Prolonged 13 c+post-tetanic depolarization of frog dorsal root fibers

Broca's region: cytoarchitectonic asymmetry and developmental changes

Functional imaging and clinical studies in children and adults have provided evidence of developmental changes in the hemispheric specialization for language. Whereas cytoarchitectonic asymmetry has been demonstrated in Broca's region of adults, the anatomical correlates of developmental changes in language dominance are largely unknown. In the present postmortem study of 34 human brains (ages ranging from 3.5 months to 85 years), the cytoarchitecture of areas 44 and 45 as the putative anatomical correlates of Broca's region, their developmental changes, and interhemispheric asymmetry were analyzed. Asymmetry as estimated by Euclidean distances between feature vectors of cytoarchitectonic profiles of left and right areas 44 and 45 was already found in 1-year-old infants. Asymmetry tended to increase with age, which was significant in area 45, but not in area 44. An adult-like, left-larger-than-right asymmetry in the volume fraction of cell bodies [gray level index (GLI)] was reached at approximately 5 years in area 45 and 11 years in area 44. These time points indicate a delayed development of the cytoarchitectonic asymmetry in Broca's region in comparison with that of the primary motor cortex. It may be hypothesized that the delayed maturation is the microstructural basis of the development of language abilities and the influence of language practice on cytoarchitecture during childhood. Interhemispheric asymmetry in the cytoarchitecture of areas 44 and 45 continues to change throughout life. We conclude that the cytoarchitectonic asymmetry of areas 44 and 45 is a result of microstructural plasticity that endures throughout almost the whole lifespan.

A four-dimensional probabilistic atlas of the human brain

The authors describe the development of a four-dimensional atlas and reference system that includes both macroscopic and microscopic information on structure and function of the human brain in persons between the ages of 18 and 90 years. Given the presumed large but previously unquantified degree of structural and functional variance among normal persons in the human population, the basis for this atlas and reference system is probabilistic. Through the efforts of the International Consortium for Brain Mapping (ICBM), 7,000 subjects will be included in the initial phase of database and atlas development. For each subject, detailed demographic, clinical, behavioral, and imaging information is being collected. In addition, 5,800 subjects will contribute DNA for the purpose of determining genotype- phenotype-behavioral correlations. The process of developing the strategies, algorithms, data collection methods, validation approaches, database structures, and distribution of results is described in this report. Examples of applications of the approach are described for the normal brain in both adults and children as well as in patients with schizophrenia. This project should provide new insights into the relationship between microscopic and macroscopic structure and function in the human brain and should have important implications in basic neuroscience, clinical diagnostics, and cerebral disorders.

Broca's region revisited: cytoarchitecture and intersubject variability

The sizes of Brodmann's areas 44 and 45 (Broca's speech region) and their extent in relation to macroscopic landmarks and surrounding areas differ considerably among the available cytoarchitectonic maps. Such variability may be due to intersubject differences in anatomy, observer-dependent discrepancies in cytoarchitectonic mapping, or both. Because a reliable definition of cytoarchitectonic borders is important for interpreting functional imaging data, we mapped areas 44 and 45 by means of an observer-independent technique. In 10 human brains, the laminar distributions of cell densities were measured vertical to the cortical surface in serial coronal sections stained for perikarya. Thousands of density profiles were obtained. Cytoarchitectonic borders were defined as statistically significant changes in laminar patterns. The analysis of the three-dimensional reconstructed brains and the two areas showed that cytoarchitectonic borders did not consistently coincide with sulcal contours. Therefore, macroscopic features are not reliable landmarks of cytoarchitectonic borders. Intersubject variability in the cytoarchitecture of areas 44 and 45 was significantly greater than cytoarchitectonic differences between these areas in individual brains. Although the volumes of area 44 differed across subjects by up to a factor of 10, area 44 but not area 45 was left-over-right asymmetrical in all brains. All five male but only three of five female brains had significantly higher cell densities on the left than on the right side. Such hemispheric and gender differences were not detected in area 45. These morphologic asymmetries of area 44 provide a putative correlate of the functional lateralization of speech production.

Immunoblot identification of 13.5 kilodalton myelin basic protein in goldfish brain myelin

Myelin isolated from goldfish brain shows a multilamellar structure with a major dense line and two intraperiod lines. Sodium dodecyl sulfate gel electrophoresis revealed that the protein profile of goldfish brain myelin is distinctly different from that of rat brain myelin. No protein migrating to the position of proteolipid protein or DM-20 was seen in goldfish myelin. Goldfish acclimated to 5 degrees, 15 degrees, and 30 degrees C showed no qualitative differences in myelin proteins. The 13.5 kD protein in goldfish brain myelin and brain homogenate was intensely immunostained with the antiserum to human basic protein by the immunoblot technique. In contrast, none of the proteins of goldfish myelin were immunostained with antiproteolipid protein serum; however, both proteolipid protein and DM-20 of rat brain myelin were immunostained. The significance of the synthesis of myelin proteins by astrocytes in the goldfish brain is discussed.