which region of the brain has changed the most during the course of vertebrate evolution

Full Answer

Which area of the brain has seen the greatest amount of evolution?

The area of the brain with the greatest amount of recent evolutionary change is called the cerebrum, or neocortex. In reptiles and fish, this area is called the pallium, and is smaller and simpler relative to body mass than what is found in mammals. According to research, the cerebrum first developed about 200 million years ago.

How has the brain changed over the course of evolution?

At the same time, during the course of evolution, the vertebrate brain has undergone changes, and become more effective. In so-called 'lower' animals, most or all of the brain structure is inherited, and therefore their behaviour is mostly instinctive.

How has the size of the brain changed over time?

In addition to just the size of the brain, scientists have observed changes in the folding of the brain, as well as in the thickness of the cortex. The more convoluted the surface of the brain is, the greater the surface area of the cortex which allows for an expansion of cortex, the most evolutionarily advanced part of the brain.

Is there a correlation between brain changes and ecological changes?

Unfortunately, most comparative neurobiologists have not taken the next step and attempted to identify correlations between brain changes and the ecological changes that accompany the origin of a new vertebrate radiation.

Which part of the brain has expanded the most during vertebrate evolution?

neocortexAnd indeed, when we trace the brain's evolution from fish to amphibians to reptiles to mammals and finally to humans, we see that the parts of the brain that have grown the most in human beings are in the neocortex, and more specifically the prefrontal cortex.

What is evolution of brain of vertebrates?

For example, the brains of vertebrates acquired their basic forms such as the forebrain (telencephalon and diencephalon), midbrain, and hindbrain in the early stage of evolution, and have changed the morphology and function of each region while maintaining the basic structures during evolution.

How has the brain changed during the course of evolution?

The increase in size and complexity of our brains opened the way to a spectacular development of cognitive and mental skills. This expansion during evolution facilitated the addition of microcircuits with a similar basic structure, which increased the complexity of the human brain and contributed to its uniqueness.

What part of the brain was vital during human evolution?

cerebellumSummary: The cerebellum -- a part of the brain once recognized mainly for its role in coordinating movement -- underwent evolutionary changes that may have contributed to human culture, language and tool use, according to a new study.

Which part of the brain is well developed in all vertebrates and why?

Optic lobes are well-developed in the midbrain of nonmammalian vertebrates, whereas in mammals the vision centers are mainly in the forebrain. In addition, a bird's cerebellum is large compared to the rest of its brain, since it controls coordination and balance in flying.

Which part of the brain is unique in some mammals in comparison to other vertebrates?

Mammalian brains have certain characteristics that differ from other vertebrates. In some, but not all mammals, the cerebral cortex, the outermost part of the cerebrum, is highly folded, allowing for a greater surface area than is possible with a smooth cortex.

What is the vertebrate brain?

The vertebrate brain is the main part of the central nervous system. In vertebrates (and most other animals) the brain is at the front, in the head. It is protected by the skull and close to the main senses of vision, hearing, balance, taste, and smell.

When did the frontal lobe evolve?

Evidence thus suggests that non-allometric expansion of the prefrontal cortex occurred at the dawn of great apes (~19–15 mya), such that selective pressures for higher cognitive functions underlie frontal lobe organization in both great apes and humans (Smaers et al.

Why did the cerebellum increase in size during human evolution?

These increases in brain size were not driven by disproportionate growth in the neocortex alone, but rather by increases in the size of many parts of the brain. Increases in the relative size of the cerebellum, which is essential for balance and movement, were also important.

What are the three evolutionary levels of the brain?

The three regions are as follows:Reptilian or Primal Brain (Basal Ganglia)Paleomammalian or Emotional Brain (Limbic System)Neomammalian or Rational Brain (Neocortex)

When brain experiences most of its growth and develops most of its potential for learning?

From birth to age 5, a child's brain develops more than at any other time in life. And early brain development has a lasting impact on a child's ability to learn and succeed in school and life.

What is Broca's area responsible for?

Broca's area is a key component of a complex speech network, interacting with the flow of sensory information from the temporal cortex, devising a plan for speaking and passing that plan along to the motor cortex, which controls the movements of the mouth.

Which area of the brain has the greatest amount of recent evolutionary change?

The area of the brain with the greatest amount of recent evolutionary change is called the neocortex. In reptiles and fish, this area is called the pallium, and is smaller and simpler relative to body mass than what is found in mammals. According to research, the cerebrum first developed about 200 million years ago.

How to understand brain evolution?

One approach to understanding overall brain evolution is to use a paleoarchaeological timeline to trace the necessity for ever increasing complexity in structures that allow for chemical and electrical signaling. Because brains and other soft tissues do not fossilize as readily as mineralized tissues, scientists often look to other structures as evidence in the fossil record to get an understanding of brain evolution. This, however, leads to a dilemma as the emergence of organisms with more complex nervous systems with protective bone or other protective tissues that can then readily fossilize occur in the fossil record before evidence for chemical and electrical signaling. Recent evidence has shown that the ability to transmit electrical and chemical signals existed even before more complex multicellular lifeforms.

How do genes control the brain?

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. Lahn and the other researchers 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, Lahn and his team decided to find the specific gene or genes that allowed for or even controlled this rapid evolution. Two genes were found to control the size of the human brain as it develops. These genes are Microcephalin (MCPH1) 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. Lahn's 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.

How to track the evolution of the brain?

One of the prominent ways of tracking the evolution of the human brain is through direct evidence in the form of fossils. The evolutionary history of the human brain shows primarily a gradually bigger brain relative to body size during the evolutionary path from early primates to hominids and finally to Homo sapiens. Because fossilized brain tissue is rare, a more reliable approach is to observe anatomical characteristics of the skull that offer insight into brain characteristics. One such method is to observe the endocranial cast (also referred to as endocasts ). Endocasts occur when, during the fossilization process, the brain deteriorates away, leaving a space that is filled by surrounding sedimentary material over time. These casts, give an imprint of the lining of the brain cavity, which allows a visualization of what was there. This approach, however, is limited in regard to what information can be gathered. Information gleaned from endocasts is primarily limited to the size of the brain ( cranial capacity or endocranial volume ), prominent sulci and gyri, and size of dominant lobes or regions of the brain. While endocasts are extremely helpful in revealing superficial brain anatomy, they cannot reveal brain structure, particularly of deeper brain areas. By determining scaling metrics of cranial capacity as it relates to total number of neurons present in primates, it is also possible to estimate the number of neurons through fossil evidence.

What is the purpose of the medulla?

The purpose of this part of the brain is to sustain fundamental homeostatic functions. The pons and medulla are major structures found there. A new region of the brain developed in mammals about 250 million years after the appearance of the hindbrain.

What is the purpose of the primitive hindbrain?

The purpose of this part of the brain is to sustain fundamental homeostatic functions.

Which part of the brain is the most advanced?

The neocortex is the most advanced and most evolutionarily young part of the human brain. It is six layers thick and is only present in mammals. It is especially prominent in humans and is the location of most higher level functioning and cognitive ability.

What are the questions about vertebrate brain evolution?

Four major questions can be asked about vertebrate brain evolution: 1) What major changes have occurred in neural organization and function? 2) When did these changes occur? 3) By what mechanisms did these changes occur? 4) Why did these changes occur? Comparative neurobiologists have been very successful in recognizing major changes in brain structure. They have also made progress in understanding the functional significance of these changes, although this understanding is primarily limited to sensory centers, rather than integrative or motor centers, because of the relative ease of manipulating the relevant stimuli. Although neuropaleontology continues to provide important insights into when changes occurred, this approach is generally limited to recognizing variation in overall brain size, and sometimes brain regions, as interpreted from the surface of an endocranial cast. In recent years, most new information regarding when neural changes occurred has been based on cladistical analysis of neural features in extant taxa. Historically, neurobiologists have made little progress in understanding how and why brains evolve. The emerging field of evolutionary developmental biology appears to be the most promising approach for revealing how changes in development and its processes produce neural changes, including the emergence of novel features. Why neural changes have occurred is the most difficult question and one that has been the most ignored, in large part because its investigation requires a broad interdisciplinary approach involving both behavior and ecology.

How do brains change?

Mechanistically, brains change either by chance or in response, directly or indirectly, to a change in selective pressures. Historically, changes in brain size or organization are correlated with phylogenetic changes, in particular the origin of a new radiation.

What is a morphocline from anamniotes to amniotes?

A morphocline from anamniotes to amniotes is characterized by an increase in the number of cell classes. Closer examination of the data, however, suggests that there is no increase in number of cell classes in the lamprey—hagfish morphocline or in the reptile—mammal morphocline.

What is the third stage of telencephalic development?

In the third stage, the medial longitudinal zone can be further divided into dorsal (dorsal pallium) and dorsomedial (medial pallium) longitudinal zones. Stage three appears to be the terminal stage of telencephalic development in amphibians, but additional stages can be recognized in reptiles, birds, and mammals.

What is the telencephalic hemisphere?

In the first stage, the telencephalic hemispheres of all tetrapods can be divided into a roof area, or pallium, and a floor area, or subpallium, separated by relatively cell-free zones. In the second stage, the pallium can be divided into lateral (lateral pallium) and medial longitudinal zones.

What does excess brain weight represent?

Jerison (1973) assumed that since the brain size of an “average” mammal was sufficient to maintain basic sensory and motor functions, the “excess” brain weight represented neurons that could be utilized for higher mental functions.

Why is Paleontological data important?

Paleontological data regarding the suspected time of origin of a taxonomic group are still critical for refining estimates of when changes in neural characters occurred. Several examples will demonstrate some of the problems encountered when trying to determine when a particular neural event occurred in evolution.

What is the first detailed map of the regions into which the brain of one of the most closely related organisms to the

Researchers have made the first detailed map of the regions into which the brain of one of the most closely-related organisms to the vertebrates is divided and which could give us an idea of what our ancestor was like.

When did the brain start?

The human brain has undergone an evolutionary process that began some 500 million years ago in the marine animals that lived submerged in the sand and which led to its first central nervous system building plan. This system has been progressively modified and is shared by all modern vertebrates.

What are the three regions of the vertebrate brain that are used to process sensory information?

"The three classic vertebrate cerebral regions (thalamus, pretectum and midbrain) would have emerged evolutionarily through the action of molecular signalling centres that lead to the expansion and division ...

What are the two main regions of the brain?

In summary, both brains, amphioxus and vertebrate, are divided into two main regions: anterior and posterior. In amphioxus, the anterior region splits into two domains, whereas in vertebrates it is divided into many more portions, including the three aforementioned regions which, jointly, would correspond to one of the parts of amphioxus.

What is the brain of an invertebrate organism?

The brain of an invertebrate organism, amphioxus (a fish-like marine chordate), whose place in the evolutionary tree is very close to the origin of the vertebrates, was used for the research.

When did the brain start?

The human brain has undergone an evolutionary process that began some 500 million years ago in the marine animals that lived submerged in the sand and which led to its first central nervous system building plan. This system has been progressively modified and is shared by all modern vertebrates.

Is the cerebral cortex found in Amphioxi?

No cerebral cortex or exclusive region giving rise to the formation of the vertebrate midbrain has been detected in amphioxi. However, a common territory inside the forebrain has been found, which they termed DiMes (Di-Mesencephalic primordium), from which both the midbrain and other important structures of the classic forebrain would derive.

What are the brains of vertebrates?

The brains of living vertebrates are a reflection of thevery diverse niches occupied by the different speciesthat comprise each major taxon (Figure 1) – agnathans(jawless vertebrates) and three radiations of jawedvertebrates: (1) the cartilaginous fishes (chimaerasand sharks, skates, and rays), (2) the ray-finned fishes(bony fishes), and (3) the sarcopterygian (fleshy-finned fish) radiation, which includes tetrapods(amphibians, mammals, reptiles, and birds). Withineach of these major taxa, brain structure varies sub-stantially, with some brains smaller relative to bodysize and less elaborate in terms of cytoarchitectureand others larger and more elaborate. The formercan be referred to as type I brains (Figure 2) and thelatter as type II (Figure 3). This type I–type II distinc-tion is a matter of degree, and where the line is drawnis necessarily somewhat arbitrary. However, withineach radiation, there are clearly some species withhighly complex and enlarged brains relative to otherspecies. Thus, this distinction is of heuristic value inappreciating the range of variation of brain evolutionthat has occurred within each major radiation.That brain enlargement and elaboration hasoccurred four times independently presents a verydifferent reality of how brain evolution has oper-ated than is perceived in the widely held folk-beliefof a sort of scale of nature, or Scala Naturae, thatranks all vertebrates along a simplistic scale. Instead,the picture now appreciated is a much more sophisti-cated and fascinating one in terms of both evolution-ary history and the mechanisms by which it hasproceeded. It is also important to note that the strate-gy of retaining a relatively simple brain in terms ofcytoarchitecture, and one that is of modest size inrelation to the body, is a successful one for manyspecies, just as brain enlargement and elaboration isfor other species. The variation in complexity andrelative brain size that exists across all living verte-brate groups and individual species is a direct func-tion of the available niches and the adaptations ofvarious species that successfully occupy them.

What is the brain of a hagfish?

The brain of hagfishes is largely terra incognita,due to the difficulty of obtaining and working withthese animals (which are covered with a copiousquantity of secreted mucus) in a laboratory setting.Also, the substantial amount of neuronal productionand migration during development results in a highlycomplex brain in terms of its cytoarchitecture, andmany features of the latter do not clearly correspondto those of other vertebrates. A telencephalon with ahighly laminated pallium is present (Figure 3), andthose pallial lamina are in receipt of olfactory infor-mation. A diencephalon is present with recognizabledivisions of epithalamus (habenula), dorsal and (per-haps) ventral thalami, and hypothalamus. Eyes, how-ever, are extremely reduced, and extraocular musclesare absent, with corresponding reduction of retinalprojections and oculomotor nuclei. No cerebellartissue has been identified. Instead of being similar toancestral jawless vertebrates, a good case can bemade for hagfish neural (and other) features beingthe consequence of evolutionary specializations.

What is the process of eversion in fish?

All ray-finned fishes, both type I and type II, undergoan almost unique process of telencephalic pallialdevelopment called eversion. The only other verte-brate that shares this developmental process, andthat to a lesser extent, is the crossopterygian fishLatimeria. Rather than undergoing an outpouchingprocess of hemispheric expansion during develop-ment, as occurs in other vertebrate groups, eversioncauses the most medial part of the telencephalic palli-um to lift upward and outward, eventually archinglaterally. In evagination, the pallium enlarges like aballoon expanding, with its most medial part remain-ing in a medial position, the dorsal part arching dor-sally, and the most lateral part remaining in its lateralposition. In contrast, during eversion, the medial pal-lium comes to lie in the most lateral position, and theoriginally lateral pallium remains most medially andventrally. The geometry of eversion is akin to that of aperson doing a back bend, such that the head, arms,and upper torso curve upwards and then backwards.Thus, as shown for both the reedfish telencephalonshown inFigure 2and that of a teleost telencepha-lon shown inFigure 3, the ventricular surface liesdorsalmost over the dorsal aspect of the everted pallia,and the ventricular cavity extends laterally over eachside to the point where the ependyma (shown as a thinline) attaches.

Do lungfish have brains?

Less information is available for lungfish brains thanfor the brains of amphibians and most other majorvertebrate groups, and very little information is avail-able for the crossopterygianLatimeria, since this ani-mal survives only at great ocean depths underconditions of high pressure. Nonetheless, the anato-mical organization of lungfish and crossopterygianbrains appears to be generally similar to that ofamphibians. As already noted, the telencephalic pal-lium of Latimeriaundergoes partial eversion duringembryological development, whereas evaginationoccurs in lungfishes and amphibians.

Overview

Early history of brain development

One approach to understanding overall brain evolution is to use a paleoarchaeological timeline to trace the necessity for ever increasing complexity in structures that allow for chemical and electrical signaling. Because brains and other soft tissues do not fossilize as readily as mineralized tissues, scientists often look to other structures as evidence in the fossil record to get an understanding of brain evolution. This, however, leads to a dilemma as the emergence of organi…

Role of embryology in the evolution of the brain

Randomizing access and scaling brains up

Brain re-arrangement

Genetic factors of recent evolution

Evolution of the human brain

See also