Fliuktuojanti asimetrija (FA) - tai asimetrijos forma, susijusi su atsitiktiniais nukrypimais nuo tikslios kūno simetrijos. Nustatyta, jog gyvūnų populiacijose FA lygis koreliuoja su tam tikrų aplinkos stresų, kuriuos individai patiria savo ontogenetiniame vystymesi, lygiu (Zakharov, 1989; Palmer, 1994). Tokiu būdu, FA gali būti aplinkos kokybės indikatoriumi: kuo mažiau asimetriškų individų populiacijoje, tuo optimalesnė aplinka. Dabartinė bebrų populiacija Lietuvoje yra susiformavusi iš keleto genetiškai skirtingų plitimo židinių. Galima daryti prielaidą, jog skirtingos genetinės struktūros populiacijos gali nevienodai reaguoti į aplinkos stresus. FA lygis buvo tiriamas dešimtyje upių baseinų lokaliose bebrų populiacijose. FA lygis buvo vertinamas pagal 5 metrinius ir 46 nemetrinius bebrų kaukolės požymius. Pirmuoju atveju FA lygis vertintas pagal skirtumų tarp kairės ir dešinės kaukolės pusių dispersiją, antruoju – pagal asimetriškų individų procentą populiacijoje. Tirtų individų imtis – 562. Tyrimų metu buvo nustatyta, kad mažiausiai FA lygis priklauso nuo bebrų lyties pagal nemetrinius kaukolės požymius. Daugiausiai – nuo individų amžinės struktūros. Mažiausiai asimetriški yra jaunikliai (FA lygis siekė 34%), dižiausias FA lygis nustatytas lytiškai subrendusių individų imtyje (46%). Taip pat nustatyta, kad juodą kailį turintys individai yra asimetriškesni už rudą kailį turinčius individus, o individai su dantų vystymosi anomalijomis yra asimetriškesni už dantų anomalijų... [toliau žr. visą tekstą] / Fluctuating asymmetry (FA) it is a form of asymmetry which is related with random deviations off accurate body symmetry. It has been stated, that in animal populations a level of FA correlates with a level of environmental stresses which occure during animals ontogenetic development (Zakharov, 1989; Palmer, 1994). Therefore FA could be an indicator of environmental quality: the less asymmetric individuals in population, the better environment. Present beaver population is formed from several genetically different places in Lithuania. So it could be that genetically different local populations can react to environmental stresses differently. Level of FA in ten river watersheds in local beaver populations has been investigated. Level of FA in skulls of beavers according to 5 metric and 46 non metric traits has been assessed. Level of FA has been assessed according to differences between left and right skull side dispersion in first case, in second case – according to percentage of asymmetric individuals in population. Number of investigated individuals is 562. It has been stated, that level of FA depends on beaver sex at least according to non metric skull traits. Mostly it depends on age structure of individuals. At least asymmetric there are juveniles (level of FA was 34%), great level of FA has been stated in adults (46%). Also it has been stated, that beavers who have black skin are more asymmetric than brown skin ones and individuals who have tooth anomalies are more... [to full text]

There is a clearly established division of functional processing between left and right hemispheres of the brain, with the pattern showing robust consistency across individuals. The finding of functional differences between the hemispheres of the brain raises two important questions: First, what mechanisms gave rise to the lateralized biases in processing function? Second, what are the consequences of functional asymmetry of cognitive processing in the human brain on our everyday behaviour? Examining the mechanisms that give rise to cerebral lateralization, Experiments 1 and 2 tested the assumption that there is a causal relationship in the degree and direction of lateralization between left- and right-hemisphere dominant tasks. In experiment 1, this relationship between left-hemisphere processing of speech sounds and right-hemisphere processing of emotional vocalizations was examined using dichotic listening tasks. An overall complementary pattern of lateralization was observed across participants, but no significant relationship was found for degree of lateralization of speech and emotional vocalization processing within individuals. These results support the view that functions in the left and right hemispheres are independently lateralized. In Experiment 2 we examined the relationship pattern in degree of lateralization between linguistic processing and melody recognition using dichotic-listening tasks. The expected left-hemisphere advantage was observed for the linguistic processing task, but the expected right-hemisphere advantage was not observed for the melody recognition task, precluding an informative assessment of complementarity between the two tasks. The division of processing between the two hemispheres of the brain has been shown to result in lateralized performance advantages and behavioural biases. Examining these consequences of lateralization, Experiments 3 through 6 explored the influence of lateral biases on everyday behaviour. Experiments 3 and 4 examined the influence of asymmetries in facial attractiveness on posing biases. Despite evidence suggesting that the right side of the face is found to be more attractive, professional modeling photographs examined in Experiment 3 revealed a leftward posing bias suggesting that asymmetries in facial attractiveness are not dominant in influencing posing behaviour, even when the purpose of the image is to highlight attractiveness. Experiment 4 controlled for image selection biases by examining posing behaviour directly and revealed a rightward posing bias when participants were asked to emphasize their attractiveness. Experiments 5 and 6 examined the influence of lateralized cognitive processing demands on seating preferences. Experiment 5 investigated the real-world seating patterns of theatre patrons during actual film screenings. It was found that, when processing expectations relied on right-hemisphere dominant processes, such as emotional, facial, or visuospatial processing, people were more likely to choose a seat to the right side of the room. Experiment 6 was designed to test two competing theories that have attempted to explain seating biases: one posits that expectation of processing demand drives the bias; the other posits that basic motor asymmetries drive the bias. Through naturalistic observation, I recorded classroom-seating choices of university students using photographs. When processing expectations relied on left-hemisphere dominant processes, such as linguistic processing, people were more likely to choose seats on the left side of the classroom; this finding contrasts the right side bias observed in theatre seating studies, providing evidence that expectation of processing demands influences the seating bias. Addressing the mechanisms that guide the evolution of lateralization, no support for the assumption of a causal relationship between complementary left-and right-lateralized cognitive functions was found. Additionally, examination of asymmetries in everyday behaviours such as seating and posing provide evidence that the lateralization of cognitive functions has a direct influence on human behaviour and interaction with the environment.

This study examines the extent to which the transfer of legislative competence to polities above and below the state problematizes a national model of membership. The study first examines fragmentation of competences determinative of social membership across the polities of two ‘asymmetric constitutions’ (constitutional structures in which both the whole and the parts are distinct territorially-bounded political communities, and in which legislative competence is allocated unevenly across the constituent polities). Two case studies then explore how those polities exercise those competences so as to define the boundaries of equal social membership, and how these boundaries interact across the constitutional structure. The study highlights three observations in support of its conclusion that constitutional asymmetry presents a challenge to a national model of membership: constituent polities of the asymmetries under examination allocate social rights primarily by reference to residence, thus lending (qualified) support to transnational and a-national theories of membership; differentiated social rights enjoyed by a particular sub-set of nationals are incompatible with the presumed equality of nationals under a national model of membership, resulting in the perception of inequity and discrimination; and the interdependence of membership competences across the constitutional asymmetry means that it is no longer possible for a polity to exclusively determine the boundaries of social membership.

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The interplay between extrinsic and intrinsic processes as they influence a cell’s behaviour is a perennial question in both cellular and developmental biology. In this thesis these two issues are examined in the context of adult stem cells, a somatic stem cell present in the adult murine brain and a germline stem cell present in the adult Drosophila melanogaster ovary. I find that both of these distinct cell types exhibit patterns of non-random chromatid segregation in which the stem cells retain chromosomes carrying the older DNA strands. This unusual behaviour seems to exclusively occur in the context of differentiation, when one cell remains a stem cell and the other goes on to differentiate. Following these studies, the effects of extrinsic processes are tested in adult murine stem cells. It is determined that such cells can only produce neural progeny regardless of their association with foreign environments. These results argue against the phenomenon of stem cell plasticity which is proposed in several other systems and seem to support a primarily intrinsic-centered view of stem cell behaviour. However, the role of adhesion mediating proteins is next studied in such cells to determine their requirement for specific environments. The results of these experiments suggest that adult murine neural stem cells require association with support cells expressing E-Cadherin. Because the loss of such association results in a loss of stem cell number, these data show that intrinsic processes are insufficient to account for all stem cell behaviour. Indeed, based on these data and the results of other studies, it is hypothesized that the extrinsic association of stem cells in these diverse systems determines their polarity and subsequent intrinsic processes that enable these to divide asymmetrically. The implications of this theory are discussed with a view to general biological issues, the proximate mechanisms underlying these phenomena and the ultimate reasons these occur.

Objective: To quantify the acceptability of facial asymmetry to plastic surgeons, orthodontists and the lay population. Methods: Facial images were animated with one of six asymmetries: jaw and nasal deviation, interocular distance, ocular height, angulation, and shape. Evaluators were asked to judge the faces based on their visual acceptability. Results: There were no differences between the groups except for in the evaluation of ocular shape. Mandibular deviation of 4mm, and nasal deviation of 3mm was judged as unacceptable. 9% rounder and 18% flatter eyes were considered unacceptable. Hypertelorism and inferior ocular dystopia was unacceptable after a change of 2mm. Hypotelorism and superior vertical dystopia was unacceptable after a change of 2.5mm. Ocular angulations of 5.5 degrees superiorly and 3.5 degrees inferiorly were unacceptable. Conclusions: Plastic surgeons, orthodontists, and lay people find specific facial asymmetries to be unacceptable at similar levels of deviation.

Objective: To quantify the acceptability of facial asymmetry to plastic surgeons, orthodontists and the lay population. Methods: Facial images were animated with one of six asymmetries: jaw and nasal deviation, interocular distance, ocular height, angulation, and shape. Evaluators were asked to judge the faces based on their visual acceptability. Results: There were no differences between the groups except for in the evaluation of ocular shape. Mandibular deviation of 4mm, and nasal deviation of 3mm was judged as unacceptable. 9% rounder and 18% flatter eyes were considered unacceptable. Hypertelorism and inferior ocular dystopia was unacceptable after a change of 2mm. Hypotelorism and superior vertical dystopia was unacceptable after a change of 2.5mm. Ocular angulations of 5.5 degrees superiorly and 3.5 degrees inferiorly were unacceptable. Conclusions: Plastic surgeons, orthodontists, and lay people find specific facial asymmetries to be unacceptable at similar levels of deviation.

The interplay between extrinsic and intrinsic processes as they influence a cell’s behaviour is a perennial question in both cellular and developmental biology. In this thesis these two issues are examined in the context of adult stem cells, a somatic stem cell present in the adult murine brain and a germline stem cell present in the adult Drosophila melanogaster ovary. I find that both of these distinct cell types exhibit patterns of non-random chromatid segregation in which the stem cells retain chromosomes carrying the older DNA strands. This unusual behaviour seems to exclusively occur in the context of differentiation, when one cell remains a stem cell and the other goes on to differentiate. Following these studies, the effects of extrinsic processes are tested in adult murine stem cells. It is determined that such cells can only produce neural progeny regardless of their association with foreign environments. These results argue against the phenomenon of stem cell plasticity which is proposed in several other systems and seem to support a primarily intrinsic-centered view of stem cell behaviour. However, the role of adhesion mediating proteins is next studied in such cells to determine their requirement for specific environments. The results of these experiments suggest that adult murine neural stem cells require association with support cells expressing E-Cadherin. Because the loss of such association results in a loss of stem cell number, these data show that intrinsic processes are insufficient to account for all stem cell behaviour. Indeed, based on these data and the results of other studies, it is hypothesized that the extrinsic association of stem cells in these diverse systems determines their polarity and subsequent intrinsic processes that enable these to divide asymmetrically. The implications of this theory are discussed with a view to general biological issues, the proximate mechanisms underlying these phenomena and the ultimate reasons these occur.

The twentieth century was dominated by two rival views of scientific explanation. The first is the causal view in which causation is primitive. According to this view, the best explanations are the ones that tell us the cause of a phenomenon, organism, or state of affairs. The second is the unification view, which seeks to unify seemingly disparate bodies of knowledge. Philip Kitcher shook up the debate by synthesizing the two views. He developed a unification theory in which causation is derivative of explanation. The intuitive idea is that the best explanations are the ones that can draw the most conclusions from the fewest basic premises, and these premises just are the causal explanations. There is a problem though. Like any theory of scientific explanation, Kitcher must show that his respects explanatory asymmetry. For instance, we want our scientific theories to say that the height of a flagpole is explanatory of the length of the flagpole's shadow, and not vice versa. Kitcher's view has come under serious attack from Eric Barnes, who claims that Kitcher's theory cannot respect the problem of asymmetry. He gives three examples in which he thinks Kitcher's view fails. Todd Jones tried to defend Kitcher in a paper, but there is still much left to be said. One of his arguments, involving a Newtonian particle system, fails. The status of two of his other arguments is unclear. My goal is to step into the debate between Jones and Barnes and tip the scales in favor of the position that Jones defended. Additionally, I consider new potential cases of asymmetry and show how Kitcher's theory is equipped to accommodate these cases too.

Introduction: A common disorder arising most frequently after a left hemisphere stroke is limb apraxia. Limb apraxia is a deficit of skilled movement, such as performance of activities of daily living (ADLs), that is not a result of primary motor or sensory impairments, or deficits in motivation, memory, or comprehension (De Renzi, 1990). Currently, clinical neuropsychological assessment of apraxia relies largely on qualitative analyses of gross movements during the performance of activities of daily living in two task conditions (pantomime and tool). Further, apraxic patients often perform ADLs with their non-dominant limb to avoid often-present right-hand hemiparesis, but the assessment does not adequately account for this. Thus, it is unclear whether movement deficits are due to non-dominant limb use or limb apraxia. Moreover, it is not known how different task conditions and aging influence the performance of ADLs in healthy populations, as well as manual asymmetries. Purpose: The purpose of this thesis was to: 1. determine if age affects the magnitude of manual asymmetry in the performance of two ADLs (drinking water from a cup and slicing a loaf of bread with a knife); 2. determine if different task demands (pantomime and tool condition) affect magnitude of manual asymmetries during the performance of ADLs; and 3. determine if aging affects how task demands are expressed during the performance of ADLs. Methods: Fifty healthy right-hand dominant (as determined via Waterloo Handedness Questionnaire) younger and older adults participated in this study. A grooved pegboard task was completed by all participants prior to performance of the two ADLs using motion tracking. Upper limb movements (dominant and non-dominant limb) were captured at 60 Hz via a motion capture system (Vicon, Oxford, UK). Participants performed two task conditions: 1) pantomime (pretending to perform an ADL without holding the tool); and 2) tool (pretending to perform an ADL while holding the tool) in two ADLs: drinking water from a cup and slicing a loaf of bread with a knife. Each ADL was performed six times by both limbs. ADLs and limbs were randomized, while task conditions were blocked randomized between participants. Results: Overall, this study found that aging slows down motor performance on the Grooved Pegboard task, as well as the performance of both ADLs. Manual asymmetries were task dependent. The cup and knife ADL were both characterized by larger manual asymmetries in older adults relative to the younger adult group, particularly in terms of angular movement. Further, it was found that task demands were expressed differently in older adults relative to younger adults, with the tool condition yielding performance improvements in both groups. Conclusions: Despite the previous research, which has shown that manual asymmetries are reduced in older adults during the performance of motor tasks, this investigation points to the opposite during the performance of activities of daily living. Aging appears to increase the degree to which manual asymmetries are expressed. Further, aging also appears to play a role in the change in temporal and angular aspects of movement during the performance of ADLs in different task conditions. The degree to which task demands as reflected in the two task conditions improve or impair performance in healthy populations should be taken into consideration when evaluating ADL performance in patients with limb apraxia. In accordance with the previous research on aging, this study has shown that upper limb movements become slower as individuals age. Kinematic relationships presented in this study provide researchers and clinicians with an insight into how manual asymmetries, aging and different task demands come into play during the performance of one cyclical and non-cyclical task.