Identifying potentially unique features of the human cerebral cortex is a first step to understanding how evolution has shaped the brain in our species. By analyzing MR images obtained from 177 humans and 73 chimpanzees, we observed a human-specific asymmetry in the superior temporal sulcus at the heart of the communication regions and which we have named the "superior temporal asymmetrical pit" (STAP). This 45-mm-long segment ventral to Heschl's gyrus is deeper in the right hemisphere than in the left in 95% of typical human subjects, from infanthood till adulthood, and is present, irrespective of handedness, language lateralization, and sex although it is greater in males than in females. The STAP also is seen in several groups of atypical subjects including persons with situs inversus, autistic spectrum disorder, Turner syndrome, and corpus callosum agenesis. It is explained in part by the larger number of sulcal interruptions in the left than in the right hemisphere. Its early presence in the infants of this study as well as in fetuses and premature infants suggests a strong genetic influence. Because this asymmetry is barely visible in chimpanzees, we recommend the STAP region during midgestation as an important phenotype to investigate asymmetrical variations of gene expression among the primate lineage. This genetic target may provide important insights regarding the evolution of the crucial cognitive abilities sustained by this sulcus in our species, namely communication and social cognition.ince Geschwind and Levitsky's (1) first attempt to identify a specifically human cortical landmark, the identification of unique features of the human brain that might explain the cognitive success of the human species has remained elusive so that anatomical targets still do not exist to inform the search for genetic mutations contributing to the human cognitive phenotype. Because hemispheric asymmetry and language processing are fundamental human traits, the perisylvian language areas have been especially scrutinized for such markers, but until now none has been forthcoming. In particular, the reported asymmetries in the planum temporale and the inferior frontal region are not as robust as initially thought (1-3) and also are observed, albeit often less marked, in other primates (4). However, we show here that asymmetry of the superior temporal sulcus (STS), at the core of the human communication system, represents a species-specific perisylvian anatomical marker. This finding is consistent with functional brain imaging studies that have emphasized the importance of STS not only for language processing in the left hemisphere but also for social communication in the right hemisphere (5, 6). Notably, in the left hemisphere a hierarchy of areas sensitive to increased levels of acoustical complexity is observed along superior temporal regions and become specifically linguistic along the STS (7, 8), whereas in the right hemisphere the presence of areas involved in voice and face recognition, gaze perception, and theory o...

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The intention behind another's action and the impact of the outcome are major determinants of human economic behavior. It is poorly understood, however, whether the two systems share a core neural computation. Here, we investigated whether the two systems are causally dissociable in the brain by integrating computational modeling, functional magnetic resonance imaging, and transcranial direct current stimulation experiments in a newly developed trust game task. We show not only that right dorsolateral prefrontal cortex (DLPFC) activity is correlated with intention-based economic decisions and that ventral striatum and amygdala activity are correlated with outcome-based decisions, but also that stimulation to the DLPFC selectively enhances intention-based decisions. These findings suggest that the right DLPFC is involved in the implementation of intention-based decisions in the processing of cooperative decisions. This causal dissociation of cortical and subcortical backgrounds may indicate evolutionary and developmental differences in the two decision systems.

Abstract. We investigated whether leukotriene B 4 (LTB 4 ) and its signaling pathway play an important role in the progression of human colon cancer via a direct stimulation of cancer cell proliferation. Remarkable expression of LTB 4 receptor 1 (BLT1) in human colon cancer tissues was detected by immunohistochemistry, and Western blot analysis revealed the BLT1 expression in cultured human colon cancer cell lines, Caco2 and HT29. The 5-lipoxygenase inhibitor AA-861 and LTB 4 -receptor antagonist U75302 showed negative effects on survival and proliferation of both Caco2 and HT-29 cells. The inhibition of cell proliferation is due to the apoptosis because nuclear condensation and increased annexin V expression were observed in the cells treated with AA-861 and U75302. Knockdown of BLT1 by small interfering RNA caused the suppression of BLT1 protein, resulting in the inhibition of cancer cell proliferation. Blockade of BLT1 by the receptor antagonist significantly suppresses the LTB 4 -stimulated extracellular signal-regulated kinase (ERK) activation in colon cancer cells. These results indicate that the blockade of the LTB 4 -signaling pathway induces apoptosis via the inhibition of ERK activation in colon cancer cells. The LTB 4 -signaling pathway might be a new therapeutic target for colon cancer.