Are language skills related to structural features in Broca's and Wernicke's area?

This study used structural magnetic resonance imaging to examine whether specific anatomical features of Broca's and Wernicke's areas are related to language functions in typically developing older subjects with no specific language expertize. Data from 231 subjects from the Zurich LHAB-study are used for this study. For these subjects, we obtained several psychometric measures from which we calculated performance measures reflecting specific psychological functions (language comprehension, verbal fluency, perceptual speed, visual memory, recognition of regularities, and logical thinking). From the MRI measurements, we calculated the cortical thickness and cortical surface of Broca's and Wernicke's areas. Applying multiple regression analyses, we identified a moderately strong relationship between language comprehension and the brain metrics from Broca's and Wernicke's areas and showed that approximately 10% of the variance in language comprehension performance is explained by the linear combination of all perisylvian brain metrics. The other psychological functions (verbal fluency, perceptual speed, visual memory, recognition of regularities, and logical thinking) are not related to these brain metrics. Subsequent detailed analyses revealed that the cortical thickness of Wernicke's area, in particular, contributed most to this structure-function relationship. The better performance in the language comprehension tests was related to a thicker cortex in Wernicke's area. Thus, this study demonstrates a structure-function relationship between the anatomical features of the perisylvian language areas and language comprehension, suggesting that particular anatomical features are associated with better language performance.

Weak correlations between body height and several brain metrics in healthy elderly subjects.

The question whether body height is related to different brain size measures has recently gained renewed interest as some studies have reported that body height correlates with intelligence and several brain size measures. In this study, we re-evaluated this question by examining the relationship between body height and different brain size measures including intracranial volume, total brain volume, total cortical surface area, total cortical volume, volume of normal-appearing white matter, white matter hyperintensity, cortical surface area, cortical thickness, subcortical grey matter volume, cerebellar cortex and cerebellar white matter in a relatively large sample (n = 216) of physically and cognitively healthy elderly subjects (mean age 71 years, age range 65-85 years). We identified small correlations (r = .11-.19) between body height and seven out of 10 brain metrics (total brain volume, cortical surface area, cortical volume, subcortical volume, normal-appearing white matter volume and cerebellar grey as well as white matter volumes) when controlling for sex and age. Based on these small relationships between body height and various brain size measures, we discuss the possible reasons and theoretical problems for these small relationships.

Scaling of brain compartments to brain size.

In this study, we examine the relationship between total brain volume (BV) and the volumes of several main brain compartmental (BC) measures (cortical thickness, cortical surface area, corpus callosum, cortical gray matter, normal appearing cerebral white matter (NAWM), amygdala, accumbens, caudate, hippocampus, putamen, pallidum, thalamus, cerebellar gray matter, and cerebellar WM) of physically and cognitively healthy elderly individuals (mean age: 71 years, age range: 65-85 years). The statistical analysis uncovered extremely different relationships between total BV and the aforementioned BC metrics. These relationships ranged from extremely strong (BV explaining 85% of the variability of cerebral WM volume) to a very small relationship (for the caudate volume and the cortical thickness). In addition, cerebral WM and the accumbens volumes scaled out of proportion with BV, whereas most other BC measures scaled less than proportional to BV. Thus, larger brains exhibit relatively larger cerebral NAWM and accumbens volumes than do smaller brains. Cortical gray matter (and most other BC measures), on the other hand, relatively decreases as BV increases, resulting in relatively small cortical gray matter volumes (and relatively small BC measures) for large brains. These relationships are discussed within the context of general allometric scaling principles for the human brain. In addition, possible methodological consequences of analyzing anatomical data on the basis of MRI measurements are also discussed.