Incorporation of fragmented visuo-olfactory episodic memory into dreams and its association with memory performance.

The question of a possible link between dream content and memory consolidation remains open. After a comprehensive review of the literature, we present novel findings from an experiment testing whether the incorporation of recently learned stimuli into dream reports is associated with improved post-sleep memory performance. Thirty-two high dream recallers freely explored new visuo-olfactory episodes for 3 consecutive days. During the nights following each non-explicit encoding, participants wore a wrist actimeter, and woke up at 5am and their usual waking time to record their dreams (intensity of all oneiric sensory perception was assessed using scales). A total of 120 dreams were reported and elements related to the encoding phase were identified in 37 of them, either learning-related (mainly visual- and rarely olfactory-related elements), or experiment-related (lab- or experimenters-related elements). On the 4th day, we found that participants with learning-related (n = 16) and participants with learning-related and/or experiment-related dreams (n = 21) had similar odor recognition and odor-evoked episodic memory with the other participants. However, they had significantly better visuo-spatial memory of the episodes in comparison to the other participants. Our results support the hypothesis that the learning phase is loosely incorporated into dreams and that this incorporation is associated with sleep related memory consolidation.

Effects of preference and sensory modality on behavioural reaction in patients with disorders of consciousness.

BACKGROUND: Reliable evaluation of patients with unresponsive wakefulness syndrome (UWS) or in a minimally conscious state (MCS) remains a major challenge. It has been suggested that the expression of residual cerebral function could be improved by allowing patients to listen to their favourite music. However, the potential effect of music on behavioural responsiveness, as well as the effect of preferred stimuli in other sensory modalities (e.g. olfaction), remain poorly understood. OBJECTIVE: The aim of our study was to investigate the effect of sensory modality (auditory versus olfactory) and preference (preferred versus neutral) of the test stimuli on patients' subsequent performance on the Coma Recovery Scale-Revised (CRS-R). RESEARCH DESIGN: Within-subject design because of inter-individual differences between patients. METHODS AND PROCEDURES: We studied four items from the CRS-R (visual pursuit using a mirror, auditory localization of the own name and two movements to command) in 13 patients (7 MCS; 6 UWS). MAIN OUTCOMES AND RESULTS: Auditory stimuli triggered higher responsiveness compared to olfactory stimuli, and preferred stimuli were followed by higher scores than did neutral stimuli. CONCLUSIONS: Findings suggest that preferred auditory stimuli at the bedside contribute to the expression of residual function and could improve the diagnostic assessment.

Cerebral imaging and olfactory disorders: a review.

Cerebral imaging and olfactory disorders: a review. Olfactory disorders are often misjudged and rarely given due clinical consideration. Nevertheless, they occur in a wide range of neurological disorders, and their evaluation can help in diagnosis. Whereas psychophysical tests have been used to evaluate olfactory dysfunction in numerous diseases, functional brain imaging using olfactory stimuli is an emergent technique and few studies have been published to date. After a reminder of cerebral imaging and analysis techniques and a rapid description of our actual knowledge of olfactory processes in healthy subjects, the current review focuses on cerebral imaging studies performed on patients with neurological disorders and presenting olfactory dysfunction. Neurological disorders such as Alzheimer's disease, Parkinson's disease, epilepsy, migraine, multiple chemical sensitivity and schizophrenia are examined.

A stimulation method using odors suitable for PET and fMRI studies with recording of physiological and behavioral signals.

A design for a semi-automatic olfactometric system is described for PET and fMRI experiments. The olfactometer presents several advantages because it enables the use of an 'infinite' number of odorants and the synchronization of stimuli with breathing. These advantages mean that the subject is recorded while breathing normally during olfactory judgment tasks. In addition, the design includes a system for recording the behavioral (rating scale) and physiological (breathing, electrodermal reaction (ED), plethysmography (PL)) signals given by the subject. Both systems present the advantage of being compatible with fMRI magnetic fields since no ferrous material is used in the Faraday cage and signals are transmitted via an optical transmission interface to an acquisition system.