I have an interest in the comparative neurobiology of mammals, with a particular focus on humans and great apes. To address questions concerning structural specialization of the brain in different species, my laboratory uses techniques including immunohistochemistry, stereology, MRI, Western blotting, qRT-PCR, RNA-seq, and mass spec. I have published extensively on the evolution of neural specializations for language and social communication functions. I have successfully managed numerous NSF, NIH, and private foundation grants, and supervised six PhD students and 12 postdoctoral fellows over the course of my 16 years as faculty. I have also coordinated the database management and sharing of rare and valuable brains from diverse mammalian species, including chimpanzees. I am committed to collaborative research that is interdisciplinary, allowing correlative analyses of cognition, behavior, brain structure (at macro- and microscopic levels), and genetic variation.
1. A primary focus of my research is directed towards understanding how the human brain differs in anatomical organization from that of closely related primates, such as chimpanzees. This is a topic that is crucial for revealing the neurobiological basis of human-specific cognition, language abilities, and vulnerability to neuropsychiatric and degenerative illnesses. This line of research has demonstrated various highly conserved aspects of brain organization that characterize all primates. For example, similar distributions of GABAergic inhibitory interneuron subtypes are found across regions of the visual and frontal cortex in all anthropoid primates. The human-great ape clade differs from other primates in having relatively greater innervation of prefrontal cortex by the neuromodulators serotonin, dopamine, acetylcholine, and neuropeptide Y. In addition, we have discovered human specializations. For instance, Broca’s area and the anterior insular cortex are among the most differentially enlarged cortical areas in humans. At the microstructural level, we have also demonstrated that the interconnectivity in the grey matter neuropil of humans is relatively greater in regions of the prefrontal cortex, including frontopolar cortex (area 10) and frontoinsular cortex, as compared to chimpanzees.
2. Another important aim of my research has been to determine how changes in brain structure across the lifespan differ among primate species, including humans and chimpanzees. Results from this research have shown that humans and chimpanzees are similar to each other, but differ from macaque monkeys, in having a mid-juvenile peak in synaptogenesis and relatively delayed development of pyramidal neuron morphology in the prefrontal cortex. Notably, however, the human neocortex is distinguished by both prolonged maturation of myelinated axons and more pronounced age-related deterioration as compared to chimpanzees. These differences might be associated with the evolution of slow growth during childhood and an extended lifespan in humans.
3. My research has also addressed the energetic costs associated with changes in brain size and organization. These studies have shown that an increased proportion of glia compared to neurons in the cerebral cortex among primates is related to brain size enlargement. This suggests that metabolic demand of the neocortex might be amplified in apes and humans. This hypothesis is supported by our findings that glutamatergic pathway genes and aerobic forms of lactate dehydrogenase expressed in synapses are upregulated with increasing brain size among primates. Additionally, we have found that the most accelerated changes in metabolome evolution among humans, chimpanzees, macaques, and mice are in prefrontal cortex and muscle tissue of humans.