Biopsychology Lecture Notes PDF

Biopsychology Left Brain – Right Brain  Biopsychology Literature This lecture helps you to prepare for the exam. You can download the Power Point file from Moodle. Without...

Biopsychology Left Brain – Right Brain  Biopsychology Literature This lecture helps you to prepare for the exam. You can download the Power Point file from Moodle. Without Chapter 4! & & All questions concerning the exam: [email protected] 2  Biopsychology Some further interesting books & 3  Biopsychology CHAPTER I HISTORY The dawn of asymmetry research is closely related to first scientific attempts to understand the functional organization of our brain. 4  Biopsychology The Dawn of Asymmetry Research: cerebral duality Arthur Ladbroke Wigan (1785 - 1847) had a friend who suddenly died. At the postmortem examination, when the skull was opened, one cerebral hemisphere was missing. This astounded Wigan and he realized that he made a relevant discovery. He looked for further cases and in 1844, after 20 years of collecting relevant evidence, he published The Duality of the Mind in which he claimed that one hemisphere clearly sufficed to support a fully human mind and that the two brains function independently: “If, for example, as I have so often stated, and now again repeat, one brain be capable of aII the emotion, sentiments, and faculties, which we call in the aggregate, mind--then it necessarily follows that man must have two minds with two brains: and however intimate and perfect their unison in their natural state, they must occasionally be discrepant, when influenced by disease, either direct, sympathetic, or reflex.” (cited by J.E. Bogen, 1986) Thus, Wigan proposed a new view on insanity! 5  Biopsychology One mind in one hemisphere - a recent case (2009) Muckli et al. (2009) report a single case study of a 10-year-old girl (AH) who lacked the entire right cortical hemisphere and most of her right eye (microphtalmus). As I turns out, the development of the AH's right cerebral hemisphere terminated within the 7. gestational week. Absence of the right hemisphere was discovered when AH was 3.5 years old because of mild seizures (brief, involuntary twitching) on the left side. These seizures were successfully treated. AH‘s development and medical history was normal:  humorous, witty and intelligent  mild hemiplegia mainly affecting fine movements of her left hand and fingers (but no paralysis of the left body)  close to normal vision in both hemifields 6 Muckli et al. (2009) PNAS 106:1303-1309  Biopsychology The Dawn of Asymmetry Research: Localizationists against Holists The discovery of brain asymmetries has its roots in the 19th century debate about cerebral organization:  Principle of localization: human mind can be broken down into brain-based building blocks; thus, it is possible to associate specific functions with specific cortical areas  Holistic (the once prevalent) view: human mind as a (holy) unity = the cerebral cortex acts as a whole and cortical areas are equipotential 7  Biopsychology The Dawn of Asymmetry Research: holists Marie-Jean-Pierre Flourens was the leading medical scientist of his time. In the beginning of the 19th century essential information on the brain was lacking. As a young promising physician Flourens was asked to investigate Gall's controversial views on cerebral localization. Flourens developed ablation as a procedure to explore brain functions in animal models (especially pigeons). His logic was straightforward: if a certain function disappears after lesioning a certain area of the brain, than this function was probably generated by this area. These experiments were M.-J.-P. Flourens the first directly proving that mind was located in the brain. (1794-1867) But he could no evidence for cerebral localization. Instead, everything seemed to be everywhere. 8  Biopsychology The Dawn of Asymmetry Research: Holists After carefully watching the operated animals, Flourans concluded: „The cerebral lobes are the exclusive site of sensations perceptions and volitions… All these sensations, perceptions, and volitions concurrently occupy the same area in these organs. Therefore, the ability to feel, perceive, and to desire constitute only one essentially single faculty. (1823)“ „The loss of function was never specific for a certain part of the brain. Instead, the birds were less agile, the more tissue I removed. Thus, functions are not localized but distributed equally over the brain. The more brain tissue you remove, the less capable is the subject. This is in perfect agreement with the homogenous appearance of the brain (1824).“ 9  Biopsychology The Dawn of Asymmetry Research: Localization theory Franz Joseph Gall was the enfant terrible of his time. Never accepted by fellow scientists, he developed a theory that became popular among lay people and physicians. The start of this endavor was an unhappy time in school: Gall observed that pupils that received more attention by teachers had protruding eyes. Later on, as an anatomist, he had the idea that an enlargement of the retroorbital cortex (positioned behind the eyeballs) could had pushed the eyes of these classmates forward. Could it be that speak was localized in this part of the brain? Then, localized cortical bumps should correlate with specific mental abilities. Gall started to tour Europe to find individuals with extreme mental abilities or habits (mathematicians, poets, savage killers, habitual burglers, etc.). He then looked for peculiar bumps on the skull of these people. Franz Joseph Gall (1758 – 1828) 10  Biopsychology The Dawn of Asymmetry Research: Localization theory Gall constructed a skull-map of mental functions with language in the front. Phrenology was born (Gall himself called it cranioscopy) His theory was never accepted by the scientific community. But Gall was the first person arguing that brains have functionally distinct regions. Much later it turned out that he was right; but for the wrong reasons. 11  Biopsychology The Dawn of Asymmetry Research: Localization theory revisited The scientific community was backing Flourens and saw Gall as a charlatan (which he was). The scientific spirit was deeply anti-localizationist. A sole exception was Jean Bouillaud, president of the French Académie de Médicine, dean of the Faculty of Medicine in Paris and commander of the legion d’honneur. Bouillaud was convinced that brain diseases have to be analyzed with upmost care and verified by subsequent autopsies. He observed that lesions of the anterior brain interfer with language and started to believe Gall that it is possible to localize brain functions (1825). He proposed to give 500 Francs to the first scientist who brings a patient Jean Bouillaud with language problems that are not associated with the frontal lobes. (1796 – 1881) 12  Biopsychology The Dawn of Asymmetry Research: Localization theory revisited Ernest Aubertin was the son-in-law of Bouillaud and also supported localization theory. On April 4th, 1861 he presented his new data to the Société Anthropologique. The case was a patient who had shot himself in the head, thereby exposing his brain. The man was still alive but dying. Aubertin decided to gently press a spatula on the frontal cortex while the man was talking. Immediately the man stopped, but continued talking as soon as the spatula was taken away. In the auditorium was Pierre Paul Broca, the young secretary of the Société. He leaned towards the localizationist view since his clinical cases only then made sense. What was missing was a perfect clinical case in which a close relationship between Ernest Aubertin structure and function could be shown. (1825-1893) It came 8 days later. 13  Biopsychology The Dawn of Asymmetry Research: The discovery A few days later, Pierre Paul Broca encountered Leborgne, his first aphasic patient. Leborgne was unable to speak for some time, but understood everything said. In April, Leborgne developed a gangrenous inflammation and died on April 17th, 1861. Upon Leborgne’s death, Broca removed his brain and examined it; he found a large lesion in the frontal lobe of the left hemisphere, just as Aubertin had predicted, and determined that it had been caused by syphilis. The next day, Broca presented Leborgne’s brain, the results of his examination, and a description of his symptoms at the Société d’Anthropologique. Pierre Paul Broca (1824-1880) Leborgne‘s brain 14  Biopsychology The Dawn of Asymmetry Research: The discovery Later that year, Broca saw Lelong, a second aphasic patient. Lelong had suffered a stroke and was capable of uttering only five words. Upon examination, Broca found that the lesion in Lelong’s brain was in the same region as Leborgne’s. At a meeting of the Société d’Anatomie, Broca stated that “the lesion occupied exactly the same seat as with the first – immediately behind the middle third…and precisely on the same side.” Broca subsequently examined the brains of more aphasic patients and concluded that speech production was localized to the third convolution of the left frontal lobe. We now call this spot “Broca’s area”. Thus, in a single step he had establishing the localization of mental functions in the brain and cerebral asymmetry research. Lelong‘s brain „Nous parlons avec l‘hemisphere gauche.“ Broca, P. (1865) Sur le siège de la Faculté du langage articulé. Bull. Soc. Anthropol. (Paris), 6: 377-393 15  Biopsychology The Dawn of Asymmetry Research: The unsong heroes While Broca had reached his apex of scientific esteem, a severe accusation became public: On March 24, 1863 Gustave Dax, the son of Marc Dax had sent a manuscript to the Académie de Médecine on left brain language control. The manuscript contained cases from his father (from 1836) and new material from Gustave Dax. Together, they suggested that language had to be left hemisphere based. Three reviewers scrutinized this study and rejected it. Their review was more than a simple rejection; it was a humiliation. But Gustave Dax didn’t give up. On April 28, 1865 he published the findings in a simple Medical Gazette. Broca possibly saw it but never recognized that the both Dax’ were first. Marc and Gustave Dax were from Sommières, a little town in the Province. There, you can find a place named after them. But even the mayor doesn’t know who they really were… 16  Biopsychology The Dawn of Handedness Research Humans have left traces of their handedness since millions of years. Counting right handed depictions of humans throught global human art shows that nothing has changed about our 90% population asymmetry of right handedness. After the discovery of the cortical location of language asymmetry, scientists were eager to find something similar for handedness. This turned out to be quite difficult… Early theories proposed that the right arm has a better blood supply or is genetically stronger. None of these theories could be Coren & Porac, 1977 substantiated. So, scientists tried to find a difference between left and right hemispheres. 17  Biopsychology The Dawn of Handedness Research Paul Flechsig (1847-1929) believed that handedness can be explained with the asymmetrical crossing of the corticospinal tract. This tract connects the motor cortex with the neurons that control hand movements. Ca. 80% of these fibers cross to the other side, while others remain ipsilateral. Flechsig discovered that in 40% of people, the crossover was asymmetric such that more right-sided axons remained ipsilateral. That could be the mechanism! But subsequent studies showed that the asymmetrical crossing does not correlate with the individuals‘ handedness. Only now, 100 years later, scientists start solving the mystery. Stay tuned… 18  Biopsychology The Dawn of Handedness Research Faurie and Raymond, 2004 Philip H. Pye-Smith (1871) proposed the “sword-and-shield” hypothesis. He assumed that when fighting with swords and shields, the left-side position of the heart posed a problem for left-handers who held their shield on the right side and the sword on the left. As strange as this hypothesis may sound today, it came back much later in modern science but in an inverted manner: Left-handers survive longer in traditional, violent societies.  Biopsychology The Dawn of Facial Asymmetry Research It was love… Freiherr Friedrich Goeler von Ravensburg (1854 - 1896) worked in his dissertation on the Venus of Milo. From his writings it is visible, that he fell in love with this woman. However, he noted that the central line of the statue’s face and the horizontal line through the lips were slightly displaced. He advised all visitors to the Louvre that it was better to observe her in profile from the right-hand side, where she seemed to express more warmth and tenderness. 20  Biopsychology The Dawn of Facial Asymmetry Research Goeler von Ravensburg’s book was badly received. Cesare Lombroso, the “father” of scientific criminology, was convinced that criminals were “born criminal” and could be identified by, e.g., facial asymmetries. Also Max Nordau, the famous physician wrote in his books on “Degeneration” that: “Die Entartung verräth sich beim Menschen durch...in erster Reihe die Asymmetrien, d.h. die ungleiche Entwicklung der beiden Hälften des Gesichts und des Schädels...“ 1835-1909 1849-1923  Biopsychology The Dawn of Facial Asymmetry Research Christoph Hasse (University Breslau) felt that these conclusions were wrong. Hasse photographed the face of the Venus and those of several people of his laboratory. He revealed similar asymmetries as in the Venus of Milo. He then studied the asymmetries of arms, legs, and back bones in 5,141 men of the German army. He could show that both of faces and bodies have asymmetries. So, asymmetry is not pathological; it is normal. Hasse, 1887  Biopsychology The Dawn of Facial Asymmetry Research Werner Wolff (1904-1957) suspected that the two halves of the human face represent two divergent personality traits with the left being the “wish”, and the right one the “official” image. He noted that strangers mainly classify the right-right composites as being more similar to the whole face. However, the photographed persons identify themselves more with the left-hand half of their face. Wolff assumed that the left hemisphere controls language so that the right hemisphere could, by default, be the seat of the unconscious. With the exception of Wolff (1933) all of previous studies on face asymmetries had been written in German. They were forgotten, until Güntürkün (1991) discovered the book of Goeler von Ravensburg (1879) in library of the university of Konstanz and started to reconstruct the whole story. 23  Biopsychology Summary  The discovery of language asymmetry laid the foundation of many basic assumptions about left-right differences. Since only humans have language, cerebral asymmetries were seen as an advanced phylogenetic trait that only exists in humans. This is wrong (chapter 2).  The extremely lateralized control of speech also fostered the view that one hemisphere controls all aspect of a function. Again, this is wrong: Asymmetry is about degree, not of kind: Both hemispheres make differential contributions to a function (e.g. chapter 4, language).  Handedness appears to be so simple, but until today its neural fundamentals are just beginning to emerge. Most importantly, all historical discoveries allude us to think that asymmetries emerge in the cortex. This is wrong and handedness might start outside of the cortex (chapter 5).  Facial asymmetry research is related both to the asymmetry of the self and (chapter 7) and to that of lateralized emotional processing (chapter 8). Thus, the human face could be battleground of different lateralized systems. 24  Biopsychology Sample Questions Who should be regarded as the discoverer of language asymmetry—father and son Dax or Pierre Paul Broca? What is the twofold implication of the scientific work of Broca for neuroscience? What are the initial theories about handedness before scientists discovered links between brain function and handedness? What is the advantage of left-handers in fencing, tennis, and person-to-person combat? Which neuroanatomical features were seen as promising candidates for the neural basis of handedness? How did research on facial asymmetries start? Were asymmetries of face and body initially seen as a normal part of nature or as a signature of abnormality? 25  II. Phylogeny Biopsychology CHAPTER II EVOLUTION OF ASYMMETRIES Behavioral asymmetries can be traced back more than 500 million years. Since then, they are part of the life of many animals, including us. This is because asymmetry pays.  II. Phylogeny Biopsychology The Cambrian Explosion – 500 Million Years Ago  II. Phylogeny Biopsychology The Dawn of Behavioral Asymmetries Asymmetries of behavior can be traced back at least 520 million years due to lateralized bite marks on trilobites: Right side Left side Both sides Cambrian 75% 22% 3% Post-Cambrian 61% 29% 10% (Trilobites represent one of the earliest known groups of arthropods. They were exclusively marine animals that developed a considerable variety of size and life habits. They were among the most successful of all early animals living in the oceans for more than 270 million years.) 28  II. Phylogeny Biopsychology The Dawn of Behavioral Asymmetries Anomalocaris captured prey with a pair of spiny frontal limbs. These limbs and the circular mouth were as hard as human fingernails and thus too soft to bite. So, Anomalocaris needed a trick to crack the trilobites. Possibly, Anomalocaris lodged the right posterior part of the trilobite in its mouth and used its right limb to hold the left frontal end of the prey to repeatedly flex the prey up and down until the hard armor cracked. Thus, Anomalocaris was “handed”. 29  II. Phylogeny Biopsychology The Right Chewing Reptile The small (ca. 40 cm) reptile Captorhinus aguti lived during the Perm. Scientists could show that in 100 fossilized individuals tooth wear was more prevalent on the right side of the jaw. For whatever reason, this little animal was a “right-chewer” and thus constitutes the earliest evidence of lateralized feeding behavior in an early vertebrate (Reisz et al., 2020).  II. Phylogeny Biopsychology Reconstructing the Evolution of Handedness in Vertebrates For 100 years after Broca scientists thought that only humans have cerebral asymmetries. We meanwhile know that this is wrong. But how should we now integrate the wealth of information from hundreds of reports on animal asymmetries? One way is to collect these papers and to reconstruct an evolutionary pedigree. (A) A pigeon uses its left foot to remove an adhesive strip (B) A kea holds an apple with its left claw. (C) A wallaby feeding using its left paw. (D) A chimp pulling out food from a tube using its right hand. Ocklenburg & Güntürkün, 2017 31  II. Phylogeny Biopsychology Reconstructing the Evolution of Handedness in Vertebrates Before starting an evolutionary analysis of hemispheric asymmetries, we have to define possible distributions of diverse asymmetrical traits in a population: Possible distributions of asymmetrical traits No Asymmetry: This trait shows no in populations asymmetry neither at the individual nor population level. Individual Asymmetry: Individuals are lateralized, but 50% are skewed to the left and 50% to the right. Population Asymmetry: the majority of individuals is asym-metric and skewed to one side. 32  II. Phylogeny Biopsychology Reconstructing the Evolution of Handedness in Vertebrates Felix Ströckens Sebastian Ocklenburg Main findings: Asymmetries of limb use are extremely widespread in vertebrates. Limb asymmetries are quite often seen at the level of population asymmetry. Common descend is very unlikely Extreme population asymmetry like in humans is very rare. 33 Ströckens et al.(2013)  II. Phylogeny Biopsychology Handedness in Primates Here only mammals are displayed with primates highlighted. Handedness in primates is widespread but both left and right population asymmetries occur. 34 Ströckens et al.(2013)  II. Phylogeny Biopsychology Handedness in Primates Fagot and Vauclair (1991) suggested that simple movements (picking, scratching, etc.) show not population asymmetry. Complex actions (manipulation of objects, gesturing, etc.) show a right arm population asymmetry. Throwing: A whole-body action Manual Gestures The TUBE task 35  II. Phylogeny Biopsychology Handedness in Primates Analysis of handedness in our closest relatives, the chimps, demonstrates that they indeed show a population asymmetry for right handedness. This, however, is only visible in more complex tasks that go beyond just holding or grasping items. In primates, only species that are able to produce such complex actions show population asymmetry. 36  II. Phylogeny Biopsychology The Evolution of Human Handedness If strong population level handedness emerges when animals develop the need for fine manipulation, it is clear why our population-level handedness is 1:9 (left/right). Our precision of hand control is unreached by any other animal and it goes along with a strong population level right- handedness. But, what about asymmetry of simple actions in humans? We do not really know! All handedness questionnaires test some sort of tool use. Indeed, studies in pre-industrialized cultures reveal that hand actions that are not related to tool-use produce a right handedness of 54%: So, no population asymmetry. Eipo (Papua New Guinea) in 1974. (A) Cutting a tuber; (B) treating a toddler with magic pig fat. Courtesy of Wulf Schiefenhövel. 37  II. Phylogeny Biopsychology The Evolution of Human Handedness Prehistoric stone artifacts from the Lower Pleistocene (up to 2 million years ago) reveal a preferential, clockwise rotation of stone cores during flaking. This pattern possibly reveals the presence of right-handed toolmakers that hold the stone core in the left hand while placing the powerful but very precise stroke with the right (Fig. A). Thus, already before the dawn of modern Homo sapiens, righthandedness must have been part of our behavioral repertoire. Indeed, the Eipo, who live in the eastern highlands of West Papua New Guinea, used to craft their adzes with this identical technique up to the 1990s (Fig. B). Courtesy of Wulf Schiefenhövel. 38  II. Phylogeny Biopsychology The Evolution of Human Handedness A further information source are neolithic cave paintings that show “negative human hands” that are drawn by blowing pigments with a tube onto one hand that is pressed on the cave wall. Faurie and Raymond (2004) showed that 77% of these paintings display the left hand, possibly due to the right hand holding the tube. The authors gave students an identical task and obtained 77.1% left hand negative paintings. Thus, no difference was detected between the two proportions of left- and right-handers, separated by more than 10,000 years. However, we don’t know if each person in the cave produced exactly one image of her/his hand (unlikely), or if a single person produced all images (also unlikely). Thus, a worldwide predominance of right-handedness is visible, but a percentage cannot be drawn. Is there a solution? YES! 39  II. Phylogeny Biopsychology The Evolution of Human Handedness Scratches on the outer face of front teeth of prehistoric skulls show deep scratches that are not found on side teeth or the back face of front teeth. Most scratches run from the upper left to the lower right side (Fig. A). Possibly, pre modern humans held pieces of meat between their teeth, pulled with the left hand (simple movement), while cutting the meat with the other hand (Fig. B; complex movement). Thereby, they scratched their teeth. When volunteers were asked to eat like this, an identical pattern emerged. Thus, the owners of the prehistoric skulls were very likely right handed during their lifetime. 40 Frayer et al.(2016)  II. Phylogeny Biopsychology The Evolution of Human Handedness At Cap Blanc (France) on a high rock shelter, 12,000 - 15,000 years ago, life-size animals were beautifully carved into the rock face and then painted. Close examination of the direction of tool blows show that the artist was left-handed. A female human skeleton of 25 - 35 years was buried in front of the frieze. Was she the artist? An anthropological examination showed that she was left-handed. The reconstruction of her head reminds us that each of the skulls that we scientists analyze was once an individual human being. 41  II. Phylogeny Biopsychology Evolution of limb asymmetries: A summary Limb preferences are a widespread phenomenon in vertebrates. Thus, human handedness is not unique. If a functional organization is so ubiquitous, it has to have an evolutionary advantage. We will speculate about this point at the end. Limb preferences have no single common ancestor within vertebrates, but appear in unrelated clades when a species specializes on some form of action. Limb preferences can be organized as individual or as population asymmetry. We don’t know why left or right. Individual asymmetry is usually observed for more simple manipulations. The strength of population asymmetry is related to the manual complexity of the action. Therefore, parrots and humans show high population asymmetry. Parrots for left, humans for right.  II. Phylogeny Biopsychology Reconstructing the Evolution of Vocalization Asymmetries Interim Summary Lateralization of vocalizations is a widespread in vertebrates. So, our language system is not unique with respect to its asymmetry. There is no common descend. There is evidence for a left hemispheric lateralization of communication in mammals. This is especially visible in primates. So, we possibly inherited our language asymmetry from our primate ancestors. 43 Ocklenburg et al.(2013)  II. Phylogeny Biopsychology The Evolution of Language Asymmetry A left sided dominance for the control of vocalization is an original trait in mammals. It did not only emerge with Homo sapiens. The planum temporale, an area of the temporal cortex that in humans overlaps with the Wernicke language area is 94% enlarged in the left hemisphere in chimps. This left-right difference is even larger in chimps than in humans. 44 Gannon et al., Science, 1998  II. Phylogeny Biopsychology The Evolution of Language Asymmetry In humans, asymmetries of language areas (planum temporale, Broca’s area) are dramatically expanded. In addition, cortical minicolumns with specialized functions in these areas are wider in humans than in apes. The whole temporal cortex has expanded in the human brain, thereby adding neural space for language functions. In addition, the arcuate fasciculus (as part of the superior longitudinal fasciculus) is expanded and grossly left sided lateralized in humans. In non-human primates the arcuate fasciculus is much smaller in chimpanzees and in macaques no laterality of this tract is evident. 45 Rilling, 2014  II. Phylogeny Biopsychology Evolution of vocalization and language systems: A summary Asymmetries of vocalization are widespread among vertebrates. So, human language asymmetry is not unique with respect to its lateralized pattern. Among vertebrates there is no common descend. For mammals, a left-hemispheric superiority for species-specific vocalizations can be traced back to the origins and is consequently found in all mammalian orders, incl. primates. In apes,64% 14% diverse structural 22% asymmetries can be found that closely match the human language system condition. From all this we can conclude that humans inherited the left-hemispheric asymmetry and a basic design of connectivities between cortical areas that now are part of our language system. The evolution of the human language system resulted in the emergence of a large number of human- specific neural entities within both the temporal and the frontal cortex. These have their human- specific morphological and connectional asymmetries like, e.g., the arcuate fasciculus. 46  II. Phylogeny Biopsychology Evolution of Asymmetries in Animals: A summary Asymmetries of body and brain are everywhere. This is true for vertebrates and invertebrates. 14% 64% 22% Güntürkün et al., Physiol. Rev., 2020. 47  II. Phylogeny Biopsychology Asymmetry pays The widespread distribution of cerebral asymmetries in the animal kingdom suggest a strong evolutionary advantage. What exactly is this advantage? First, asymmetry increases perceptual or motor learning effects in a single hemisphere. This gives the individual a much higher lifelong training effect than with the distribution of training would between both hemispheres. Perception: The more one eye is visually dominant, the better are the visual discrimination scores in a natural foraging task in individual pigeons. Güntürkün et al. (2000) 48  II. Phylogeny Biopsychology Asymmetry pays The widespread distribution of cerebral asymmetries in the animal kingdom suggest a strong evolutionary advantage. What exactly is this advantage? First, asymmetry increases perceptual or motor learning effects in a single hemisphere. This gives the individual a much higher lifelong training effect than with the distribution of training would between both hemispheres. processing information in parallel Language/Writing: The more one hand-system is trained, the faster and better we can produce hand writing. 49  II. Phylogeny Biopsychology Asymmetry pays The widespread distribution of cerebral asymmetries in the animal kingdom suggest a strong evolutionary advantage. What exactly is this advantage? First, asymmetry increases perceptual or motor learning effects in a single hemisphere. This gives the individual a much higher lifelong training effect than with the distribution of training would between both hemispheres. Action: Half of sailfish slash fish with a left-, the other half with a right-turn. Each individual is specialized and trained for this one side. There is no population asymmetry. Thus, fish cannot predict which side of the sailfish is dominant. So, they do not know where to escape. Kurvers et al. (2017) 50  II. Phylogeny Biopsychology Asymmetry pays The widespread distribution of cerebral asymmetries in the animal kingdom suggest a strong evolutionary advantage. What exactly is this advantage? First, asymmetry increases perceptual or motor learning effects in a single hemisphere. This gives the individual a much higher lifelong training effect than with the distribution of training would between both hemispheres. Action: Half of sailfish slash fish with a left-, the other half with a right-turn. Each individual is specialized and trained for this one side. There is no population asymmetry. Thus, fish cannot predict which side of the sailfish is dominant. So, they do not know where to escape. Kurvers et al. (2017) 51  II. Phylogeny Biopsychology Asymmetry pays The widespread distribution of cerebral asymmetries in the animal kingdom suggest a strong evolutionary advantage. What exactly is this advantage? Increased learning with one perceptual or motor system also decreases reaction times, resulting in a time advantage of the dominant side. Reaction time: Humans have a right hemisphere advantage to process figures. Even in simple visual figure recognition tasks, they can respond faster when the figure is projected to their right hemisphere. Hausmann & Güntürkün (2000) 52  II. Phylogeny Biopsychology Asymmetry pays The widespread distribution of cerebral asymmetries in the animal kingdom suggest a strong evolutionary advantage. What exactly is this advantage? Parallel and complementary processing during task execution reduces processing redundancy and doubles cognitive power. Asymmetry pays. Visual asymmetry in domestic chicks enables to perform two tasks in parallel (Rogers et al., (2004). In this study chicks had to find grains among pebbles (right eye superiority) and were simultaneously forced to be vigilant for birds of prey (left eye superiority). Lateralized birds could do this well and found more grains, while non-lateralized ones failed. Rogers et al., (2004) 53  II. Phylogeny Biopsychology Summary Asymmetries are at least 500 million years old and so not unique to humans. Cladistic analyses of limb preferences and vocalization asymmetries show that they have emerged and vanished again and again in the vertebrate tree of life. Thus, there is no common ancestor for “brain asymmetry”. However, in primates, common ancestry exists for both a left hemispheric dominance for complex actions and for species-specific communication. Due to our dexterity, we have developed an extreme right hand population bias. Such a strong bias is otherwise only known from parrots. The evolution of our human-specific language system is associated with the development of unique left-hemispheric language areas and pathways. Asymmetries pay. First, by selectively increasing the perceptual- and motor-learning effect in one hemisphere. Second, due to this unihemispheric learning effect, by decreasing reaction times that are controlled by this hemisphere. Third, brain asymmetries provide the great advantage of parallel and complementary processing during task execution. 54  II. Phylogeny Biopsychology Questions What is the evidence for behavioral asymmetries in the Cambrian period and what kind of left-right difference did they reveal? Summarize four main findings from the cladistic analysis of limb preferences. What is an individual- and what is a population-level asymmetry? What is the pattern of human handedness during the execution of simple tasks like picking an object vs during using a tool like a screwdriver? What are the evidences of right-handedness in pre modern humans? Shortly outline the results of what can be said about the evolution of perceptual and production- related species-typical communicative vocalization asymmetries in non-human animals and humans. Why does asymmetry pay? Give three main reasons. 55  III. Connected Hemispheres Biopsychology CHAPTER III The Connected Hemispheres— The Role of the Corpus Callosum for Hemispheric Asymmetries Our two hemispheres have to talk to each other. And they do so mostly via the corpus callosum. Disrupting this large commissure creates two persons in one skull. 56  III. Connected Hemispheres Biopsychology Neuroanatomy of the Corpus callosum and other Commissures Viewing the human brain from the outside, it is obvious that it consists of two halves. While it looks as if these are completely separated by the medial longitudinal fissure, they are in fact connected at several different points. These connections are called “commissures” (from Latin “committere,” which means to join, or to bring together). Commissures consist of tracts of nerve fibers that connect structures in the left and the right hemispheres across the midline. As such, cortical commissures are an extension of the cortical white matter. 57  III. Connected Hemispheres Biopsychology Neuroanatomy of the Corpus callosum and other Commissures The main commissures in the human brain are: Corpus callosum: Connects the left and right frontal, temporal, parietal and occipital lobes of the cerebral cortex Anterior commissure: Connects the left and right temporal lobe of the cerebral cortex and the left and right amygdala Hippocampal commissure: Connects the left and right hippocampus Adhesio interthalamica The Adhesio interthalamica is NOT a commissure but a bilateral bulge of the two thalami that results in their adhesion along the midline. 58  III. Connected Hemispheres Biopsychology Neuroanatomy of the Corpus callosum The largest commissure in the brain of all existing animals is the corpus callosum. The corpus callosum transfers information, and especially action-oriented information between the two hemispheres. Therefore, it is crucial for bilateral integration of sensory, motor or higher cognitive functions. According to Hofer and Frahm (2006) we can distinguish 5 main components: 1. Prefrontal connections 2. Premotor and supplementary motor 3. Motor connections 4. Sensory connections 5. Parietal, temporal, and occipital 59 Hofer an Frahm (2006)  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The History September 1961 W. J. PNAS, 1962 California Institute of Technology Michael Gazzaniga Roger Sperry (CalTech) 60  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The History In the 1960s pharmaceutical aid for epileptic patients was in its infancy. For many patients nothing could be done. The idea to cut the corpus callosum was born out of a “last option” thinking, to prevent (in case of a unihemispheric source of the disease) the seizure to also affect the healthy hemisphere. Practically nothing was known about the corpus callosum. So, animal experiments were conducted to learn more about its function. Corpus Callosum 61  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The History In the normal visual system, optic fibers cross partially at the optic chiasm, such that both eyes see both visual fields (left and right) but each brain hemisphere only sees the contralateral visual field. Roger W. Sperry (1913 – 1994) Nobel Prize 1981 62  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The History Roger Sperry tested the function of the corpus callosum for the transmission of visual information between hemispheres by testing cats in which the corpus callosum was transsected (= hemispheres don‘t interchange information anymore). These studies showed that commissurotomy prevented transfer between hemispheres. But otherwise everything looked normal: the cats and monkeys ate, walked, behaved normally. 63  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The History Josef Bogen So, the first patients were commissurotomized by the neurophysiologist and surgeon Josef Bogen. 64  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The Facts Studies with split-brain patients used the visual half field technique: In a visual half field paradigm the subject is asked to fixate a cross in the middle of the screen. Then a picture is briefly shown on one side, say on the left. Everything to the left of the screen is projected into the the right hemisphere and vice versa. If the subject has to respond quickly with the left hand, the activated sensorimotor circuit is mainly confined to the right half brain that has seen the stimulus. 65  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The Facts Using the visual half field technique it became evident that only the left hemisphere is able to talk. So, all concious communication is confined to an interaction with only half the person. Gazzaniga (2000) 66  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The Facts Vicky is a split-brain patient. Watch her behavior. Is there something unusual? 67  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The Facts In the first months after her surgery, shopping for groceries was infuriating. Standing in the supermarket aisle, Vicki would look at an item on the shelf and know that she wanted to place it in her trolley — but she couldn't. “I'd reach with my right for the thing I wanted, but the left would come in and they'd kind of fight,” she says. “Also like getting dressed posed a similar challenge: Vicki couldn't reconcile what she wanted to put on with what her hands were doing. Sometimes she ended up wearing three outfits at once. “I'd have to dump all the clothes on the bed, catch my breath and start again.” 68  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The Facts Stepwise CC-transsections show that the frontal part of the corpus callosum does not transfer pictures but concepts and meanings. 69  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The Facts The right hemisphere is specialized for spatial processes. Consequently, a commissurotomy obliterates the postoperative ability to draw 3D-objects with the right hand. The right hand is controlled by the left brain. Obviousy, the left hemisphere relied on the right hemispheric 3D-competence before surgery. 70  III. Connected Hemispheres Biopsychology Research with Split-Brain Patients: The Facts The subject is able to say if two horizontal lines that are shown to both hemispheres are broken at the vertical meridian or not. But they are unable to say if the left line is higher or lower than the right line. Patients can decide if two numbers, that are shown separately to the hemispheres, add up to 10 or more. But they cannot say what the additive number is. Patients can say if the two letters shown to each hemisphere make a word or not. But they cannot name this word. They can vaguely describe a person shown to the right hemisphere. But they cannot say who this person is. Especially in split-brain patients that were operated decades ago, a subtle interhemispheric transfer emerges. But this transfer is not fine-grained or declarative but with low resolution and category-based. 71 Sergent, 1987  III. Connected Hemispheres Biopsychology Hemispheric Asymmetries in Information Processing Especially Gazzaniga assumes that the left hemisphere is an „interpreter“ who constantly makes sense of own actions (it interpretes right-hemispheric choices in the context of ist own knowledge). The evidence is a bit anecdotal. Michael Gazzaniga An example is the story of a split-brain patient who was shown a winter scene and a chicken claw and was asked to point with both hands to a matching picture. The left hemisphere made a “Oh, that's simple. The chicken claw goes „farmhouse story“ about this. with the chicken, and you need a shovel to clean out the chicken shed”(Gazzaniga, 2000) 72 Gazzaniga (2000)  III. Connected Hemispheres Biopsychology Hemispheric Asymmetries in Information Processing The left hemisphere seems not only to seek to understand events but also to grasp underlying causes. Thus, it interprets own behavioral acts and generates a logic story according to existing knowledge and unconscious emotional states. 73 Gazzaniga (2000)  III. Connected Hemispheres Biopsychology Hemispheric Asymmetries in Information Processing What the right What the left hemisphere saw: hemisphere saw: 74  III. Connected Hemispheres Biopsychology Hemispheric Asymmetries in Information Processing What the right What the left hemisphere saw: hemisphere saw: What the right hemisphere wrote: What the left hemisphere said: skipping rope 75  III. Connected Hemispheres Biopsychology Hemispheric Asymmetries in Information Processing 80% 20% There are 2 strategies: „Frequency matching“ = 68% (0.8 × 0.8 + 0.2 × 0.2) „Maximizing“ = 80% Thus, maximizing is more successful than calculating the probability of the next event! ? or ? Gazzaniga (2000) 76  III. Connected Hemispheres Biopsychology Hemispheric Asymmetries in Information Processing Asymmetries in hypothesis generation: probability guessing in random events Participant have to predict if a light will appear above or below the horizontal meridian. Arrows indicate, which visual field to make a prediction in. If the arrows pointed to the right, they were told that either a small red square would be presented toward the top of the computer screen on the right side or a small green square would be presented toward the bottom of the screen on the right side and vice versa. Probability differs between the visual fields: while in 80% of cases the red light appears on top of the right visual field, it appears only in 70% of trials in the left visual field. LH = probability matching; RH = maximizing 77 Wolford et al., 2000  III. Connected Hemispheres Biopsychology Research with Callosal Agenesis In rare cases no corpus callosum develops during early ontogeny. We then have a case of callosal agenesis. These patients are different from split-brain patients; their brains had time to adjust to the absence of interhemispheric transfer. For long it was therefore assumed that subcortical commissure can completely compensate the corpus callosum. But as newer studies reveal, this was a wrong assumption. Ocklenburg et al., 2015 78  III. Connected Hemispheres Biopsychology Research with callosal agenesis First of all, patients with callosal agenesis have a major pathway that is lacking in healthy subjects: The Probst bundle is a pathway that is constituted by callosal fibers that tried to pass to the other hemisphere and that now connect the cortex from front to back. We have no idea if this creates a different processing capacity at cortical level. A) Probst bundle in an acallosal subject. B) Equivalent fiber tract in a Bochum psychology student. 79  III. Connected Hemispheres Biopsychology Research with Callosal Agenesis: Handedness Patients with callosal agenesis have a very unusual handedness organization. Their ambidextricity scores is extremely high. Thus, these patients used their hands about equally. On average their handedness was drastically reduced. 80 Ocklenburg et al., 2015  III. Connected Hemispheres Biopsychology Research with Callosal Agenesis: Language Similar to handedness, patients with callosal agenesis have no clear language asymmetry as indicated by dichotic listening: left- and right-ear scores were about the same. Thus, patients with callosal agenesis have a drastic reorganization of their cognitive and motor functions, resulting in a reduction of asymmetries. 81 Ocklenburg et al., 2015  III. Connected Hemispheres Biopsychology Research with Callosal Agenesis: Handedness Erhan Genç analyzed the activity of the primary motor cortex during finger movements. In control subjects the BOLD-signal activity pattern reflected a higher inhibition from left M1 onto right M1 and a lower effort that is necessary for left M1 to activate the dominant right hand. In agenesis patients ipsilateral BOLD was very high. Thus, the low BOLD in controls was a result of inhibition from the other cortex. In addition, there was no difference between left and right contralateral BOLD in patients. This picture shows that handedness results in part from interhemispheric inhibition. Controls Acallosal patients Genç et al., 2015 82  III. Connected Hemispheres Biopsychology Questions How did research on split-brain patients advance our knowledge about hemispheric asymmetries? What is callosal agenesis? What is the functional role of the corpus callosum for functional hemispheric asymmetries? How can interhemispheric integration be experimentally assessed? What is metacontrol? Please describe an experiment to investigate this phenomenon. 83  IV. Structural Asymmetries Biopsychology Structural Hemispheric Asymmetries Due to the shortage of time, this book chapter will not be a part of the lecture. Questions from this book chapter shall also not be part of the exam. 84  V. Language Biopsychology Chapter V Language and the Left Hemisphere Language is the most complex cognitive system that ever evolved. It is orchestrated mostly, but not entirely by the left hemisphere. As complicated this system might be, as intricate the contribution of both hemispheres are arranged – the reason why we have lateralized language is astonishingly simple.  V. Language Biopsychology Lateralized language processing: Basic facts The core areas of the human language system are the Wernicke and the Broca areas. Each of them make specific contribution to language. Since time analysis is mostly left hemisphere based, the left hemisphere can understand words that contain consonants much better. Since frequency analysis is dominated by the right hemisphere, this brain half is mostly related to prosody. Language in total is a bihemispheric feature. However, many critical aspects reside primarily in the left hemisphere. 86  V. Language Biopsychology Language processing: Wernicke‘s area primary auditory cortex Wernicke‘s area secondary auditory cortex 87  V. Language Biopsychology Language processing stream: Wernicke area Carl Wernicke assumed that the Wernicke area contained the memory for the associations between auditory sequences and words. Lesions of this area should render the patient unable to ‚hear‘ a word when listening to its auditory pattern. Indeed, Wernicke patients are defined by comprehension problems while at the same time having a largely preserved ability to speak. This condition is also called pure word deafness. These patients hear everything, of course also spoken words. They also understand the meaning of sounds like doorbells and birdsong. But specifically the comprehension of words is lost. Patient N.B.: „I hear everything. I also know what to do with sounds that are not words. But when you start speaking, it is like listening to a foreign language“. 88  V. Language Biopsychology Challenges of speech processing: Spectogram of a sentence Spectrum analysis visualizes the complex spectral structure of speech (formants): X-axis. Time and intensity (color code) Y-axis: frequency components Level of sound (color coded) Wernicke Area 89 „To return to the main menu, press the star key“.  V. Language Biopsychology Temporal resolution: The narrower the window, the more details of changes over time are we able to detect.  V. Language Biopsychology Temporal resolution: The narrower the window, the Frequency / Spectral resolution more details of changes over time are we able to detect.  V. Language Biopsychology Temporal resolution: The narrower the window, the Frequency / Spectral resolution more details of changes over time are we able to detect.  V. Language Biopsychology Temporal resolution: The narrower the window, the Frequency / Spectral resolution more details of changes over time are we able to detect.  V. Language Biopsychology Temporal resolution: The narrower the window, the Frequency / Spectral resolution: The broader the more details of changes over time are we able to detect. window, the more we can detect slow frequency changes over time. Frequency and time are canonically conjugate variables of sound waves: f· t ≥ 1 / 4π Here, 1f is the standard deviation of frequency and 1t is the standard deviation of time from the peak intensity of the signal. Thus, temporal resolution only comes at the expense of spectral resolution and vice versa.  V. Language Biopsychology Information processing in the temporal gyrus The superior temporal gyrus acts as computational hub that disambiguates complex sounds by isolating different properties of the acoustic information (e.g., temporal and frequency variation) and matches them to stored templates. But what makes the left anterior and posterior superior temporal gyrus so special? Frequency variation Temporal variation frequency Subjects had to discriminate sounds that either varied in the frequency or in the temporal dimension. time 95 Zattore et al., 2001  IV. Language Biopsychology Information processing in the temporal gyrus left primary auditory cortex (AC) right primary auditory cortex (AC) frequency p