Facial emotion recognition in agenesis of the corpus callosum

Adaptive behavior in primary agenesis of the corpus callosum

BACKGROUND AND AIMS

Primary agenesis of the corpus callosum (ACC) is a congenital neurological disorder characterized by the absence, either partial or complete, of the corpus callosum in individuals who do not have intellectual disability and are otherwise neurologically asymptomatic. While mild to moderate neurocognitive deficits have been observed in individuals with primary ACC using neuropsychological assessments, the impact of this syndrome on adaptive behavior remains insufficiently understood.

METHODS

This study used self- and informant-ratings on the Adaptive Behavior Assessment System, Second Edition (ABAS-II) to evaluate adaptive behavior in 35 adults diagnosed with primary ACC.

RESULTS

While adults with primary ACC reported adaptive functioning comparable to an age-adjusted normative sample, family informants rated their adaptive ability below norms in several skill domains, particularly social skills.

CONCLUSIONS

This pattern of lower ratings by informants than self-ratings suggests adults with ACC may have poor understanding of their own behavior and its consequences. This study demonstrates that informants observe significant deficiencies in the conceptual, social, and practical aspects of adaptive behavior in persons with primary ACC, and that these deficiencies are not seen as clearly by the persons themselves.

Rodent Models for ASD Biomarker Development

Advances in molecular biology and genetics are increasingly revealing the complex etiology of autism spectrum disorder (ASD). In parallel, a number of biochemical, anatomical, and electrophysiological measures are emerging as potential disease-relevant biomarkers that could inform the diagnosis and clinical management of ASD. Rodent ASD models play a key role in ASD research as essential experimental tools. Nevertheless, there are challenges and limitations to the validity and translational value of rodent models, including genetic relevance and cognitive performance differences between humans and rodents. In this chapter, we begin with a brief history of autism research, followed by prominent examples of disease-relevant mouse models enabled by current knowledge of genetics, molecular biology, and bioinformatics. These ASD-associated rodent models enable quantifiable biomarker development. Finally, we discuss the prospects of ASD biomarker development.

Larger corpus callosum volume is favorable for theory of mind development in healthy children

While previous research has demonstrated a link between the corpus callosum (CC) and theory of mind (ToM) abilities in individuals with corpus callosum agenesis (ACC), the relationship between CC volume and ToM remains unclear in healthy children. The present study examined whether CC volume influences children's performance on ToM tasks that assess their understanding of pretense, emotion recognition, and false beliefs. Forty children aged 6-12 years underwent structural magnetic resonance imaging (MRI) and a cognitive test battery. We found that larger mid-anterior and central subsections of the CC significantly correlated with better ToM abilities. We could also demonstrate age- and sex-related effects, as the CC-ToM relationship differed between younger (6-8 years) and older (9-12 years) children, and between female and male participants. Importantly, the older children drove the association between the CC mid-anterior and central subsection volumes and ToM abilities. This study is the first to demonstrate that CC size is associated with ToM abilities in healthy children, underlining the idea that the CC plays a vital role in their socio-cognitive development. CC subsection volumes may thus not only serve as a measure of heterogeneity in neurodevelopmental populations known to exhibit socio-cognitive deficits, but also in typically developing children.

Neural correlates of successful emotion recognition in healthy elderly: a multimodal imaging study

The ageing process is associated with reduced emotional recognition (ER) performance. The ER ability is an essential part of non-verbal communication, and its role is crucial for proper social functioning. Here, using the 'Cambridge Centre for Ageing and Neuroscience cohort sample', we investigated when ER, measured using a facial emotion recognition test, begins to consistently decrease along the lifespan. Moreover, using structural and functional MRI data, we identified the neural correlates associated with ER maintenance in the age groups showing early signs of ER decline (N = 283; age range: 58-89 years). The ER performance was positively correlated with greater volume in the superior parietal lobule, higher white matter integrity in the corpus callosum and greater functional connectivity in the mid-cingulate area. Our results suggest that higher ER accuracy in older people is associated with preserved gray and white matter volumes in cognitive or interconnecting areas, subserving brain regions directly involved in emotional processing.

Processing objects of perceptual expertise: Differential interhemispheric transmission efficiency but similar transmission direction advantages

Faces and Chinese characters are both objects of perceptual expertise. In this study, we investigated the characteristics of interhemispheric transmission times (IHTTs) in both transmission direction and transmission efficiency during the processing of objects of perceptual expertise. A total of 112 participants engaged in a divided visual field paradigm for faces, Chinese characters, and houses in both upright and inverted orientations. The N170 amplitudes elicited by the objects of perceptual expertise (faces and Chinese characters) involved in this study were larger than those elicited by the non-perceptual expertise objects (houses). We used the latencies of the N170 component of the event-related potential (ERP) recorded in the left and right hemispheres to calculate the IHTTs. For all objects, the N170-related IHTTs from the right to the left hemispheres were shorter than those in the opposite direction. Essentially, the N170-related IHTTs for faces were shorter, that is, more efficient than those for Chinese characters and houses. This result indicates that the IHTTs during perceptual expertise and non-perceptual expertise object processing share a common transmission direction advantage, but transmission efficiency is face-specific.

Corpus callosum structural characteristics in very preterm children and adolescents: Developmental trajectory and relationship to cognitive functioning

Previous studies suggest that structural alteration of the corpus callosum, i.e., the largest white matter commissural pathway, occurs after a preterm birth in the neonatal period and lasts across development. The present study aims to unravel corpus callosum structural characteristics across childhood and adolescence in very preterm (VPT) individuals, and their associations with general intellectual, executive and socio-emotional functioning. Neuropsychological assessments, T1-weighted and multi-shell diffusion MRI were collected in 79 VPT and 46 full term controls aged 6-14 years. Volumetric, diffusion tensor and neurite orientation dispersion and density imaging (NODDI) measures were extracted on 7 callosal portions using TractSeg. A multivariate data-driven approach (partial least squares correlation) and a cohort-based age normative modelling approach were used to explore associations between callosal characteristics and neuropsychological outcomes. The VPT and a full-term control groups showed similar trends of white-matter maturation over time, i.e., increase FA and reduced ODI, in all callosal segments, that was associated with increase in general intellectual functioning. However, using a cohort-based age-related normative modelling, findings show atypical pattern of callosal development in the VPT group, with reduced callosal maturation over time that was associated with poorer general intellectual and working memory functioning, as well as with lower gestational age.

Hydrocephalus: A neuropsychological and theoretical primer

Hydrocephalus is a common neurological condition, the hallmark feature of which is an excess in production, or accumulation, of cerebrospinal fluid in the ventricles. Although it is associated with diffuse damage to paraventricular brain areas, patients are broadly typified by a particular pattern of cognitive impairments that include deficits in working memory, attention, and spatial abilities. There have, however, been relatively few neuropsychological accounts of the condition. Moreover, theories of the relationship between aetiology and impairment appear to have emerged in isolation of each other, and proffer fundamentally different accounts. In this primer, we aim to provide a comprehensive and contemporary overview of hydrocephalus for the neuropsychologist, covering cognitive sequelae and theoretical interpretations of their origins. We review clinical and neuropsychological assays of cognitive profiles, along with the few studies that have addressed more integrative behaviours. In particular, we explore the distinction between congenital or early-onset hydrocephalus with a normal-pressure variant that can be acquired later in life. The relationship between these two populations is a singularly interesting one in neuropsychology since it can allow for the examination of typical and atypical developmental trajectories, and their interaction with chronic and acute impairment, within the same broad neurological condition. We reflect on the ramifications of this for our subject and suggest avenues for future research.

Mirror movements and callosal dysgenesis in a family with a DCC mutation: Neuropsychological and neuroimaging outcomes

Corpus callosum dysgenesis is a congenital abnormality whereby the corpus callosum fails to develop normally, and has been associated with a range of neuropsychological outcomes. One specific finding in some individuals with corpus callosum dysgenesis is "congenital mirror movement disorder", which is the presence of involuntary movements on one side of the body that mimic voluntary movements of the other side. Mirror movements have also been associated with mutations in the deleted in colorectal carcinoma (DCC) gene. The current study aims to comprehensively document the neuropsychological outcomes and neuroanatomical mapping of a family (a mother, daughter and son) with known DCC mutations. All three family members experience mirror movements, and the son additionally has partial agenesis of the corpus callosum (pACC). All family members underwent extensive neuropsychological testing, spanning general intellectual functioning, memory, language, literacy, numeracy, psychomotor speed, visuospatial perception, praxis and motor functioning, executive functioning, attention, verbal/nonverbal fluency, and social cognition. The mother and daughter had impaired memory for faces, and reduced spontaneous speech, and the daughter demonstrated scattered impairments in attention and executive functioning, but their neuropsychological abilities were largely within normal limits. By contrast, the son showed areas of significant impairment across multiple domains including reduced psychomotor speed, fine motor dexterity and general intellectual functioning, and he was profoundly impaired across areas of executive functioning and attention. Reductions in his verbal/non-verbal fluency, with relatively intact core language, resembled dynamic frontal aphasia. His relative strengths included aspects of memory and he demonstrated largely sound theory of mind. Neuroimaging revealed an asymmetric sigmoid bundle in the son, connecting, via the callosal remnant, the left frontal cortex with contralateral parieto-occipital cortex. Overall, this study documents a range of neuropsychological and neuroanatomical outcomes within one family with DCC mutations and mirror movements, including one with more severe consequences and pACC.

Social anxiety disorder in an adolescent with agenesis of the corpus callosum: a case report

BACKGROUND

The agenesis of corpus callosum (ACC) could impair the connectivity of the hemispheres of the cerebral cortex and cause cognitive impairments, social and behavioral issues, and even psychiatric disorders. Although social deficits are common in ACC patients, it is rare for a social anxiety disorder to occur.

CASE PRESENTATION

To report a 17-year-old adolescent with complete ACC associated with social anxiety disorder, depression, impulsive behavior, and other neurodevelopmental defects such as intellectual disabilities. His avoidance and fear were improved after treatment with sertraline.

CONCLUSIONS

This is the first report of social anxiety disorder in ACC patients. The possible relationship between brain structural abnormities and anxiety syndrome should be investigated in more studies.

Interhemispheric Brain Communication and the Evolution of Turn-Taking in Mammals

In the last 20 years, research on turn-taking and duetting has flourished in at least three, historically separate disciplines: animal behavior, language sciences, and music cognition. While different in scope and methods, all three ultimately share one goal—namely the understanding of timed interactions among conspecifics. In this perspective, we aim at connecting turn-taking and duetting across species from a neural perspective. While we are still far from a defined neuroethology of turn-taking, we argue that the human neuroscience of turn-taking and duetting can inform animal bioacoustics. For this, we focus on a particular concept, interhemispheric connectivity, and its main white-matter substrate, the corpus callosum. We provide an overview of the role of corpus callosum in human neuroscience and interactive music and speech. We hypothesize its mechanistic connection to turn-taking and duetting in our species, and a potential translational link to mammalian research. We conclude by illustrating empirical venues for neuroethological research of turn-taking and duetting in mammals.

Neuropsychological functions in a pediatric case of partial agenesis of the corpus callosum: Clinical implications

The corpus callosum (CC) is involved in several cognitive processes and the interhemispheric transfer of information. The current case study investigated neurocognitive and emotional processes in a 7-year-old female with partial agenesis of the corpus callosum, with an absent splenium and posterior body, with comorbid autism and ADHD. We measured cognitive functions, such as response inhibition, error monitoring, attentional disengagement, and attention capture by irrelevant emotional stimuli. We found that response inhibition was intact in the case. When happy faces were used as stop-signals, it interfered with response inhibition compared to angry-face-stop-signals. Similarly, happy faces (relative to angry faces) interfered with error monitoring; irrelevant angry faces captured attention more than happy faces. Attentional disengagement functions were impaired in the case compared to healthy controls. The findings give an insight into the interaction between cognition and emotion in pediatric partial agenesis of the CC, and have important clinical and theoretical implications.

Everyday Executive Function and Self-Awareness in Agenesis of the Corpus Callosum

OBJECTIVE

Agenesis of the corpus callosum (AgCC) is associated with a range of cognitive deficits, including mild to moderate problems in higher order executive functions evident in neuropsychological assessments. Previous research has also suggested a lack of self-awareness in persons with AgCC.

METHOD

We investigated daily executive functioning and self-awareness in 36 individuals with AgCC by analyzing self-ratings on the Behavior Rating Inventory of Executive Function-Adult Version (BRIEF-A), as well as ratings on the same instrument from close relatives. Discrepancies between self- and informant-ratings were compared to the normative sample and exploratory analyses examined possible moderating effects of participant and informant characteristics.

RESULTS

Significant deficiencies were found in the Behavioral Regulation and Metacognitive indices for both the self and informant results, with elevated frequency of metacognition scores in the borderline to clinical range. Informants also endorsed elevated frequency of borderline to clinically significant behavioral regulation scores. The proportion of AgCC participants whose self-ratings indicated less metacognitive impairment than informant-ratings was greater than in the normative sample. Self-ratings of behavioral regulation impairment decreased with age and informant-ratings of metacognition were higher in males than females.

CONCLUSIONS

These findings provide evidence that individuals with AgCC experience mild to moderate executive functioning problems in everyday behavior which are observed by others. Results also suggest a lack of self-understanding or insight into the severity of these problems in the individuals with AgCC, particularly with respect to their metacognitive functioning.

Interference of commissural connections through the genu of the corpus callosum specifically impairs sensorimotor gating

White matter abnormalities in schizophrenic patients are characterized as regional tract-specific. Myelin loss at the genu of the corpus callosum (GCC) is one of the most consistent findings in schizophrenic patients across the different populations. We characterized the axons that pass through the GCC by stereotactically injecting an anterograde axonal tracing viral vector into the forceps minor of the corpus callosum in one hemisphere, and identified the homotopic brain structures that have commissural connections in the two hemispheres of the prefrontal cortex, including the anterior cingulate area, the prelimbic area, the secondary motor area, and the dorsal part of the agranular insular area, along with commissural connections with the primary motor area, caudoputamen, and claustrum. To investigate whether dysmyelination in these commissural connections is critical for the development of schizophrenia symptoms, we generated a mouse model with focal demyelination at the GCC by stereotactically injecting demyelinating agent lysolecithin into this site, and tested these mice in a battery of behavioral tasks that are used to model the schizophrenia-like symptom domains. We found that demyelination at the GCC influenced neither the social interest or mood state, nor the locomotive activity or motor coordination. Nevertheless, it specifically reduced the prepulse inhibition of acoustic startle that is a well-known measure of sensorimotor gating. This study advances our understanding of the pathophysiological contributions of the GCC-specific white matter lesion to the related disease, and demonstrates an indispensable role of interhemispheric communication between the frontal cortices for the top-down regulation of the sensorimotor gating.

Alexithymia and Somatization in Agenesis of the Corpus Callosum

Deficient communication between the cerebral hemispheres is one of several prevailing neurobiological explanations for alexithymia and has been strongly supported by research on patients with commissurotomy. We examined self-reported symptoms of alexithymia in adults with agenesis of the corpus callosum (AgCC), a condition characterized by more subtle reductions in interhemispheric transfer than in commissurotomy. 16 adults with AgCC and FSIQ > 80 were compared with 15 age- and IQ-matched neurotypical controls. The AgCC group endorsed greater difficulty identifying and describing feelings and more vague physical symptoms than controls, but similar levels of emotional experience and emotional coping. This finding of impaired emotional interpretation with intact emotional experience is consistent with findings in callosotomy patients, implicating the critical role of the corpus callosum in cognitive dimensions of emotion processing. Further study of alexithymia in AgCC using task-based measures may help clarify the nature of this relationship.

Case Report: Theory of Mind and Figurative Language in a Child With Agenesis of the Corpus Callosum

In this case report, we studied Theory of Mind (ToM) and figurative language comprehension in a 7.2-year-old child, conventionally named RJ, with isolated and complete agenesis of the corpus callosum (ACC), a rare malformation due to the absence of the corpus callosum, the major tract connecting the two brain hemispheres. To study ToM, which is the capability to infer the other’s mental states, we used the classical false belief tasks, and to study figurative language, i.e., those linguistic usages involving non-literal meanings, we used tasks assessing metaphor and idiom comprehension. RJ’s intellectual level and his phonological, lexical, and grammatical abilities were all adequate. In both the ToM false belief tasks and novel sensory metaphor comprehension, RJ showed a delay of 3 years and a significant gap compared to a typically developing control group, while in idioms, his performance was at the border of average. These outcomes suggest that RJ has a specific pragmatic difficulty in all tasks where he must interpret the other’s communicative intention, as in ToM tasks and novel sensory metaphor comprehension. The outcomes also open up interesting insights into the relationships between ToM and figurative language in children with isolated and complete ACC.

Cortical lateralization of cheirosensory processing in callosal dysgenesis

The paradoxical absence of a split-brain syndrome in most cases of callosal dysgenesis has originated three main hypotheses, namely, (i) bilateral cortical representation of language, (ii) bilateral thalamocortical projections of somatosensory pathways conveyed by the spinothalamic-medial lemniscus system, and (iii) a variable combination of (i) and (ii). We used functional neuroimaging to investigate the cortical representation and lateralization of somatosensory information from the palm of each hand in six cases of callosal dysgenesis (hypothesis [ii]). Cortical regions of interest were contralateral and ipsilateral S1 (areas 3a and 3b, 1 and 2 in the central sulcus and postcentral gyrus) and S2 (parts of areas 40 and 43 in the parietal operculum). The degree of cortical asymmetry was expressed by a laterality index (LI), which may assume values from −1 (fully left-lateralized) to +1 (fully right-lateralized). In callosal dysgenesis, LI values for the right and the left hands were, respectively, −1 and + 1 for both S1 and S2, indicating absence of engagement of ipsilateral S1 and S2. In controls, LI values were − 0.70 (S1) and − 0.51 (S2) for right hand stimulation, and 0.82 (S1) and 0.36 (S2) for left hand stimulation, reflecting bilateral asymmetric activations, which were significantly higher in the hemisphere contralateral to the stimulated hand. Therefore, none of the main hypotheses so far entertained to account for the callosal dysgenesis-split-brain paradox have succeeded. We conclude that the preserved interhemispheric transfer of somatosensory tactile information in callosal dysgenesis must be mediated by a fourth alternative, such as aberrant interhemispheric bundles, reorganization of subcortical commissures, or both.

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We studied the cortical sensory representation of the hands in callosal dysgenesis.

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The representation of the hands was bilateral but asymmetric in controls.

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The representation of the hands was strictly contralateral in callosal dysgenesis.

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The representation of the hands is a distinguishing feature of callosal dysgenesis.

The Neuropsychological Syndrome of Agenesis of the Corpus Callosum

BACKGROUND

Agenesis of the corpus callosum (AgCC) involves congenital absence of all or part of the corpus callosum. Because the disorder can only be firmly diagnosed via neuroradiology, it has a short research history, and only recently has the cognitive syndrome become clear.

PURPOSE

Our purpose is to review the primary deficits in AgCC that constitute the core syndrome.

CONCLUSIONS

The cores syndrome includes: (1) reduced interhemispheric transfer of sensory-motor information; (2) reduced cognitive processing speed; and (3) deficits in complex reasoning and novel problem-solving. These domains do not appear to reflect different neuroanatomical abnormalities, but rather different domains of expression of reduced interhemispheric communication from callosal absence.

IMPLICATIONS

These core deficits are expressed across various domains of cognitive, behavioral, and social functioning. The impact of these deficits varies across development and may be moderated by individual factors such as co-occurrence of other neurodevelopmental conditions, general intellectual capacity, and environmental support. (JINS, 2019, 25, 324-330).

Awareness of consequences in agenesis of the corpus callosum: Semantic analysis of responses

OBJECTIVE

Agenesis of the corpus callosum (AgCC) in individuals with general intelligence within the normal range results in a syndrome of mild to moderate deficiencies in cognitive, emotional, and social functioning that are still being explored. Anecdotal accounts from families suggest that these cognitive and psychosocial deficiencies affect the ability of these individuals to anticipate the consequences of their decisions and behaviors. This research was designed to clarify the nature of social and emotional cognition in AgCC with respect to imagination of the consequences of decisions by assessing responses from the Awareness of Consequences Scale (AOCS).

METHOD

Verbal AOCS responses from persons with AgCC and age and IQ-matched neurotypical controls were scored in the normal manner, and also subjected to semantic analyses using both latent semantic analysis and Linguistic Inquiry and Word Count.

RESULTS

It was found that, relative to neurotypical controls, individuals with AgCC scored significantly lower on the typical scoring of the AOCS, had nontypical semantic content in their responses, and used fewer emotion and cognitive content (insight) words. These results were apparent in responses to the three most complex of the AOCS scenarios.

CONCLUSIONS

Results were consistent with the hypothesis that persons with AgCC are deficient in the capacity to imagine the emotional and cognitive consequences of potential actions on others. particularly in the face of greater situational and social complexity. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Understanding facial expressivity in autism spectrum disorder: An inside out review of the biological basis and clinical implications

Deficits in decoding and understanding facially expressed emotions occur commonly in persons with autism spectrum disorder (ASD), which contribute to the impairment of social communication that serves as one of its core diagnostic criteria. Research suggests that abnormalities of visual scanning of the face, activation of key nodes within the "social brain" by facially expressed emotions, functional connectivity within and between nodes of the "social brain", and transduction of specific neurotransmitter/neuromodulatory signals contribute to the pathogenesis of these deficits in at least some persons with ASD. Importantly, the etiologies of these deficits are heterogeneous and include genetic, immunologic, and inflammatory mechanisms, as well as in utero exposures to drugs and toxins. The manifestation and severity of these deficits can also be influenced by developmental age, IQ and genetic background. Consistent with the goals of the Special Issue, the current Review is intended to familiarize the readership with several of the leading neurobiological mechanisms proposed to underlie these deficits in decoding facially expressed emotions and stimulate interest in translational preclinical and clinical investigations, whose ultimate purpose is to attenuate their severity and, thereby, improve functional outcomes of persons with ASD.

MAP1B mutations cause intellectual disability and extensive white matter deficit

Discovery of coding variants in genes that confer risk of neurodevelopmental disorders is an important step towards understanding the pathophysiology of these disorders. Whole-genome sequencing of 31,463 Icelanders uncovers a frameshift variant (E712KfsTer10) in microtubule-associated protein 1B (MAP1B) that associates with ID/low IQ in a large pedigree (genome-wide corrected P = 0.022). Additional stop-gain variants in MAP1B (E1032Ter and R1664Ter) validate the association with ID and IQ. Carriers have 24% less white matter (WM) volume (β = −2.1SD, P = 5.1 × 10⁻⁸), 47% less corpus callosum (CC) volume (β = −2.4SD, P = 5.5 × 10⁻¹⁰) and lower brain-wide fractional anisotropy (P = 6.7 × 10⁻⁴). In summary, we show that loss of MAP1B function affects general cognitive ability through a profound, brain-wide WM deficit with likely disordered or compromised axons.

Intellectual disability (ID) is characterized by an intelligence quotient of below 70 and impaired adaptive skills. Here, analyzing whole genome sequences from 31,463 Icelanders, Walters et al. identify variants in MAP1B associated with ID and extensive brain-wide white matter deficits.

Split-brain patients: Visual biases for faces

Split-brain patients constitute a small subpopulation of epileptic patients who have received the surgical resection of the callosal fibers in an attempt to reduce the spread of epileptic foci between the cerebral hemispheres. The study of callosotomy patients allowed neuropsychologists to investigate the effects of the hemispheric disconnection, shedding more light on the perceptual and cognitive abilities of each hemisphere in isolation. This view that callosotomy completely isolates the hemispheres has now been revised, in favor of the idea of a dynamic functional reorganization of the two sides of the brain; however, the evidence collected from split-brain patients is still a milestone in the neurosciences. The right-hemispheric superiority found in the healthy population concerning face perception has been further supported with split-brains, and it has been shown that the right disconnected hemisphere appears superior to the left hemisphere in recognizing and processing faces with similar characteristics as the observers' (e.g., gender, identity, etc.). Even more controversial is the field of hemispheric asymmetries for processing facial emotion, some evidence suggesting a right-hemispheric superiority for all emotions, some others showing a complementary hemispheric asymmetry depending on the positive or negative emotional valence. Although the practice of callosotomy is mostly abandoned today in favor of pharmacological alternatives, further studies on the remaining split-brain patients could help advance our understanding of hemispheric specialization for social stimuli.

The roots of empathy: Through the lens of rodent models

Empathy is a phenomenon often considered dependent on higher-order emotional control and an ability to relate to the emotional state of others. It is, by many, attributed only to species having well-developed cortical circuits capable of performing such complex tasks. However, over the years, a wealth of data has been accumulated showing that rodents are capable not only of sharing emotional states of their conspecifics, but also of prosocial behavior driven by such shared experiences. The study of rodent empathic behaviors is only now becoming an independent research field. Relevant animal models allow precise manipulation of neural networks, thereby offering insight into the foundations of empathy in the mammalian brains. Here we review the data on empathic behaviors in rat and mouse models, their neurobiological and neurophysiological correlates, and the factors influencing these behaviors. We discuss how simple rodent models of empathy enhance our understanding of how brain controls empathic behaviors.

Altered intra- and interregional synchronization in the absence of the corpus callosum: a resting-state fMRI study

Agenesis of the corpus callosum (AgCC) can result in subtle to severe cognitive deficits. Individuals with impaired cognition often show abnormalities on resting-state functional magnetic resonance imaging (rs-fMRI). This study used rs-fMRI to investigate changes in regional homogeneity (ReHo) and functional connectivity (FC) among individuals with AgCC. AgCC individuals (n = 10) and age-, sex-, and education-matched healthy control subjects (n = 19) were included in this study. The ReHo values were calculated to represent spontaneous brain activity. The regions which showed altered ReHo were selected as seeds to compare FC with the whole brain between the AgCC group and the healthy control group. Compared with healthy control subjects, the AgCC individuals had increased ReHo in the left anterior cingulate gyrus, left rolandic operculum, and right precuneus and decreased ReHo in the right calcarine, right cingual gyrus and right cuneus gyrus. The right calcarine and the right lingual gyrus in the AgCC exhibited decreased FC with bilateral cuneus, superior occipital gyrus, Rolandic operculum, superior temporal gyrus, posterior central gyrus, and midcingulate gyrus.The right cuneus gyrus in the AgCC individuals exhibited decreased FC with the bilateral calcarine gyrus, left cuneus, and left superior occipital gyrus. Our study revealed several subareas within the visual cortex exhibited remarkable abnormalities of spontaneous brain activity and decreased FC with the higher-order cognitive cortex.The abnormalities of ReHo and FC in AgCC individuals may provide new insights into the neurological pathophysiology.

An fMRI study of visual hemifield integration and cerebral lateralization

The human brain integrates hemifield-split visual information via interhemispheric transfer. The degree to which neural circuits involved in this process behave differently during word recognition as compared to object recognition is not known. Evidence from neuroimaging (fMRI) suggests that interhemispheric transfer during word viewing converges in the left hemisphere, in two distinct brain areas, an "occipital word form area" (OWFA) and a more anterior occipitotemporal "visual word form area" (VWFA). We used a novel fMRI half-field repetition technique to test whether or not these areas also integrate nonverbal hemifield-split string stimuli of similar visual complexity. We found that the fMRI responses of both the OWFA and VWFA while viewing nonverbal stimuli were strikingly different than those measured during word viewing, especially with respect to half-stimulus changes restricted to a single hemifield. We conclude that normal reading relies on left-lateralized neural mechanisms, which integrate hemifield-split visual information for words but not for nonverbal stimuli.

Mental State Understanding in Children with Agenesis of the Corpus Callosum

Impaired social functioning is a well-known outcome of individuals with agenesis of the corpus callosum. Social deficits in nonliteral language comprehension, humor, social reasoning, and recognition of facial expression have all been documented in adults with agenesis of the corpus callosum. In the present study, we examined the emotional and mentalizing deficits that contributing to the social-cognitive development in children with isolated corpus callosum agenesia, including emotion recognition, theory of mind, executive function, working memory, and behavioral impairments as assessed by the parents. The study involved children between the age of 6 and 8 years along with typically developing children who were matched by IQ, age, gender, education, and caregiver's education. The findings indicated that children with agenesis of the corpus callosum exhibited mild impairments in all social factors (recognizing emotions, understanding theory of mind), and showed more behavioral problems than control children. Taken together, these findings suggest that reduced callosal connectivity may contribute to the development of higher-order social-cognitive deficits, involving limits of complex and rapidly occurring social information to be processed. The studies of AgCC shed lights of the role of structural connectivity across the hemispheres in neurodevelopmental disorders.

The BTBR mouse model of idiopathic autism - Current view on mechanisms

Autism spectrum disorder (ASD) is the most commonly diagnosed neurodevelopmental disorder, with current estimates of more than 1% of affected children across nations. The patients form a highly heterogeneous group with only the behavioral phenotype in common. The genetic heterogeneity is reflected in a plethora of animal models representing multiple mutations found in families of affected children. Despite many years of scientific effort, for the majority of cases the genetic cause remains elusive. It is therefore crucial to include well-validated models of idiopathic autism in studies searching for potential therapeutic agents. One of these models is the BTBR T⁺Itpr3^tf/J mouse. The current review summarizes data gathered in recent research on potential molecular mechanisms responsible for the autism-like behavioral phenotype of this strain.

Microstructural Correlates of Emotional Attribution Impairment in Non-Demented Patients with Amyotrophic Lateral Sclerosis

Impairments in the ability to recognize and attribute emotional states to others have been described in amyotrophic lateral sclerosis patients and linked to the dysfunction of key nodes of the emotional empathy network. Microstructural correlates of such disorders are still unexplored. We investigated the white-matter substrates of emotional attribution deficits in a sample of amyotrophic lateral sclerosis patients without cognitive decline. Thirteen individuals with either probable or definite amyotrophic lateral sclerosis and 14 healthy controls were enrolled in a Diffusion Tensor Imaging study and administered the Story-based Empathy Task, assessing the ability to attribute mental states to others (i.e., Intention and Emotion attribution conditions). As already reported, a significant global reduction of empathic skills, mainly driven by a failure in Emotion Attribution condition, was found in amyotrophic lateral sclerosis patients compared to healthy subjects. The severity of this deficit was significantly correlated with fractional anisotropy along the forceps minor, genu of corpus callosum, right uncinate and inferior fronto-occipital fasciculi. The involvement of frontal commissural fiber tracts and right ventral associative fronto-limbic pathways is the microstructural hallmark of the impairment of high-order processing of socio-emotional stimuli in amyotrophic lateral sclerosis. These results support the notion of the neurofunctional and neuroanatomical continuum between amyotrophic lateral sclerosis and frontotemporal dementia.

Learning and memory in individuals with agenesis of the corpus callosum

Damage to long white matter pathways in the cerebral cortex is known to affect memory capacity. However, the specific contribution of interhemispheric connectivity in memory functioning is only beginning to become understood. The present study examined verbal and visual memory processing in individuals with agenesis of the corpus callosum (AgCC) using the Wechsler Memory Scale-Third Edition (WMS-III; Wechsler, 1997b). Thirty participants with AgCC (FSIQ >78) were compared against 30 healthy age and IQ matched controls on auditory/verbal (Logical Memory, Verbal Paired Associates) and visual (Visual Reproduction, Faces) memory subtests. Performance was worse in AgCC than controls on immediate and delayed verbal recall for rote word pairs and on delayed recall of faces, as well as on percent recall for these tasks. Immediate recall for thematic information from stories was also worse in AgCC, but groups did not differ on memory for details from narratives or on recall for thematic information following a time delay. Groups also did not differ on memory for abstract figures or immediate recall of faces. On all subtests, individuals with AgCC had greater frequency of clinically significant impairments than predicted by the normal distribution. Results suggest less efficient overall verbal and visual learning and memory with relative weaknesses processing verbal pairs and delayed recall for faces. These findings suggest that the corpus callosum facilitates more efficient learning and recall for both verbal and visual information, that individuals with AgCC may benefit from receiving verbal information within semantic context, and that known deficits in facial processing in individuals with AgCC may contribute to their impairments in recall for faces.

Development of an itemwise efficiency scoring method: Concurrent, convergent, discriminant, and neuroimaging-based predictive validity assessed in a large community sample

Traditional "paper-and-pencil" testing is imprecise in measuring speed and hence limited in assessing performance efficiency, but computerized testing permits precision in measuring itemwise response time. We present a method of scoring performance efficiency (combining information from accuracy and speed) at the item level. Using a community sample of 9,498 youths age 8-21, we calculated item-level efficiency scores on 4 neurocognitive tests, and compared the concurrent, convergent, discriminant, and predictive validity of these scores with simple averaging of standardized speed and accuracy-summed scores. Concurrent validity was measured by the scores' abilities to distinguish men from women and their correlations with age; convergent and discriminant validity were measured by correlations with other scores inside and outside of their neurocognitive domains; predictive validity was measured by correlations with brain volume in regions associated with the specific neurocognitive abilities. Results provide support for the ability of itemwise efficiency scoring to detect signals as strong as those detected by standard efficiency scoring methods. We find no evidence of superior validity of the itemwise scores over traditional scores, but point out several advantages of the former. The itemwise efficiency scoring method shows promise as an alternative to standard efficiency scoring methods, with overall moderate support from tests of 4 different types of validity. This method allows the use of existing item analysis methods and provides the convenient ability to adjust the overall emphasis of accuracy versus speed in the efficiency score, thus adjusting the scoring to the real-world demands the test is aiming to fulfill. (PsycINFO Database Record