Age and the neural network of personal familiarity

Why do mothers never stop grieving for their deceased children? Enduring alterations of brain connectivity and function

A child's death is a profound loss for mothers and affects hundreds of thousands of women. Mothers report inconsolable and progressive grief that is distinct from depression and impacts daily emotions and functions. The brain mechanisms responsible for this relatively common and profound mental health problem are unclear, hampering its clinical recognition and care. In an initial exploration of this condition, we used resting state functional MRI (fMRI) scans to examine functional connectivity in key circuits, and task-based fMRI to examine brain network activity in grieving mothers in response to pictures of their deceased child and as well as recognizable deceased celebrities and unfamiliar individuals. We compared nine mothers who had lost an adult child and aged-matched control mothers with a living child of a similar age. Additionally, we collected diffusion imaging scans to probe structural connectivity and complemented the imaging studies with neuropsychological assessments. Increased functional activation in Ventral Attention/Salience Networks accompanied by a reduced activation in the medial prefrontal cortex in response to the deceased child's picture robustly distinguished the grieving mothers from controls. Heightened resting-state functional connectivity between the paraventricular thalamic nucleus (PVT) and the amygdala distinguished the grieving mothers from the controls and correlated with subjective grief severity. Structurally, maternal grief and its severity were associated with alterations in corticolimbic white matter tracts. Finally, grieving mothers performed worse than controls on neuropsychological tests of learning, memory, and executive function, linked with grief severity. Reduced activation in cortical regions inhibiting emotions and changes in the PVT circuitry-a region involved in long-term emotional memories and decision making under conflict-distinguish grieving mothers from controls. Notably, the magnitude of neurobiological changes correlates with the subjective severity of grief. Together, these new discoveries delineate a prevalent and under-recognized mental health syndrome and chart a path for its appreciation and care.

The Early Start Denver Model Intervention and Mu Rhythm Attenuation in Autism Spectrum Disorders

We examined the relationship between the Early start Denver model (ESDM) intervention and mu rhythm attenuation, an EEG paradigm reflecting neural processes associated with action perception and social information processing. Children were assigned to either receive comprehensive ESDM intervention for two years, or were encouraged to pursue resources in the community. Two years after intervention, EEG was collected during the execution and observation of grasping actions performed by familiar and unfamiliar agents. The ESDM group showed significantly greater attenuation when viewing a parent or caregiver executing a grasping action, compared with an unfamiliar individual executing the same action. Our findings suggest that the ESDM may have a unique impact on neural circuitry underlying social cognition and familiarity.

Recognition of Famous and Unfamiliar Faces among Patients Suffering from Amnesia Mild Cognitive Impairment (AMCI) and Alzheimer's Disease

Objective: Memory assessment for the early diagnosis of cortical dementia is a complicated process which depends on important factors such as facial recognition and naming. These factors could be considered to carry a predictive power to detect neurodegenerative disorders. The present study aimed to study and compare naming or recognizing famous faces with the recognition of newly learned faces among patients with Amnesia Mild Cognitive Impairment (AMCI) and Alzheimer's disease. Method : To collect data, 60 AMCI patients, 62 patients suffering from Alzheimer's disease, and 63 cognitively healthy individuals were assessed using Wechsler Memory Scale-III Faces test (WMS-III faces) and Famous Faces test. Results: The results of one-way ANOVA indicated that the patients suffering from AMCI and Alzheimer's disease scored significantly worse than the control group on naming (p < 0.001), recognition (p < 0.001) section of the Famous Faces test, and immediate or delayed recognition on the WMS-III Faces test (p < 0.001). Also, the obtained results showed that the patients groups received lower scores on WMS-III Faces compared to the Famous Faces test. Conclusion: The results of this study suggested that the unfamiliar and Famous Faces tests allow the quantification of patients' face recognition and name recall abilities which, in turn, makes it possible to make more accurate predictions about cases of dementia. These tests can be used for clinical and research purposes to screen those who may be prone to dementia and need further neuropsychological assessment.

Neural Responses to Faces of Attachment Figures and Unfamiliar Faces: Associations With Organized and Disorganized Attachment Representations

The neural response to faces of attachment figures compared with unfamiliar faces still remains elusive. In particular, the modulation of the neural response by the organized (secure, insecure) compared with disorganized attachment representation of the subject investigated is unknown. For the present study, 38 healthy participants (age range, 21-71 years) were recruited. Three attachment groups (secure, n = 14; insecure, n = 15; disorganized, n = 9) were assessed using the Adult Attachment Projective. The participants were shown pictures of the faces of attachment figures (romantic partner/parents) and unfamiliar faces in a blocked factorial design, using functional magnetic resonance imaging. Showing pictures of attachment figures activated parts of a neural social judgment network, important for inferring others' affective and cognitive mental states (e.g., inferior parietal lobe/superior temporal gyrus) in securely attached healthy individuals. In contrast, disorganized attached individuals with the experience of unresolved attachment trauma in their biography showed deactivations in these areas.

Recognition of personally familiar faces and functional connectivity in Alzheimer's disease

Studies have reported that patients in the severe stages of Alzheimer's disease (AD) experience difficulties recognizing their own faces in recent photographs. Two case reports of late-stage AD showed that this loss of self-face recognition was temporally graded: photographs from the remote past were recognized more easily than more recent photographs. Little is known about the neural correlates of own face recognition abilities in AD patients, while neuroimaging studies in healthy adults have related these abilities to a bilateral fronto-parieto-occipital network. In this study, two behavioral experiments (experiments 1 and 2) and one functional magnetic resonance imaging (fMRI) experiment (second part of experiment 2) were conducted to compare mild AD patients (experiment 1) and moderate AD patients (experiment 2) with healthy older participants in a recognition task involving self and familiar faces from different decades of the participants' life. In moderate AD patients, variable performance allowed us to examine correlations between scores and resting-state fMRI in order to link behavioral data to cerebral activity. At the behavioral level, the results revealed that, in mild AD, self and familiar face recognition was preserved. Moreover, mild AD patients and healthy older participants showed an inverse temporal gradient, with faster recognition of self and familiar recent photographs than self and familiar remote photographs. However, in moderate AD, both self and familiar face recognition were affected. fMRI results showed that the higher the connectivity between the dorsomedial prefrontal cortex (dMPFC) and the right superior frontal gyrus (rSFG), the lower the self and familiar face recognition scores in moderate AD patients. Given that previous studies have related the superior frontal region to control processes rather than face recognition processes, these results might reflect less segregation and more interference between brain networks in AD. In other words, impaired face recognition in AD may be related to functional dedifferentiation of specific brain regions.

Therapy-induced brain reorganization patterns in aphasia

Both hemispheres are engaged in recovery from word production deficits in aphasia. Lexical therapy has been shown to induce brain reorganization even in patients with chronic aphasia. However, the interplay of factors influencing reorganization patterns still remains unresolved. We were especially interested in the relation between lesion site, therapy-induced recovery, and beneficial reorganization patterns. Thus, we applied intensive lexical therapy, which was evaluated with functional magnetic resonance imaging, to 14 chronic patients with aphasic word retrieval deficits. In a group study, we aimed to illuminate brain reorganization of the naming network in comparison with healthy controls. Moreover, we intended to analyse the data with joint independent component analysis to relate lesion sites to therapy-induced brain reorganization, and to correlate resulting components with therapy gain. As a result, we found peri-lesional and contralateral activations basically overlapping with premorbid naming networks observed in healthy subjects. Reduced activation patterns for patients compared to controls before training comprised damaged left hemisphere language areas, right precentral and superior temporal gyrus, as well as left caudate and anterior cingulate cortex. There were decreasing activations of bilateral visuo-cognitive, articulatory, attention, and language areas due to therapy, with stronger decreases for patients in right middle temporal gyrus/superior temporal sulcus, bilateral precuneus as well as left anterior cingulate cortex and caudate. The joint independent component analysis revealed three components indexing lesion subtypes that were associated with patient-specific recovery patterns. Activation decreases (i) of an extended frontal lesion disconnecting language pathways occurred in left inferior frontal gyrus; (ii) of a small frontal lesion were found in bilateral inferior frontal gyrus; and (iii) of a large temporo-parietal lesion occurred in bilateral inferior frontal gyrus and contralateral superior temporal gyrus. All components revealed increases in prefrontal areas. One component was negatively correlated with therapy gain. Therapy was associated exclusively with activation decreases, which could mainly be attributed to higher processing efficiency within the naming network. In our joint independent component analysis, all three lesion patterns disclosed involved deactivation of left inferior frontal gyrus. Moreover, we found evidence for increased demands on control processes. As expected, we saw partly differential reorganization profiles depending on lesion patterns. There was no compensatory deactivation for the large left inferior frontal lesion, with its less advantageous outcome probably being related to its disconnection from crucial language processing pathways.

Associative learning beyond the medial temporal lobe: many actors on the memory stage

Decades of research have established a model that includes the medial temporal lobe, and particularly the hippocampus, as a critical node for episodic memory. Neuroimaging and clinical studies have shown the involvement of additional cortical and subcortical regions. Among these areas, the thalamus, the retrosplenial cortex, and the prefrontal cortices have been consistently related to episodic memory performance. This article provides evidences that these areas are in different forms and degrees critical for human memory function rather than playing only an ancillary role. First we briefly summarize the functional architecture of the medial temporal lobe with respect to recognition memory and recall. We then focus on the clinical and neuroimaging evidence available on thalamo-prefrontal and thalamo-retrosplenial networks. The role of these networks in episodic memory has been considered secondary, partly because disruption of these areas does not always lead to severe impairments; to account for this evidence, we discuss methodological issues related to the investigation of these regions. We propose that these networks contribute differently to recognition memory and recall, and also that the memory stage of their contribution shows specificity to encoding or retrieval in recall tasks. We note that the same mechanisms may be in force when humans perform non-episodic tasks, e.g., semantic retrieval and mental time travel. Functional disturbance of these networks is related to cognitive impairments not only in neurological disorders, but also in psychiatric medical conditions, such as schizophrenia. Finally we discuss possible mechanisms for the contribution of these areas to memory, including regulation of oscillatory rhythms and long-term potentiation. We conclude that integrity of the thalamo-frontal and the thalamo-retrosplenial networks is necessary for the manifold features of episodic memory.

Anterior temporal face patches: a meta-analysis and empirical study

Evidence suggests the anterior temporal lobe (ATL) plays an important role in person identification and memory. In humans, neuroimaging studies of person memory report consistent activations in the ATL to famous and personally familiar faces and studies of patients report resection or damage of the ATL causes an associative prosopagnosia in which face perception is intact but face memory is compromised. In addition, high-resolution fMRI studies of non-human primates and electrophysiological studies of humans also suggest regions of the ventral ATL are sensitive to novel faces. The current study extends previous findings by investigating whether similar subregions in the dorsal, ventral, lateral, or polar aspects of the ATL are sensitive to personally familiar, famous, and novel faces. We present the results of two studies of person memory: a meta-analysis of existing fMRI studies and an empirical fMRI study using optimized imaging parameters. Both studies showed left-lateralized ATL activations to familiar individuals while novel faces activated the right ATL. Activations to famous faces were quite ventral, similar to what has been reported in previous high-resolution fMRI studies of non-human primates. These findings suggest that face memory-sensitive patches in the human ATL are in the ventral/polar ATL.

Social cognition and the anterior temporal lobes: a review and theoretical framework

Memory for people and their relationships, along with memory for social language and social behaviors, constitutes a specific type of semantic memory termed social knowledge. This review focuses on how and where social knowledge is represented in the brain. We propose that portions of the anterior temporal lobe (ATL) play a critical role in representing and retrieving social knowledge. This includes memory about people, their names and biographies and more abstract forms of social memory such as memory for traits and social concepts. This hypothesis is based on the convergence of several lines of research including anatomical findings, lesion evidence from both humans and non-human primates and neuroimaging evidence. Moreover, the ATL is closely interconnected with cortical nuclei of the amygdala and orbitofrontal cortex via the uncinate fasciculus. We propose that this pattern of connectivity underlies the function of the ATL in encoding and storing emotionally tagged knowledge that is used to guide orbitofrontal-based decision processes.

Neural substrates of the self-memory system: new insights from a meta-analysis

The self has been the topic of philosophical inquiry for centuries. Neuropsychological data suggest that the declarative self can be fractionated into three functionally independent systems processing personal information at several levels of abstraction, including episodic memories of one's own life (episodic autobiographical memory, EAM), semantic knowledge of facts about one's own life (semantic autobiographical memory, SAM), and semantic summary representations of one's personal identity (conceptual self, CS). Our proposal here was to present a comprehensive description of the neural networks underpinning self-representations. To this aim, we performed three meta-analyses, one each for EAM, SAM, and CS, using the activation likelihood estimation (ALE) method. We expected a shift from posterior to anterior structures associated with the incrementally increasing level of abstraction of self-representations. The key finding was that EAM predominantly activates posterior and limbic regions including hippocampus. SAM is associated with anterior activations and also posterior and limbic activations in a lesser degree than EAM. CS mainly recruits medial prefrontal structures. Interestingly, medial prefrontal cortex is activated irrespective of the level of abstraction, but a more caudal part is recruited during CS, while SAM and EAM activate more rostral portions. To conclude, in line with the previous proposals, our results corroborate the idea that the declarative self is not monolithic but a multidimensional construct comprising distinct representations at different levels of abstraction.

Visual personal familiarity in amnestic mild cognitive impairment

BACKGROUND

Patients with amnestic mild cognitive impairment are at high risk for developing Alzheimer's disease. Besides episodic memory dysfunction they show deficits in accessing contextual knowledge that further specifies a general concept or helps to identify an object or a person.

METHODOLOGY/PRINCIPAL FINDINGS

Using functional magnetic resonance imaging, we investigated the neural networks associated with the perception of personal familiar faces and places in patients with amnestic mild cognitive impairment and healthy control subjects. Irrespective of stimulus type, patients compared to control subjects showed lower activity in right prefrontal brain regions when perceiving personally familiar versus unfamiliar faces and places. Both groups did not show different neural activity when perceiving faces or places irrespective of familiarity.

CONCLUSIONS/SIGNIFICANCE

Our data highlight changes in a frontal cortical network associated with knowledge-based personal familiarity among patients with amnestic mild cognitive impairment. These changes could contribute to deficits in social cognition and may reduce the patients' ability to transition from basic to complex situations and tasks.