The vertebrate cerebrum is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres; each of these hemispheres has an outer layer of grey matter, the cerebral cortex, supported by an inner layer of white matter. In eutherian mammals, the hemispheres are linked by the corpus callosum, a large bundle of nerve fibers. Smaller commissures, including the anterior commissure, the posterior commissure and the fornix join the hemispheres and these are present in other vertebrates; these commissures transfer information between the two hemispheres to coordinate localized functions. There are three known poles of the cerebral hemispheres: the occipital pole, the frontal pole, the temporal pole; the central sulcus is a prominent fissure which separates the parietal lobe from the frontal lobe and the primary motor cortex from the primary somatosensory cortex. Macroscopically the hemispheres are mirror images of each other, with only subtle differences, such as the Yakovlevian torque seen in the human brain, a slight warping of the right side, bringing it just forward of the left side.
On a microscopic level, the cytoarchitecture of the cerebral cortex, shows the functions of cells, quantities of neurotransmitter levels and receptor subtypes to be markedly asymmetrical between the hemispheres. However, while some of these hemispheric distribution differences are consistent across human beings, or across some species, many observable distribution differences vary from individual to individual within a given species; each cerebral hemisphere has an outer layer of cerebral cortex, of grey matter and in the interior of the cerebral hemispheres is an inner layer or core of white matter known as the centrum semiovale. The interior portion of the hemispheres of the cerebrum includes the lateral ventricles, the basal nuclei, the white matter. There are three poles of the cerebrum, the occipital pole, the frontal pole, the temporal pole. If the upper part of either hemisphere be removed, at a level about 1.25 cm above the corpus callosum, the central white matter will be exposed as an oval-shaped area, the centrum ovale minus, surrounded by a narrow convoluted margin of gray substance, studded with numerous minute red dots, produced by the escape of blood from divided bloodvessels.
If the remaining portions of the hemispheres be drawn apart a broad band of white substance, the corpus callosum, will be observed, connecting them at the bottom of the longitudinal fissure. Each labium is part of the cingulate gyrus described. If the hemispheres be sliced off to a level with the upper surface of the corpus callosum, the white substance of that structure will be seen connecting the two hemispheres; the large expanse of medullary matter now exposed, surrounded by the convoluted margin of gray substance, is called the centrum ovale majus. The blood supply to the centrum ovale is from the superficial middle cerebral artery; the cortical branches of this artery descend to provide blood to the centrum ovale. The cerebral hemispheres are derived from the telencephalon, they arise five weeks after conception as bilateral invaginations of the walls. The hemispheres grow round in a C-shape and back again, pulling all structures internal to the hemispheres with them; the intraventricular foramina allows communication with the lateral ventricles.
The choroid plexus is formed from vascular mesenchyme. Broad generalizations are made in popular psychology about certain functions being lateralized, that is, located in the right or left side of the brain; these claims are inaccurate, as most brain functions are distributed across both hemispheres. Most scientific evidence for asymmetry relates to low-level perceptual functions rather than the higher-level functions popularly discussed. In addition to this lateralization of some functions, the low-level representations tend to represent the contralateral side of the body; the best example of an established lateralization is that of Broca's and Wernicke's Areas where both are found on the left hemisphere. These areas correspond to handedness however, meaning the localization of these areas is found on the hemisphere opposite to the dominant hand. Function lateralization such as semantics, intonation, prosody, etc. has since been called into question and been found to have a neuronal basis in both hemispheres.
Perceptual information is processed in both hemispheres, but is laterally partitioned: information from each side of the body is sent to the opposite hemisphere. Motor control signals sent out to the body come from the hemisphere on the opposite side. Thus, hand preference is related to hemisphere lateralization. In some aspects, the hemispheres are asymmetrical. There are higher levels of the neurotransmitter norepinephrine on the right and higher levels of dopamine on the left. There is more white matter on the more grey matter on the left. Linear reasoning functions of language such as grammar and word production are late
Situs solitus is the normal position of thoracic and abdominal organs. Anatomically, this means that the heart is on the left with the pulmonary atrium on the right and the systemic atrium on the left along with the cardiac apex. Right-sided organs are the liver, the gall bladder and a trilobed lung as well as the inferior vena cava, while left-sided organs are the stomach, single spleen, a bilobed lung, the aorta. Variants on the normal picture are uncommon. Complete reversal of all organs is known as situs inversus, while reversal of some organs but not others is called situs ambiguus or heterotaxy. Isolated reversal of the heart with normally-patterned viscera otherwise is termed dextrocardia. Although much of humans' external anatomy is bilaterally symmetric, many internal structures must be signaled to develop asymmetrically in order to form the normal situs solitus orientation; this induced asymmetry is thought to be achieved by a number of morphological factors that guide development. For instance, different levels of NODAL proteins on opposite sides of the embryo have been linked to proper bending of the embryonic heart, giving it its asymmetrical form.
As for the question as to how these development-guiding proteins themselves become distributed asymmetrically throughout the embryo, a certain type of embryonic node cell has been identified with cilia that move only in a counter-clockwise orientation, thus producing a sort of'current' in the embryo that would asymmetrically distribute these molecules. Situs inversus Situs ambiguus Chirality
Lateralization of brain function
The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The medial longitudinal fissure separates the human brain into two distinct cerebral hemispheres, connected by the corpus callosum. Although the macrostructure of the two hemispheres appears to be identical, different composition of neuronal networks allows for specialized function, different in each hemisphere. Lateralization of brain structures is based on general trends expressed in healthy patients; each human's brain develops differently leading to unique lateralization in individuals. This is different from specialization as lateralization refers only to the function of one structure divided between two hemispheres. Specialization is much easier to observe as a trend; the best example of an established lateralization is that of Broca's and Wernicke's areas where both are found on the left hemisphere. These areas correspond to handedness, meaning that the localization of these areas is found on the hemisphere corresponding to the dominant hand.
Function lateralization such as semantics, accentuation, etc. has since been called into question and been found to have a neuronal basis in both hemispheres. Another example is. In the cerebellum this is the same bodyside, but in the forebrain this is predominantly the contralateral side. Language functions such as grammar and literal meaning are lateralized to the left hemisphere in right handed individuals. While language production is left-lateralized in up to 90% of right-handers, it is more bilateral, or right-lateralized, in 50% of left-handers. Broca's area and Wernicke's area areas associated with the production of speech and comprehension of speech are located in the left cerebral hemisphere for about 95% of right-handers, but about 70% of left-handers; the processing of visual and auditory stimuli, spatial manipulation, facial perception, artistic ability are represented bilaterally. Numerical estimation and online calculation depend on bilateral parietal regions while exact calculation and fact retrieval are associated with left parietal regions due to their ties to linguistic processing.
The two hemispheres appear to have different value systems. The left hemisphere prefers to reduce moral questions to arithmetic, while the right hemisphere sees the "bigger picture." Depression is linked with a hyperactive right hemisphere, with evidence of selective involvement in "processing negative emotions, pessimistic thoughts and unconstructive thinking styles", as well as vigilance and self-reflection, a hypoactive left hemisphere, "specifically involved in processing pleasurable experiences" and "relatively more involved in decision-making processes". Additionally, "left hemisphere lesions result in an omissive response bias or error pattern whereas right hemisphere lesions result in a commissive response bias or error pattern." The delusional misidentification syndromes, reduplicative paramnesia and Capgras delusion are often the result of right hemisphere lesions. Damage to either the right or left hemisphere, its resulting deficits provide insight into the function of the damaged area.
Left hemisphere damage has many effects on language perception. Damage or lesions to the right hemisphere can result in a lack of emotional prosody or intonation when speaking. Right hemisphere damage has grave effects on understanding discourse. People with damage to the right hemisphere have a reduced ability to generate inferences and produce main concepts, a reduced ability to manage alternative meanings. Furthermore, people with right hemisphere damage exhibit discourse, abrupt and perfunctory or verbose and excessive, they can have pragmatic deficits in situations of turn taking, topic maintenance and shared knowledge. Lateral brain damage can affect visual perceptual spatial resolution. People with left hemisphere damage may have impaired perception of high resolution, or detailed, aspects of an image. People with right hemisphere damage may have impaired perception of low resolution, or big picture, aspects of an image. If a specific region of the brain, or an entire hemisphere, is injured or destroyed, its functions can sometimes be assumed by a neighboring region in the same hemisphere or the corresponding region in the other hemisphere, depending upon the area damaged and the patient's age.
When injury interferes with pathways from one area to another, alternative connections may develop to communicate information with detached areas, despite the inefficiencies. Broca's aphasia is a specific type of expressive aphasia and is so named due to the aphasia that results from damage or lesions to the Broca's area of the brain, that exists most in the left inferior frontal hemisphere. Thus, the aphasia that develops from the lack of functioning of the Broca's area is an expressive and non-fluent aphasia, it is called'non-fluent' due the issues that arise because Broca's area is critical for language pronunciation and production. The area controls some motor aspects of speech production and articulation of thoughts to words and as such lesions to the area result in the specific non-fluent aphasia. Wernicke's aphasia is the result of damage to the area of the brain, in the left hemisphere above the sylvian fissure. Damage to this area causes a defi
In boxing, a southpaw stance is where the boxer has their right hand and right foot forward, leading with right jabs, following with a left cross right hook. It is the normal stance for a left-handed boxer; the corresponding designation for a right-handed boxer is orthodox and is a mirror-image of the southpaw stance. Left-handed boxers are taught to fight in a southpaw stance, but right-handed fighters can fight in the southpaw stance for many reasons. Fighting in a southpaw stance is believed to give the fighter a strategic advantage because of the tactical and cognitive difficulties of coping with a fighter who moves in a mirror-reverse of the norm; this is. Another reason some left-handed fighters are brought up fighting in the orthodox stance is due to the limited number of trainers who specialize in training the southpaw stance. A skilled right-hander, such as Roy Jones Jr. Terence Crawford or Marvin Hagler, may switch to the left-handed stance to take advantage of the fact that most fighters lack experience against lefties.
In addition, a right-hander in southpaw with a powerful left cross obtains an explosively different combination. The converted southpaw may use a right jab followed by a left cross, with the intention of making the opponent slip to the outside of their left side; the converted right-hander can turn their body left and face their opponent, placing them in orthodox, follow up with an unexpected right cross. If the southpaw fighter is right-hand dominant with a strong left cross, this puts the opponent in danger of knockout from each punch in the combination, as jabs with the power hand can stun or knock out in heavier weight classes. While rare, the reverse is true for left-handers. In MMA if one stands in a southpaw stance, one must train one's cross and left low kick to make it fast and dangerous. While rare, cross-dominant MMA fighters and kickboxers could benefit from fighting from a southpaw stance; the "American Heritage Dictionary of the English Language" cites the conventional wisdom that the word "southpaw" originated "from the practice in baseball of arranging the diamond with the batter facing east to avoid the afternoon sun."
Though many claim that the term originated due to the orientation of baseball playing fields in order to keep the sun out of the players' eyes and the resulting alignment of a left-handed pitcher's throwing arm causing the pitcher to have his left hand on the south side of his body, the term had been used decades prior to that to indicate "not-usual". Boxing: Manny Pacquiao, Marvin Hagler, Hector Camacho, Pernell Whitaker, Joe Calzaghe, Vicente Saldivar, Tiger Flowers, Young Corbett III, Gabriel Elorde, Sergio Martínez, Ivan Calderon, Freddie Miller, Victor Ortiz, Sultan Ibragimov, Naseem Hamed, Lucian Bute, Vasyl Lomachenko, László Papp, Ruslan Chagaev Muay Thai/Kickboxing/K-1: Mirko Filipovic, Giorgio Petrosyan, Raymond Daniels MMA: Conor McGregor, Stephen Thompson, Luke Rockhold, Anthony Pettis, Darren Till, Nick Diaz, Nate Diaz, Anderson Silva, Holly Holm, Robbie Lawler, Matt Mitrione, Vitor Belfort, Benson Henderson, Sam Alvey List of left-handed boxers
In combat sports such as boxing, an orthodox stance is one in which the boxer places his left foot farther in front of the right foot, thus having his weaker side closer to the opponent. As it favors the stronger, dominant side—often the right side, see laterality—the orthodox stance is the most common stance in boxing, it is used by right-handed boxers. Many boxing champions, such as Jack Johnson, Anthony Joshua, Marco Antonio Barrera, Evander Holyfield, Rocky Marciano, Ingmar Johansson, Roberto Durán, Floyd Mayweather Jr. Sugar Ray Robinson, Muhammad Ali, Amir Khan, Peter Buckley, Johnny Tapia, Joyce Gracie, Mike Tyson, Larry Holmes, Lennox Lewis, Joseph Parker, Vitali Klitschko, Wladimir Klitschko, Tyson Fury, fought in an orthodox stance; the corresponding designation for a left-handed boxer is southpaw and is a mirror image of the orthodox stance. A southpaw boxer jabs with his right hand; some famous boxers who use southpaw are Marvelous Marvin Hagler, Tyson Fury, Victor Ortiz, Sultan Ibragimov, Naseem Hamed, Joe Calzaghe, Manny Pacquiao, Lucian Bute.
Francisco Palacios, Andre Ward, Terence Crawford fight as orthodox, but switch to a southpaw stance to confuse their opponents. Hagler was the opposite fighting southpaw but able to switch to orthodox; some fighters who are left-handed fight in the orthodox stance with the advantage of a fast, hard jab and left hook, including Oscar De La Hoya, Miguel Angel Cotto, Gerry Cooney, Marco Antonio Barrera. Vasyl Lomachenko is a right-handed fighter who stands in the southpaw stance. Deciding between orthodox or southpaw, expertboxing.com, retrieved 2012-12-19 Southpaws, coxcorner.com, retrieved 2012-12-19 Boxing basics, learnhowtobox.com, retrieved 2013-01-11 Stands and on guard, myboxingcoach.com, retrieved 2012-12-20 What is southpaw in boxing, innovateus.net, retrieved 2012-12-20
In human neuroanatomy, brain asymmetry can refer to at least two quite distinct findings: Neuroanatomical differences between the left and right sides of the brain Lateralized functional differences: lateralization of brain function Neuroanatomical differences themselves exist on different scales, from neuronal densities, to the size of regions such as the planum temporale, to—at the largest scale—the torsion or "wind" in the human brain, reflected shape of the skull, which reflects a backward protrusion of the left occipital bone and a forward protrusion of the right frontal bone. In addition to gross size differences, both neurochemical and structural differences have been found between the hemispheres. Asymmetries appear in the spacing of cortical columns, as well as dendritic structure and complexity. Larger cell sizes are found in layer III of Broca's area; the human brain has rightward anterior asymmetry. There are large asymmetries in the frontal and occipital lobes, which increase in asymmetry in the antero-posterior direction beginning at the central region.
Leftward asymmetry can be seen in the Heschl gyrus, parietal operculum, Silvian fissure, left cingulate gyrus, temporo-parietal region and planum temporale. Rightward asymmetry can be seen in the right central sulcus, lateral ventricle, entorhinal cortex and temporo-parieto-occipital area. Sex-dependent brain asymmetries are common. For example, human male brains are more asymmetrically lateralized than those of females. However, gene expression studies done by Hawrylycz and colleagues and Pletikos and colleagues, were not able to detect asymmetry between the hemispheres on the population level. In the mid-19th century scientists first began to make discoveries regarding lateralization of the brain, or differences in anatomy and corresponding function between the brain’s two hemispheres. Franz Gall, a German anatomist, was the first to describe what is now known as the Doctrine of Cerebral Localization. Gall believed that, rather than the brain operating as a single, whole entity, different mental functions could be attributed to different parts of the brain.
He was the first to suggest language processing happened in the frontal lobes. However, Gall’s theories were controversial among many scientists at the time. Others were convinced by experiments such as those conducted by Marie-Jean-Pierre Flourens, in which he demonstrated lesions to bird brains caused irreparable damage to vital functions. Flourens's methods, were not precise. In 1861 surgeon Paul Broca provided evidence. Broca discovered that two of his patients who had suffered from speech loss had similar lesions in the same area of the left frontal lobe. While this was compelling evidence for localization of function, the connection to “sidedness” was not made immediately; as Broca continued to study similar patients, he made the connection that all of the cases involved damage to the left hemisphere, in 1864 noted the significance of these findings—that this must be a specialized region. He also—incorrectly—proposed theories about the relationship of speech areas to “handedness”. Accordingly, some of the most famous early studies on brain asymmetry involved speech processing.
Asymmetry in the Sylvian fissure, which separates the frontal and parietal lobes from the temporal lobe, was one of the first incongruencies to be discovered. Its anatomical variances are related to the size and location of two areas of the human brain that are important for language processing, Broca’s area and Wernicke's area, both in the left hemisphere. Around the same time that Broca and Wernicke made their discoveries, neurologist Hughlings Jackson suggested the idea of a “leading hemisphere”—or, one side of the brain that played a more significant role in overall function—which would pave the way for understanding hemispheric “dominance” for various processes. Several years in the mid-20th century, critical understanding of hemispheric lateralization for visuospatial and perception, auditory and emotional processing came from patients who underwent split-brain procedures to treat disorders such as epilepsy. In split-brain patients, the corpus callosum is cut, severing the main structure for communication between the two hemispheres.
The first modern split-brain patient was a war veteran known as Patient W. J. whose case contributed to further understanding of asymmetry. Brain asymmetry is not unique to humans. In addition to studies on human patients with various diseases of the brain, much of what is understood today about asymmetries and lateralization of function has been learned through both invertebrate and vertebrate animal models, including zebrafish, pigeons and many others. For example, more recent studies revealing sexual dimorphism in brain asymmetries in the cerebral cortex and hypothalamus of rats show that sex differences emerging from hormonal signaling can be an important influence on brain structure and function. Work with zebrafish has been informative because this species provides the best model for directly linking asymmetric gene expression with asymmetric morphology, for behavioral analyses; the left and right hemispheres operate the contralateral sides of the body. Each hemisphere contains sections of all 4 lobes: the frontal lobe, parietal lobe, temporal lobe, occipital lobe.
The two hemispheres are separated along the mediated longitudinal fissure and
Psychology is the science of behavior and mind. Psychology includes the study of conscious and unconscious phenomena, as well as feeling and thought, it is an academic discipline of immense scope. Psychologists seek an understanding of the emergent properties of brains, all the variety of phenomena linked to those emergent properties; as a social science it aims to understand individuals and groups by establishing general principles and researching specific cases. In this field, a professional practitioner or researcher is called a psychologist and can be classified as a social, behavioral, or cognitive scientist. Psychologists attempt to understand the role of mental functions in individual and social behavior, while exploring the physiological and biological processes that underlie cognitive functions and behaviors. Psychologists explore behavior and mental processes, including perception, attention, intelligence, motivation, brain functioning, personality; this extends to interaction between people, such as interpersonal relationships, including psychological resilience, family resilience, other areas.
Psychologists of diverse orientations consider the unconscious mind. Psychologists employ empirical methods to infer causal and correlational relationships between psychosocial variables. In addition, or in opposition, to employing empirical and deductive methods, some—especially clinical and counseling psychologists—at times rely upon symbolic interpretation and other inductive techniques. Psychology has been described as a "hub science" in that medicine tends to draw psychological research via neurology and psychiatry, whereas social sciences most draws directly from sub-disciplines within psychology. While psychological knowledge is applied to the assessment and treatment of mental health problems, it is directed towards understanding and solving problems in several spheres of human activity. By many accounts psychology aims to benefit society; the majority of psychologists are involved in some kind of therapeutic role, practicing in clinical, counseling, or school settings. Many do scientific research on a wide range of topics related to mental processes and behavior, work in university psychology departments or teach in other academic settings.
Some are employed in industrial and organizational settings, or in other areas such as human development and aging, sports and the media, as well as in forensic investigation and other aspects of law. The word psychology derives from Greek roots meaning study of soul; the Latin word psychologia was first used by the Croatian humanist and Latinist Marko Marulić in his book, Psichiologia de ratione animae humanae in the late 15th century or early 16th century. The earliest known reference to the word psychology in English was by Steven Blankaart in 1694 in The Physical Dictionary which refers to "Anatomy, which treats the Body, Psychology, which treats of the Soul."In 1890, William James defined psychology as "the science of mental life, both of its phenomena and their conditions". This definition enjoyed widespread currency for decades. However, this meaning was contested, notably by radical behaviorists such as John B. Watson, who in his 1913 manifesto defined the discipline of psychology as the acquisition of information useful to the control of behavior.
Since James defined it, the term more connotes techniques of scientific experimentation. Folk psychology refers to the understanding of ordinary people, as contrasted with that of psychology professionals; the ancient civilizations of Egypt, China and Persia all engaged in the philosophical study of psychology. In Ancient Egypt the Ebers Papyrus mentioned thought disorders. Historians note that Greek philosophers, including Thales and Aristotle, addressed the workings of the mind; as early as the 4th century BC, Greek physician Hippocrates theorized that mental disorders had physical rather than supernatural causes. In China, psychological understanding grew from the philosophical works of Laozi and Confucius, from the doctrines of Buddhism; this body of knowledge involves insights drawn from introspection and observation, as well as techniques for focused thinking and acting. It frames the universe as a division of, interaction between, physical reality and mental reality, with an emphasis on purifying the mind in order to increase virtue and power.
An ancient text known as The Yellow Emperor's Classic of Internal Medicine identifies the brain as the nexus of wisdom and sensation, includes theories of personality based on yin–yang balance, analyzes mental disorder in terms of physiological and social disequilibria. Chinese scholarship focused on the brain advanced in the Qing Dynasty with the work of Western-educated Fang Yizhi, Liu Zhi, Wang Qingren. Wang Qingren emphasized the importance of the brain as the center of the nervous system, linked mental disorder with brain diseases, investigated the causes of dreams and insomnia, advanced a theory of hemispheric lateralization in brain function. Distinctions in types of awareness appear in the ancient thought of India, influenced by Hinduism. A central idea of the Upanishads is the distinction between a person's transient mundane self and their eternal unchanging soul. Divergent Hindu doctrines, Buddhism, have challenged this hierarchy of selves, but have all emphasized the importance of reaching higher