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Scientific Understanding of Consciousness |
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Facial Recognition Improves from Infancy to Adulthood
Science 06 Jan 2017: Vol. 355, Issue 6320, pp. 68-71 Microstructural proliferation in human cortex is coupled with the development of face processing Jesse Gomez, et.al. Neurosciences Program, Stanford University School of Medicine, Stanford, CA 94305, USA. Psychology Department, Stanford University, Stanford, CA 94305, USA. Edmond and Lily Safra Center for Brain Sciences (ELSC), Hebrew University of Jerusalem, Jerusalem, Israel. Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Jülich, Germany. Cécile and Oskar Vogt Institute for Brain Research, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany. JARA-BRAIN Research Division, Jülich Aachen Research Alliance (JARA), Jülich, Germany. Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Aachen, Germany. Stanford Neurosciences Institute, Stanford University, Stanford, CA 94305, USA. [paraphrase] Our ability to recognize faces improves from infancy to adulthood. This improvement depends on specific face-selective regions in the visual system. Gomez et al. tested face memory and place recognition in children and adults while scanning relevant brain regions. Anatomical changes co-occurred with functional changes in the brain. Some regions in the high-level visual cortex showed profound developmental maturation, whereas others were stable. Thus, improvements in face recognition involve an interplay between structural and functional changes in the brain. How does cortical tissue change as brain function and behavior improve from childhood to adulthood? By combining quantitative and functional magnetic resonance imaging in children and adults, we find differential development of high-level visual areas that are involved in face and place recognition. Development of face-selective regions, but not place-selective regions, is dominated by microstructural proliferation. This tissue development is correlated with specific increases in functional selectivity to faces, as well as improvements in face recognition, and ultimately leads to differentiated tissue properties between face- and place-selective regions in adulthood, which we validate with postmortem cytoarchitectonic measurements. These data suggest a new model by which emergent brain function and behavior result from cortical tissue proliferation rather than from pruning exclusively. The ability to recognize faces, which is critical for everyday social interactions, improves from childhood to adulthood. This improvement depends on functional development of face-selective regions in the fusiform gyrus. Understanding how anatomical changes co-occur with cortical functional development has implications for understanding normative and atypical development. However, if and how the cortical tissue of high-level visual cortex changes across development and the functional significance of these changes remain unknown. Because the fusiform gyrus is a hominoid-specific structure, this question can only be answered by obtaining measurements of structure, function, and behavior in awake, behaving humans. Recent advances in quantitative magnetic resonance imaging (qMRI) enabled us to quantify and compare between individuals the amount of brain tissue within a voxel (the region of a tissue slice that corresponds to a pixel in the MRI image), referred to as the macromolecular and lipid tissue volume (MTV), as well as the composition of the tissue, such as the lipid and cholesterol content of cell walls and myelin, as measured by proton relaxation time (T1). These measurements can disambiguate developmental hypotheses to test if, during childhood, macromolecular tissue (i) is pruned, predicting lower MTV and longer T1 in adults than children; (ii) proliferates, predicting higher MTV and shorter T1 in adults than children; or remains stable. In 22 children (between 5 and 12 years of age) and 25 adults (between 22 and 28 years of age), we combined measurements of functional MRI (fMRI; 2.4 mm isotropic voxels, repetition time (TR) = 1 s, multiplex factor = 3), qMRI (1 mm isotropic voxels; four spoiled gradient echo scans using flip angles of 4°, 10°, 20°, and 30°), and visual recognition memory (supplementary materials and methods). Using fMRI, we identified functional regions of interest (fROIs) in each subject’s ventral temporal cortex (VTC) selective for faces in the posterior and mid fusiform gyrus (pFus- and mFus-faces, respectively) and for places in the collateral sulcus (CoS-places). Using qMRI, we obtained maps of T1 and MTV in each individual. Subsequent analyses focused on T1 because it is sensitive to both MTV and tissue composition. Overall, these data suggest a rethinking of the anatomical development of cortex throughout childhood. First, we found a differential development of VTC; some regions showed profound changes, while others remained stable. Second, we found evidence for microstructural proliferation in the fusiform gyrus during childhood, which implicates a different mechanism than the pruning that occurs during infant development. These findings suggest that improvements in behavior are a product of an interplay between structural and functional changes in cortex. [end of paraphrase]
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