Clinical, audiometric, radiologic, and genetic profiles of Southeast Asian children with hearing loss due to enlarged vestibular aqueduct.

OBJECTIVE: Analysis of the clinical, audiometric, radiologic, and genotypic characteristics of a cohort of Southeast Asian patients with hearing loss (HL) associated with enlarged vestibular aqueduct (EVA). PATIENTS: Ten consecutive children with sensorineural HL and EVA detected on computed tomographic scanning of the temporal bone. INTERVENTIONS: Audiometric, radiologic, and genetic analysis of the patient cohort of 10 children. MAIN OUTCOME MEASURES: Audiometric, radiologic analysis.Genetic analysis to assess for the presence of Connexin 26, Connexin 30, A1555G, and Pendrin gene variants. RESULTS: The novel 1693insA and 1521delT variants were identified in our study group. When both loci were considered simultaneously, 8 (80%) of 10 patients studied carried variants in either the pendrin (n = 5) or connexin 26 (n = 6) genes. When analyzing (using the Mann-Whitney U test) for a correlation between an increased probability of either a larger VA, bilateral EVA, or higher rate of progression of HL in the presence of pendrin or connexin 26 gene variants (as opposed to the absence of these variants), there was no statistically significant difference found. This differs from other studies where there was a significantly wider VA and a wider vestibule in subjects with pendrin mutations. CONCLUSION: There is a significant delay in the diagnosis of EVA in children with HL in our Southeast Asian population. An increased awareness of EVA as a differential diagnosis among professionals managing these children is important to reduce this delay.

The past tense debate: is phonological complexity the key to the puzzle?

Theorists disagree over whether our language faculty is a single system or a dual one. Those supporting the latter position believe that English regular and irregular past tense verbs reflect this duality, with some proposing that each is processed by a rule mechanism and memorised lexicon respectively. Single system proponents believe instead that all verbs are processed by the same system, differing only in their degree of reliance on phonological and semantic representations. Regular past tense verbs involve greater phonological processing partly because they are phonologically more complex than irregulars. Early neuroimaging studies showing activation differences between the two have been taken as evidence for a dual system. However, it has been proposed recently that greater activation related to regular verb inflection was instead due to the failure to match regular and irregular verbs for phonological complexity (PC). Using a 2×3 ANOVA, the current event-related fMRI study tested this idea directly by manipulating regularity (regular, irregular) and PC (low, mid,and high) in 19 English-speaking monolingual participants. We found a main effect of PC, supporting the idea that phonological complexity cannot be ignored when considering differences between regular and irregular verbs. However we also found a main effect of regularity, demonstrating that differences over and above phonological complexity exist between the two types of verb. Even with phonological complexity matched, several regions including left inferior frontal gyrus and caudate were more activated for regular verb inflection. Temporal lobe regions and left hippocampus were among regions activated relatively more for irregular verb inflection. These latter findings suggest it may be premature to rule out a dual system account.

IQ-related fMRI differences during cognitive set shifting.

This event-related functional magnetic resonance imaging study compared neural correlates of executive function (cognitive set-shifting) in 28 healthy participants with either high (HIQ) or average (AIQ) intelligence. Despite comparable behavioral performance (except for slower reactions), the AIQ participants showed greater (especially prefrontal) activation during response selection; the HIQ participants showed greater activation (especially parietal) during feedback evaluation. HIQ participants appeared to engage cognitive resources to support more efficient strategies (planning during feedback in preparation for the upcoming response) which resulted in faster responses and less need for response inhibition and conflict resolution. Whether greater intelligence is associated with more or less brain activity (the "neural efficiency" debate) depends therefore on the specific component of the task being examined as well as the brain region recruited. One implication is that caution must be exercised when drawing conclusions from differences in activation between groups of individuals in whom IQ may differ (e.g., psychiatric vs. control samples).