Perspective taking to assess self-personality: what's modified in Alzheimer's disease?

Personality and resilience to Alzheimer's disease neuropathology: a prospective autopsy study

Alzheimer's disease (AD) neuropathology is found at autopsy in approximately 30% of cognitively normal older individuals. We examined whether personality traits are associated with such resilience to clinical dementia in individuals with AD neuropathology. Broad factors and specific facets of personality were assessed up to 28 years (mean 11 ± 7 years) before onset of dementia and up to 30 years (mean 15 ± 7 years) before death in a cohort (n = 111) evaluated for AD neuropathology at autopsy. Individuals with higher baseline scores on vulnerability to stress, anxiety, and depression (neuroticism: odds ratio, 2.0; 95% confidence interval, 1.2-3.5), or lower scores on order and competence (conscientiousness: odds ratio, 0.4; 95% confidence interval, 0.2-0.9) were less likely to remain asymptomatic in the presence of AD neuropathology. Neuroticism (r = 0.26), low agreeableness (r = -0.34), and some facets were also significantly associated with advanced stages of neurofibrillary tangles, but the associations between personality traits and risk of clinical dementia were mostly unchanged by controlling for the extent of neurofibrillary tangles and Aβ neuritic plaques. In sum, a resilient personality profile is associated with lower risk or delay of clinical dementia even in persons with AD neuropathology.

My belief or yours? Differential theory of mind deficits in frontotemporal dementia and Alzheimer's disease

Theory of mind reasoning-the ability to understand someone else's mental states, such as beliefs, intentions and desires-is crucial in social interaction. It has been suggested that a theory of mind deficit may account for some of the abnormalities in interpersonal behaviour that characterize patients affected by behavioural variant frontotemporal dementia. However, there are conflicting reports as to whether understanding someone else's mind is a key difference between behavioural variant frontotemporal dementia and other neurodegenerative conditions such as Alzheimer's disease. Literature data on the relationship between theory of mind abilities and executive functions are also contradictory. These disparities may be due to underestimation of the fractionation within theory of mind components. A recent theoretical framework suggests that taking someone else's mental perspective requires two distinct processes: inferring someone else's belief and inhibiting one's own belief, with involvement of the temporoparietal and right frontal cortices, respectively. Therefore, we performed a neuropsychological and neuroimaging study to investigate the hypothesis whereby distinct cognitive deficits could impair theory of mind reasoning in patients with Alzheimer's disease and patients with behavioural variant frontotemporal dementia. We used a three-option false belief task to assess theory of mind components in 11 patients with behavioural variant frontotemporal dementia, 12 patients with Alzheimer's disease and 20 healthy elderly control subjects. The patients with behavioural variant frontotemporal dementia and those with Alzheimer's disease were matched for age, gender, education and global cognitive impairment. [(18)F]-fluorodeoxyglucose-positron emission tomography imaging was used to investigate neural correlates of theory of mind reasoning deficits. Performance in the three-option false belief task revealed differential impairments in the components of theory of mind reasoning; patients with Alzheimer's disease had a predominant deficit in inferring someone else's belief, whereas patients with behavioural variant frontotemporal dementia were selectively impaired in inhibiting their own mental perspective. Moreover, inhibiting one's own perspective was strongly correlated with inhibition in a Stroop task but not with other subprocesses of executive functions. This finding suggests that self-perspective inhibition may depend on cognitive processes that are not specific to the social domain. Last, the severity of the deficit in inferring someone else's beliefs correlated significantly over all subjects with hypometabolism in the left temporoparietal junction, whereas the severity of the deficit in self-perspective inhibition correlated significantly with hypometabolism in the right lateral prefrontal cortex. In conclusion, our findings provided clinical and imaging evidence to support differential deficits in two components of theory of mind reasoning (subserved by distinct brain regions) in patients with Alzheimer's disease and patients with behavioural variant frontotemporal dementia.

On the role of the ventromedial prefrontal cortex in self-processing: the valuation hypothesis

With the development of functional neuroimaging, important progress has been made in identifying the brain regions involved in self-related processing. One of the most consistent findings has been that the ventromedial prefrontal cortex (vMPFC) is activated when people contemplate various aspects of themselves and their life, such their traits, experiences, preferences, abilities, and goals. Recent evidence suggests that this region may not support the act of self-reflection per se, but its precise function in self-processing remains unclear. In this article, I examine the hypothesis that the vMPFC may contribute to assign personal value or significance to self-related contents: stimuli and mental representations that refer or relate to the self tend to be assigned unique value or significance, and the function of the vMPFC may precisely be to evaluate or represent such significance. Although relatively few studies to date have directly tested this hypothesis, several lines of evidence converge to suggest that vMPFC activity during self-processing depends on the personal significance of self-related contents. First, increasing psychological distance from self-representations leads to decreased activation in the vMPFC. Second, the magnitude of vMPFC activation increases linearly with the personal importance attributed to self-representations. Third, the activity of the vMPFC is modulated by individual differences in the interest placed on self-reflection. Finally, the evidence shows that the vMPFC responds to outer aspects of self that have high personal value, such as possessions and close others. By assigning personal value to self-related contents, the vMPFC may play an important role in the construction, stabilization, and modification of self-representations, and ultimately in guiding our choices and decisions.

Age differences in default and reward networks during processing of personally relevant information

We recently found activity in default mode and reward-related regions during self-relevant tasks in young adults. Here we examine the effect of aging on engagement of the default network (DN) and reward network (RN) during these tasks. Previous studies have shown reduced engagement of the DN and reward areas in older adults, but the influence of age on these circuits during self-relevant tasks has not been examined. The tasks involved judging personality traits about one's self or a well known other person. There were no age differences in reaction time on the tasks but older adults had more positive Self and Other judgments, whereas younger adults had more negative judgments. Both groups had increased DN and RN activity during the self-relevant tasks, relative to non-self tasks, but this increase was reduced in older compared to young adults. Functional connectivity of both networks during the tasks was weaker in the older relative to younger adults. Intrinsic functional connectivity, measured at rest, also was weaker in the older adults in the DN, but not in the RN. These results suggest that, in younger adults, the processing of personally relevant information involves robust activation of and functional connectivity within these two networks, in line with current models that emphasize strong links between the self and reward. The finding that older adults had more positive judgments, but weaker engagement and less consistent functional connectivity in these networks, suggests potential brain mechanisms for the "positivity bias" with aging.

Self, memory, and the self-reference effect: an examination of conceptual and methodological issues

The author argues that the self is a multifaceted entity that does not easily submit to clear and precise description. The aspect of self studied by most investigators is actually a subset of the cognitive and neural underpinnings of "self" and not the "self" of first-person subjectivity. The author then looks at the dominant theoretical treatment of human long-term memory-the systems approach-and examines how the construct of "self" is situated in this framework. Finally, he reviews the best-known paradigm for exploring the role of self in memory-the self-reference effect (SRE) manipulation. He argues that there is not one SRE but rather a family of related SREs that are influenced by a variety of variables and contexts. Accordingly, researchers must exercise caution when attempting to draw conclusions about the self from the results of SRE memory performance.

Comparing the neural bases of self-referential processing in typically developing and 22q11.2 adolescents

The investigation of self-reflective processing during adolescence is relevant, as this period is characterized by deep reorganization of the self-concept. It may be the case that an atypical development of brain regions underlying self-reflective processing increases the risk for psychological disorders and impaired social functioning. In this study, we investigated the neural bases of self- and other-related processing in typically developing adolescents and youths with 22q11.2 deletion syndrome (22q11DS), a rare neurogenetic condition associated with difficulties in social interactions and increased risk for schizophrenia. The fMRI paradigm consisted in judging if a series of adjectives applied to the participant himself/herself (self), to his/her best friend or to a fictional character (Harry Potter). In control adolescents, we observed that self- and other-related processing elicited strong activation in cortical midline structures (CMS) when contrasted with a semantic baseline condition. 22q11DS exhibited hypoactivation in the CMS and the striatum during the processing of self-related information when compared to the control group. Finally, the hypoactivation in the anterior cingulate cortex was associated with the severity of prodromal positive symptoms of schizophrenia. The findings are discussed in a developmental framework and in light of their implication for the development of schizophrenia in this at-risk population.

Experimental research on dreaming: state of the art and neuropsychoanalytic perspectives

Dreaming is still a mystery of human cognition, although it has been studied experimentally for more than a century. Experimental psychology first investigated dream content and frequency. The neuroscientific approach to dreaming arose at the end of the 1950s and soon proposed a physiological substrate of dreaming: rapid eye movement sleep. Fifty years later, this hypothesis was challenged because it could not explain all of the characteristics of dream reports. Therefore, the neurophysiological correlates of dreaming are still unclear, and many questions remain unresolved. Do the representations that constitute the dream emerge randomly from the brain, or do they surface according to certain parameters? Is the organization of the dream's representations chaotic or is it determined by rules? Does dreaming have a meaning? What is/are the function(s) of dreaming? Psychoanalysis provides hypotheses to address these questions. Until now, these hypotheses have received minimal attention in cognitive neuroscience, but the recent development of neuropsychoanalysis brings new hopes of interaction between the two fields. Considering the psychoanalytical perspective in cognitive neuroscience would provide new directions and leads for dream research and would help to achieve a comprehensive understanding of dreaming. Notably, several subjective issues at the core of the psychoanalytic approach, such as the concept of personal meaning, the concept of unconscious episodic memory and the subject's history, are not addressed or considered in cognitive neuroscience. This paper argues that the focus on singularity and personal meaning in psychoanalysis is needed to successfully address these issues in cognitive neuroscience and to progress in the understanding of dreaming and the psyche.

Studying the self in people with dementia: How might we proceed?

The impact of dementia on the self has become the subject of much research over the last few years, mainly due to the implications for support and care for people with dementia. However, there are a number of limitations of this research that make it difficult to integrate the existing evidence and to draw any firm conclusions regarding the persistence of self. This highlights the need for a different approach to studying the self in people with dementia in order to obtain more robust evidence from future studies. This paper attempts to integrate current research using an existing systematic and comprehensive framework of the self, and outlines the advantages and limitations of using such a framework as the basis for future studies.

Lack of awareness of symptoms in people with dementia: the structural and functional basis

OBJECTIVE

To review studies investigating the brain correlates of unawareness of cognitive and behavioural symptoms in people with dementia.

DESIGN

A detailed search of the literature was conducted to include all the peer-reviewed studies published in English aimed at identifying the structural or functional brain correspondents of unawareness in dementia patients. Their results were interpreted in relation to the methodological differences in terms of type of dementia studied, the protocol adopted to measure lack of awareness, the imaging techniques employed, the experimental designs and statistical analyses performed.

RESULTS

Eighteen studies undertaken to explore the functional and structural correlates of unawareness of cognitive symptoms in dementia were identified. Although their results showed a disparate range of brain correlates, they were mainly localized in frontal and temporo-parietal regions.

CONCLUSIONS

Although the anatomical correlates of unawareness of disease in dementia have not yet been exhaustively explored, understanding the correlates of unawareness may also contribute to understand the brain correlates of self-awareness and self-reflection. We discuss the current knowledge base and consider potential future directions for research.

Neural networks involved in self-judgement in young and elderly adults

Recent studies have shown that both young and elderly subjects activate the ventromedial prefrontal cortex (VMPFC) when they make self-referential judgements. However, the VMPFC might interact with different brain regions during self-referencing in the two groups. In this study, based on data from Ruby et al. (2009), we have explored this issue using psychophysiological interaction analyses. Young and elderly participants had to judge adjectives describing personality traits in reference to the self versus a close friend or relative (the other), taking either a first-person or a third-person perspective. The physiological factor was the VMPFC activity observed in all participants during self-judgement, and the psychological factor was the self versus other referential process. The main effect of first-person perspective in both groups revealed that the VMPFC was co-activated with the left parahippocampal gyrus and the precuneus for self versus other judgments. The main effect of age showed a stronger correlation between activity in the VMPFC and the lingual gyrus in young compared to elderly subjects. Finally, in the interaction, the VMPFC was specifically co-activated with the orbitofrontal gyrus and the precentral gyrus when elderly subjects took a first-person perspective for self-judgements. No significant result was observed for the interaction in young subjects. These findings show that, although the VMPFC is engaged by both young and older adults when making self-referential judgements, this brain structure interacts differently with other brain regions as a function of age and perspective. These differences might reflect a tendency by older people to engage in more emotional/social processing than younger adults when making self-referential judgements with a first-person perspective.

Anosognosia for behavioral disturbances in frontotemporal dementia and corticobasal syndrome: A voxel-based morphometry study

BACKGROUND

Patients with syndromes of the frontotemporal dementia spectrum are frequently unaware of their behavioral changes.

METHODS

Seventy patients with a clinical diagnosis of behavioral variant frontotemporal dementia (bv-FTD, n = 27), aphasic variant frontotemporal dementia (a-FTD, n = 12) and corticobasal syndrome (CBS, n = 31) participated in the study. Anosognosia for behavioral disturbances was measured as discrepancy between caregiver's and patient's ratings on the Frontal Systems Behavior Scale for present and premorbid behavioral symptoms. Voxel-based morphometry analysis of MRI data was performed to explore the association between anosognosia and gray matter loss.

RESULTS

Although behavioral symptoms were reported in all the groups, the comparison between present and premorbid anosognosia revealed that bv-FTD patients not only underestimated their present behavioral disturbances compared to their caregivers, but also overestimated their premorbid behavioral disturbances. Across all groups, the degree of anosognosia for present behavioral impairment correlated with gray matter atrophy in a posterior region of the right superior temporal sulcus (adjacent to the temporoparietal junction).

CONCLUSION

These results confirm the role of the right temporoparietal cortex in the genesis of anosognosia and suggest that, in clinical syndromes of the frontotemporal dementia spectrum, anosognosia is associated with the dysfunction of temporoparietal mechanisms of self versus others knowledge.