Postural Sway and Self-Motion Perception Theory

Postural Sway and Self-Motion Perception Theory Tharushi Kaluarachchi People are often faced with a sensation of motion when gazing at moving clouds or when a train on an adjacent track moves at a railway station (Dichgans Brandt, 1978). Multiple senses contribute to this common visual illusion of self-motion. Optic flow stimuli induces a conflict between visual input, signalling movement of the body and vestibular input from inertial motion cues (A1). Visual-vestibular interactions also play an important role in maintaining postural stability (A4). Thus it is proposed that there is a common underlying mechanism between postural sway during quiet-stance and vection (A5). Recent research has shown that quiet-stance postural sway can be used to predict subsequent vection strength (A5). While many different types of global optic flow can generate self-motion (A2), this relationship has only been demonstrated for radial flow (Apthorp, Nagle, Palmisano, 2014). Therefore, does quiet-stance postural sway predict differences between multiple vection types, or is it simply a global measure distinguishing vection from non-vection? Concepts The experience of vection describes compelling visual illusions of perceived self-motion that are induced by presenting large patterns of optic flow to physically stationary observers (Palmisano, Allison, Schira, Barry, 2015). Optic flow fields provide visual signals for effective navigation through the three-dimensional environment. It describes a pattern of visual motion on the retina used to rapidly estimate the direction of movement (Duffy Wurtz, 1993). This direction is dependent on the nature of this field, differing with radial, lamellar, rotary and spiral patterns of flow (Britten, 2008). A radial pattern refers to expanding and contracting optic flow (Apthorp et al., 2014). A lamellar pattern refers to optic flow with horizontally parallel flow (Stoffregen, 1985). A rotary pattern of optic flow describes a rotating pattern also parallel to the medial-lateral axis. A spiral pattern of optic flow combines radial and rotary patterns, with the rotary component superimposed in radially expanding flow (Nakamura, 2011). The postural system concerns the position and orientation of body segments to organise balance and movement (Massion, 1994). Postural sway refers to readjustments in posture which can occur with medial-lateral (ML), side-to-side, or anterior-posterior (AP), back-and-forth sway (Ruhe, Fejer, Walker, 2011). Quiet-stance postural sway refers to both eyes open and eyes closed postural sway while standing which occurs prior to the onset of vection (Apthorp et al., 2014). Assumptions A1 (vection). Self-motion perception is a multisensory experience induced by conflicts between optic flow stimuli indicating movement and vestibular input which detects no variation in body position or velocity (Lestienne, Soechting, Berthoz, 1977). A2 (optic flow). Radially expanding and contracting optic flow stimulates forwards and backwards linear vection, respectively (Apthorp et al., 2014). For lamellar optic flow, it generates an illusion of self-translation parallel to the direction of flow (Stoffregen, 1985). A rotary pattern induces roll vection parallel to the plane of the presented flow (Tanahashi, Ujike, Kozawa, Ukai, 2007). Spiral optic flow induces a combination of roll and linear vection (Nakamura, 2011). A3 (optic flow and vection). The magnitude of vection varies with the nature of the optic flow, depending on the area, velocity, depth and spatial frequency of the pattern (Palmisano, Apthorp, Seno, Stapley, 2014). In general, more compelling vection will be induced by optic flow displays that generate significant sensory conflict (Palmisano et al., 2015). A4 (vision and posture). Maintenance of upright posture also depends on visual-vestibular cues (Del Percio et al., 2007). The extent of reliance on visual input in particular, indicates variations in posture, with a greater dependence resulting in more postural readjustments (Apthorp et al., 2014). A5 (postural sway and vection). Quiet-stance postural sway and vection are underpinned by the same basic mechanisms. This supports the use of quiet-stance postural sway measures to predict subsequent vection strength. (Palmisano et al., 2014). A6 (postural sway and vection). During upright stance, ML sway involves the control of hip and trunk muscles, whereas AP sway is regulated by ankle muscles. As these are controlled separately by the postural control system, independent variations in ML and AP are predictive of sway differences between vection types (Tucker, Kavanagh, Morrison, Barrett, 2010). Hypotheses Considering that vection magnitude varies with vection type (A3), it is hypothesised that global differences in the magnitude of future vection will be predicted by changes in quiet-stance. In addition, it is proposed that vection magnitude will be stronger for individuals who rely more on their vision for postural stability. Using local differences in sway axes, it is proposed that changes in AP sway will predict radial flow as it stimulates forwards-and-backwards self-motion (A2). For lamellar flow, which induces self-translation and roll vection generated from rotary flow (A2), it is hypothesised that ML changes will be more predictive. In addition, the combination of roll and linear vection from spiral flow may be predicted by sway in both ML and AP axes. Operationalisation Vection magnitude can be operationalised through a subjective verbal vection rating. Subjects verbally rate the strength of their vection experience on a 100 point scale, with ‘0’ indicating no perceived self-motion and ‘100’ indicating complete self-motion (Apthorp et al., 2014). Though self-report measures can be susceptible to subject cognitions, subjective ratings of vection are reasonably reliably as vection is a subjective experience (Palmisano et al., 2015). The multisensory visual-vestibular interaction for posture can be operationalised through postural sway measures. Quiet-stance postural sway, has been shown to predict subsequent vection, which makes it a viable measure of vection (Palmisano et al., 2014). Postural sway can be operationalised through the changes to the location of the centre of foot pressure (CoP) in the AP and ML direction (Ruhe et al., 2011). Larger sway amplitudes are indicative of greater postural instability. Though CoP is an indirect sway measure as it measures motor system activity, it is a practical method of measuring postural sway in standing (Ruhe et al., 2011). References Apthorp, D., Nagle, F., Palmisano, S. (2014). Chaos in balance: non-linear measures of postural control predict individual variations in visual illusions of motion. PloS one, 9(12). Britten, K. H. (2008). Mechanisms of self-motion perception. Annu. Rev. Neurosci., 31, 389-410. Del Percio, C., Brancucci, A., Bergami, F., Marzano, N., Fiore, A., Di Ciolo, E., . . . Eusebi, F. (2007). Cortical alpha rhythms are correlated with body sway during quiet open-eyes standing in athletes: a high-resolution EEG study. Neuroimage, 36(3), 822-829. Dichgans, J., Brandt, T. (1978). Visual-Vestibular Interaction: Effects on Self-Motion Perception and Postural Control. In R. Held, H. Leibowitz H.-L. Teuber (Eds.), Perception (Vol. 8, pp. 755-804): Springer Berlin Heidelberg. Duffy, C. J., Wurtz, R. H. (1993). An illusory transformation of optic flow fields. Vision Research, 33(11), 1481-1490. Lestienne, F., Soechting, J., Berthoz, A. (1977). Postural readjustments induced by linear motion of visual scenes. Exp Brain Res, 28(3-4), 363-384. Massion, J. (1994). Postural control system. Curr Opin Neurobiol, 4(6), 877-887. Nakamura, S. (2011). Effects of viewpoint jitters on roll vection. i-Perception, 2(4), 254-262. Palmisano, S., Allison, R., Schira, M., Barry, R. J. (2015). Future Challenges for Vection Research: Definitions, Functional Significance, Measures and Neural Bases. Frontiers in Psychology, 6. Palmisano, S., Apthorp, D., Seno, T., Stapley, P. (2014). Spontaneous postural sway predicts the strength of smooth vection. Exp Brain Res, 232(4), 1185-1191. Ruhe, A., Fejer, R., Walker, B. (2011). Center of pressure excursion as a measure of balance performance in patients with non-specific low back pain compared to healthy controls: a systematic review of the literature. European Spine Journal, 20(3), 358-368. Stoffregen, T. A. (1985). Flow Structure Versus Retinal Location in the Optical Control of Stance. Journal of Experimental Psychology: Human Perception and Performance, 11(5), 554-565. Tanahashi, S., Ujike, H., Kozawa, R., Ukai, K. (2007). Effects of visually simulated roll motion on vection and postural stabilization. Journal of neuroengineering and rehabilitation, 4(1), 39-39. Tucker, M. G., Kavanagh, J. J., Morrison, S., Barrett, R. S. (2010). Differences in rapid initiation and termination of voluntary postural sway associated with ageing and falls-risk. J Mot Behav, 42(5), 277-287.

Raymond Carver Essay

Raymond Carver was a short story writer who was born in the Pacific Northwest. He was a textbook editor, lecturer and teacher while writing. His stories featured some of his trademarks of, alcohol, poverty, and people in real life situations. Carver was influenced to write about these trademarks through experiences he had lived and influences that were brought upon him, like alcoholism and divorce. Raymond Carver and his father were alcoholics and had both been divorced and remarried through out their lives which is why alcohol, divorce, and fading love are some of the biggest themes he incorporates in his stories. Raymond Carver also expresses puzzlement about the odd and battered condition of love in his profound themes. Specifically in his two short stories, â€Å"What We Talk About When We Talk About Love† and â€Å"Popular Mechanics.† As a writer Carver always tried to add some aspect of intensity or menace in his work. He was known as a literary minimalist because he likes to shorten sentences by removing words or phrases. This writing technique he uses creates a sense of uncertainty in the sentences and leaves the reader guessing. Minimalist writers like Carver, won’t tell you exactly what to think through their diction, instead, they leave their work open ended so the reader can participate in the interpretation of the story and fill in the blank themselves. Carver even says in one of his books called â€Å"Fires†: â€Å"I like it when there is some sense of menace in short stories†¦. there has to be a tension, a sense that something is imminent†¦.† ( Fires 17). Carver creates that state of uncertainty in â€Å"What We Talk About When We Talk About Love† when the four characters are conversing amongst each other about love. Terri and Mel tell stories about their past marriages. Mel had a very demanding wife while Terri was involved with a guy that abused her. The conversation in the room gradually becomes quieter and quieter as they continue to talk about love and drink gin. Mel says to Terri: â€Å"Just shut up for once in your life, Mel said very quietly. Will you do me a favor and do that for a minute?† (What We Talk About 146) Sentences like these seem out of place in a conversation about love, and because of those lines Mel and Terri’s relationship seems unclear and uncertain. The entire story revolves around a certain speech or passage by Mel. As Mel drinks more and more the title of the story, â€Å"What We Talk About When We Talk About Love†, has more meaning and makes the reader and the characters think, just what do we talk about when we talk about love. Even though Mel is drunk when he says his speech, there is truth in his words: â€Å"What do any of us really know about love? Mel Said. ‘It seems to me we’re just beginners at love†¦Ã¢â‚¬ ¦..Am I wrong? Am I way off base? Because I want you to set me straight if you think I’m wrong. I want to know. I mean, I don’t know anything, and I’m the first one to admit it.† (What We Talk About 144-145) Fred Moramarco, a professor at San Diego State University, wrote an article called â€Å"Carver’s Couples Talk About Love† and said: â€Å"When I read this passage in my class, my Southern California students, nearly all of them from families that have experienced divorce, both understand it and are bewildered by it simultaneously. Which is to say they recognize it as the contemporary world they live in, a world of serial relationships where one year’s love is the next year’s courtroom adversary.† (Carver’s Couples Talk About Love-Moramarco) This article is beneficial in explaining and showing how relationships can be deceiving and not always straight forward. This is an other example of how Carver’s condition of love puzzled Moramarco’s students even when they understood it. Raymond Carver underlines the confusion about love with two motifs. He uses his structural element or symbolic structure in his story through things like alcohol and light. Carver uses a symbolic structure in his work that he excepts the reader to make sense of. He uses symbolic images like metaphors to help add to the interpreting the story. In the first paragraph of â€Å"What We Talk About When We Talk About Love† Carver says: â€Å"Sunlight filled the kitchen from the big window behind the sink.†(What We Talk About 137) Which is a symbolic comment because as the characters talk about their experiences with love the light that once filled the room is gone and the story ends with: â€Å"Not one of us moving, not even when the room went dark. (What We Talk About154) These lines show that as the characters keep drinking they start to think, and realize the complexity of love until they figure out that love is not as straight forward as they think. Carver again links alcohol and light when Nick says: â€Å"Maybe we were a little drunk by then. I know it was hard keeping things in focus. The light was draining out of the room, going back through the window where it had come from. Yet nobody made a move to get up from the table to turn on the overhead light.†(What We Talk About 152) The transient love that the characters experience is short and it makes them feel that they have arrived somewhere, but really they have not accomplished much. As the story progresses and the characters keep drinking, they talk more and more about love. Also as they talk about their experiences with love it becomes clear to them that they do not know as much about love as they thought they did. The stories conclusion hits the characters with a sense of reality. All the gin is finished and Nick and the readers hear the sound of four human hearts beating in the darkness: â€Å"I could hear my heart beating. I could hear everyone’s heart. I could hear the human noise we sat there making, not one of us moving, not even when the room went dark.† (What We Talk About 154) Raymond Carver uses the same symbolic structure in his short story, â€Å"Popular Mechanics.† In â€Å"Popular Mechanics† Carver uses great detail and many symbols to carry his theme that not all relationships end happily. He uses these things to bring out the theme of this depressing, but truthful story that many couples these days experience. Carver starts off the story with: â€Å"Early that day the weather turned and cars slushed by on the street outside, where it was getting dark. But it was getting dark on the inside too.† (Popular Mechanics 288) This line represents the relationship between the man and the woman. The line: â€Å"it was getting dark on the inside too† (Popular Mechanics 288), is representative of the feelings of the couple, which are changing from happiness to hatred and anger. He uses the same symbolic structure again when the weather outside is dark and he says: â€Å"But it was getting dark on the inside too.† Sentences like these make the reader believe that there is something wrong in the relationship. The details Carver uses helps the reader interpret so many images and help the reader piece together the big picture. Also it is very obvious to see that the man and women are unhappy just by their attitudes towards each other. The couple argues about who will take the baby to the point where they are both pulling on it. By showing the couple arguing immaturely, Carver tries to show that they are far from happy. He lets us know this through his extreme detail in his symbolic structure. It is essential to look for these symbolic elements to understand the meanings of Raymond Carver’s work. Carver is known for his minimal writing style, simplified language, and irregular plots. His writing style helps capture the experiences and emotions his characters face, which often include guilt, grief, hopelessness, and the effects of fading love. Also his common themes are a response to his history involving the influence of alcoholism and divorce with himself and his parents. In â€Å"What We Talk About When We Talk About Love† Carver hints puzzlement and confusion about love through his symbolic lines about alcohol and light, along with expressing the confusion more clearly through certain passages his characters say like Mel’s speech. However in â€Å"Popular Mechanics† Carver shows it by using great detail, symbols, and through the actions of his characters.

Lovelace Happy Feet

Every Emperor Penguin sings a unique song called a â€Å"heartsong† to attract a mate. If the male penguin's heartsong matches the female's song, the two penguins mate. Norma Jean, a female penguin, falls for Memphis, a male penguin and they become mates.They lay an egg, which is left in Memphis' care, while Norma Jean leaves with the other females to fish. While the males struggle through the harsh winter, Memphis briefly drops the egg.The resulting chick, Mumble, has no vocal talent, but can tap dance. Nevertheless, he is enamored with Gloria, a female penguin who is regarded as the most talented of his age. One day, Mumble encounters a group of hostile Skua, with a leader who is tagged with a yellow band, which he claims to have been from an alien abduction.Mumble narrowly escapes the hungry birds by falling into a crevice.Years later, an adult Mumble is now an outcast who is frowned upon by his elders. After being shunned during the graduates' song, he is attacked by a leo pard seal. After escaping, he befriends a group of Adelie Penguins called â€Å"the Amigos†, who embrace Mumble's dance moves and assimilate him into their group.After seeing a hidden human excavatorin an avalanche, they opt to ask Lovelace, aRockhopper Penguin, about its origin. Lovelace has the plastic rings of a six pack entangled around his neck, which he claims to have been bestowed upon him by mystic beings.For the emperor penguins, it is mating season and Gloria is the center of attention.Ramon tries to help Mumble win her affection by singing a Spanish version of â€Å"My Way†, with Mumble lip syncing. When Gloria sees Ramon behind Mumble's back, she becomes angry and turns away. As a last resort, Mumble begins tap dancing in synch with her song.She falls for him and all the youthful penguins join in for singing and dancing to â€Å"Boogie Wonderland†. The elders are appalled by Mumble's conduct, which they see as the reason for their lean fishing season .Memphis begs Mumble to stop dancing, for his own sake, but when Mumble refuses, he is banished.Mumble and the Amigos return to Lovelace, only to find him being choked by the plastic rings. Lovelace confesses they were snagged on him while swimming off the forbidden shores, beyond the land of the elephant seals.Not long into their journey, they are met by Gloria, who wishes to join with Mumble as his mate. Fearing for her safety, he ostracizes Gloria, driving her away.At the forbidden shore, the group finds a fishing boat. Mumble pursues it solo to the brink of exhaustion.He is eventually washed up on the shore of Australia, where he is rescued and kept at Marine World with Magellanic Penguins. After a long and secluded confinement in addition to fruitlessly trying to communicate with the humans, he nearly succumbs to madness. When a girl attempts to interact with Mumble by tapping the glass, he starts dancing, which attracts a large crowd.He is released back into the wild, with a t racking device attached to his back. He returns to his colony and challenges the will of the elders. Memphis reconciles with him, just as a research team arrives, proving the aliens to be true. The whole of the colony, even Noah, engages in dance.The research team returns their expedition footage, prompting a worldwide debate. The governments realize they are overfishing, leading to the banning of all Antarctic fishing. At this, the Emperor Penguins and the Amigos celebrate. In the final scene, a baby penguin is seen dancing next to Mumble and Gloria, revealed to be their son Erik in Happy Feet Two.

Mental Illness And Its Effects On Society - 985 Words

Comprehensive Case Study Vanessa Brown University of South Carolina SOWK 760 Professor Jennifer Butler 11/20/16 Introduction In the United States, there are many people who suffer from a mental illness. Mental illness is described as causing disruptions in one’s emotional state, thought processes, and behaviors. When analyzing this this concept, one can see that mental illness is a blanket term that encompasses a wide array of mental disorders that range from mild or to severe. No one completely understands the direct cause of mental illness. Some believe that it is attributed to a biological component which argues that it is a bodily process or chemical imbalance in the brain. On the other hand, others argue that mental illness has more to do with the psychological aspect which states that one’s environment and upbringing has a huge influence. Whatever the case may be, mental illness is definitely occurring within our society, and this is a very important issue that needs to constantly be addressed. Too many times within our society, mental illness goes unaddressed because it is not discuss ed as much as it should be, people stay in denial so they do not admit they have an issue; thus foregoing, treatment due to taboo; some may not know they have an issue; or some may know they have an issue but do not have the appropriate resources to get the assistance needed for treatment. In this paper, I am going to address a case study of a client who is actually aware ofShow MoreRelatedMental Illness And Its Effects On Society1405 Words   |  6 Pagesonce stated, â€Å"Mental illness is nothing to be ashamed of, but stigma and bias shame us all.† Mental illness comes with multiple influences towards the daily life of an individual. On one hand, these individuals must try to manage the symptoms that arise with their disease. 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