A Tale of Two Brains or The Sinistral Quasimodality of Language

Four experiments show that people differ strongly in the extent to v^ich they depend on linguistic structure during language comprehension.Structure-dependent people are immediately affected by grammatical variables,vrtiile structure-independent people are less affected by such variables. A surprising population difference between the two types of people suggests a genetic and neurological basis for the behavioral difference. All subjects were right-handed. However, structure-dependent people report no left-handers in their family, while structure-independent people do report left-handers in their family. This suggests that the neurological organization for linguistic ability in right handers with familial left-handedness, is more diffuse than for right handers with no familial left-handedness. Other facts connect this to a current hormonal theory of the ontogenesis of hemispheric asymmetries

Familial Handedness and Access to Words, Meaning, and Syntax During Sentence Comprehension

We compared right-handed familial dextral (FS-) and familial sinistral (FS+) participants who were aged either 10-13 years (children) or 18-23 years (adults). In word probe and associative probe tasks, FS+ adults responded faster than all other groups and FS+ children responded more slowly than all other groups. In the word probe task, only the FS- adults showed a significant effect of the serial position of the target word. We interpret these differences to support an analysis-by-synthesis model of comprehension in which individuals who differ in familial handedness and age emphasize different linguistic representations during comprehension. In general, FS+ individuals focus on words and meaning, while FS- individuals focus on syntactic representations. In FS+ individuals, age-related experiences with language produce a shift in responding from compositional meaning to words and their associations. In FS- individuals, age-related experiences with language produce a shift toward responding based more on detailed syntactic representations, including the serial order of words and possibly the structural roles of clauses

Accessing Meaning vs. Form at Different Levels of Comprehension Skill

We examined adult and 10-13 year old skilled and average comprehenders' representation of spoken sentences. In immediate probe tasks, skilled adults were better than average adults at accessing word order information, but they were poorer at accessing sentence meaning. After hearing a text, skilled adults were more accurate than average adults in recognizing meaning, but they were less accurate in recognizing the wording of test sentences. Speeded speech increased the differences between skill groups more for memory for wording than for memory for meaning. The results suggest that comprehenders compute representations of surface form and meaning independently and simultaneously. These representations compete for attention

C-C chemokine receptor 6-regulated entry of TH-17 cells into the CNS through the choroid plexus is required for the initiation of EAE

Interleukin 17-producing T helper cells (T(H)-17 cells) are important in experimental autoimmune encephalomyelitis, but their route of entry into the central nervous system (CNS) and their contribution relative to that of other effector T cells remain to be determined. Here we found that mice lacking CCR6, a chemokine receptor characteristic of T(H)-17 cells, developed T(H)-17 responses but were highly resistant to the induction of experimental autoimmune encephalomyelitis. Disease susceptibility was reconstituted by transfer of wild-type T cells that entered into the CNS before disease onset and triggered massive CCR6-independent recruitment of effector T cells across activated parenchymal vessels. The CCR6 ligand CCL20 was constitutively expressed in epithelial cells of choroid plexus in mice and humans. Our results identify distinct molecular requirements and ports of lymphocyte entry into uninflamed versus inflamed CNS and suggest that the CCR6-CCL20 axis in the choroid plexus controls immune surveillance of the CNS