[Memory alterations in post-traumatic stress disorder]. / Les altérations de la mémoire dans le trouble de stress post-traumatique.

Post-Traumatic Stress Disorder (PTSD) is a disorder that develops following the experience of a highly stressful event, which involves a confrontation with death or the threat of death, serious injury or sexual violence. It is characterized by symptoms such as intrusions, avoidance and hypervigilance. According to the literature, PTSD is associated with an imbalance between a privileged memorization of the emotional and sensory aspects of the traumatic event and a failure to memorize the contextual aspects. That is why PTSD is now considered a memory disorder whose effects extend to several components. In this review article, we focus on how PTSD affects long-term memory. The first part describes the long-term effects of PTSD on episodic memory with emphasis on the difficulties in encoding certain elements of the traumatic event and their consequences. These difficulties may be manifested in the narration of the trauma, with a discourse of the traumatic event lacking in contextual details. They may also lead to reliving and generalizing the fear to other contexts, whether they are related to the trauma or not. The second part of the article discusses how PTSD affects autobiographical memory and has consequences for the construction of identity and the perception of the past, present and future of people with this disorder. Autobiographical memory, which plays a key role in the storage of past personal memories as well as in identity formation, shows several forms of disruption induced by PTSD. First, a decrease in contextual details associated with memories of the personal past is observed, meaning that people with PTSD tend to remember their past experiences less accurately. Second, a propensity to project the future in a more negative and unpredictable manner is evidenced, related to a feeling of uncertainty about the future in PTSD suffering individuals. Finally, alterations in the encoding of present events due to the disruptive effects of post-traumatic stress symptoms during the encoding process are also identified.

Title: Les altérations de la mémoire dans le trouble de stress post-traumatique. Abstract: Le Trouble de Stress Post-Traumatique (TSPT) est une pathologie qui se développe chez une personne qui a fait l'expérience d'un événement hautement stressant impliquant une confrontation à la mort ou à une menace de mort, à une blessure grave ou à des violences sexuelles. Ce trouble se caractérise par plusieurs symptômes dont les intrusions, l'évitement et l'hypervigilance. Le TSPT est associé à un déséquilibre entre une mémorisation exacerbée des aspects émotionnels et sensoriels de l'événement traumatique et un défaut de mémorisation des aspects contextuels. En conséquence, le TSPT est aujourd'hui considéré comme un trouble de la mémoire dont les retentissements s'étendent à plusieurs de ses composantes. Cet article expose les conséquences du TSPT sur la mémoire à long terme et met la focale sur deux mécanismes : l'encodage partiel de l'événement traumatique en mémoire épisodique et l'influence de cette expérience traumatique sur les souvenirs personnels en mémoire autobiographique. L'article aborde en première partie les difficultés d'encodage de certains éléments de l'événement traumatique et leurs conséquences, comprenant les reviviscences ainsi que la persistance et la généralisation de la peur à d'autres contextes plus ou moins liés à l'événement traumatique. La deuxième partie aborde la façon dont le trouble affecte la mémoire autobiographique et l'identité en occasionnant une réduction de la précision des événements du passé, des altérations de la capacité à se projeter dans des événements futurs et un encodage incomplet de nouveaux événements.

[Memory tests]. / Tests de mémoire.

MEMORY TESTS. Memory tests used in clinical practice mainly concern anterograde memory through the evaluation of learning, short- or long-term retention, and retrieval of information. They use different types of material (verbal or visual) and different tasks to assess the integrity of the different memory processes: encoding, storage and retrieval.

TESTS DE MÉMOIRE. Les tests de mémoire utilisés en pratique clinique concernent principalement la mémoire antérograde au travers de l'évaluation des capacités d'apprentissage, de maintien à court ou long terme des informations, et de récupération de celles-ci. Ils utilisent différents types de matériel (verbal ou visuel) et différentes tâches permettant de statuer sur l'intégrité des différents processus mnésiques : encodage, stockage et récupération.

Functional connectivity of the medial prefrontal cortex related to mindreading abilities.

The medial prefrontal cortex is a key region of mindreading belonging to the mentalizing system, a set of brain areas underlying mental state inference based on reasoning on social concepts. The aim of this study was to characterize the functional connectivity between regions involved in mindreading and to highlight the processes it underpins, focusing on the dorsal and ventral parts of the medial prefrontal cortex. We analyzed resting-state functional magnetic resonance imaging of 56 healthy volunteers, to study the relationship between mindreading abilities and functional connectivity of the medial prefrontal cortex. Cognitive mindreading performances were correlated with connectivity between the medial prefrontal cortex and frontal regions involved in the regulation of the salience of one's own mental contents, with a distinction between the dorsal part connected to regions subtending inhibition processes and the ventral part to emotional regions. Affective mindreading performances were negatively correlated with negative connectivity of the ventro- and dorsomedial prefrontal cortex with sensorimotor regions belonging to the mirror neuron system subtending the simulation of mental states. These findings suggested a role of the medial prefrontal cortex to decrease the salience of one's own mental content and in the antisynchronous interaction between the mentalizing and mirror neurons systems.

Avoidance behaviour generalizes to eye processing in posttraumatic stress disorder.

Background: Avoidance describes any action designed to prevent an uncomfortable situation or emotion from occurring. Although it is a common reaction to trauma, avoidance becomes problematic when it is the primary coping strategy, and plays a major role in the development and maintenance of posttraumatic stress disorder (PTSD). Avoidance in PTSD may generalize to non-harmful environmental cues that are perceived to be unsafe. Objective: We tested whether avoidance extends to social cues (i.e. emotional gazes) that are unrelated to trauma. Method: A total of 159 participants (103 who had been exposed to the 2015 Paris terrorist attacks and 56 who had not) performed a gaze-cueing task featuring sad, happy and neutral faces. Attention to the eye area was recorded using an eyetracker. Of the exposed participants, 52 had been diagnosed with PTSD (PTSD+) and 51 had not developed PTSD (PTSD-). As a result of the preprocessing stages, 52 PTSD+ (29 women), 50 PTSD- (20 women) and 53 nonexposed (31 women) participants were included in the final analyses. Results: PTSD+ participants looked at sad eyes for significantly less time than PTSD- and nonexposed individuals. This effect was negatively correlated with the intensity of avoidance symptoms. No difference was found for neutral and happy faces. Conclusions: These findings suggest that maladaptive avoidance in PTSD extends to social processing, in terms of eye contact and others' emotions that are unrelated to trauma. New therapeutic directions could include targeting sociocognitive deficits. Our findings open up new and indirect avenues for overcoming maladaptive avoidance behaviours by remediating eye processing.Trial registration: ClinicalTrials.gov identifier: NCT02810197. HIGHLIGHTS: Avoidance is a key symptom of posttraumatic stress disorder (PTSD).Avoidance is often viewed as limited to reminders linked to the trauma.Results show that attention to the eyes of sad faces is also affected by PTSD. This effect is correlated with avoidance symptoms in PTSD.

Antecedentes: La evitación describe cualquier acción diseñada para prevenir una situación o emoción desagradable. Aunque es una reacción común al trauma, la evitación se vuelve problemática cuando es la principal estrategia de afrontamiento, y desempeña un papel importante en el desarrollo y mantenimiento del trastorno de estrés postraumático (TEPT). La evitación en el TEPT puede generalizarse a señales ambientales no dañinas que se perciben como inseguras. Objetivo: Probamos si la evitación se extiende a las señales sociales (es decir, las miradas emocionales) que no están relacionadas con el trauma. Método: Un total de 159 participantes (103 que habían estado expuestos a los atentados terroristas de París del 2015 y 56 que no lo habían estado) realizaron una tarea de captación de miradas con rostros tristes, felices y neutros. La atención a la zona de los ojos se registró mediante un rastreador ocular. De los participantes expuestos, 52 habían sido diagnosticados con TEPT (TEPT+) y 51 no habían desarrollado TEPT (TEPT-). Resultados: Los participantes con TEPT+ miraron los ojos tristes durante un tiempo significativamente menor que los individuos con TEPT- y los no expuestos. Este efecto se correlacionó negativamente con la intensidad de los síntomas de evitación. No se encontraron diferencias para las caras neutras y felices Conclusiones: Estos hallazgos sugieren que la evitación desadaptativa en el TEPT se extiende al procesamiento social, en cuanto al contacto visual y las emociones de los demás que no están relacionadas con el trauma. Las nuevas direcciones terapéuticas podrían incluir centrarse en los déficits sociocognitivos. Nuestros hallazgos abren vías nuevas e indirectas para superar las conductas de evitación desadaptativas mediante la remediación del procesamiento ocular.

When affect overlaps with concept: emotion recognition in semantic variant of primary progressive aphasia.

The most recent theories of emotions have postulated that their expression and recognition depend on acquired conceptual knowledge. In other words, the conceptual knowledge derived from prior experiences guide our ability to make sense of such emotions. However, clear evidence is still lacking to contradict more traditional theories, considering emotions as innate, distinct and universal physiological states. In addition, whether valence processing (i.e. recognition of the pleasant/unpleasant character of emotions) also relies on semantic knowledge is yet to be determined. To investigate the contribution of semantic knowledge to facial emotion recognition and valence processing, we conducted a behavioural and neuroimaging study in 20 controls and 16 patients with the semantic variant of primary progressive aphasia, a neurodegenerative disease that is prototypical of semantic memory impairment, and in which an emotion recognition deficit has already been described. We assessed participants' knowledge of emotion concepts and recognition of 10 basic (e.g. anger) or self-conscious (e.g. embarrassment) facial emotional expressions presented both statically (images) and dynamically (videos). All participants also underwent a brain MRI. Group comparisons revealed deficits in both emotion concept knowledge and emotion recognition in patients, independently of type of emotion and presentation. These measures were significantly correlated with each other in patients and with semantic fluency in patients and controls. Neuroimaging analyses showed that both emotion recognition and emotion conceptual knowledge were correlated with reduced grey matter density in similar areas within frontal ventral, temporal, insular and striatal regions, together with white fibre degeneration in tracts connecting frontal regions with each other as well as with temporal regions. We then performed a qualitative analysis of responses made during the facial emotion recognition task, by delineating valence errors (when one emotion was mistaken for another of a different valence), from other errors made during the emotion recognition test. We found that patients made more valence errors. The number of valence errors correlated with emotion conceptual knowledge as well as with reduced grey matter volume in brain regions already retrieved to correlate with this score. Specificity analyses allowed us to conclude that this cognitive relationship and anatomical overlap were not mediated by a general effect of disease severity. Our findings suggest that semantic knowledge guides the recognition of emotions and is also involved in valence processing. Our study supports a constructionist view of emotion recognition and valence processing, and could help to refine current theories on the interweaving of semantic knowledge and emotion processing.

Influence of emotional complexity on the neural substrates of affective theory of mind.

Affective theory of mind (ToM) depends on both the decoding of emotional expressions and the reasoning on emotional mental states from social situations. While previous studies characterized the neural substrates underlying these processes, it remains unclear whether the nature of the emotional state inferred from others can influence the brain activation associated with affective ToM. In the present study, we focused on two types of emotions: basic emotions (BEs) (e.g., anger and surprise), which are innate and universal and self-conscious emotions (e.g., pride and embarrassment), which correspond to a special class of emotions involving the self and including a representation of one's relative reactions to internal and external standards. Specifically, we used an ecological functional MRI paradigm, on 21 healthy young subjects, to compare brain activations during the decoding of and the reasoning on others' self-conscious, basic and neutral mental states. Our results showed that compared to neutral states, the inference of self-conscious and basic emotional states from others elicited more activation in several core regions of affective ToM. Direct comparisons between emotional conditions revealed more activation for self-conscious than BEs in the right temporoparietal junction during the reasoning process and in left middle occipital regions during the decoding process. Further analyses using a localizer task showed that the extrastriate body area was more recruited for decoding others' self-conscious versus BEs, which emphasize the importance of body clues to properly infer these emotions. Using an original task allowing for an ecological assessment of the affective ToM, these results demonstrate that the complexity of the emotion inferred to others can influence the recruitment of ToM network. This study also validates the use of our task as an ecological tool to assess the affective ToM, constituting an avenue for the characterization of ToM impairments in neurological conditions.

Specific cognitive theory of mind and behavioral dysfunctions in early manifest Huntington disease: a case report.

Huntington's disease (HD) is a devastating illness, associated with progressive motor, behavioral and cognitive dysfunctions. However, some studies emphasized that social cognition impairment could occur prior to the onset of these other symptoms. Here, we report the case of a 47 years old patient with early manifest HD, whose complaint was mainly related to the behavioral sphere. He exhibited a significant impairment of Theory of Mind abilities as well as behavioral, and discrete motor symptoms without noticeable cognitive decline. This case study suggests that social cognition impairments and behavioral changes could be in some cases a feature of the disease and may represent a major disability, in early stages of manifest HD.

Neurocognitive determinants of theory of mind across the adult lifespan.

Although theory of mind (ToM) has been extensively explored in aging, few studies have used the same tool to simultaneously assess and compare its cognitive and affective components. When we administered the Movie for Assessment of Social Cognition, a dynamic sequence of social scenes, to 60 healthy participants (20-75 years), we observed no different age-related decreases in both cognitive and affective ToM. While each component was associated with cognitive measures (i.e., episodic memory and processing speed were predictive of cognitive ToM, and recognition of facial emotion expressions and inhibition were predictive of affective ToM), mediation analyses showed that these measures only mediated the effect of age on affective ToM. Voxelwise regressions with grey-matter volume showed that the components partly rely on the same neural substrates, reflecting either ToM per se or other cognitive processes elicited by this multi-determinant task. We discuss the specific substrates of each ToM component, emphasising the importance of considering the impact of other aspects of cognition, present in more ecological situations, on ToM functioning.

Role of context in affective theory of mind in Alzheimer's disease.

Affective theory of mind (ToM) is defined as the ability to deal with affective mental states. Attributing an affective mental state from a facial expression relies mainly on processes that allow information in the environment to be perceived and decoded. Reasoning processes are required when information is not directly available in the environment (e.g., when making an affective mental state attribution in a social situation where there is no visible facial expression of emotion). Although facial emotion decoding deficits have been reported in Alzheimer's disease (AD), few studies have assessed emotional reasoning processes. Long-term social knowledge may also contribute to mental state attribution, given its involvement in social situations, but the links between these two domains have not yet been properly explored. The aim of the present study was therefore to assess both decoding and reasoning processes in AD, as well as the effect of context on emotion attribution (i.e., whether prior presentation of a congruent vs. noncongruent social situation influences emotion recognition from faces). We also aimed to improve current understanding of the relationship between ToM processes and social knowledge. Participants were 20 patients with AD, 20 healthy older individuals, and 20 healthy young individuals. They performed three tasks testing ToM: a context task (emotion attribution in a social situation); a face task (facial emotion recognition); and a context-face task (determining whether the facial emotion was consistent with the emotion inferred from the social situation, e.g., an embarrassing situation followed by a proud face). All participants underwent a neuropsychological battery that included an assessment of social norm knowledge (e.g., determining whether it is socially acceptable to phone in a church). Results showed deficits in the patients with AD for decoding emotions from faces and for reasoning about emotions inferred from a social context. Patients were found to consider contextual information in such a way that congruency either helped or hindered the decoding of stimuli in the environment. As expected, we found that ToM abilities were linked to social norm knowledge. Overall, our findings suggest that patients with AD have difficulty attributing emotional mental states, and deficits in social norm knowledge and the presence of incongruent information may heighten this difficulty.

Distinct neural substrates of affective and cognitive theory of mind impairment in semantic dementia.

Using structural MRI, we investigated the brain substrates of both affective and cognitive theory of mind (ToM) in 19 patients with semantic dementia. We also ran intrinsic connectivity analyses to identify the networks to which the substrates belong and whether they are functionally disturbed in semantic dementia. In line with previous studies, we observed a ToM impairment in patients with semantic dementia even when semantic memory was regressed out. Our results also highlighted different neural bases according to the nature (affective or cognitive) of the representations being inferred. The affective ToM deficit was associated with atrophy in the amygdala, suggesting the involvement of emotion-processing deficits in this impairment. By contrast, cognitive ToM performances were correlated with the volume of medial prefrontal and parietal regions, as well as the right frontal operculum. Intrinsic connectivity analyses revealed decreased functional connectivity, mainly between midline cortical regions and temporal regions. They also showed that left medial temporal regions were functionally isolated, a further possible hindrance to normal social cognitive functioning in semantic dementia. Overall, this study addressed for the first time the neuroanatomical substrates of both cognitive and affective ToM disruption in semantic dementia, highlighting disturbed connectivity within the networks that sustain these abilities.

Social Cognition in the Frontal Variant of Alzheimer's Disease: A Case Study.

Although frontal presentations of Alzheimer's disease (fv-AD) have already been described in the literature, we still know little about patients' social cognitive abilities, especially their theory of mind (ToM). We report the case of FT, a 61-year-old woman who was diagnosed with fv-AD. Two assessments of social cognition, using a false-belief task, the Reading the Mind in the Eyes test, and a task probing knowledge of social norms, were performed one year apart. FT exhibited cognitive ToM and social knowledge deficits from the onset. Affective ToM was initially preserved, but deteriorated as the disease progressed.

Preserved Self-Evaluation in Amnesia Supports Access to the Self through Introspective Computation.

Encounters with new people result in the extraction and storage in memory of both their external features, allowing us to recognize them later, and their internal traits, allowing us to better control our current interactions with them and anticipate our future ones. Just as we extract, encode, store, retrieve and update the representations of others so, too, do we process representations of ourselves. These representations, which rely on declarative memory, may be altered or cease to be accessible in amnesia. Nonetheless, studies of amnesic patients have yielded the surprising observation that memory impairments alone do not prevent patients from making accurate trait self-judgments. In this review article, we discuss prevailing explanations for preserved self-evaluation in amnesia and propose an alternative one, based on the concept of introspective computation. We also consider molecular and anatomical aspects of brain functioning that potentially support introspective computation.

Physiological and Cognitive Effects of Acute Normobaric Hypoxia and Modulations from Oxygen Breathing.

INTRODUCTION: The emergence of normobaric devices for hypoxia awareness training makes crucial the study of physiological and cognitive effects induced by acute normobaric hypoxia (NH) exposure. Our study aimed to 1) investigate the effects of acute NH exposure on physiological variables and working memory; and 2) investigate the physiological and cognitive effects of oxygen breathing before and after acute NH exposure. METHODS: There were 86 healthy men who were randomized into 4 groups: the Normoxia-Air group (N = 23), whose subjects were breathing air; the Hypoxia-Air group (N = 22), where NH exposure was preceded and followed by air breathing; the Normoxia-O2group (N = 21), whose protocol was similar to the Normoxia-Air group, except with the addition of 100% O2breathing periods; and the Hypoxia-O2group (N = 20), whose participants were exposed to 100% O2before and after NH exposure. Working memory was assessed with the Paced Auditory Serial Addition Test. Peripheral oxygen saturation (Spo2), heart rate (HR), and electroencephalogram (EEG) were recorded. RESULTS: Acute NH exposure induced a classical physiological response (i.e., decreased Spo2and increased HR), but not identical to the well-described physiological response to acute hypobaric hypoxia. Acute NH also caused a strong impairment in working memory. Oxygen breathing following NH exposure induced a slowing in the EEG associated with a worsening of working memory performance. DISCUSSION: Acute NH exposure revealed a good surrogate for the classical hypobaric chamber for refresher hypoxia awareness training. Because the association between hypoxia and hyperoxia seems deleterious for the brain, we suggest that NH exposure should be surrounded by air breathing.

Self-reference effect on memory in healthy aging, mild cognitive impairment and Alzheimer's disease: Influence of identity valence.

The self-reference effect (SRE) has been shown to benefit episodic memory in healthy individuals. In healthy aging, its preservation is acknowledged, but in Alzheimer's disease (AD), the jury is still out. Furthermore, there has yet to be a study of the SRE in amnestic mild cognitive impairment (aMCI). As self-reference implies subjective self-representations, and positive information enhance memory performance, we set out to examine the effects of 1) material and 2) identity valence on the SRE across the early stages of AD. Twenty healthy older individuals and 40 patients (20 diagnosed with aMCI and 20 diagnosed with mild AD) performed a memory task. Participants had to judge positive and negative personality trait adjectives with reference to themselves or to another person, or else process these adjectives semantically. We then administered a recognition task. Participants also completed a questionnaire on identity valence. Among healthy older individuals, the SRE benefited episodic memory independently of material and identity valence. By contrast, among aMCI patients, we only observed the SRE when the material was positive. When self-referential material was negative, patients' performance depended on the valence of their self-representations: negative self-representations correlated with poor recognition of negative self-referential adjectives. Finally, performance of patients with mild AD by condition and material valence were too low and inappropriate to be subjected to relevant analyses. The persistence of an SRE for positive adjectives in aMCI suggests the existence of a positivity effect for self-related information, which contributes to wellbeing. The absence of an SRE for negative adjectives, which led aMCI patients to dismiss negative self-related information, could be due to low self-esteem. These results corroborate the mnenic neglect model and point out the importance of the psychoaffective dimension in patients with aMCI, which could constitute a major factor for the preservation of their self-esteem and self-related memory.

An exploration of the semantic network in Alzheimer's disease: Influence of emotion and concreteness of concepts.

Semantic deficits are often reported in even the very early stages of Alzheimer's disease (AD), but investigations usually focus on concrete and non-emotional entities, ignoring the broad range of concepts that feature in everyday conversations. Emotional concepts (e.g., snake) have been found to be processed more accurately than neutral ones (e.g., chair) in AD. Our aim here was therefore to explore the dimensions of both concreteness and emotion within the semantic framework, and in particular to determine whether abstract emotional words (e.g., grief) are processed as accurately as concrete emotional ones (e.g., snake) in AD. We administered a semantic priming (SP) task (lexical decision), yielding an implicit measurement of semantic memory, to 15 patients with AD and 31 normal controls. Concrete and abstract word pairs either shared a semantic relationship (e.g., table-chair, motive-reason), a semantic and emotional relationship (e.g., snake-viper; grief-sadness), or no relationship at all (e.g., pencil-horse). On the basis of response time differences between these conditions, we obtained four SP scores: concrete neutral SP, abstract neutral SP, concrete emotional SP, and abstract emotional SP. In the AD group, the SP score for abstract neutral concepts was not significant, and significantly below the other three SP scores, that seems to reflect a major deterioration in these concepts. An abnormal hyperpriming effect was observed in the concrete neutral SP condition (SP score significantly higher than that of controls), reflecting a partial deterioration in these concepts. These results suggest that, without an emotional relationship, abstract words deteriorate more quickly than concrete words. No such dissociation linked to the concreteness effect was observed with emotional words. Therefore, in AD, emotional concepts would be affected later, be they concrete or abstract.

Neural substrate of cognitive theory of mind impairment in amyotrophic lateral sclerosis.

We now know that amyotrophic lateral sclerosis (ALS) is not restricted to the motor system. Indeed, a large proportion of patients with ALS exhibit cognitive impairment, especially executive dysfunction or language impairment. Although researchers have recently turned their attention to theory of mind (ToM) in ALS, only five studies have been performed so far, and they reported somewhat contradictory results. Moreover, the neural basis of the potential ToM deficit in ALS remains largely unknown. The present study was therefore designed to clarify whether a cognitive ToM deficit is indeed associated with ALS, specify the putative link between cognitive ToM deficits and executive dysfunction in ALS, and identify the dysfunctional brain regions responsible for any social cognition deficits. We investigated cognitive ToM and executive functions in a group of 23 patients with ALS and matched healthy controls, using an original false-belief task and a specially designed battery of executive tasks. We also performed an (18)F-fluorodeoxyglucose positron emission tomography examination. Results confirmed the presence of cognitive ToM deficits in patients compared with controls, and revealed significant correlations between ToM and executive functions, although the cognitive ToM deficit persisted when a composite executive function score was entered as a covariate. Using statistical parametric mapping, we calculated positive correlations between tracer uptake and false-belief scores on a voxel-by-voxel basis in the patient sample. Results showed that the cognitive ToM deficit correlated with the dorsomedial and dorsolateral prefrontal cortices, as well as the supplementary motor area. Our findings provide compelling clinical and imaging evidence for the presence of a genuine cognitive ToM deficit in patients with ALS.

When the zebra loses its stripes but is still in the savannah: results from a semantic priming paradigm in semantic dementia.

Studies using semantic priming paradigms to measure the integrity of the features underlying concepts in semantic dementia (SD) reported differential impairment, in that functional features appeared to be more robust to brain damage than other features, such as perceptual ones. However, these prior studies were single case reports and the inclusion of too many heterogeneous features under the "functional features" heading casts doubts on their apparent preservation. To verify the robustness of functional features compared with perceptual ones, we carried out a group study where we deliberately restricted the exploration of semantic features to two clearly defined types of attribute: visuoperceptual ("visual") versus contextual-functional ("contextual"). We administered an implicit lexical-decision priming task to 8 SD patients and 31 healthy matched controls, at baseline. Four of the patients underwent a follow-up assessment at one year. For controls, we found a significant priming effect in the visual condition, but not in the contextual one, whereas the SD group exhibited the reverse pattern of performances. The follow-up data provided evidence of the robustness of the dissociation between priming performances in the two attribute conditions. The fact that a particular priming effect was observed in the SD patients but not in controls could be regarded as a sign of semantic disequilibrium. Since perceptual features have been shown to be a core determinant of similarity-based/taxonomic relationships, whereas complementary-based/thematic processing relies mainly on contextual relationships, we interpreted our findings in terms of the differential recruitment of one of the two systems of semantic relationships (taxonomic vs. thematic). Moreover, these two distinct and parallel systems have previously been reported to coexist - and compete - in healthy adults. We thus argue that controls automatically drew on similarity-based/taxonomic relationships, leading to a significant priming effect for visual features but not for contextual ones. By contrast, their impaired perceptual features forced the SD patients to resort to the system of thematic relationships.

Working memory impairment in pilots exposed to acute hypobaric hypoxia.

INTRODUCTION: During an acute hypoxia exposure, impairment of memory is one of the most frequently reported symptoms, either during hypoxia awareness training of aircrews or after an in-flight hypoxic incident. However, the effects of acute hypoxia on memory have been little studied in laboratory-controlled conditions. Moreover, none of these studies were performed in hypobaric conditions. The main aim of our study was to investigate the effects of acute hypobaric hypoxia on working memory (WM). This study also aimed to find links between physiological measurements and cognitive performance during acute hypoxia exposure. METHODS: During hypoxia awareness training, 28 subjects (experimental group) were exposed to a simulated altitude level of 10,000 m (31,000 ft) in a hypobaric chamber, while 29 subjects (control group) stayed at sea level. WM was assessed in both groups with the Paced Auditory Serial Addition Test (PASAT). Peripheral oxygen saturation (SpO2) and heart rate were recorded. RESULTS: WM was strongly impaired in the hypoxic group. One major finding is that hypoxia highly increased the mean error frequency rate. WM performance decreased linearly with hypoxemia, but SpO2 was weakly predictive of PASAT performance and vice versa. DISCUSSION: WM is impaired by acute hypobaric hypoxia. Given the importance of WM in aircraft piloting and its sensitivity to hypoxia, the PASAT, in association with SpO2 and EEG recordings, could improve both hypoxia training and our understanding of the effects of hypoxia on memory.

Cognitive and affective Theory of Mind in mild to moderate Alzheimer's disease.

Theory of Mind (ToM) allows one's own and others' cognitive and emotional mental states to be inferred. Although many patients with Alzheimer's disease (AD) display impaired social functioning as their disease progresses, very few studies have investigated ToM in AD. Those that have done so suggest that patients' ToM deficits are the consequence of other cognitive impairments. The aim of this study was thus to investigate changes in both the cognitive and the affective dimensions of ToM in AD, using tasks designed to circumvent the patients' comprehension difficulties. Sixteen mild to moderate AD patients and 15 healthy controls matched on age, sex and education level underwent cognitive (preference judgment and first- and second-order false belief) and affective (Reading the Mind in the Eyes) ToM assessments. Comprehension of false belief stories was verified and an additional neuropsychological examination was undergone. We observed impaired performances by AD patients on all the ToM tasks. While working memory and executive functioning impairments contributed to the deterioration in the more complex aspects of cognitive ToM abilities as highlighted by a correlation analysis, we failed to observe any comprehension difficulties in patients who performed poorly on simple cognitive ToM tasks, which suggests that AD truly affects cognitive ToM.

Theory of mind impairments in patients with semantic dementia.

Semantic dementia is characterized by semantic deficits and behavioural abnormalities that occur in the wake of bilateral inferolateral and predominantly left-sided anterior temporal lobe atrophy. The temporal poles have been shown to be involved in theory of mind, namely the ability to ascribe cognitive and affective mental states to others that regulates social interactions by predicting and interpreting human behaviour. However, very few studies have examined theory of mind in semantic dementia. In this study, we investigated both cognitive and affective theory of mind in a group of patients with semantic dementia, using separate objective and subjective assessment tasks. Results provided objective evidence of an impact of semantic dementia on cognitive and affective theory of mind, consistent with the patients' atrophy in the left temporal lobe and hypometabolism in the temporal lobes and the medial frontal cortex. However, the subjective assessment of theory of mind suggested that awareness of the affective but not cognitive theory of mind deficit persists into the moderate stage of the disease.