Imaginative elaboration in agenesis of the corpus callosum: topic modeling and perplexity.

OBJECTIVE: Previous studies have found deficits in imaginative elaboration and social inference to be associated with agenesis of the corpus callosum (ACC; Renteria-Vasquez et al., 2022; Turk et al., 2009). In the current study, Thematic Apperception Test (TAT) responses from a neurotypical control group and a group of individuals with ACC were used to further study the capacity for imaginative elaboration and story coherence. METHOD: Topic modeling was employed utilizing Latent Diritchlet Allocation to characterize the narrative responses to the pictures used in the TAT. A measure of the difference between models (perplexity) was used to compare the topics of the responses of individual participants to the common core model derived from the responses of the control group. Story coherence was tested using sentence-to-sentence Latent Semantic Analysis. RESULTS: Group differences in perplexity were statistically significant overall, and for each card individually (p < .001). There were no differences between the groups in story coherence. CONCLUSIONS: TAT narratives from persons with ACC were normally coherent, but more conventional (i.e., more similar to the core text) compared to those of neurotypical controls. Individuals with ACC can make conventional social inferences about socially ambiguous stimuli, but are restricted in their imaginative elaborations, resulting in less topical variability (lower perplexity values) compared to neurotypical controls.

Verbal problem-solving in agenesis of the corpus callosum: Analysis using semantic similarity.

OBJECTIVE: Previous studies demonstrated that individuals with agenesis of the corpus callosum (AgCC) experience difficulties in novel and complex problem-solving. The present study investigated verbal problem-solving, deductive reasoning, and semantic inference in AgCC. METHOD: Capacity for semantic inference was tested in 25 individuals with AgCC and normal-range intelligence compared to 29 neurotypical controls. The Word Context Test (WCT) of Delis-Kaplan Executive Function System was used, employing a novel method of analysis (semantic similarity) to detect trial-by-trial progress toward a solution. RESULTS: With respect to the typical WCT scores, persons with AgCC had fewer total consecutive correct responses. In addition, semantic similarity to the correct word was significantly lower overall in persons with AgCC than in controls. CONCLUSION: These findings indicated that individuals with AgCC who have intelligence in the normal range are less able at the WCT taking all trials into account, although they often solve the problem eventually. This outcome is consistent with previous research indicating that callosal absence in AgCC results in a restricted imagination for possibilities, limiting their problem-solving and inferential capacities. The results also highlight the usefulness of semantic similarity as a means of scoring the WCT. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Social Inferences in Agenesis of the Corpus Callosum and Autism: Semantic Analysis and Topic Modeling.

Impoverished capacity for social inference is one of several symptoms that are common to both agenesis of the corpus callosum (AgCC) and Autism Spectrum Disorder (ASD). This research compared the ability of 14 adults with AgCC, 13 high-functioning adults with ASD and 14 neurotypical controls to accurately attribute social meaning to the interactions of animated triangles. Descriptions of the animations were analyzed in three ways: subjective ratings, Linguistic Inquiry and Word Count, and topic modeling (Latent Dirichlet Allocation). Although subjective ratings indicated that all groups made similar inferences from the animations, the index of perplexity (atypicality of topic) generated from topic modeling revealed that inferences from individuals with AgCC or ASD displayed significantly less social imagination than those of controls.

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. Sixteen adults with AgCC and full-scale intelligence quotient >80 were compared with 15 neurotypical controls group-matched for age and intelligence score. 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.

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.

Appreciation of Social Norms in Agenesis of the Corpus Callosum.

OBJECTIVE: Anecdotal reports regarding high-functioning adults with agenesis of the corpus callosum (AgCC) suggest that they often lack psychosocial insight. We attempted to determine whether adults with AgCC are able to correctly identify appropriate behaviors within social contexts using the Social Norms Questionnaire. METHOD: The Social Norms Questionnaire measures knowledge of norms and judgments of what is appropriate to do in particular contexts. It was administered online to individuals with AgCC and control participants. RESULTS: Individuals with AgCC scored significantly lower in understanding social norms than controls, tending to over-adhere to social norms significantly more than controls. There was no significant difference regarding breaking of social norms. CONCLUSION: Results suggest that adults with AgCC have deficient judgment regarding the nuances of appropriate behaviors in social contexts. They adhere to social norms concretely, lacking the ability to integrate context in social scenarios to make appropriately nuanced judgments.

Integration Between Cerebral Hemispheres Contributes to Defense Mechanisms.

Defense mechanisms are mental functions which facilitate coping when real or imagined events challenge personal wishes, needs, and feelings. Whether defense mechanisms have a specific neural basis is unknown. The present research tested the hypothesis that interhemispheric integration plays a critical role in defense mechanism development, by studying a unique sample of patients born without the corpus callosum (agenesis of the corpus callosum; AgCC). Adults with AgCC (N = 27) and matched healthy volunteers (N = 30) were compared on defense mechanism use across increasing levels of developmental maturity (denial, least; projection, intermediate; identification, most). Narratives generated in response to Thematic Apperception Test images were scored according to the Defense Mechanism Manual. Greater use of denial and less identification was found in persons with AgCC, compared to healthy comparisons. This difference emerged after age 18 when full maturation of defenses among healthy individuals was expected. The findings provide clinically important characterization of social and emotional processing in persons with AgCC. More broadly, the results support the hypothesis that functional integration across the hemispheres is important for the development of defense mechanisms.

Attention, impulsivity, and vigilance in agenesis of the corpus callosum.

OBJECTIVE: Questions regarding the role of the corpus callosum in attention are raised by the reports of attention problems in some persons with agenesis of the corpus callosum (AgCC), as well as by abnormalities in callosal size in persons with attention-deficit/hyperactive disorder. The current study assessed inattention, impulsivity, and vigilance in individuals with AgCC. METHOD: These domains of attention were assessed using the Conners' Continuous Performance Test II in 18 older adolescents and adults (ages 16-52) with complete AgCC and normal intelligence (full scale intelligence quotient > 80). Scores were converted to T scores using age-specific norms and assessed for departure from the normative sample. RESULTS: Scores were significantly elevated in older adolescents with AgCC for errors of commission (p = .050, d = 0.55) and detectability (p = .03, d = 0.58). Older adolescents were worse than adults for commissions (p = .06, ηp² = .201) and detectability (p = .03, ηp² = .273). Also, male individuals had significantly higher (worse) scores than did female in vigilance (p = .01, ηp² = .337). CONCLUSION: These results suggest moderate levels of difficulties in sustained attention in AgCC, particularly in maintaining response inhibition and in vigilance, that are modulated by age and sex. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

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).

Emotional Intelligence in Agenesis of the Corpus Callosum.

People with agenesis of the corpus callosum (AgCC) with normal general intelligence have deficits in complex cognitive processing, as well as in social cognition. It is uncertain the extent to which impoverished processing of emotions may contribute to social processing deficiencies. We used the Mayer-Salovey-Caruso Emotional Intelligence Test to clarify the nature of emotional intelligence in 16 adults with AgCC. As hypothesized, persons with AgCC exhibited greater disparities from norms on tests involving more socially complex aspects of emotions. The AgCC group did not differ from norms on the Experiential subscale, but they were significantly below norms on the Strategic subscale. These findings suggest that the corpus callosum is not essential for experiencing and thinking about basic emotions in a "normal" way, but is necessary for more complex processes involving emotions in the context of social interactions.

Proverb comprehension in individuals with agenesis of the corpus callosum.

Comprehension of non-literal language involves multiple neural systems likely involving callosal connections. We describe proverb comprehension impairments in individuals with isolated agenesis of the corpus callosum (AgCC) and normal-range general intelligence. Experiment 1 compared Gorham Proverb Test (Gorham, 1956) performance in 19 adults with AgCC and 33 neurotypical control participants of similar age, sex, and intelligence. Experiment 2 used the Proverbs subtest of the Delis-Kaplan Executive Function System (D-KEFS, 2001) to compare 19 adults with AgCC and 17 control participants with similar age, sex, and intelligence. Gorham Proverbs performance was impaired in the AgCC group for both the free-response and multiple-choice tasks. On the D-KEFS proverbs test, the AgCC group performed significantly worse on the free-response task (and all derivative scores) despite normal levels of performance on the multiple-choice task. Covarying verbal intelligence did not alter these outcomes. However, covarying a measure of non-literal language comprehension considerably reduced group differences in proverb comprehension on the Gorham test, but had little effect on the D-KEFS group differences. The difference between groups seemed to be greatest when participants had to generate their own interpretation (free response), or in the multiple choice format when the test included many proverbs that were likely to be less familiar. Taken together, the results of this study clearly show that proverb comprehension is diminished in individuals with AgCC compared to their peers.

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.

Verbal learning and memory in agenesis of the corpus callosum.

The role of interhemispheric interactions in the encoding, retention, and retrieval of verbal memory can be clarified by assessing individuals with complete or partial agenesis of the corpus callosum (AgCC), but who have normal intelligence. This study assessed verbal learning and memory in AgCC using the California Verbal Learning Test-Second Edition (CVLT-II). Twenty-six individuals with AgCC were compared to 24 matched controls on CVLT-II measures, as well as Donders׳ four CVLT-II factors (i.e., Attention Span, Learning Efficiency, Delayed Memory, and Inaccurate Memory). Individuals with AgCC performed significantly below healthy controls on the Delayed Memory factor, confirmed by significant deficits in short and long delayed free recall and cued recall. They also performed less well in original learning. Deficient performance by individuals with AgCC during learning trials, as well as deficits in all forms of delayed memory, suggest that the corpus callosum facilitates interhemispheric elaboration and encoding of verbal information.

Facial emotion recognition in agenesis of the corpus callosum.

BACKGROUND: Impaired social functioning is a common symptom of individuals with developmental disruptions in callosal connectivity. Among these developmental conditions, agenesis of the corpus callosum provides the most extreme and clearly identifiable example of callosal disconnection. To date, deficits in nonliteral language comprehension, humor, theory of mind, and social reasoning have been documented in agenesis of the corpus callosum. Here, we examined a basic social ability as yet not investigated in this population: recognition of facial emotion and its association with social gaze. METHODS: Nine individuals with callosal agenesis and nine matched controls completed four tasks involving emotional faces: emotion recognition from upright and inverted faces, gender recognition, and passive viewing. Eye-tracking data were collected concurrently on all four tasks and analyzed according to designated facial regions of interest. RESULTS: Individuals with callosal agenesis exhibited impairments in recognizing emotions from upright faces, in particular lower accuracy for fear and anger, and these impairments were directly associated with diminished attention to the eye region. The callosal agenesis group exhibited greater consistency in emotion recognition across conditions (upright vs. inverted), with poorest performance for fear identification in both conditions. The callosal agenesis group also had atypical facial scanning (lower fractional dwell time in the eye region) during gender naming and passive viewing of faces, but they did not differ from controls on gender naming performance. The pattern of results did not differ when taking into account full-scale intelligence quotient or presence of autism spectrum symptoms. CONCLUSIONS: Agenesis of the corpus callosum results in a pattern of atypical facial scanning characterized by diminished attention to the eyes. This pattern suggests that reduced callosal connectivity may contribute to the development and maintenance of emotion processing deficits involving reduced attention to others' eyes.

The role of corpus callosum development in functional connectivity and cognitive processing.

The corpus callosum is hypothesized to play a fundamental role in integrating information and mediating complex behaviors. Here, we demonstrate that lack of normal callosal development can lead to deficits in functional connectivity that are related to impairments in specific cognitive domains. We examined resting-state functional connectivity in individuals with agenesis of the corpus callosum (AgCC) and matched controls using magnetoencephalographic imaging (MEG-I) of coherence in the alpha (8-12 Hz), beta (12-30 Hz) and gamma (30-55 Hz) bands. Global connectivity (GC) was defined as synchronization between a region and the rest of the brain. In AgCC individuals, alpha band GC was significantly reduced in the dorsolateral pre-frontal (DLPFC), posterior parietal (PPC) and parieto-occipital cortices (PO). No significant differences in GC were seen in either the beta or gamma bands. We also explored the hypothesis that, in AgCC, this regional reduction in functional connectivity is explained primarily by a specific reduction in interhemispheric connectivity. However, our data suggest that reduced connectivity in these regions is driven by faulty coupling in both inter- and intrahemispheric connectivity. We also assessed whether the degree of connectivity correlated with behavioral performance, focusing on cognitive measures known to be impaired in AgCC individuals. Neuropsychological measures of verbal processing speed were significantly correlated with resting-state functional connectivity of the left medial and superior temporal lobe in AgCC participants. Connectivity of DLPFC correlated strongly with performance on the Tower of London in the AgCC cohort. These findings indicate that the abnormal callosal development produces salient but selective (alpha band only) resting-state functional connectivity disruptions that correlate with cognitive impairment. Understanding the relationship between impoverished functional connectivity and cognition is a key step in identifying the neural mechanisms of language and executive dysfunction in common neurodevelopmental and psychiatric disorders where disruptions of callosal development are consistently identified.

Decision-making in individuals with agenesis of the corpus callosum: expectancy-valence in the Iowa Gambling Task.

Individuals with agenesis of the corpus callosum (ACC) can have intelligence within the normal range, but nevertheless have deficiencies in decision-making and complex novel problem-solving. The specific nature of these problems is not yet clearly understood. The Iowa Gambling Task was used to test decision-making ability and problem-solving in 40 individuals with complete or partial ACC (full-scale intelligence quotient >80) and 26 control participants. The expectancy-valence (EV) model was applied to the trial-by-trial responses of each participant to elucidate differences in decision processes utilized by each group. The ACC group had a lower overall net gain and fewer advantageous choices than controls, but these differences were not statistically significant. Within the EV model, individuals with ACC exhibited significantly higher attention to losses, less consistency in their choice strategy, and greater frequency of switching between decks. They also showed a tendency to be more influenced by recent trials. This outcome is similar to that seen in individuals with Asperger's disorder. Taken together, these results suggest that individuals with ACC have difficulty in inferring game contingencies and forming a coherent selection strategy, implicating the corpus callosum in these decision processes.

Processing speed delays contribute to executive function deficits in individuals with agenesis of the corpus callosum.

Corpus callosum malformation and dysfunction are increasingly recognized causes of cognitive and behavioral disability. Individuals with agenesis of the corpus callosum (AgCC) offer unique insights regarding the cognitive skills that depend specifically upon callosal connectivity. We examined the impact of AgCC on cognitive inhibition, flexibility, and processing speed using the Color-Word Interference Test (CWIT) and Trail Making Test (TMT) from the Delis-Kaplan Executive Function System. We compared 36 individuals with AgCC and IQs within the normal range to 56 matched controls. The AgCC cohort was impaired on timed measures of inhibition and flexibility; however, group differences on CWIT Inhibition, CWIT Inhibition/Switching and TMT Number-Letter Switching appear to be largely explained by slow performance in basic operations such as color naming and letter sequencing. On CWIT Inhibition/Switching, the AgCC group was found to commit significantly more errors which suggests that slow performance is not secondary to a cautious strategy. Therefore, while individuals with agenesis of the corpus callosum show real deficits on tasks of executive function, this impairment appears to be primarily a consequence of slow cognitive processing. Additional studies are needed to investigate the impact of AgCC on other aspects of higher order cortical function.

Social cognition in individuals with agenesis of the corpus callosum.

Past research has revealed that individuals with agenesis of the corpus callosum (ACC) have deficits in interhemispheric transfer, complex novel problem-solving, and the comprehension of paralinguistic aspects of language. Case studies and family reports also suggest problems in social cognition. The performance of 11 individuals with complete ACC and with normal intelligence was compared to that of 13 IQ- and age-matched controls on three measures of social cognition. Individuals with ACC were indistinguishable from controls on the Happe Theory of Mind Stories and the Adult Faux Pas Test, but performed significantly worse on various portions of the Thames Awareness of Social Inference Test (TASIT) involving interpretations of videotaped social vignettes. Further analysis of the TASIT indicated that individuals with ACC showed deficiency in the recognition of emotion, weakness in understanding paradoxical sarcasm, and particular difficulty interpreting textual versus visual social cues. These results suggest that the tendency for deficient social cognition in individuals with ACC stems from a combination of difficulty integrating information from multiple sources, using paralinguistic cues for emotion, and understanding nonliteral speech. Together, these deficits would contribute to a less robust theory of mind.