Impact of Semantic Relatedness on Associative Memory: An ERP Study

Encoding and retrieval processes in memory for pairs of pictures are thought to be influenced by inter-item similarity and by features of individual items. Using Event-Related Potentials (ERP), we aimed to identify how these processes impact on both the early mid-frontal FN400 and the Late Positive Component (LPC) potentials during associative retrieval of pictures. Twenty young adults undertook a sham task, using an incidental encoding of semantically related and unrelated pairs of drawings. At test, we conducted a recognition task in which participants were asked to identify target identical pairs of pictures, which could be semantically related or unrelated, among new and rearranged pairs. We observed semantic (related and unrelated pairs) and condition effects (old, rearranged and new pairs) on the early mid-frontal potential. First, a lower amplitude was shown for identical and rearranged semantically related pairs, which might reflect a retrieval process driven by semantic cues. Second, among semantically unrelated pairs, we found a larger negativity for identical pairs, compared to rearranged and new ones, suggesting additional retrieval processing that focuses on associative information. We also observed an LPC old/new effect with a mid-parietal and a right occipito-parietal topography for semantically related and unrelated old pairs, demonstrating a recollection phenomenon irrespective of the degree of association. These findings suggest that associative recognition using visual stimuli begins at early stages of retrieval, and differs according to the degree of semantic relatedness among items. However, either strategy may ultimately lead to recollection processes

Attentional capture mediates the emergence and suppression of intrusive memories

International audienceIntrusive memories hijack consciousness and their control may lead to forgetting. However, the contribution of reflexive attention to qualifying a memory signal as interfering is unknown. We used machine learning to decode the brain's electrical activity and pinpoint the otherwise hidden emergence of intrusive memories reported during a memory suppression task. Importantly, the algorithm was trained on an independent attentional model of visual activity, mimicking either the abrupt and interfering appearance of visual scenes into conscious awareness or their deliberate exploration. Intrusion of memories into conscious awareness were decoded above chance. The decoding accuracy increased when the algorithm was trained using a model of reflexive attention. Conscious detection of intrusive activity decoded from the brain signal was central to the future silencing of suppressed memories and later forgetting. Unwanted memories require the reflexive orienting of attention and access to consciousness to be suppressed effectively by inhibitory control

Changes in sleep theta rhythm are related to episodic memory impairment in early Alzheimer's disease.

International audienceImpairments have been reported both in sleep structure and episodic memory in Alzheimer's disease [AD]. Our objective was to investigate the relationships between episodic memory deficits and electro-encephalography [EEG] abnormalities occurring during sleep in patients with early AD. Postlearning sleep was recorded in 14 patients with mild to moderate AD, and 14 healthy elderly controls after they performed an episodic memory task derived from the Grober and Buschke's procedure. For each sleep stage, the relative power and mean frequency in each band were analyzed. Relative to agematched controls, AD patients presented faster mean theta frequency in both REM sleep and slow wave sleep [SWS]. In AD patients, a correlative analysis revealed that faster theta frequency during SWS was associated with better delayed episodic recall. We assume that increased theta activity reflects changes in neuronal activity to maintain memory performance, indicating that compensatory mechanisms already described at the waking state could also be engaged during SWS

Attentional capture mediates the emergence and suppression of intrusive memories

International audienceIntrusive memories hijack consciousness and their control may lead to forgetting. However, the contribution of reflexive attention to qualifying a memory signal as interfering is unknown. We used machine learning to decode the brain's electrical activity and pinpoint the otherwise hidden emergence of intrusive memories reported during a memory suppression task. Importantly, the algorithm was trained on an independent attentional model of visual activity, mimicking either the abrupt and interfering appearance of visual scenes into conscious awareness or their deliberate exploration. Intrusion of memories into conscious awareness were decoded above chance. The decoding accuracy increased when the algorithm was trained using a model of reflexive attention. Conscious detection of intrusive activity decoded from the brain signal was central to the future silencing of suppressed memories and later forgetting. Unwanted memories require the reflexive orienting of attention and access to consciousness to be suppressed effectively by inhibitory control

Evaluation des effets résiduels de psychotropes sur les capacités à conduire et l'éveil : interaction médicamenteuse. In S. Gaymard, T. Tiplica (Eds), Sécurité des déplacements, protection des usagers et de l'environnement. Maîtrise des risques et prévention. Tome 1

L'utilisation d'un Îhicule associé à la consommation de psychotropes relève de pratiques relativement courantes (21% des causes d'accident en 2013 selon l'Observatoire National Interministériel de Sécurité Routière). Les données épidémiologiques et les pourcentages de consommation de médicaments ne permettent pas de faire un lien de causalité direct entre un produit donné et une éventuelle détérioration de la conduite automobile. Des études sont aujourd'hui menées pour tenter d'appréhender les facteurs influençant les variations du niveau d'éveil dans le domaine de la conduite. Notre expérience s'intègre dans ce cadre et en particulier sur l'influence de psychotropes administrés à dose thérapeutique par une prescription médicale standard. Nous avons mené une expérience de conduite sur simulateur avec des sujets sains (matures - 55-65 ans), après une nuit complète de sommeil. Dans cette expérience, les psychotropes étudiés étaient administrés seuls ou combinés et comparés à un placebo. Nous nous sommes plus particulièrement intéressés aux effets résiduels d'un hypnotique et aux effets aigus d'un analgésique. Nos résultats sur l'effet combiné d'un analgésique et d'un hypnotique ne suggèrent aucune interaction pharmacologique entre ces deux produits chez des sujets matures et sains. Cependant, nous observons des effets indépendants de chacun de ces psychotropes sur la performance de conduite aussi bien sur le plan qualitatif que quantitatifs (maintien de la trajectoire et régulation de la vitesse). Nos résultats mettent en évidence une augmentation de la somnolence avec la prise combinée d'un analgésique et d'un hypnotique lors de l'évaluation objective (EEG) après une heure de conduite simulée. Ce résultat suggère une interaction entre la durée de la tâche de conduite et la prise combinée d'un analgésique et d'un hypnotique

Evaluation des effets résiduels de psychotropes sur les capacités à conduire et l'éveil : interaction médicamenteuse. In S. Gaymard, T. Tiplica (Eds), Sécurité des déplacements, protection des usagers et de l'environnement. Maîtrise des risques et prévention. Tome 1

L'utilisation d'un Îhicule associé à la consommation de psychotropes relève de pratiques relativement courantes (21% des causes d'accident en 2013 selon l'Observatoire National Interministériel de Sécurité Routière). Les données épidémiologiques et les pourcentages de consommation de médicaments ne permettent pas de faire un lien de causalité direct entre un produit donné et une éventuelle détérioration de la conduite automobile. Des études sont aujourd'hui menées pour tenter d'appréhender les facteurs influençant les variations du niveau d'éveil dans le domaine de la conduite. Notre expérience s'intègre dans ce cadre et en particulier sur l'influence de psychotropes administrés à dose thérapeutique par une prescription médicale standard. Nous avons mené une expérience de conduite sur simulateur avec des sujets sains (matures - 55-65 ans), après une nuit complète de sommeil. Dans cette expérience, les psychotropes étudiés étaient administrés seuls ou combinés et comparés à un placebo. Nous nous sommes plus particulièrement intéressés aux effets résiduels d'un hypnotique et aux effets aigus d'un analgésique. Nos résultats sur l'effet combiné d'un analgésique et d'un hypnotique ne suggèrent aucune interaction pharmacologique entre ces deux produits chez des sujets matures et sains. Cependant, nous observons des effets indépendants de chacun de ces psychotropes sur la performance de conduite aussi bien sur le plan qualitatif que quantitatifs (maintien de la trajectoire et régulation de la vitesse). Nos résultats mettent en évidence une augmentation de la somnolence avec la prise combinée d'un analgésique et d'un hypnotique lors de l'évaluation objective (EEG) après une heure de conduite simulée. Ce résultat suggère une interaction entre la durée de la tâche de conduite et la prise combinée d'un analgésique et d'un hypnotique

A combined neuropsychological and brain imaging study of obstructive sleep apnea.

International audiencePatients with obstructive sleep apnea (OSA) show neuropsychological impairments ranging from vigilance decrements, attentional lapses and memory gaps to decreased motor coordination, but their cognitive profile, and the origin of the impairments, remain unclear. We sought to establish the neuropsychological profile of 16 newly diagnosed apneics and to highlight both their morphological and functional brain abnormalities. We used an extensive neuropsychological test battery to investigate attention and vigilance, executive functions, episodic memory and motor domains. For brain imaging, we used the optimized voxel-based morphometry procedure for the MRI data, resting-state (18)F-fluoro-2-deoxy-D-Glucose positron emission tomography ((18)FDG-PET) with correction for partial volume effects (PVEs) and voxel-based analyses. In terms of neurobehavioral performance, our patients displayed objective daytime somnolence but little impairment in memory and motor domains. Cerebral data revealed gray matter loss in the frontal and temporo-parieto-occipital cortices, the thalamus, hippocampal region, some basal ganglia and cerebellar regions, mainly in the right hemisphere. The decrease in brain metabolism was also right-lateralized, but more restricted than the gray matter density changes, and involved the precuneus, the middle and posterior cingulate gyrus, and the parieto-occipital cortex, as well as the prefrontal cortex. To conclude, despite the presence of only minor memory and motor impairments, our patients displayed significant cerebral changes in terms of both gray matter density and metabolic levels, and may have benefited from cognitive reserve and compensatory mechanisms. Thus, cerebral changes in OSA patients may precede the onset of notable neuropsychological consequences

Impact of semantic relatedness on associative memory: an ERP study 1 2

International audienceEncoding and retrieval processes in memory for pairs of pictures are thought to be influenced by inter-item similarity and by features of individual items. Using Event-Related Potentials, we aimed to identify how these processes impact on both the early mid-frontal FN400 and the Late Positive Component (LPC) potentials during associative retrieval of pictures. Twenty young adults undertook a sham task, using an incidental encoding of semantically related and unrelated pairs of drawings. At test, we conducted a recognition task in which participants were asked to identify target identical pairs of pictures, which could be semantically related or unrelated, among new and rearranged pairs. We observed semantic (related and unrelated pairs) and condition effects (old, rearranged, and new pairs) on the early mid-frontal potential. First, a lower amplitude was shown for identical and rearranged semantically related pairs, which might reflect a retrieval process driven by semantic cues. Second, among semantically unrelated pairs, we found a larger negativity for identical pairs, compared to rearranged and new ones, suggesting additional retrieval processing that focuses on associative information. We also observed an LPC old/new effect with a mid-parietal and a right occipito-parietal topography for semantically related and unrelated old pairs, demonstrating a recollection phenomenon irrespective of the degree of association. These findings suggest that associative recognition using visual stimuli begins at early stages of retrieval, and differs according to the degree of semantic relatedness among items. However, either strategy may ultimately lead to recollection processes

Long-term modulation of cardiac activity induced by inhibitory control over emotional memories

International audienceEfforts to exclude past experiences from conscious awareness can lead to forgetting. Memory suppression is central to affective disorders, but we still do not really know whether emotions, including their physiological causes, are also impacted by this process in normal functioning individuals. In two studies, we measured the after-effects of suppressing negative memories on cardiac response in healthy participants. Results of Study 1 revealed that efficient control of memories was associated with long-term inhibition of the cardiac deceleration that is normally induced by disgusting stimuli. Attempts to suppress sad memories, by contrast, aggravated the cardiac response, an effect that was closely related to the inability to forget this specific material. In Study 2, electroencephalography revealed a reduction in power in the theta (3-8 Hz), alpha (8-12 Hz) and low-beta (13-20 Hz) bands during the suppression of unwanted memories, compared with their voluntary recall. Interestingly, however, the reduction of power in the theta frequency band during memory control was related to a subsequent inhibition of the cardiac response. These results provide a neurophysiological basis for the influence of memory control mechanisms on the cardiac system, opening up new avenues and questions for treating intrusive memories using motivated forgetting