Compared to other primates, our brains stand out for their enormous size. Why?
Epidemiological studies examining neurons from diverse primate species have identified distinct genetic adaptations unique to humans, which enable our brains to cope effectively with the constant wear and tear. Dubbed “advanced neuroprotection,” researchers have shed light on the evolutionary process that enabled humans’ massive cerebral cortices to develop their intricate structure, complex connectivity, and remarkable processing capabilities.
It’s nowhere near as wanting to go back into the past. The findings may also foster innovative approaches to address schizophrenia, as well as addiction, due to the gradual degeneration of specific neural cells. Understanding these complex wirings may ultimately lead to the development of synthetic brains capable of studying and learning in ways reminiscent of our own human cognition.
Data hasn’t yet been thoroughly evaluated by various experts in the scientific community. To André Sousa at the University of Wisconsin–Madison, he had expressed no concerns about the project, focusing instead on “the intricacies of human mind evolution and the myriad complexities, including both destructive and optimistic implications.”
Greater Mind, Greater Worth
Approximately six million years ago, our lineage diverged from that of our closest living relative, the chimpanzee, sharing a common ancestral species.
Our minds underwent a sudden and localized expansion in cognitive dimensions. One idea stood out at the forefront of thought. The prefrontal cortex is often referred to as the “executive control center,” enabling us to exercise judgment, make difficult decisions, and cultivate self-discipline by governing our thoughts and behaviors. Buried in the recesses of our minds, a mysterious realm orchestrates emotional responses, allowing for effortless teleportation through mere mental whispers.
Two primary areas are responsible for prepared communication, with their conversation potentially generating components of our minds and social interactions, mirroring the concept of thoughts – where we can accurately assess another individual’s emotions, beliefs, and intentions. Dopamine-producing neurons, a type of vital brain cell, facilitate the bridging of this crucial neural connection.
They could sound acquainted. Dopamine, released by these neurons, earns its nickname as the “feel-good” molecule. While individuals may attain success through various means, Dopamine neurons are distributed throughout the brain, modulating the activity of specific neural networks, including those involved in regulating emotion and movement. Dopamine neurons act as subtle regulators, gradually adjusting the intensity of movement rather than abruptly switching between extremes, allowing for nuanced control over motor responses.
Researchers at the University of California, San Francisco, including writer Alex Palli, explain that various mental faculties are coordinated by specific brain cells.
The puzzle? Compared to our primate cousins, our species boasts only a modest twofold increase in dopamine neurons, an insignificant expansion in light of the remarkable growth in brain size. Researchers scanned the brains of humans and macaque monkeys to uncover key differences in neural structures, revealing a significant expansion of the prefrontal cortex by approximately 18 times, as well as a roughly 7-fold increase in the striatum.
Each dopamine neuron must strive to function more robustly to generate the expanded cognitive territories.
While neurons possess extensive axonal “branches,” they are far from being mere passive conduits. Typically, devices that demand robust performance necessitate substantial amounts of energy to function efficiently. The majority of cellular energy originates from powerful organelles called mitochondria, resembling small peas in shape. As remarkably eco-friendly, neurons naturally decline with age and degenerate in cases of neurodegenerative disorders, such as Parkinson’s disease.
Due to the toxic byproducts produced during dopamine synthesis, dopamine neurons exhibit an inherent vulnerability to degeneration compared to other types of neurons. Forming a potent threat to cellular health, reactive oxygen species behave like microscopic assassins, targeting and ravaging cell components such as mitochondrial membranes and cytoplasmic barriers.
Dopamine-producing neurons employ various mechanisms to counteract their dysfunction. The cells of our body pump out powerful antioxidants and possess sophisticated mechanisms to neutralize toxic compounds. However, ultimately these defenses crumble – especially when confronted by a truly formidable intellect. As the bond between reasoning and emotion within the mind starts to unravel.
Accrued damage to the brain’s most essential neural components cannot be tolerated as a necessary step in the construction of more complex cognitive architectures during evolutionary processes. Despite the intensity of the experience, our brains managed to sidestep the full impact of the trauma. What was the purpose of the brand-new examination?
Evolution in a Dish
Researchers successfully created 3D biomaterials by cultivating stem cells derived from humans and nonhuman primates – including chimpanzees, orangutans, and macaques – into complex structures. After four weeks, the hybrid mini-brains began to secrete dopamine in significant quantities.
While unconventional, the approach of pooling cells from distinct species sets a foundation for in-depth genetic analysis. As cells from diverse species converge into a single mass, researchers found that any differences in gene expression are more likely attributed to an organism’s origins rather than environmental factors or other influences, according to the study.
The ultimate human-chimpanzee-primates hybrid pool comprised cells from eight individuals, seven chimpanzees, a single orangutan, and three macaque monkeys.
The cells functioned harmoniously, generating a comprehensive sample replicating dopamine neurons throughout the striatum, extending connections to the frontal regions of the brain? After culturing cells for approximately 100 days, researchers successfully harvested genetic material from each cell, enabling them to determine which genes were actively expressed and which remained dormant. Scientists thoroughly examined more than 105,000 individual cells in their study.
Compared to various other species, human stem cells are remarkably versatile in their capabilities. The embryonic stem cells gave rise not only to dopamine-producing neurons, but also various other brain cell types. With this unique advantage, humans possessed an additional edge over their primate cousins; whereas dopamine neurons in chimpanzees were less adept at responding to the oxidative stress caused by reactive oxygen species.
Studies on gene expression revealed that human dopamine-producing cells exhibited significantly broader transcriptional profiles for enzymes involved in detoxifying harmful chemicals compared to non-human primates, thereby constraining damage to vulnerable neurons.
When confronted with a pesticide that triggers an influx of reactive oxygen species, the human brain’s neurons mounted a defence by upregulating the production of brain-derived neurotrophic factor (BDNF), a nurturing protein essential for neuronal health. The molecule has long been celebrated in neuroscience for its remarkable ability to stimulate the genesis and maturation of new neurons, as well as reorganize existing neural pathways? Research suggests that BDNF may facilitate ketamine’s antidepressant effects by reorganizing neural connections in the brain.
Unlike their human counterparts, mini-brain neurons derived from chimpanzees failed to increase the production of protective proteins in response to exposure to pesticides.
Carry on Preventing
The researchers scrutinized the nascent hybrid mini-brains during an exceptionally early phase of development, predicated on the assumption that they would not yet possess the capacity for sentience or consciousness.
Researchers aimed to understand how our brains, specifically dopamine neurons, have evolved to develop resilience in the face of injury, tolerating the energy costs associated with a larger brain.
However, the potential outcomes could further improve mobile protection strategies for individuals affected by dopamine-related disorders. Mutations in protective genes identified in the study may actually increase disease susceptibility in certain individuals. Testing them in animal fashion ways paves the path for even more targeted therapies to address these concerns.
Understanding the intricate mechanisms of dopamine’s function at the molecular level across various species provides a fascinating glimpse into what sets humanity apart from its evolutionary antecedents. This breakthrough research has the potential to significantly expand our comprehension of human-enriched challenges, thereby facilitating the identification of innovative therapeutic strategies and optimizing drug development.
