Angela D. Friederici

Michael Petrides

Constance Scharff

The evolution of human language has been discussed for centuries from different perspectives. Linguistic theory has proposed grammar as a core part of human language that has to be considered in this context. Recent advances in neurosciences have allowed us to take a new neurobiological look on the similarities and dissimilarities of cognitive capacities and their neural basis across both closely and distantly related species. A couple of decades ago the comparisons were mainly drawn between human and non-human primates, investigating the cytoarchitecture of particular brain areas and their structural connectivity. Moreover, comparative studies were conducted with respect to their ability to process grammars of different complexity. So far the available data suggest that non-human primates are able to learn simple probabilistic grammars, but not hierarchically structured complex grammars. The human brain, which easily learns both grammars, differs from the non-human brain (among others) in how two language-relevant brain regions (Broca’s area and superior temporal cortex) are connected structurally. Whether the more dominant dorsal pathway in humans compared to non-human primates is causally related to this behavioral difference is an issue of current debate. Ontogenetic findings suggest at least a correlation between the maturation of the dorsal pathway and the behavior to process syntactically complex structures, although a causal prove is still not available. Thus the neural basis of complex grammar processing in humans remains to be defined. More recently it has been reported that songbirds are also able to distinguish between sound sequences reflecting complex grammar. Interestingly, songbirds learn to sing by imitating adult song in a process not unlike language development in children. Moreover, the neural circuits supporting this behavior in songbirds bear anatomical and functional similarities to those in humans. In adult humans the fiber tract connecting the auditory cortex and motor cortex dorsally is known to be involved in the repetition of spoken language. This pathway is present already at birth and is taken to play a major role during language acquisition. In songbirds, detailed information exist concerning the interaction of auditory, motor and cortical-basal ganglia processing during song learning, and present a rich substrate for comparative studies. The scope of the Research Topic is to bring together contributions of researchers from different fields, who investigate grammar processing in humans, non-human primates and songbirds with the aim to find answers to the question of what constitutes the neurobiological basis of grammar learning. Open questions are: Which brain networks are relevant for grammar learning? Is there more than one dorsal pathway (one from temporal cortex to motor cortex and one to Broca’s area) and if so what are their functions? Has the ability to process sequences of a given hierarchical complexity evolved in different phylogenetic lines (birds, primates, other vocal production learners such as bats)? Is the presence of a sensory-to-motor circuit in humans a precondition for development of a dorsal pathway between the temporal cortex and Broca’s area? What role do subcortical structures (Basal Ganglia) play in vocal and grammar learning?

Neurobiology of human language and its evolution: Primate and Nonprimate Perspectives

Atlas of the Morphology of the Human Cerebral Cortex on the Average MNI Brain provides a comprehensive identification of the sulci and gyri of the human brain on a series of coronal sections of the average MNI brain and identifies the likely location of the cytoarchitectonic areas of the cerebral cortex. Presentation in MNI Stereotaxic Space enables the atlas to serve as a useful working tool for structural/functional neuroimagers attempting to identify the sulcus or gyrus and the likely cytoarchitectonic area within which a functional activation or a structural change has occurred. A brief introductory section discusses the history and current state of studies of the sulcal and gyral morphology and cytoarchitecture of the human cerebral cortex. Identifies all sulci and gyri of both hemispheres of the average MNI brain (rather than those of a single brain with its individual peculiarities) so that the average surface morphology of the human cerebral cortex is clearly revealed Presents the likely location of architectonic areas on the average MNI brain so that researchers can report their findings in a manner that is readily translatable from laboratory to laboratory Offers succinct commentary on the relation of sulci and gyri to architectonic areas, which will be useful to those looking to identify the cortical area within which functional or structural changes occurred Offers succinct commentaries on the diversity of names often used to refer to the exact same area that will be useful to those struggling to navigate the often confusing cerebral cortex nomenclature

Michael Petrides

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