Reduced Slow-Wave Rebound during Daytime Recovery Sleep in Middle-Aged Subjects

in PLoS ONE (2012), 7(8), 43224

Short wavelength light modulation of cognitive and emotional brainfunction in humans. New roles for melanopsin photopigment in non-visual and visual functions symposium.

Conference (2011, July)

Short wavelength light modulation of cognitive and emotional brainfunction in humans

Conference (2011, June)

Le système non-visuel chez l'être humain : lumière, oeil et cerveau

Poster (2011, March)

Non-visual brain sensitivity to light in aging

Poster (2011, March)

Functional neuroimaging of the reciprocal influences between sleep and wakefulness.

in Pflugers Archiv : European journal of physiology (2011), 463(1), 103-9

The activity patterns adopted by brain neuronal populations differ dramatically between wakefulness and sleep. However, these vigilance states are not independent and they reciprocally interact. Here, we ... [more ▼]

The activity patterns adopted by brain neuronal populations differ dramatically between wakefulness and sleep. However, these vigilance states are not independent and they reciprocally interact. Here, we provide evidence that in humans, regional brain activity during wakefulness is influenced by sleep regulation, namely by the interaction between sleep homeostasis and circadian signals. We also show that, by contrast, regional brain activity during sleep is influenced by the experience acquired during the preceding waking period. These data reveal the dynamic interactions by which the succession of vigilance states support normal brain function and human cognition. [less ▲]

The impact of blue light on non-visual brain functions changes with age

in NeuroImage (2011), 56(Suppl. 1),

Pupil light reflects in response to monochromatic light stimuli in younger and older subjects

in Sleep (2011), 34(Suppl. 1),

Neural precursors of delayed insight

in Journal of Cognitive Neuroscience (2011), 23(8), 1900-1910

The solution of a problem left unresolved in the evening can sometimes pop into mind as a sudden insight after a night of sleep in the following morning. Although favorable effects of sleep on insightful ... [more ▼]

The solution of a problem left unresolved in the evening can sometimes pop into mind as a sudden insight after a night of sleep in the following morning. Although favorable effects of sleep on insightful behavior have been experimentally confirmed, the neural mechanisms determining this delayed insight remain unknown. Here, using functional magnetic resonance imaging (fMRI), we characterize the neural precursors of delayed insight in the number reduction task (NRT), in which a hidden task structure can be learned implicitly, but can also be recognized explicitly in an insightful process, allowing immediate qualitative improvement in task performance. Normal volunteers practiced the NRT during two fMRI sessions (training and retest), taking place 12 hours apart after a night of sleep. After this delay, half of the subjects gained insight into the hidden task structure ("solvers," S), whereas the other half did not ("nonsolvers," NS). Already at training, solvers and nonsolvers differed in their cerebral responses associated with implicit learning. In future solvers, responses were observed in the superior frontal sulcus, posterior parietal cortex, and the insula, three areas mediating controlled processes and supporting early learning and novice performance. In contrast, implicit learning was related to significant responses in the hippocampus in nonsolvers. Moreover, the hippocampus was functionally coupled with the basal ganglia in nonsolvers and with the superior frontal sulcus in solvers, thus potentially biasing participants' strategy towards implicit or controlled processes of memory encoding, respectively. Furthermore, in solvers but not in nonsolvers, response patterns were further transformed overnight, with enhanced responses in ventral medial prefrontal cortex, an area previously implicated in the consolidation of declarative memory. During retest in solvers, before they gain insight into the hidden rule, significant responses were observed in the same medial prefrontal area. After insight, a distributed set of parietal and frontal areas is recruited among which information concerning the hidden rule can be shared in a so-called global workspace. [less ▲]

Sleep slow wave changes during the middle years of life

in European Journal of Neuroscience (2011), 33(4), 758-66

Slow waves (SW; < 4 Hz and > 75 muV) during non-rapid eye movement (NREM) sleep in humans are characterized by hyperpolarization [surface electroencephalogram (EEG) SW negative phase], during which ... [more ▼]

Slow waves (SW; < 4 Hz and > 75 muV) during non-rapid eye movement (NREM) sleep in humans are characterized by hyperpolarization [surface electroencephalogram (EEG) SW negative phase], during which cortical neurons are silent, and depolarization (surface EEG positive phase), during which the cortical neurons fire intensively. We assessed the effects of age, sex and topography on the dynamics of SW characteristics in a large population (n = 87) of healthy young (23.3 +/- 2.4 years) and middle-aged (51.9 +/- 4.6 years) volunteers. Older subjects showed lower SW density and amplitude than young subjects. Age-related lower SW density in men was especially marked in prefrontal/frontal brain areas, where they originate more frequently. Older subjects also showed longer SW positive and negative phase durations. These last results indicate that, in young subjects, cortical neurons would synchronously enter the SW hyperpolarization and depolarization phases, whereas this process would take longer in older subjects, leading to lower slope and longer SW positive and negative phases. Importantly, after controlling for SW amplitude, middle-aged subjects still showed lower slope than young subjects in prefrontal, frontal, parietal and occipital derivations. Age-related effects on SW density, frequency and positive phase duration were more prominent at the beginning of the night, when homeostatic sleep pressure is at its highest. Age-related SW changes may be associated with changes in synaptic density and white matter integrity and may underlie greater sleep fragmentation and difficulty in recuperating and maintaining sleep under challenges in older subjects. [less ▲]