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Robert P, Zatorre R, Gupta A, Sein J, Anton JL, Belin P, Thoret E, Morillon B. Auditory hemispheric asymmetry for actions and objects. Cereb Cortex 2024; 34:bhae292. [PMID: 39051660 DOI: 10.1093/cercor/bhae292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 06/08/2024] [Accepted: 07/03/2024] [Indexed: 07/27/2024] Open
Abstract
What is the function of auditory hemispheric asymmetry? We propose that the identification of sound sources relies on the asymmetric processing of two complementary and perceptually relevant acoustic invariants: actions and objects. In a large dataset of environmental sounds, we observed that temporal and spectral modulations display only weak covariation. We then synthesized auditory stimuli by simulating various actions (frictions) occurring on different objects (solid surfaces). Behaviorally, discrimination of actions relies on temporal modulations, while discrimination of objects relies on spectral modulations. Functional magnetic resonance imaging data showed that actions and objects are decoded in the left and right hemispheres, respectively, in bilateral superior temporal and left inferior frontal regions. This asymmetry reflects a generic differential processing-through differential neural sensitivity to temporal and spectral modulations present in environmental sounds-that supports the efficient categorization of actions and objects. These results support an ecologically valid framework of the functional role of auditory brain asymmetry.
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Affiliation(s)
- Paul Robert
- Institut de Neurosciences des Systèmes (INS), Inserm/UMR1106, Aix Marseille University, 27 Bd Jean Moulin, Marseille 13005, France
| | - Robert Zatorre
- Montreal Neurological Institute (MNI), Cognitive Neuroscience Unit, McGill University, 3801 Rue University, Montréal, QC H3A 2B4, Canada
- Centre for Research in Brain, Language, and Music (CRBLM), McGill University, Faculty of Medicine 3640 de la Montagne, Montreal QC H3G 2A8, Canada
| | - Akanksha Gupta
- Institut de Neurosciences des Systèmes (INS), Inserm/UMR1106, Aix Marseille University, 27 Bd Jean Moulin, Marseille 13005, France
| | - Julien Sein
- Institut de Neurosciences de la Timone (INT), CNRS/UMR7289, Aix Marseille University, 27 Bd Jean Moulin, Marseille 13005, France
| | - Jean-Luc Anton
- Institut de Neurosciences de la Timone (INT), CNRS/UMR7289, Aix Marseille University, 27 Bd Jean Moulin, Marseille 13005, France
| | - Pascal Belin
- Institut de Neurosciences de la Timone (INT), CNRS/UMR7289, Aix Marseille University, 27 Bd Jean Moulin, Marseille 13005, France
| | - Etienne Thoret
- Institut de Neurosciences de la Timone (INT), CNRS/UMR7289, Aix Marseille University, 27 Bd Jean Moulin, Marseille 13005, France
- PRISM Laboratory, CNRS/UMR7061, Aix Marseille University, 31 Chemin Joseph Aiguier, Marseille, 13402 Cedex 20, France
- Laboratoire d'Informatique et Systèmes (LIS), CNRS/UMR7020, Aix Marseille University, 52 Av Escadrille Normandie Niemen, Marseille, 13397 Cedex 20, France
- Institute of Language, Communication, and the Brain (ILCB), Aix Marseille University, 5 avenue Pasteur, Aix-en-Provence, 13604 Cedex 1, France
| | - Benjamin Morillon
- Institut de Neurosciences des Systèmes (INS), Inserm/UMR1106, Aix Marseille University, 27 Bd Jean Moulin, Marseille 13005, France
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Washington SD, Shattuck K, Steckel J, Peremans H, Jonckers E, Hinz R, Venneman T, Van den Berg M, Van Ruijssevelt L, Verellen T, Pritchett DL, Scholliers J, Liang S, C Wang P, Verhoye M, Esser KH, Van der Linden A, Keliris GA. Auditory cortical regions show resting-state functional connectivity with the default mode-like network in echolocating bats. Proc Natl Acad Sci U S A 2024; 121:e2306029121. [PMID: 38913894 PMCID: PMC11228507 DOI: 10.1073/pnas.2306029121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 05/19/2024] [Indexed: 06/26/2024] Open
Abstract
Echolocating bats are among the most social and vocal of all mammals. These animals are ideal subjects for functional MRI (fMRI) studies of auditory social communication given their relatively hypertrophic limbic and auditory neural structures and their reduced ability to hear MRI gradient noise. Yet, no resting-state networks relevant to social cognition (e.g., default mode-like networks or DMLNs) have been identified in bats since there are few, if any, fMRI studies in the chiropteran order. Here, we acquired fMRI data at 7 Tesla from nine lightly anesthetized pale spear-nosed bats (Phyllostomus discolor). We applied independent components analysis (ICA) to reveal resting-state networks and measured neural activity elicited by noise ripples (on: 10 ms; off: 10 ms) that span this species' ultrasonic hearing range (20 to 130 kHz). Resting-state networks pervaded auditory, parietal, and occipital cortices, along with the hippocampus, cerebellum, basal ganglia, and auditory brainstem. Two midline networks formed an apparent DMLN. Additionally, we found four predominantly auditory/parietal cortical networks, of which two were left-lateralized and two right-lateralized. Regions within four auditory/parietal cortical networks are known to respond to social calls. Along with the auditory brainstem, regions within these four cortical networks responded to ultrasonic noise ripples. Iterative analyses revealed consistent, significant functional connectivity between the left, but not right, auditory/parietal cortical networks and DMLN nodes, especially the anterior-most cingulate cortex. Thus, a resting-state network implicated in social cognition displays more distributed functional connectivity across left, relative to right, hemispheric cortical substrates of audition and communication in this highly social and vocal species.
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Affiliation(s)
- Stuart D Washington
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA 02139
- Molecular Imaging Laboratory, Department of Radiology, Howard University, College of Medicine, Washington, DC 20060
- Department of Anatomy, Howard University, College of Medicine, Washington, DC 20060
| | - Kyle Shattuck
- Department of Rehabilitation Medicine, Georgetown University Medical Center, Washington, DC 20057
- Department of Neurology, Georgetown University Medical Center, Washington, DC 20057
| | - Jan Steckel
- Department of Electronics-Information and Communication Technology, Cosys Lab, University of Antwerp, Antwerp B-2020, Belgium
- Flanders Make Strategic Research Center, Oude Diestersebaan 133, Lommel 3920, Belgium
| | - Herbert Peremans
- Department of Engineering Management, University of Antwerp, Antwerp B-2000, Belgium
| | - Elisabeth Jonckers
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
- µNeuro Research Centre for Excellence, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
| | - Rukun Hinz
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
| | - Tom Venneman
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
| | - Monica Van den Berg
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
- µNeuro Research Centre for Excellence, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
| | - Lisbeth Van Ruijssevelt
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
| | - Thomas Verellen
- Department of Electronics-Information and Communication Technology, Cosys Lab, University of Antwerp, Antwerp B-2020, Belgium
| | - Dominique L Pritchett
- Department of Biology, Howard University, College of Arts and Sciences, Washington, DC 20059
| | - Jan Scholliers
- Department of Biology, Drie Eiken Campus, University of Antwerp, Antwerp B-2610, Belgium
- Department of Biomedical Sciences, Drie Eiken Campus, University of Antwerp, Antwerp B-2610, Belgium
| | - Sayuan Liang
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
| | - Paul C Wang
- Molecular Imaging Laboratory, Department of Radiology, Howard University, College of Medicine, Washington, DC 20060
- Department of Physics, Fu Jen Catholic University, Taipei 24205, Taiwan
| | - Marleen Verhoye
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
- µNeuro Research Centre for Excellence, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
| | - Karl-Heinz Esser
- Institute of Zoology, University of Veterinary Medicine, Hannover 30559, Germany
| | - Annemie Van der Linden
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
- µNeuro Research Centre for Excellence, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
| | - Georgios A Keliris
- Bio-Imaging Lab, Drie Eiken Campus, Department of Biomedical Sciences, University of Antwerp, Antwerp B-2610, Belgium
- Institute of Computer Science, Foundation for Research and Technology-Hellas, Heraklion, Crete, GR 700 13, Greece; and
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston 02115, MA
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Papanicolaou AC. Non-Invasive Mapping of the Neuronal Networks of Language. Brain Sci 2023; 13:1457. [PMID: 37891824 PMCID: PMC10605023 DOI: 10.3390/brainsci13101457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 09/13/2023] [Accepted: 10/05/2023] [Indexed: 10/29/2023] Open
Abstract
This review consists of three main sections. In the first, the Introduction, the main theories of the neuronal mediation of linguistic operations, derived mostly from studies of the effects of focal lesions on linguistic performance, are summarized. These models furnish the conceptual framework on which the design of subsequent functional neuroimaging investigations is based. In the second section, the methods of functional neuroimaging, especially those of functional Magnetic Resonance Imaging (fMRI) and of Magnetoencephalography (MEG), are detailed along with the specific activation tasks employed in presurgical functional mapping. The reliability of these non-invasive methods and their validity, judged against the results of the invasive methods, namely, the "Wada" procedure and Cortical Stimulation Mapping (CSM), is assessed and their use in presurgical mapping is justified. In the third and final section, the applications of fMRI and MEG in basic research are surveyed in the following six sub-sections, each dealing with the assessment of the neuronal networks for (1) the acoustic and phonological, (2) for semantic, (3) for syntactic, (4) for prosodic operations, (5) for sign language and (6) for the operations of reading and the mechanisms of dyslexia.
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Affiliation(s)
- Andrew C Papanicolaou
- Department of Pediatrics, Division of Pediatric Neurology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN 38013, USA
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Fernandes VFL, Glaser Y, Iwashita M, Yoshizawa M. Evolution of left-right asymmetry in the sensory system and foraging behavior during adaptation to food-sparse cave environments. BMC Biol 2022; 20:295. [PMID: 36575431 PMCID: PMC9795734 DOI: 10.1186/s12915-022-01501-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 12/12/2022] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Laterality in relation to behavior and sensory systems is found commonly in a variety of animal taxa. Despite the advantages conferred by laterality (e.g., the startle response and complex motor activities), little is known about the evolution of laterality and its plasticity in response to ecological demands. In the present study, a comparative study model, the Mexican tetra (Astyanax mexicanus), composed of two morphotypes, i.e., riverine surface fish and cave-dwelling cavefish, was used to address the relationship between environment and laterality. RESULTS The use of a machine learning-based fish posture detection system and sensory ablation revealed that the left cranial lateral line significantly supports one type of foraging behavior, i.e., vibration attraction behavior, in one cave population. Additionally, left-right asymmetric approaches toward a vibrating rod became symmetrical after fasting in one cave population but not in the other populations. CONCLUSION Based on these findings, we propose a model explaining how the observed sensory laterality and behavioral shift could help adaptation in terms of the tradeoff in energy gain and loss during foraging according to differences in food availability among caves.
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Affiliation(s)
| | - Yannik Glaser
- Department of Information and Computer Sciences, University of Hawai'i at Mānoa, Honolulu, Hawai'i, USA
| | - Motoko Iwashita
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, Hawai'i, USA
| | - Masato Yoshizawa
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, Hawai'i, USA.
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Washington SD, Pritchett DL, Keliris GA, Kanwal JS. Hemispheric and Sex Differences in Mustached Bat Primary Auditory Cortex Revealed by Neural Responses to Slow Frequency Modulations. Symmetry (Basel) 2021; 13. [PMID: 34513031 DOI: 10.3390/sym13061037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The mustached bat (Pteronotus parnellii) is a mammalian model of cortical hemispheric asymmetry. In this species, complex social vocalizations are processed preferentially in the left Doppler-shifted constant frequency (DSCF) subregion of primary auditory cortex. Like hemispheric specializations for speech and music, this bat brain asymmetry differs between sexes (i.e., males>females) and is linked to spectrotemporal processing based on selectivities to frequency modulations (FMs) with rapid rates (>0.5 kHz/ms). Analyzing responses to the long-duration (>10 ms), slow-rate (<0.5 kHz/ms) FMs to which most DSCF neurons respond may reveal additional neural substrates underlying this asymmetry. Here, we bilaterally recorded responses from 176 DSCF neurons in male and female bats that were elicited by upward and downward FMs fixed at 0.04 kHz/ms and presented at 0-90 dB SPL. In females, we found inter-hemispheric latency differences consistent with applying different temporal windows to precisely integrate spectrotemporal information. In males, we found a substrate for asymmetry less related to spectrotemporal processing than to acoustic energy (i.e., amplitude). These results suggest that in the DSCF area, (1) hemispheric differences in spectrotemporal processing manifest differently between sexes, and (2) cortical asymmetry for social communication is driven by spectrotemporal processing differences and neural selectivities for amplitude.
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Affiliation(s)
- Stuart D Washington
- Department of Radiology, Howard University Hospital, 2041 Georgia Ave NW, Washington, DC 20060, USA
- Laboratory of Auditory Communication and Cognition, Georgetown University, Department of Neurology, 3700 O St. NW, Washington, DC 20057, USA
| | - Dominique L Pritchett
- Department of Biology, EE Just Hall Building, Howard University, 415 College St. NW, Washington, DC 20059, USA
| | - Georgios A Keliris
- Bio-Imaging Lab, Department of Biomedical Sciences, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
| | - Jagmeet S Kanwal
- Laboratory of Auditory Communication and Cognition, Georgetown University, Department of Neurology, 3700 O St. NW, Washington, DC 20057, USA
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Flinker A, Doyle WK, Mehta AD, Devinsky O, Poeppel D. Spectrotemporal modulation provides a unifying framework for auditory cortical asymmetries. Nat Hum Behav 2019; 3:393-405. [PMID: 30971792 PMCID: PMC6650286 DOI: 10.1038/s41562-019-0548-z] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 01/28/2019] [Indexed: 11/29/2022]
Abstract
The principles underlying functional asymmetries in cortex remain debated. For example, it is accepted that speech is processed bilaterally in auditory cortex, but a left hemisphere dominance emerges when the input is interpreted linguistically. The mechanisms, however, are contested: what sound features or processing principles underlie laterality? Recent findings across species (humans, canines, bats) provide converging evidence that spectrotemporal sound features drive asymmetrical responses. Typically, accounts invoke models wherein the hemispheres differ in time-frequency resolution or integration window size. We develop a framework that builds on and unifies prevailing models, using spectrotemporal modulation space. Using signal processing techniques motivated by neural responses, we test this approach employing behavioral and neurophysiological measures. We show how psychophysical judgments align with spectrotemporal modulations and then characterize the neural sensitivities to temporal and spectral modulations. We demonstrate differential contributions from both hemispheres, with a left lateralization for temporal modulations and a weaker right lateralization for spectral modulations. We argue that representations in the modulation domain provide a more mechanistic basis to account for lateralization in auditory cortex.
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Affiliation(s)
- Adeen Flinker
- Department of Psychology, New York University, New York, NY, USA. .,Department of Neurology, New York University School of Medicine, New York, NY, USA.
| | - Werner K Doyle
- Department of Neurosurgery, New York University School of Medicine, New York, NY, USA
| | - Ashesh D Mehta
- Department of Neurosurgery, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Manhasset, NY, USA
| | - Orrin Devinsky
- Department of Neurology, New York University School of Medicine, New York, NY, USA
| | - David Poeppel
- Department of Psychology, New York University, New York, NY, USA.,Max Planck Institute for Empirical Aesthetics, Frankfurt, Germany
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Washington SD, Hamaide J, Jeurissen B, van Steenkiste G, Huysmans T, Sijbers J, Deleye S, Kanwal JS, De Groof G, Liang S, Van Audekerke J, Wenstrup JJ, Van der Linden A, Radtke-Schuller S, Verhoye M. A three-dimensional digital neurological atlas of the mustached bat (Pteronotus parnellii). Neuroimage 2018; 183:300-313. [PMID: 30102998 DOI: 10.1016/j.neuroimage.2018.08.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 07/26/2018] [Accepted: 08/09/2018] [Indexed: 12/24/2022] Open
Abstract
Substantial knowledge of auditory processing within mammalian nervous systems emerged from neurophysiological studies of the mustached bat (Pteronotus parnellii). This highly social and vocal species retrieves precise information about the velocity and range of its targets through echolocation. Such high acoustic processing demands were likely the evolutionary pressures driving the over-development at peripheral (cochlea), metencephalic (cochlear nucleus), mesencephalic (inferior colliculus), diencephalic (medial geniculate body of the thalamus), and telencephalic (auditory cortex) auditory processing levels in this species. Auditory researchers stand to benefit from a three dimensional brain atlas of this species, due to its considerable contribution to auditory neuroscience. Our MRI-based atlas was generated from 2 sets of image data of an ex-vivo male mustached bat's brain: a detailed 3D-T2-weighted-RARE scan [(59 × 63 x 85) μm3] and track density images based on super resolution diffusion tensor images [(78) μm3] reconstructed from a set of low resolution diffusion weighted images using Super-Resolution-Reconstruction (SRR). By surface-rendering these delineations and extrapolating from cortical landmarks and data from previous studies, we generated overlays that estimate the locations of classic functional subregions within mustached bat auditory cortex. This atlas is freely available from our website and can simplify future electrophysiological, microinjection, and neuroimaging studies in this and related species.
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Affiliation(s)
- Stuart D Washington
- Bio-Imaging Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Julie Hamaide
- Bio-Imaging Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Ben Jeurissen
- Imec-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | | | - Toon Huysmans
- Imec-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Jan Sijbers
- Imec-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Steven Deleye
- Molecular Imaging Center Antwerp, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Jagmeet S Kanwal
- Laboratory for Auditory Communication and Cognition, Georgetown University Medical Center, The Research Building, rm WP09, 3900 Reservoir Rd, NW, Washington, DC 20057, United States of America
| | - Geert De Groof
- Bio-Imaging Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Sayuan Liang
- Bio-Imaging Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Johan Van Audekerke
- Bio-Imaging Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium
| | - Jeffrey J Wenstrup
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH, 44272, United States of America
| | | | - Susanne Radtke-Schuller
- Division of Neurobiology, Biocenter of Ludwig Maximilians University, Grosshadernerstrasse 2, 82152, Planegg-Martinsried, Germany
| | - Marleen Verhoye
- Bio-Imaging Lab, University of Antwerp, Universiteitsplein 1, B-2610, Wilrijk, Belgium.
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Theofanopoulou C. Brain asymmetry in the white matter making and globularity. Front Psychol 2015; 6:1355. [PMID: 26441731 PMCID: PMC4564653 DOI: 10.3389/fpsyg.2015.01355] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 08/24/2015] [Indexed: 12/15/2022] Open
Abstract
Recent studies from the field of language genetics and evolutionary anthropology have put forward the hypothesis that the emergence of our species-specific brain is to be understood not in terms of size, but in light of developmental changes that gave rise to a more globular braincase configuration after the split from Neanderthals-Denisovans. On the grounds that (i) white matter myelination is delayed relative to other brain structures and, in humans, is protracted compared with other primates and that (ii) neural connectivity is linked genetically to our brain/skull morphology and language-ready brain, I argue that one significant evolutionary change in Homo sapiens' lineage is the interhemispheric connectivity mediated by the Corpus Callosum. The size, myelination and fiber caliber of the Corpus Callosum present an anterior-to-posterior increase, in a way that inter-hemispheric connectivity is more prominent in the sensory motor areas, whereas "high- order" areas are more intra-hemispherically connected. Building on evidence from language-processing studies that account for this asymmetry ('lateralization') in terms of brain rhythms, I present an evo-devo hypothesis according to which the myelination of the Corpus Callosum, Brain Asymmetry, and Globularity are conjectured to make up the angles of a co-evolutionary triangle that gave rise to our language-ready brain.
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