Pascal Hot

Modulation of cognitive processing by emotional valence studied through event-related potentials in humans.

This experiment investigated whether the emotional content of a stimulus could modulate its cognitive processing. Particularly, we focused on the influence of the valence dimension on the cognitive processing triggered by a non emotional oddball task. To this end, event-related potentials (ERPs) were recorded from 25 sites during a visual oddball paradigm. Three sets of pictures (unpleasant, neutral and pleasant) with low arousal values served as rare target items. Subjects were simply asked to realize a standard/target categorization task, irrespective of the picture valence. A temporal principal component analysis allowed us to identify several evoked components (i.e. P1, P2, N2, P3a and P3b). Emotional effects observed on P1, P2 and P3b showed that the valence content of the stimulus modulates the cognitive processes at several points in the information processing stream.

Electrical autonomic correlates of emotion.

This paper focussed on how electrophysiological autonomic data may contribute to better understand neural substrates of emotional processing. The utility of autonomic electrophysiological markers for assessing emotional and cognitive processes is presented in the context of an important bodily arousal interface. Components of general autonomic control are reviewed and relevant neural modulations of specific autonomic variables were discussed. The role of autonomic feedback on central processes is emphasized and neural influences on autonomic activities as an index of arousal dimension, the electrodermal activity (EDA), are outlined. An overview of brain mechanisms governing generation and control of EDA is presented, and the contribution of electrodermal parameters as indices of emotional activation illustrated by data related to diurnal emotional reactivity and to non consciously subjective emotionality. Conclusions highlight the role of electrical autonomic expressions as tools to explore emotional components of mind-body-mind relationships.

Event-related P3a and P3b in response to unpredictable emotional stimuli

In natural situations, unpredictable events processing often interacts with the ongoing cognitive activities. In a similar manner, the insertion of deviant unpredictable stimuli into a classical oddball task evokes both the P3a and P3b event-related potentials (ERPs) components that are, respectively, thought to index reallocation of attentional resources or inhibitory process and memory updating mechanism. This study aims at characterising the influence of the emotional arousal and valence of a deviant and unpredictable non-target stimulus on these components. ERPs were recorded from 28 sites during a visual three-stimulus oddball paradigm. Unpleasant, neutral and pleasant pictures served as non-target unpredictable items and subjects were asked to realize a perceptually difficult standard/target discrimination task. A temporal principal component analysis (PCA) allowed us to show that non-target pictures elicited both a P3a and a P3b. Moreover, the P3b component was modulated by the emotional arousal and the valence of the pictures. Thus, the memory updating process may be modulated by the affective arousal and valence of unpredictable disturbing stimuli, even if the task does not require any explicit emotional categorization.

Is there a link between sleep changes and memory in Alzheimer's disease?

Aging and Alzheimers disease (AD) are both characterized by memory impairments and sleep changes. We investigated the potential link between these disturbances, focusing on sleep spindles, involved in memory consolidation. Two episodic memory tasks were given to young and old healthy participants, as well as to AD patients. Postlearning sleep was recorded. Sleep spindles were globally reduced in aging and AD. AD patients also exhibited a further decrease in fast spindles. Besides, mean intensity of fast spindles was positively correlated, in AD patients, with immediate recall performance. Our results are the first report of a specific decrease in fast spindles in AD, associated with learning abilities. They also give further hints for a functional differentiation between slow and fast spindles.

Diurnal variations of tonic electrodermal activity.

Diurnal variability of skin conductance level (SCL) was examined in two complementary experiments, simultaneously with variability of skin temperature (ST) and that of simple reaction time (RT) which was recorded as a behavioural index of arousal. In Experiment I, 6 subjects spent 6 days in the laboratory in homogeneous conditions. Three recording sessions, each lasting 2 h, began, respectively, at 9:00 a.m. (morning), 1:00 p.m. (afternoon) and 5:00 p.m. (evening). Results indicated that SCL increased linearly throughout the day. Experiment II was undertaken to test whether this effect could still be observed in more heterogeneous conditions. Subjects (n = 12) attended to their own activities between the two 30-min sessions beginning, respectively, at 9:30 a.m. and 6:00 p.m. during a single experimental day. Again, SCL was higher in the evening than in the morning. In both experiments the SCL pattern seemed to be asynchronous with ST and RT variations. Taken as a whole, these data bring additional evidence of temporal electrodermal variation, a phenomenon which should be further taken into account in EDA research.

An ERP investigation of emotional processing in European and Japanese individuals

This article examined neural time course differences in the processing of emotional pictures in European and Asian individuals. Event-related potentials (ERPs) were recorded in 15 French and 15 Japanese volunteers during the presentation of neutral and emotional pictures in their own country. ERPs were analyzed by means of spatio-temporal Principal Component Analysis (PCA) and allow to evaluate cultural influences on emotional processing along three temporal windows: 105 to 140 ms, 176 to 230 ms and 255 to 455 ms. Main results highlight that (1) early ERP components coded emotional charge but were not modulated by cultural background, (2) later components showed a significant decrease of amplitudes at parieto-occipital areas for Japanese participants compared to French ones in emotional condition. These findings suggest that, in both populations, similar neurocognitive processes are involved in the early stage of the emotional stimuli processing and effects observed on later components may reflect a poorer engagement of parietal areas, known to be involved in emotional arousal dimension. Considering that cognitive judgments were similar in both populations, electrophysiological findings suggest that cultural influences on later stage of emotional processing could be related to the known lower level of emotionally expressive behavior in Japanese than in Caucasians.

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

Impairments have been reported both in sleep structure and episodic memory in Alzheimers 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 Buschkes 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.

Emotional Decoding Abilities in Alzheimer's Disease: A Meta-Analysis

Studies on emotional processing in Alzheimers disease (AD) have reported abnormalities in emotional decoding. However, it remains unclear whether the impairment depends on a general cognitive decline that characterizes these patients or is an independent deficit. We conducted a comprehensive meta-analysis of existing studies that compared AD patients with age-matched healthy older adults (HOA) on measures of emotional decoding abilities. Our first goal was to quantify the magnitude of the AD patients deficit. The second goal was to identify variables that may modulate the deficit, including emotional task design and participants characteristics. The random-effects model analysis on 212 effect sizes indicated that AD patients showed significant impairment in emotional decoding abilities. This deficit is consistent regardless of the emotional task, stimuli, type of emotion considered, or disease severity. After we controlled for cognitive status, the emotional performance in AD patients was still poorer than that in HOA. The effect size of emotional performance was significantly lower when the cognitive status was considered than when it was not. Thus, our results suggest that impaired emotion processing in AD patients cannot be solely explained by the cognitive deficit. These findings provide evidence that progressive neuropathological changes characterizing the disease could affect emotional processing, which may suggest that clinicians should be sensitive to the emergence of impairments in emotional decoding. Further research that addresses the limitations of existing studies is needed to draw conclusions about methodological issues and the impact of the AD patients depression symptoms on emotional decoding.

Preserved and Impaired Emotional Memory in Alzheimer’s Disease

Patients with early atrophy of both limbic structures involved in memory and emotion processing in Alzheimer’s disease (AD) provide a unique clinical population for investigating how emotion is able to modulate retention processes. This review focuses on the emotional enhancement effect (EEE), defined as the improvement of memory for emotional events compared with neutral ones. The assessment of the EEE for different memory systems in AD suggests that the EEE could be preserved under specific retrieval instructions. The first part of this review examines these data in light of compelling evidence that the amygdala can modulate processes of hippocampus-dependent memory. We argue that the EEE could be a useful paradigm to reduce impairment in episodic memory tasks. In the second part, we discuss theoretical consequences of the findings in favor of an EEE, according to which a compensatory mechanism in patients with AD solicits greater amygdala functioning or additional networks, even when amygdala atrophy is present. These considerations emphasize the relevance of investigating patients with AD to understand the relationship between emotion and memory processes.

Diurnal autonomic variations and emotional reactivity.

Diurnal temporal variations of emotional reactivity were investigated in relationship with fluctuations of psychophysiological state, evaluated by tonic autonomic activity. Neutral and unpleasant pictures, selected to constitute seven matched sets, were evaluated by 12 participants during seven sessions in the course of daytime. Skin conductance level (SCL) was recorded at the beginning of each session, whereas skin conductance responses (SCRs), affective evaluation and emotional experience were measured during or after each session. Data show significant temporal variations for SCL, SCRs and emotional experience which follow similar patterns during the daytime. Discussion highlights the role of temporal patterns of autonomic activity as an interesting basis to better understand the emotional regulation and affective disorders.