Research and Publications on Agenesis of the Corpus Callosum
Human Brain and Cognition Laboratory, Travis Research Institute – 2025
Principal Investigators Warren S. Brown Ph.D. and Lynn K. Paul Ph.D
The audio summaries of published articles listed below were generated using Google Notebook AI Podcast Generator in hopes that, by presenting the material in a more accessible format, the research might better serve families affected by Agenesis of the Corpus Callosum. The audio files have been carefully edited for accuracy and clarity. For questions or a copy of an article email [email protected].
General Studies
The Neuropsychological Syndrome of Agenesis of the Corpus Callosum
This paper reviews research illustrating the primary deficits in ACC that constitute a core syndrome, that is: (1) reduced interhemispheric transfer of sensory-motor information; (2) reduced cognitive processing speed; (3) deficits in complex reasoning and novel problem-solving. These core deficits are expressed across various domains of cognitive, behavioral, and social functioning.
Cognitive and Psychosocial Deficits in Agenesis of the Corpus Callosum with Normal Intelligence
Cognitive and psychosocial deficits were studied in two adolescents with ACC. Test results indicated poor performance on tests of reasoning and concept formation, as well as on tests of social insight, proverb interpretation, social logic, self-perception, and interpretation of ambiguous stimuli.
Agenesis of the Corpus Callosum: Genetic, Developmental, and Functional Aspects of Connectivity
An extensive overview of the neurological, genetic, clinical, and research issues in ACC and disorders of the corpus callosum.
Daily Functioning Skills
Social and Behavioral Problems of Children with Agenesis of the Corpus Callosum
Parent observations indicated that younger children with ACC (ages 2–5) primarily had problems with sleep. Older children with ACC (ages 6–11) manifested problems in attention, social function, thought, and somatic complaints. However, they were less impaired than children with autism.
Adaptive Behavior in Primary Agenesis of the Corpus Callosum
This study used self- and informant-ratings on the Adaptive Behavior Assessment System to evaluate adaptive behavior in persons with ACC. While the persons with ACC reported their functioning to be normal, family informants rated their adaptive ability below norms with respect to their conceptual, social, and practical skills.
Daily Executive Function in Agenesis of the Corpus Callosum
Daily behavioral self-modulation and self-awareness were studied in individuals with ACC. Deficiencies were found in their capacity for behavioral regulation and thought monitoring when rated by both themselves and a family observer. Lower observer-ratings than self-ratings suggested reduced self-insight regarding their problems in daily functioning.
Impulsivity, Vigilance and Attention in Agenesis of the Corpus Callosum
This study assessed symptoms of ADHD (inattention, impulsivity, and vigilance) in individuals with ACC. Scores were significantly elevated in older adolescents with ACC for errors of commission and stimulus detectability. These results suggest difficulties in sustained attention in ACC, particularly in maintaining response inhibition and vigilance.
Social Abilities
Social Cognition in Individuals with Agenesis of the Corpus Callosum
Individuals with ACC performed worse than those with a corpus callosum on the Thames Awareness of Social Inference Test, a test involving interpretations of videotaped social vignettes. They were particularly deficient in the recognition of emotions, understanding paradoxical sarcasm, and interpreting textual versus visual social cues.
Social Processing Deficits in Agenesis of the Corpus Callosum: Narratives from the Thematic Apperception Test
Stories told by individuals with ACC to emotionally provocative pictures from the Thematic Apperception Test were found to be impaired in story logic, social understanding, and common content.
Social Cognition in Agenesis of the Corpus Callosum: Computational Linguistic Analysis of the Awareness of Consequences Scale
This research assessed social cognition and the imagination of behavioral consequences in ACC. Individuals with ACC scored significantly low on the Awareness on Consequences Scale. They also used non-typical semantic content in their descriptions of consequences, and used fewer words about emotions and thinking. Thus, persons with ACC are deficient in the capacity to imagine the consequences of potential actions in social contexts.
Appreciation of Social Norms in Agenesis of the Corpus Callosum
On the Social Norms Questionnaire, individuals with ACC scored significantly low in understanding social norms, tending to over-adhere to social norms. Thus, persons with ACC have deficient judgment regarding the nuances of appropriate behaviors in social contexts, applying norms concretely and lacking the ability to integrate context to make more nuanced judgments.
Emotions
Emotional Intelligence in Agenesis of the Corpus Callosum
On a test of emotional intelligence, persons with ACC exhibited greater disparities from norms on tests involving complex cognitive processing of emotions, that is, the strategic understanding of emotional contexts. These findings suggest that a corpus callosum is not essential for experiencing and thinking about basic emotions, but is necessary for cognitive processing of emotions in the context of social interactions.
Facial Emotion Recognition in Agenesis of the Corpus Callosum
We examined recognition of facial emotion and its association with the focus of gaze in persons with ACC. Individuals with ACC exhibited impairments in recognizing emotions—fear and anger, in particular—and these impairments were associated with atypical facial scanning (i.e., lower time spent looking at eyes). These results suggest that ACC contributes to deficits in recognizing emotion in faces due to reduced attention to the eyes of other persons.
Emotional Arousal in Agenesis of the Corpus Callosum
Adults with ACC showed larger variability in ratings of positive or negative emotions in pictures, and insensitivity to the emotion category, especially for negative emotions. Despite lower ratings of arousal, they often showed large skin-conductance responses. Thus, ACC interferes with emotion ratings, despite normal bodily emotional responses.
Alexithymia and Somatization in Agenesis of the Corpus Callosum
Adults with ACC were tested for alexithymia: difficulty talking about one’s emotion. They had higher than normal scores on the Toronto Alexithymia Scale, reporting greater difficulty identifying and describing their feelings. In addition, they reported experiencing more physical symptoms. Thus, ACC contributes to difficulty identifying one’s emotions and to the tendency to somaticize.
Memory
Memory Functioning in Individuals with Agenesis of the Corpus Callosum
This study examined verbal and visual memory processing in individuals with ACC. Immediate and delayed verbal recall were worse in ACC than controls. In visual recall of faces, they were not deficient in immediate recall, but delayed recall was worse. Results suggest that the corpus callosum facilitates more efficient learning and recall for both verbal and visual information.
Verbal Learning and Memory in Agenesis of the Corpus Callosum
This study assessed verbal learning and memory in ACC. Individuals with ACC performed significantly below healthy controls on both short and long delayed free recall and cued recall, as well as on original learning. This suggests that the corpus callosum facilitates the elaboration and encoding of verbal information.
Language
Communicative Deficits in Individuals with Agenesis of the Corpus Callosum: Nonliteral Language and Affective Prosody
In this study, persons with ACC exhibited impairments in understanding nonliteral language, interpreting proverbs, and recognizing emotional prosody. These impairments were similar to patients with right hemisphere brain damage.
Paralinguistic Processing in Children with Callosal Agenesis: Emergence of Neurolinguistic Deficits
Children with ACC were somewhat deficient in comprehension of the precise meaning of literal and nonliteral language expressions. However, children with ACC were not as markedly deficient as adults with ACC, most likely due to incomplete callosal development in children without ACC.
Proverb Comprehension in Individuals with Agenesis of the Corpus Callosum
Proverbs comprehension was impaired in persons with ACC for both the free-response and multiple-choice tasks. The difference between groups in proverb interpretation seemed to be greatest when participants had to generate their own interpretation (free response).
Comprehension of Humor in Primary Agenesis of the Corpus Callosum
Individuals with ACC performed poorly on a test of understanding narrative jokes, but performed more normally on a test of understanding cartoons. The problem in narrative joke comprehension was related to issues in understanding second-order (nonliteral) language meanings.
Elaborative Thinking, Inference, and Creativity
Social Inferences in Agenesis of the Corpus Callosum and Autism: Semantic Analysis and Topic Modeling
This research investigated the ability of adults with ACC or autism to infer social meaning to the interactions of animated triangles. Although scoring by raters indicated that both groups made typical basic inferences, the index of perplexity generated from topic modeling revealed that inferences from individuals with ACC or ASD displayed abnormally low levels of social imagination.
Social Narratives in Agenesis of the Corpus Callosum: Linguistic Analysis of the Thematic Apperception Test
Analysis of the linguistic content of stories told by persons with ACC in response to emotionally provocative pictures from the Thematic Apperception Test revealed fewer words pertaining to emotionality, cognitive processes, and social processes than persons with a corpus callosum. These findings suggest that ACC results in difficulty imagining the mental, emotional, and social functioning of others.
Imaginative Elaboration in Agenesis of the Corpus Callosum: Topic Modeling and Perplexity
Responses of persons with ACC to the emotionally provocative scenes of the Thematic Apperception Test were used to study the capacity for imaginative elaboration and story coherence. The narratives from persons with ACC were coherent but more conventional, involving significantly less imaginative elaboration and social inference.
The Corpus Callosum and Creativity Revisited
This article argued for the critical role of the corpus callosum and hemispheric specialization in creativity. An in-depth discussion of creativity in persons with ACC is presented that strongly supports the critical and unique role of the corpus callosum in creativity.
Problem Solving and Decision-Making
Decision-Making in Agenesis of the Corpus Callosum: Expectancy-Valence in the Iowa Gambling Task
On a test of decision-making and problem-solving, individuals with ACC exhibited higher attention to losses, less consistency in their choice strategy, greater frequency of switching between response options, and were more influenced by recent trials. These results suggest that individuals with ACC had difficulty forming a coherent test strategy.
Verbal Problem Solving in Agenesis of the Corpus Callosum: Analysis Using Semantic Similarity
This study investigated the capacity of persons with ACC to infer the meaning of a nonsense word from sentence context. Semantic similarity to the correct word was significantly lower overall in persons with ACC than in controls, suggesting that persons with ACC are less able to make semantic inferences and have a restricted imagination for semantic possibilities.
Processing Speed Delays Contribute to Executive Function Deficits in Individuals with Agenesis of the Corpus Callosum
Individuals with ACC were impaired in their response speed, but showed little impairment in response inhibition and flexibility. This deficiency is primarily a consequence of slow mental processing speed and a cautious response strategy.
Psychological Functioning
Integration Between Cerebral Hemispheres Contributes to Defense Mechanisms
This study tested the development of defense mechanisms in people with ACC as reflected in responses to Thematic Apperception Test cards. Persons with ACC showed greater denial and less identification. This finding suggests that ACC impacts the development of patterns of psychological defenses.
The Corpus Callosum and Psychosocial Functioning: MMPI-2-RF in Callosal Agenesis
This study examined the MMPI-2-RF profiles of individuals with ACC, finding that they reported issues in social awareness, as well as somatic and cognitive complaints.
Interhemispheric Interactions
Bimanual Motor Coordination in Agenesis of the Corpus Callosum
Persons with ACC were tested on speed and accuracy on a test of two-hand coordination (like an Etch-a-Sketch). They performed slower and less accurately than individuals with a normal corpus callosum.
Spatial Tactile Interhemispheric Transfer and Task Complexity in Agenesis of the Corpus Callosum
Interhemispheric transfer of tactile/spatial information was assessed in persons with ACC. During a task involving transfer of tactile learning, persons with ACC were slower overall and benefited less from transfer of learning from the dominant to the nondominant hand. Likewise, inter-hand transfer of finger touch information was less accurate. Thus, ACC results in reduced interhemispheric transfer of spatial-tactile information.
Bilateral Field Advantage and Evoked Potential Interhemispheric Transmission in Commissurotomy and Callosal Agenesis
In persons with a normal corpus callosum, matching two letters is faster and more accurate when the letters are presented one to each visual field (that is, each hemisphere). This bilateral advantage in visual matching of simple letters was found in ACC but not in persons with a surgically split brain.
Interhemispheric Stroop Effect in Partial and Complete Agenesis of the Corpus Callosum
Color-word and color-patch congruent and incongruent pairs were presented either unilaterally (color-patch and color-word in the same visual field) or bilaterally (patch and word in different visual fields). Similar between-hemisphere interference from word-patch incongruence was found for both ACC and non-ACC groups.
Spatial Attention in Agenesis of the Corpus Callosum: Shifting Attention Between Visual Fields
The capacity to shift spatially focused visual attention between the right and left visual fields was tested in persons with ACC. Individuals with ACC had significantly greater difficulty reorienting visual attention when attention had first been drawn to the opposite visual field.
Interhemispheric Transfer in Normals and Acallosals: Latency Adjusted Evoked Potential Averaging
Demonstrates in persons with ACC an absence of interhemispheric transfer of a visual from one hemisphere to the other. A diminished neural signal was found in the visual cortex opposite to the hemisphere where the signal was originally sensed.
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