April 16, 2018What's New
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Researchers show for the first time that healthy older men and women can generate just as many new brain cells as 1) ___ people. There has been controversy over whether adult humans grow new neurons, and some research has previously suggested that the adult brain was hard-wired and that adults did not grow new 2) ___. This study, which appeared in the journal Cell Stem Cell on April 5, 2018, counters that notion. According to the authors the findings may suggest that many senior citizens remain more cognitively and emotionally intact than commonly believed. Results showed that older people have similar ability to make thousands of hippocampal new neurons from progenitor 3) ___ as younger people do. The study also found equivalent volumes of the hippocampus (a brain structure used for emotion and cognition) across ages. Nevertheless, older individuals had less vascularization and maybe less ability of new neurons to make connections.
For the study, the authors autopsied hippocampi from 28 previously healthy individuals aged 14-79 who had died suddenly. This is the first time it was possible to look at newly formed neurons and the state of blood vessels within the entire human hippocampus soon after 4) ___. The researchers had determined that study subjects were not cognitively impaired and had not suffered from depression or taken antidepressants, which the authors had previously found could impact the production of new brain cells. In rodents and primates, the ability to generate new hippocampal cells declines with 5) ___. Waning production of neurons and an overall shrinking of the dentate gyrus, part of the hippocampus thought to help form new episodic memories, was believed to occur in aging humans as well.
The authors from Columbia University and New York State Psychiatric Institute found that even the oldest brains they studied produced new brain cells. While they found similar numbers of intermediate neural progenitors and thousands of immature neurons, older individuals form fewer new 6) ___ vessels within brain structures and possess a smaller pool of progenitor cells -- descendants of stem cells that are more constrained in their capacity to differentiate and self-renew. The authors surmised that reduced cognitive-emotional resilience in old age may be caused by this smaller pool of neural stem cells, the decline in vascularization, and reduced cell-to-cell connectivity within the hippocampus. The authors hypothesized that it is possible that ongoing hippocampal neurogenesis sustains human-specific cognitive function throughout 7) ___ and that declines may be linked to compromised cognitive-emotional resilience.
The authors feel future research on the aging brain will continue to explore how neural cell proliferation, maturation, and survival are regulated by hormones, transcription factors, and other inter-cellular pathways. Other researchers are focusing on brain evolution and have suggested that there are specific genes that control the size of the human brain. These genes continue to play a role in brain evolution, implying that the brain is continuing to evolve.
The study began with the researchers assessing 214 genes that are involved in brain development. These genes were obtained from humans, macaques, rats and mice. The authors noted points in the DNA sequences that caused protein alterations. These DNA changes were then scaled to the evolutionary time that it took for those changes to occur. The data showed the genes in the human brain evolved much faster than those of the other species. Once this genomic evidence was acquired, the authors decided to find the specific gene or genes that allowed for or even controlled this rapid 8) ___. Two genes were found to control the size of the human brain as it develops. These genes are Microcephalin and Abnormal Spindle-like Microcephaly (ASPM). The researchers at the University of Chicago were able to determine that under the pressures of selection, both of these genes showed significant DNA sequence changes.
Earlier studies displayed that Microcephalin experienced rapid evolution along the primate lineage which eventually led to the emergence of Homo sapiens. After the emergence of humans, Microcephalin seems to have shown a slower evolution rate. On the contrary, ASPM showed its most rapid evolution in the later years of human evolution once the divergence between chimpanzees and humans had already occurred. Each of the gene sequences went through specific changes that led to the evolution of 9) ___ from ancestral relatives. In order to determine these alterations, the authors used DNA sequences from multiple primates then compared and contrasted the sequences with those of humans. Following this step, the researchers statistically analyzed the key differences between the primate and human DNA to come to the conclusion, that the differences were due to natural selection. The changes in DNA sequences of these 10) ___ accumulated to bring about a competitive advantage and higher fitness that humans possess in relation to other primates. This comparative advantage is coupled with a larger brain size which ultimately allows the human mind to have a higher cognitive awareness.
Sources and Researchers: Maura Boldrini, Camille A. Fulmore, Alexandria N. Tartt, Laika R. Simeon, Ina Pavlova, Verica Poposka, Gorazd B. Rosoklija, Aleksandar Stankov, Victoria Arango, Andrew J. Dwork, Ren? Hen, J. John Mann. Human Hippocampal Neurogenesis Persists throughout Aging. Cell Stem Cell, 2018; 22 (4): 589 DOI: 10.1016/j.stem.2018.03.015. Cell Press. "Older adults grow just as many new brain cells as young people." ScienceDaily. ScienceDaily, 5 April 2018. www.sciencedaily.com/releases/2018/04/180405223413.htm; Wikipedia
ANSWERS: 1) younger; 2) neurons; 3) cells; 4) death; 5) age; 6) blood; 7) life; 8) evolution; 9) humans; 10) genes