Exploring the Event-Related Potentials' Time Course of Associative Recognition in Autism

Behavioral data on episodic recollection in autism spectrum disorders (ASD) point limited relational memory functioning. However, the involvement of successive memory processes in the profile of episodic memory in ASD needs more study. Here, we used event-related potentials (ERP) to investigate the time course of episodic recollection with an associative recognition paradigm with picture pairs. Twenty-two participants with ASD and 32 with typical development (TD), all right-handed, were included. Behavioral results confirmed difficulties in correctly recognizing identical pairs in the ASD relative to TD group. We found an unexpected amplitude decrement on the P2 (220-270 msec) and FN400 (350-470 msec) potentials, suggesting diminished priming and familiarity effects in the ASD relative to TD group. However, ERP data revealed that the recognition of associative information relies on the same electrophysiological process (old/new effect in the 600-700-msec late positive component) in ASD participants as in TD ones, with a parietal extension in the ASD group. These results suggest that the electrophysiological processes of associative recognition are qualitatively similar in individuals with and without ASD but may differ quantitatively. This difference may be driven by the reduced early processing of picture pairs that may in turn lead to their diminished integration into the semantic memory system, being partially compensated by a greater involvement of associative memory during the recollection process. Other studies would be useful to go further in identifying these cognitive processes involved in atypical recognition in ASD and their neural substrates. LAY SUMMARY: We identified diminished performance on the associative recognition of picture pairs in adolescents and young adults with autism when compared to typical development. Electrophysiological data revealed qualitative similarities but quantitative differences between-group, with diminished priming and familiarity processes partially compensated by an enhanced parietal recollection process

Distinct Gamma-Band Components Reflect the Short-Term Memory Maintenance of Different Sound Lateralization Angles

Oscillatory activity in human electro- or magnetoencephalogram has been related to cortical stimulus representations and their modulation by cognitive processes. Whereas previous work has focused on gamma-band activity (GBA) during attention or maintenance of representations, there is little evidence for GBA reflecting individual stimulus representations. The present study aimed at identifying stimulus-specific GBA components during auditory spatial short-term memory. A total of 28 adults were assigned to 1 of 2 groups who were presented with only right- or left-lateralized sounds, respectively. In each group, 2 sample stimuli were used which differed in their lateralization angles (15° or 45°) with respect to the midsagittal plane. Statistical probability mapping served to identify spectral amplitude differences between 15° versus 45° stimuli. Distinct GBA components were found for each sample stimulus in different sensors over parieto-occipital cortex contralateral to the side of stimulation peaking during the middle 200–300 ms of the delay phase. The differentiation between “preferred” and “nonpreferred” stimuli during the final 100 ms of the delay phase correlated with task performance. These findings suggest that the observed GBA components reflect the activity of distinct networks tuned to spatial sound features which contribute to the maintenance of task-relevant information in short-term memory

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

Local Processing Bias Impacts Implicit and Explicit Memory in Autism

Autism spectrum disorder (ASD) is characterized by atypical perception, including processing that is biased toward local details rather than global configurations. This bias may impact on memory. The present study examined the effect of this perception on both implicit (Experiment 1) and explicit (Experiment 2) memory in conditions that promote either local or global processing. The first experiment consisted of an object identification priming task using two distinct encoding conditions: one favoring local processing (Local condition) and the other favoring global processing (Global condition) of drawings. The second experiment focused on episodic (explicit) memory with two different cartoon recognition tasks that favored either local (i.e., processing specific details) or a global processing (i.e., processing each cartoon as a whole). In addition, all the participants underwent a general clinical cognitive assessment aimed at documenting their cognitive profile and enabling correlational analyses with experimental memory tasks. Seventeen participants with ASD and 17 typically developing (TD) controls aged from 10 to 16 years participated to the first experiment and 13 ASD matched with 13 TD participants were included for the second experiment. Experiment 1 confirmed the preservation of priming effects in ASD but, unlike the Comparison group, the ASD group did not increase his performance as controls after a globally oriented processing. Experiment 2 revealed that local processing led to difficulties in discriminating lures from targets in a recognition task when both lures and targets shared common details. The correlation analysis revealed that these difficulties were associated with processing speed and inhibition. These preliminary results suggest that natural perceptual processes oriented toward local information in ASD may impact upon their implicit memory by preventing globally oriented processing in time-limited conditions and induce confusion between explicit memories that share common details

Exploration of neural correlates of movement intention based on characterisation of temporal dependencies in electroencephalography

Brain computer interfaces (BCIs) provide a direct communication channel by using brain signals, enabling patients with motor impairments to interact with external devices. Motion intention detection is useful for intuitive movement-based BCI as movement is the fundamental mode of interaction with the environment. The aim of this paper is to investigate the temporal dynamics of brain processes using electroencephalography (EEG) to explore novel neural correlates of motion intention. We investigate the changes in temporal dependencies of the EEG by characterising the decay of autocorrelation during asynchronous voluntary finger tapping movement. The evolution of the autocorrelation function is characterised by its relaxation time, which is used as a robust marker for motion intention. We observed that there was reorganisation of temporal dependencies in EEG during motion intention. The autocorrelation decayed slower during movement intention and faster during the resting state. There was an increase in temporal dependence during movement intention. The relaxation time of the autocorrelation function showed significant (p < 0.05) discrimination between movement and resting state with the mean sensitivity of 78.37 ± 8.83%. The relaxation time provides movement related information that is complementary to the well-known event-related desynchronisation (ERD) by characterising the broad band EEG dynamics which is frequency independent in contrast to ERD. It can also detect motion intention on average 0.51s before the actual movement onset. We have thoroughly compared autocorrelation relaxation time features with ERD in four frequency bands. The relaxation time may therefore, complement the well-known features used in motion-based BCI leading to more robust and intuitive BCI solutions. The results obtained suggest that changes in autocorrelation decay may involve reorganisation of temporal dependencies of brain activity over longer duration during motion intention. This opens the possibilities of investigating further the temporal dynamics of fundamental neural processes underpinning motion intention

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

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

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