Adaptation and survival: hypotheses about the neural mechanisms of unihemispheric sleep.

Sleep and wakefulness are opposite brain and body conditions that accomplish different but complementary functions. However, these opposing conditions have been combined in some animals by the adoption of a sleep/wake strategy that allows them to survive, while maintaining both an interaction with the environment at the same time as enabling brain and body recovery. They sleep with half of the brain while keeping the other half awake: a state known as unihemispheric sleep (US).

The effect of monocular deprivation on unihemispheric sleep in light and dark incubated/reared domestic chicks.

Unihemispheric sleep is an aspect of the cerebral lateralization of certain species of birds. During sleep, domestic chicks (Gallus gallus) show brief periods of monocular-unihemispheric sleep (Mo-Un sleep): one eye is open and the connected hemisphere is awaken while the other eye remains shut and the connected hemisphere sleeps. The time spent in Mo-Un sleep was investigated following a brief monocular deprivation (MD) in chicks hatched from eggs incubated in darkness and reared in light (D-L), incubated in light and reared in light (L-L) and incubated in darkness and reared in darkness (D-D).

Unihemispheric sleep and asymmetrical sleep: behavioral, neurophysiological, and functional perspectives.

Sleep is a behavior characterized by a typical body posture, both eyes' closure, raised sensory threshold, distinctive electrographic signs, and a marked decrease of motor activity. In addition, sleep is a periodically necessary behavior and therefore, in the majority of animals, it involves the whole brain and body. However, certain marine mammals and species of birds show a different sleep behavior, in which one cerebral hemisphere sleeps while the other is awake.

Local sleep: a spatial learning task enhances sleep in the right hemisphere of domestic chicks (Gallus gallus).

During sleep, domestic chicks (Gallus gallus) show brief and transient periods during which one eye is open while the other remains shut. Electrophysiological recordings showed that the hemisphere contralateral to the open eye exhibited an EEG with fast waves typical of wakefulness, whereas the hemisphere contralateral to the closed eye exhibited an electroencephalogram (EEG) typical of slow-wave sleep. We investigated the time spent in sleep and in monocular-unihemispheric sleep (Mo-Un sleep) following the learning of a spatial discrimination task.

Monocular sleep following passive avoidance learning in chicks.

Monocular sleep following passive avoidance learning was investigated in young chicks. One group of animals (Experimental Group) was presented with a bead coated with an aversive substance; a second group (Control Group 1) underwent bead presentations as in the Experimental Group but with the bead coated with water rather than with the aversive substance, and a third group (Control Group 2) did not undergo to any bead presentation. Binocular and monocular sleep was recorded during the 8h subsequent the learning (or the control) event.

The relationship between visuo-spatial attention and nonword reading in developmental dyslexia.

Focused visuo-spatial attention was studied in 10 developmental dyslexic children with impaired nonword reading, 10 dyslexic children with intact nonword reading, and 12 normally reading children. Reaction times to lateralized visual stimuli in a cued detection task showed that attentional facilitation of the target at the cued location was symmetrical in the three groups. However, dyslexics with impaired nonword reading selectively showed a lack of attentional inhibition for targets at the uncued location in the right visual field.

The effects of early post-hatching changes of imprinting object on the pattern of monocular/unihemispheric sleep of domestic chicks.

The pattern of monocular/unihemispheric sleep (Mo-Un sleep) was studied behaviourally in male and female chicks after early post-hatching changes of the imprinting object. Chicks were reared with an imprinting object on day 1 post-hatching which was removed or changed on day 2. On day 1, time spent in binocular sleep (both eyes closed) was similar in male and female chicks, though the number of episodes was lower in females than in males.

Monocular sleep in male domestic chicks.

Behavioural sleep during the first 2 weeks after hatching was studied in male chicks reared with an imprinting object (I-chicks) and in social isolation (NI-chicks). Time spent in sleeping with both eyes closed (binocular sleep) decreased gradually with age in both I-chicks and in NI-chicks whilst the number of episodes of binocular sleep decreased with age in NI-chicks but not in I-chicks. The pattern of monocular sleep (only one eye closed) of both I-chicks and NI-chicks showed no significant bias towards predominant left- or right-eye closure during the first week.

Stimulus-driven attentional capture: An empirical comparison of display-size and distance methods.

Four experiments examined attentional capture by colour as assessed by two different investigative methods. Subjects performed a visual search task for a vertical-target line embedded among tilted-distractor lines, presented inside 4, 8, or 12 coloured discs. Interestingly, when the colour singleton was task irrelevant, and data were analysed by means of the display-size method combined with the zero-slope criterion, no evidence for attentional capture by colour was found.

The time course of attentional focusing in dyslexic and normally reading children.

A cue size procedure was used to evaluate the time course of visuo-spatial attention in dyslexic and normally reading children. When a stimulus target is presented inside a large cue vs a small cue the identification time is slower. In the present study two cue-target delays (100 and 500 ms) were used.

Auditory and visual automatic attention deficits in developmental dyslexia.

Several studies have provided evidence for a phonological deficit in developmental dyslexia. However, recent studies provide evidence for a multimodal temporal processing deficit in dyslexia. In fact, dyslexics show both auditory and visual abnormalities, which could result from a more general problem in the perceptual selection of stimuli.

The role of visuospatial attention in developmental dyslexia: evidence from a rehabilitation study.

Shifting of visual attention induced by peripheral cues was studied in 24 children with specific reading disorder (SRD) or dyslexia and was compared with that of 19 normal readers by means of a covert orienting paradigm. This paradigm presents participants with valid, neutral and invalid spatial cues preceding the presentation of a target stimulus. As compared to normal readers, in SRD children the inhibition effect (i.

Light exposure of the chick embryo influences monocular sleep.

Together with some aquatic mammals, several species of birds, such as the domestic fowl, exhibit a particular behavioural and electrophysiological state called 'unihemispheric sleep', in which one cerebral hemisphere is awake and the other is sleeping. Slow-wave sleep in one hemisphere is associated with closure of the contralateral eye, whilst the eye contralateral to the awake hemisphere is open; closure of both eyes, in contrast, is associated with bihemispheric slow-wave sleep or with REM sleep. During the last few days of incubation the chick embryo is turned in the egg so that it occludes its left eye, whereas light entering through the shell can stimulate the right eye.