User:Peanutbutter.05/Evolutionary neuroscience

Evolutionary neuroscience

Evolutionary neuroscience is the scientific study of the evolution of nervous systems. Evolutionary neuroscientists investigate the evolution and natural history of nervous system structure, functions and emergent properties. The field draws on concepts and findings from both neuroscience and evolutionary biology. Historically, most empirical work has been in the area of comparative neuroanatomy, and modern studies often make use of phylogenetic comparative methods. Selective breeding and experimental evolution approaches are also being used more frequently.

Conceptually and theoretically, the field is related to fields as diverse as cognitive genomics, neurogenetics, developmental neuroscience, neuroethology, comparative psychology, evo-devo, behavioral neuroscience, cognitive neuroscience, behavioral ecology, biological anthropology and sociobiology.

Evolutionary neuroscientists examine changes in genes, anatomy, physiology, and behavior to study the evolution of changes in the brain. They study a multitude of processes including the evolution of vocal, visual, auditory, taste, and learning systems as well as language evolution and development. In addition, evolutionary neuroscientists study the evolution of specific areas or structures in the brain such as the amygdala , forebrain and cerebellum as well as the motor or visual cortex.

History

Studies of the brain began during ancient Egyptian times but studies in the field of evolutionary neuroscience began after the publication of Darwin's On the Origin of Species in 1859. At that time, brain evolution was largely viewed at the time in relation to the incorrect scala naturae. Phylogeny and the evolution of the brain were still viewed as linear. During the early 20th century, there were several prevailing theories about evolution. Darwinism was based on the principles of natural selection and variation, Lamarckism was based on the passing down of acquired traits, Orthogenesis was based on the assumption that tendency towards perfection steers evolution, and Saltationism argued that discontinuous variation creates new species. Darwin's became the most accepted and allowed for people to starting thinking about the way animals and their brains evolve.

The 1936 book The Comparative Anatomy of the Nervous System of Vertebrates Including Man by the Dutch neurologist C.U. Ariëns Kappers (first published in German in 1921) was a landmark publication in the field. Following the Evolutionary Synthesis, the study of comparative neuroanatomy was conducted with an evolutionary view, and modern studies incorporate developmental genetics. It is now accepted that phylogenetic changes occur independently between species over time and can not be linear. It is also believed that an increase with brain size correlates with an increase in neural centers and behavior complexity.

Major Arguments

Over time, there are several arguments that would come to define the history of evolutionary neuroscience. The first is the argument between Etienne Geoffro St. Hilaire and George Cuvier over the topic of "common plan versus diversity". Geoffrey argued that all animals are built based on a single plan or archetype and he stressed the importance of homologies between organisms, while Cuvier believed that the structure of organs was determined by their function and that knowledge of the function of one organ could help discover the functions of other organs. He argued that there were at least four different archetypes. After Darwin, the idea of evolution was more accepted and Geoffrey's idea of homologous structures was more accepted. The second major argument is that of the Scala Naturae (scale of nature) versus the phylogenetic bush. The Scala Naturae, later also called the phylogenetic scale, was based on the premise that phylogenies are linear or like a scale while the phylogenetic bush argument was based on the idea that phylogenies were nonlinear and resembled a bush more than a scale. Today it is accepted that phylogenies are nonlinear. A third major argument dealt with the size of the brain and whether relative size or absolute size was more relevant in determining function. In the late 18th century, it was determined that brain to body ratio reduces as body size increases. However more recently, there is more focus on absolute brain size as this scales with internal structures and functions, with the degree of structural complexity, and with the amount of white matter in the brain, all suggesting that absolute size is much better predictor of brain function. Finally, a fourth argument is that of natural selection (Darwinism) versus developmental constraints (concerted evolution). It is now accepted that the evolution of development is what causes adult species to show differences and evolutionary neuroscientists maintain that many aspects of brain function and structure are conserved across species.

Techniques

Throughout history, we see how evolutionary neuroscience has been dependent on developments in biological theory and techniques. The field of evolutionary neuroscience has been shaped by the development of new techniques that allow for the discovery and examination of parts of the nervous system. In 1873, Camillo Golgi devised the silver nitrate method which allowed for the description of the brain at the cellular level as opposed to simply the gross level. Santiago Ramon and Pedro Ramon used this method to analyze numerous parts of brains, broadening the field of comparative neuroanatomy. In the second half of the 19th century, new techniques allowed scientists to identify neuronal cell groups and fiber bundles in brains. In 1885, Vittorio Marchi discovered a staining technique that let scientists see induced axonal degeneration in myelinated axons, in 1950, the “original Nauta procedure” allowed for more accurate identification of degenerating fibers, and in the 1970s, there were several discoveries of multiple molecular tracers which would be used for experiments even today. In the last 20 years, cladistics has also become a useful tool for looking at variation in the brain.

Evolution of the Human Brain

Darwin's theory allowed for people to start thinking about the way animals and their brains evolve.

Reptile Brain

The cerebral cortex of reptiles resembles that of mammals, although simplified. Although the evolution and function of the human cerebral cortex is still shrouded in mystery, we know that it is the most dramatically changed part of the brain during recent evolution. Allegedly, we inherited the reptile brain from ancients lizards. This part of the brain is also known as the deepest layer nd it contains our survival instincts.

Visual perception

Research about how visual perception has developed in evolution is today best understood through studying present-day primates, since the organization of the brain cannot be ascertained only by analyzing fossilized skulls.

As knowledge of the human brain has evolved, researchers discover that our visual perception is much closer to a construction of the brain than a direct "photograph" of what is in front of us. This can lead to misperceiving certain situations or elements in the brain's attempt to keep us safe. For example, an on-edge soldier believing a young child with a stick is a grown man with a gun, as the brain's sympathetic system, or fight-or-flight mode, is activated.

The rabbit–duck illusion is a famous ambiguous image in which a rabbit or a duck can be seen. The earliest known version is an unattributed drawing from the 23 October 1892 issue of Blätter, a German humour magazine. Wikipedia

Visual perception is just that; a subjective perception of the world from the visuals our brain interprets. Based on context alone, the brain can change the firing of its own neurons, therefore changing what we "see". Think back to the last abstract image you saw, where you couldn't tell what you were looking at until somebody told you. As soon as this is registered in your brain, you cannot unsee it. For example, the Rabbit–duck illusion as pictured below.

Much like our other experiences, our visual perception is constructed by the brain. This means that the eyes are not truly seeing, they are receiving stimuli and translating them to the brain, which interprets them as "seeing".

Auditory Perception

The organization of human auditory cortex is divided into core, belt and parabelt. This closely resembles that of present-day primates.

For humans to understand different situations using their hearing ability and differentiate them, they have something called abstraction. Abstraction is defined as an ability to perceive meaning beyond physical in objects and symbols. Multiple functions can occur from the same physical object. Abstraction lets us interpret having a coffee with your boss who says " Congratulations " because of your new promotion differently than you having coffee with your friend who says " You'll do better next time " because you failed your exam. It shows how different scenarios occur with same physical objects that influence our auditory perception on the world around us.

Language development

Evidence of a rich cognitive life in primate relatives of humans are extensive, and a wide range of specific behaviors in line with Darwinian theory are well documented. However, until recently, research has disregarded nonhuman primates in the context of evolutionary linguistics, primarily because unlike vocal learning birds, our closest relatives seem to lack imitative abilities. Evolutionary speaking, there is great evidence suggesting a genetical groundwork for the concept of languages has been in place for millions of years, as with many other capabilities and behaviors observed today.

While evolutionary linguists agree on the fact that volitional control over vocalizing and expressing language is a quite recent leap in the history of the human race, that is not to say auditory perception is a recent development as well. Research has shown substantial evidence of well defined neural pathways linking cortices to organize auditory perception in the brain. Thus, the issue lies in our abilities to imitate sounds.

Beyond the fact that primates may be poorly equipped to learn sounds, studies have shown them to learn and use gestures far better. Visual cues and motoric pathways developed millions of years earlier in our evolution, which seems to be one reason for an earlier ability to understand and use gestures.

Cognitive specializations

Cognitive specialization is an adaptive mechanism used by organisms throughout periods of time to better adapt to a habitat and assure survival. Humans have the ability to pass down these behaviours through genes to an offspring, while other animals are only able to inherit specializations to a certain extent. Specifically, cognitive specializations entail traits and behaviours such as the aquisition, development and evolution of languages, diverse social skills such as trust, the ability to think critically and mutualism, and even problem solving skills and self-awareness. As previously mentioned, very few species are able to inherit select specializations, these species comprise of chimpanzees and bottlenose dolphins, which explains their intelligence and success in the animal kingdom.

The ventromedial prefrontal cortex (VMPFC), which is thought to play a key role in the cognitive control of social interactions, differs in complexity among humanoids. Humanoid species having an underdeveloped VMPFC, like orangutans, show lesser social skills with simple social organizations and solitary lifestyles, while humans, with a well developed VMPFC, show the opposite. The evolution of this part of the brain in primates was likely for the cognitive control of social interactions. High social problem solving pressure would have forced the evolution of the VMPFC in humans. The complexity and development of human brains over other humanoids is proven to be true through the "Theory of Mind" hypothesis: a branch of cognitive sciences. For example, Theory of Mind is proven to be a cognitive specialization specific to humans, with a few possible exceptions. It's defined as the ability to assign mental states to others and differentiate accidental actions from purposeful actions. Theory of mind also helps us understand why another's thoughts and opinions would vary from our own. This ability is found to be crucial for the survival of the human species due to its use in social environments, where communication and global cooperation is needed.

Researchers

• John Allman
• William H. Calvin
• Paul Cisek
• Terrence Deacon
• Merlin Donald
• Jon Kaas
• Glenn Northcutt
• Georg F. Striedter
• Suzana Herculano-Houzel
• Ludwig Edinger
• G. Carl Huber
• Elizabeth C. Crosby
• J. B. Johnston
• C. Judson Herrick
• Sir Grafton Elliot Smith
• George Ellet Coghill
• Nils Holmgren
• James W. Papez
• Olaf Larsell
• Tilly Edinger
• Dorothy L. Cheney

See also

• Evolution of the brain
• Evolution of nervous systems
• Evolutionary physiology
• Evolutionary psychology
• FOXP2 and human evolution
• Neuroethology
• Noogenesis

References

1. Rhodes, J. S., and T. J. Kawecki. 2009. Behavior and neurobiology. Pp. 263–300 in Theodore Garland, Jr. and Michael R. Rose, eds. Experimental Evolution: Concepts, Methods, and Applications of Selection Experiments. University of California Press, Berkeley.
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References

2. Stout, D. 2010. The Evolution of Cognitive Control. Topics in Cognitive Science 2(4):614-630