Multipoint genome-wide linkage scan for nonword repetition in a multigenerational family further supports chromosome 13q as a locus for verbal trait disorders.

Verbal trait disorders encompass a wide range of conditions and are marked by deficits in five domains that impair a person's ability to communicate: speech, language, reading, spelling, and writing. Nonword repetition is a robust endophenotype for verbal trait disorders that is sensitive to cognitive processes critical to verbal development, including auditory processing, phonological working memory, and motor planning and programming. In the present study, we present a six-generation extended pedigree with a history of verbal trait disorders. Using genome-wide multipoint variance component linkage analysis of nonword repetition, we identified a region spanning chromosome 13q14-q21 with LOD = 4.45 between 52 and 55 cM, spanning approximately 5.5 Mb on chromosome 13. This region overlaps with SLI3, a locus implicated in reading disability in families with a history of specific language impairment. Our study of a large multigenerational family with verbal trait disorders further implicates the SLI3 region in verbal trait disorders. Future studies will further refine the specific causal genetic factors in this locus on chromosome 13q that contribute to language traits.

Bilateral subcortical heterotopia with partial callosal agenesis in a mouse mutant.

Cognition and behavior depend on the precise placement and interconnection of complex ensembles of neurons in cerebral cortex. Mutations that disrupt migration of immature neurons from the ventricular zone to the cortical plate have provided major insight into mechanisms of brain development and disease. We have discovered a new and highly penetrant spontaneous mutation that leads to large nodular bilateral subcortical heterotopias with partial callosal agenesis. The mutant phenotype was first detected in a colony of fully inbred BXD29 mice already known to harbor a mutation in Tlr4. Neurons confined to the heterotopias are mainly born in midgestation to late gestation and would normally have migrated into layers 2-4 of overlying neocortex. Callosal cross-sectional area and fiber number are reduced up to 50% compared with coisogenic wildtype BXD29 substrain controls. Mutants have a pronounced and highly selective defect in rapid auditory processing. The segregation pattern of the mutant phenotype is most consistent with a two-locus autosomal recessive model, and selective genotyping definitively rules out the Tlr4 mutation as a cause. The discovery of a novel mutation with strong pleiotropic anatomical and behavioral effects provides an important new resource for dissecting molecular mechanisms and functional consequences of errors of neuronal migration.

Increased variability of stimulus-driven cortical responses is associated with genetic variability in children with and without dyslexia.

Individuals with dyslexia exhibit increased brainstem variability in response to sound. It is unknown as to whether increased variability extends to neocortical regions associated with audition and reading, extends to visual stimuli, and whether increased variability characterizes all children with dyslexia or, instead, a specific subset of children. We evaluated the consistency of stimulus-evoked neural responses in children with (N = 20) or without dyslexia (N = 12) as measured by magnetoencephalography (MEG). Approximately half of the children with dyslexia had significantly higher levels of variability in cortical responses to both auditory and visual stimuli in multiple nodes of the reading network. There was a significant and positive relationship between the number of risk alleles at rs6935076 in the dyslexia-susceptibility gene KIAA0319 and the degree of neural variability in primary auditory cortex across all participants. This gene has been linked with neural variability in rodents and in typical readers. These findings indicate that unstable representations of auditory and visual stimuli in auditory and other reading-related neocortical regions are present in a subset of children with dyslexia and support the link between the gene KIAA0319 and the auditory neural variability across children with or without dyslexia.

Mutation of Dcdc2 in mice leads to impairments in auditory processing and memory ability.

Dyslexia is a complex neurodevelopmental disorder characterized by impaired reading ability despite normal intellect, and is associated with specific difficulties in phonological and rapid auditory processing (RAP), visual attention and working memory. Genetic variants in Doublecortin domain-containing protein 2 (DCDC2) have been associated with dyslexia, impairments in phonological processing and in short-term/working memory. The purpose of this study was to determine whether sensory and behavioral impairments can result directly from mutation of the Dcdc2 gene in mice. Several behavioral tasks, including a modified pre-pulse inhibition paradigm (to examine auditory processing), a 4/8 radial arm maze (to assess/dissociate working vs. reference memory) and rotarod (to examine sensorimotor ability and motor learning), were used to assess the effects of Dcdc2 mutation. Behavioral results revealed deficits in RAP, working memory and reference memory in Dcdc2(del2/del2) mice when compared with matched wild types. Current findings parallel clinical research linking genetic variants of DCDC2 with specific impairments of phonological processing and memory ability.

The incidence of awareness, and amnesia for perioperative events, after cardiac surgery with lorazepam and fentanyl anesthesia.

One hundred patients (mean age 59 +/- 10 years) were premedicated with morphine, 0.15 mg/kg, and scopolamine, 0.008 mg/kg. Anesthesia was induced with lorazepam, 50 microg/kg, followed by fentanyl, 50 microg/kg, oxygen and pancuronium, 0.15 mg/kg. Isoflurane was given for short periods before and after cardiopulmonary bypass to 57 patients when hypertension was uncontrolled by addition of fentanyl and/or nitroglycerin. Morphine was used as the sole sedative postoperatively. Patients were interviewed following discharge from the surgical intensive care unit to assess the incidence of operative awareness, and to assess amnesia for events occurring during four preoperative and two postoperative periods of the patients' hospital stay. During three preoperative periods (day of admission, evening before, and morning before operation), 1%, 3%, and 2% of patients had complete amnesia, and 19%, 41%, and 31% had partial amnesia of events. Fifty-five percent of patients exhibited complete, and 34% of patients exhibited partial amnesia to events occurring in the preinduction period. Two patients reported intraoperative awareness (noises, conversation) occurring at the end of the anesthetic. In the two postoperative periods (morning of the day after surgery and intensive care stay), 9% and 15% of patients had complete, and 35% and 47% of patients exhibited partial amnesia. Amnesia was statistically significantly greater in patients over 60 years of age in the preinduction period. Duration of cardiopulmonary bypass did not affect the incidence of amnesia.