This study describes the gyrification patterns and surface areas of Heschl’s gyrus (HG) in 430 healthy volunteers mapped with magnetic resonance imaging. Among the 232 right-handers, we found a large occurrence of duplication (64 %), especially on the right (49 vs. 37 % on the left). Partial duplication was twice more frequent on the left than complete duplication. On the opposite, in the right hemisphere, complete duplication was 10 % more frequent than partial duplication. The most frequent inter-hemispheric gyrification patterns were bilateral single HG (36 %) and left single-right duplication (27 %). The least common patterns were left duplication-right single (22 %) and bilateral duplication (15 %). Duplication was associated with decreased anterior HG surface area on the corresponding side, independently of the type of duplication, and increased total HG surface area (including the second gyrus). Inter-hemispheric gyrification patterns strongly influenced both anterior and total HG surface area asymmetries, leftward asymmetry of the anterior HG surface was observed in all patterns except double left HG, and total HG surface asymmetry favored the side of duplication. Compared to right-handers, the 198 left-handers exhibited lower occurrence of duplication, and larger right anterior HG surface and total HG surface areas. Left-handers’ HG surface asymmetries were thus significantly different from those of right-handers, with a loss of leftward asymmetry of their anterior HG surface, and with significant rightward asymmetry of their total HG surface. In summary, gyrification patterns have a strong impact on HG surface and asymmetry. The observed reduced lateralization of HG duplications and anterior HG asymmetry in left-handers highlights HG inter-hemispheric gyrification patterns as a potential candidate marker of speech lateralization.

We investigated the regional correlates of differences in hemispheric lateralization in 297 healthy volunteers [including 153 left-handers (LH)] previously classified into three types of language lateralization according to their hemispheric functional lateralization index measured with fMRI during covert sentence production versus word list production (PRODSENT-LIST): 250 leftward asymmetrical Typicals, 10 rightward asymmetrical Strong-atypicals (only LH), and 37 Ambilaterals with weak lateralization. Using a functionally driven homotopic atlas (AICHA), we compared patterns of regional asymmetry during PRODSENT-LIST in these three groups. Among the 192 homotopic regions of interest (hROIs) of the AICHA atlas, 58 exhibited a significant effect of the type of lateralization on their BOLD signal variation during PRODSENT-LIST. The analyses of patterns of asymmetry of these 58 hROIs showed that (1) hROIs asymmetries in Strong-atypicals were significantly negatively correlated with those observed in Typicals, which indicates that their regional pattern of rightward asymmetries was comparable to the regional pattern of leftward language asymmetries of Typicals; (2) right- and left-handed Typicals had identical profiles, whereas left-handed Ambilaterals exhibited reduced leftward asymmetry as compared either to right-handed Ambilaterals or to Typicals. Moreover, left-handed Ambilaterals pattern of hROIs asymmetries significantly positively correlated with those of both Typicals and Strong-atypicals. In 291 of the participants, we tested the hypothesis that differences in language lateralization were associated with differences in inter-hemispheric connectivity during resting state by measuring their regional homotopic inter-hemispheric intrinsic connectivity coefficient (rHIICC) in 36 of the 58 hROIs known to be connected via the corpus callosum. Mean rHIICCs were negatively correlated with task-induced functional asymmetries, suggesting that enhanced inter-hemispheric cooperation at rest translates into increased inter-hemispheric cooperation during language production. In addition, the left-handed Ambilaterals exhibited a significantly larger rHIICC compared with right-handed Ambilaterals and Typicals, confirming a difference in inter-hemispheric organization in this group.

No abstract

The planum temporale (PT) is a critical region of the language functional network in the human brain showing a striking size asymmetry toward the left hemisphere. Historically considered as a structural landmark of the left-brain specialization for language, a similar anatomical bias has been described in great apes but never in monkeys-indicating that this brain landmark might be unique to Hominidae evolution. In the present in vivo magnetic resonance imaging study, we show clearly for the first time in a nonhominid primate species, an Old World monkey, a left size predominance of the PT among 96 olive baboons (Papio anubis), using manual delineation of this region in each individual hemisphere. This asymmetric distribution was quasi-identical to that found originally in humans. Such a finding questions the relationship between PT asymmetry and the emergence of language, indicating that the origin of this cerebral specialization could be much older than previously thought, dating back, not to the Hominidae, but rather to the Catarrhini evolution at the common ancestor of humans, great apes and Old World monkeys, 30-40 million years ago.

The baboon (Papio) brain is a remarkable model for investigating the brain. The current work aimed at creating a population-average baboon (Papio anubis) brain template and its left/right hemisphere symmetric version from a large sample of T1-weighted magnetic resonance images collected from 89 individuals. Averaging the prior probability maps output during the segmentation of each individual also produced the first baboon brain tissue probability maps for gray matter, white matter and cerebrospinal fluid. The templates and the tissue probability maps were created using state-of-the-art, freely available software tools and are being made freely and publicly available: http://www.nitrc.org/projects/haiko89/ or http://lpc.univ-amu.fr/spip.php?article589. It is hoped that these images will aid neuroimaging research of the baboon by, for example, providing a modern, high quality normalization target and accompanying standardized coordinate system as well as probabilistic priors that can be used during tissue segmentation.

Sleep is markedly altered in intensive care unit (ICU) patients and may alter respiratory performance. Our objective was to assess the impact of sleep alterations on weaning duration.We conducted a prospective physiological study at a French teaching hospital. ICU patients intubated for at least 24 h and difficult to wean were included. Complete polysomnography (PSG) was performed after the first spontaneous breathing trial failure. Presence of atypical sleep, duration of sleep stages, particularly rapid eye movement (REM) sleep, and electroencephalogram (EEG) reactivity at eyes opening were assessed by a neurologist.20 out of 45 patients studied (44%) had atypical sleep that could not be classified according to the standard criteria. Duration of weaning between PSG and extubation was significantly longer in patients with atypical sleep (median (interquartile range) 5 (2-8) 2 (1-2) days; p=0.001) and in those with no REM sleep compared with the others. Using multivariate logistic regression analysis, atypical sleep remained independently associated with prolonged weaning (>48 h after PSG). Altered EEG reactivity at eyes opening was a good predictor of atypical sleep.Our results suggest for the first time that brain dysfunction may have an influence on the ability to breathe spontaneously.

This study investigates the structure-function relationships between the anatomy of Heschl's gyri (HG) and speech hemispheric lateralization in 281 healthy volunteers (135 left-handers). Hemispheric lateralization indices (HFLIs) were calculated with Wilke's method from the activations obtained via functional magnetic resonance imaging while listening to lists of words (LIST). The mean HFLI during LIST was rightward asymmetrical, and left-handers displayed a trend toward decreased rightward asymmetry. The correlations between LIST BOLD contrast maps and individual HFLIs demonstrated that among the cortical areas showing significant asymmetry during LIST, only phonological regions explained HFLI variability. Significant positive correlations were present among the left HG, supramarginal gyri, and the anterior insula. Significant negative correlations occurred in the mid-part of the right superior temporal sulcus. Left HG had the largest functional activity during LIST and explained 10% of the HFLI variance. There was a strong anatomo-functional link in the HG: duplication was associated with a decrease in both the surface area of the anterior HG and HG functional activity. Participants with a single left HG exhibited leftward anatomical and functional asymmetry of HG, but participants with a left duplication lost either anatomical and/or functional leftward asymmetries. Finally, manual preference was related to HG anatomy, but not to HG functional asymmetries measured during LIST. The anatomical characteristics of left-handers (lower occurrence of right HG duplication and a smaller surface area of the right first HG) thus appeared to be unrelated to variations in speech lateralization with handedness.

Understanding speech in background noise poses a challenge in daily communication, which is a particular problem among the elderly. Although musical expertise has often been suggested to be a contributor to speech intelligibility, the associations are mostly correlative. In the present multisite study conducted in Germany and Switzerland, 156 healthy, normal-hearing elderly were randomly assigned to either piano playing or music listening/musical culture groups. The speech reception threshold was assessed using the International Matrix Test before and after a 6 month intervention. Bayesian multilevel modeling revealed an improvement of both groups over time under binaural conditions. Additionally, the speech reception threshold of the piano group decreased during stimuli presentation to the left ear. A right ear improvement only occurred in the German piano group. Furthermore, improvements were predominantly found in women. These findings are discussed in the light of current neuroscientific theories on hemispheric lateralization and biological sex differences. The study indicates a positive transfer from musical training to speech processing, probably supported by the enhancement of auditory processing and improvement of general cognitive functions.