information, especially in tasks with brief duration stimuli presented at a high frequency.

Effects of sleep reduction on the phonological and visuospatial components of working memory.

Sleep reduction impairs the performance of many tasks, so it may affect a basic cognitive process, such as working memory, crucial for the execution of a broad range of activities. Working memory has two storage components: a phonological and a visuospatial component. The objective of this study was to analyze the effects of sleep reduction for 5 days on the storage components of working memory. Thirteen undergraduate students (18.77±2.20 years of age), 5 men and 8 women, responded two N-Back tasks (auditory and visual), with three sections each (0-Back, 1-Back, and 2-Back). These tasks were performed at 13:00 h under the following conditions: before sleep reduction (control; C); on the first (SR1), fourth (SR4), and fifth (SR5) days of sleep reduction (4 h of sleep per night); and one day after they slept freely (recovery, R). Sleep reduction produced a decrement in accuracy on the auditory 2-Back section the fifth day of sleep reduction (C=87.86±13.35%; SR5=74.76±16.37%; F=14.57, p<0.01). In the visual 2-Back section accuracy decreased (C=88.10±9.95%; SR1=82.45±11.57%; SR5=77.76±14.14%; F=10.80, p<0.05), and reaction time increased (C=810.02±173.96 ms; SR1=913.51±172.25 ms; SR5=874.78±172.27 ms; F=10.80, p<0.05) on the first and fifth day of sleep reduction. In conclusion, five days of sleep reduction produces a decrease in the phonological and visuospatial storage components of working memory, which may interfere with processing verbal information and solving problems that require spatial analysis.

Circadian and homeostatic variation in sustained attention.

Human performance is modulated by circadian rhythms and homeostatic changes. Changes in efficiency in the performance of many tasks might be produced by variation in a basic cognitive process, such as sustained attention. This cognitive process is the capacity to respond efficiently to the environment during prolonged periods (from minutes to hours). There are three indices of sustained attention: general stability of efficiency, time on task stability, and short-term stability. The objective of this work was to analyze circadian and homeostatic influences on the indices of sustained attention. Participants were nine undergraduate female student volunteers (mean age 17.67 yrs, SD = 1.00, range 16-19 yrs) who attended school from 07:00-13:30 h, Monday to Friday. They were assessed while adhering to a modified 28 h constant-routine protocol during which feeding, room temperature, motor activity, and room illumination were controlled. Rectal temperature was recorded each minute, and indices of sustained attention were assessed hourly through a continuous performance task (CPT). General stability was measured as standard deviation of correct responses and reaction time, time on task stability was measured as the linear regression of correct responses and reaction time throughout the task, and short-term stability was measured as hit runs and error runs. Rectal temperature showed circadian variation; subjective somnolence and tiredness increased, while general performance and all indices of sustained attention declined throughout the 28 h recording session. General stability exhibited circadian variation, whereas time on task did not. Short-term stability showed circadian variations in short-error runs, long-error runs, and short-hit runs, but long-hit runs did not. There was a 26 sec short interval at the beginning of the task, characterized by a very high efficiency level of performance. Execution during this safe period was not affected by time awake and did not show circadian variation. Overall, these results suggest a dissociation of the effects of circadian and homeostatic factors on the indices of sustained attention. General stability, short- and long-error runs, and short-hit runs were modulated by both a homeostatic factor and a circadian effect, while long-hit runs and time on task stability were modulated only by a homeostatic factor and did not show circadian variation. There was also a 26 sec "safe period" that seems to be independent of circadian and homeostatic influences. These results suggest that performance at work deteriorates at the end of a shift due to a decrease in general stability, an increase in error runs, decrease of long-hit runs, and decline with time on task. Night shiftworkers are exposed to an additional deterioration of performance during the nighttime due to a decrease in general stability and an increase in error runs.

Efectos psicofisiológicos de la eliminación del horario de verano en una población nunca antes expuesta a éste / Psychological effects of daylight saving time elimination in a population never before exposed to it

El horario de verano consiste en adelantar el reloj una hora, y se introdujo por primera vez en cuatro estados del noreste de nuestro país, del 3 de marzo al 30 de octubre de 1988. El objetivo del presente estudio es analizar los efectos que provoca la eliminación del horario de verano (retrasar el reloj una hora) en una población nunca antes expuesta a este tipo de cambio. Se realizó un registro diario del inicio, de la terminación y de la latencia del dormir en 19 trabajadores durante 26 días, 9 días antes y 17 días después de la eliminación del horario de verano. Además, al inicio y al final del estudio, se aplicaron los siguientes cuestionarios: Evaluación de trastornos del dormir, Escala de Depresión de Zung y Autoevaluación de la Fase Circadiana. Después de la eliminación del horario de verano, todos los trabajadores despertaron más tarde. doce de ellos se acostaron más tarde (de 23:04 A 24:04 hd, horas: minutos, hd=hora del día) y durmieron menos (de 8:01 a 7:38 h), pero tuvieron menos cansancio al despertar. Las otras siete personas siguieron acostándose aproximadamente a la misma hora (de 23:19 a 23:40 hd), pero disminuyeron su latencia y sus dificultades para empezar a dormir. Estos resultados tienden a apoyar la hipótesis de que la eliminación del horario de verano (retraso de una hora), produce menos problemas sobre el sistema circadiano que su introducción (adelanto de una hora)