Elsevier

Brain and Language

Volume 93, Issue 2, May 2005, Pages 135-139
Brain and Language

Paralinguistic processing in children with callosal agenesis: Emergence of neurolinguistic deficits

https://doi.org/10.1016/j.bandl.2004.09.003Get rights and content

Abstract

Recent research revealed impaired processing of both nonliteral meaning and affective prosody in adults with agenesis of the corpus callosum (ACC) and normal intelligence. Since normal children have incomplete myelination of the corpus callosum, it was hypothesized that paralanguage deficits in children with ACC would be less apparent relative to their peers. The Familiar and Novel Language Comprehension Test (FANL-C) and Prosody Test were given to 18 children with ACC and normal intelligence and 17 controls matched for age (7–13 years), education, and IQ (83–122). When controlling for age, children with ACC were significantly poorer in comprehension of the precise meaning of both literal and nonliteral items on the FANL-C. Adults with ACC had previously been shown to have difficulty only on nonliteral items. The effect size for nonliteral comprehension in children with ACC was smaller than that seen in adults. There was only a trend for the child ACC group to perform worse on the recognition of affective prosody. Thus, while deficits in paralinguistic processing were apparent, children with ACC were not as clearly different from age peers as adults, and were equally deficient at comprehending literal and nonliteral expressions. The differences in results between adults and children with ACC are thought to reflect incomplete callosal development in normal children, and the importance of the corpus callosum in the early stages of the development of the ability to process literal language.

Introduction

The study of children with agenesis of the corpus callosum (ACC) who have normal-range IQs promises to provide insight into the specific role of the corpus callosum in the development of neuropsychological abilities. While many children with ACC are mentally retarded, there exists a large group of individuals with ACC who have normal intelligence and few, if any, other neurological abnormalities or disorders.

The most consistent domain of neuropsychological deficit in individuals who have ACC and normal intelligence seems to be complex novel problem solving (Brown and Paul, 2000, Schieffer et al., 1998). These results lead to the generalization that individuals with ACC have deficits in fluid intelligence, even when crystallized aspects of intelligence are normal.

A few studies have focused on basic language processing in individuals with ACC, with various subtle deficits having been described with respect to phonemic recognition (Temple et al., 1989, Temple et al., 1990) and syntactic processing (Dennis, 1981, Sanders, 1989). However, families of normally intelligent children and adolescents with ACC report that they have marked difficulties with the social and pragmatic aspects of language, but no apparent problems in basic language skills. Thus, development of paralinguistic skills may be more susceptible to callosal absence than other aspects of language.

Consistent with the observations of family members, we recently reported data from adults with ACC and normal IQ demonstrating significant deficits in paralinguistic processing (Paul, Van Lancker-Sidtis, Schieffer, Dietrich, & Brown, 2003). Adults with ACC had normal ability to understand literal expressions, but significant deficits in comprehension of nonliteral expressions. In addition, adults with ACC had difficulty understanding affective prosody, and a deficiency in the comprehension of proverbs (as indicated in both multiple choice and free-answer response formats). While these deficits are clear in adults with ACC, the level of deficit in either the appreciation of prosody or the understanding of nonliteral language in children with ACC has not previously been studied.

Integration into language comprehension and expression of right-lateralized linguistic processing would appear to depend on interhemispheric interactions. There is evidence to suggest that the processing of nonliteral phrases such as idioms is particularly affected by dysfunction of the right cerebral hemisphere (Benton, 1968, Brownell et al., 1986, Kempler et al., 1999, Van Lancker and Kempler, 1987, Weylman et al., 1989, Winner and Gardner, 1977). A unique role of the right (nondominant) hemisphere in processing prosody and emotional speech has also been reported (Bowers et al., 1993, Heilman et al., 1975, Starkstein et al., 1994, Tucker, 1981, Weintraub and Mesulam, 1983). Other studies suggest that the left and right hemispheres play complementary roles in processing of the prosodic aspects of language (Pell and Baum, 1997, Robin et al., 1990, Van Lancker and Sidtis, 1992, Zatorre et al., 1992). A role for interhemispheric pathways in the production and comprehension of affective prosody has been suggested by several studies (Cancelliere and Kertesz, 1990, Van Lancker and Breitenstein, 2000, Van Lancker et al., 1996).

In normal children, the corpus callosum is not fully myelinated until sometime during the early years of the second decade of life (Giedd et al., 1994, Yakovlev and Lecours, 1967). Increased myelinization of the corpus callosum would contribute to the speed and efficiency of interhemispheric interactions. Similarly, paralinguistic skills in normal children have also been found to develop between approximately 5 and 10 years old (Cohen et al., 1990, Kempler et al., 1999, Van Lancker et al., 1989). The deficits in paralinguistic process in adults with ACC which we previously demonstrated (Paul et al., 2003) suggest that callosal development may be important for the emergence of the comprehension of nonliteral language and prosody.

This report is a follow-up on our study of adults with ACC (Paul et al., 2003). We describe linguistic processing in children with ACC with respect to comprehension of both literal and nonliteral expressions, and recognition of affective prosody. While deficits similar to those found in adults with ACC were expected in children with ACC, given the lack of complete development of both the corpus callosum and paralinguistic processing ability in normal children, it was hypothesized that the degree of difference in performance between normal children and children with ACC would be less than that seen in adults.

Section snippets

Participants

Participants included 18 children (ages 7–13; mean age = 9.3) with complete ACC and IQs in the borderline to high average range (FSIQ 83–122, mean = 91.0). Magnetic resonance images (MRIs; a CT scan in one case) and neuroradiological reports were obtained for all individuals with ACC. The diagnosis of ACC was confirmed by a second neuroradiologist, who inspected scans for presence or absence of the CC and anterior commissure, and for any evidence of other brain malformations.

Control participants

Results

Means and standard deviations for outcome measures can be found in Table 1. Since paralinguistic skills are developing normally during this developmental period and are presumably affected by intelligence, age and FSIQ were used as covariates in all statistical tests. Age was found to be a significant covariate with respect to interpretation of both literal (F = 5.89, df = 1,31, p < .021) and nonliteral (F = 24.82, df = 1,31, p < .001) statements, but was not significant for affective prosody (F = 1.04, df = 

Discussion

These results demonstrate that children with ACC have significantly greater difficulty than controls in understanding both literal and nonliteral language, as well as suggesting that they also may have difficulty in comprehending affective prosody. This outcome is generally consistent with the previous study of adults with ACC in that adults with ACC were found to have deficits in the comprehension of nonliteral language and affective prosody (Paul et al., 2003). However, there were several

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