September 2011 Archives

Visual Illusions

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Last week in my neurobiology class we were to read papers by David Eagleman, neurobiologist and author of Incognito: The secret lives of the brain. He also came to our class for a short Q&A. I was intrigued on his paper about visual illusions. His main interest was in flash lag illusion and the wagon wheel effect.
Flash lag illusion: a visual illusion when a flash and moving object appear to be in the same place but are perceived to be displaced. One theory is that your visual cue predicts the trajectory of the moving object(Nijhawan, 1994). Another theory is that your visual system can process moving objects more quickly than flashed objects. This basically means that by the time your brain has processed the flash the moving object has already changed positions(Nijhawan, 1994). Eagleman however proposed that "visual awareness is neither predictive nor on-line, but is instead postdictive, such that the percept attributed to the time of the flash is a function of events that happen in the ~80 msec following the flash."
Wagon Wheel effect: Optical illusion in which a spiked wheel seems to rotate differently from its true direction. A 2004 study(Eagleman) revealed that the incidences of reversed rotation were independent in different parts of the visual field.
Obviously with all research there are more questions to be addressed, but the study of illusions allows for understanding of biological proccess and provides insight in the field of neurobiology.
If you are interested in visual illusions or just find them interesting to look at i suggest you to look at the link below or simply google it. First you don't see it, now you do.

Lets get moving!

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This week in my neurobiology class we read a research article titles How Animals Move: An Integrative View. I found this article particular interesting, simply because the general population views movement as just the extension and relaxation of muscles, but never really thinks of the subject in the view of neural mechanical feedback. The paper goes into explain how different animals move in way that is most beneficial to them and that the movement can be influenced on their habitat. Also, that certain movement can allow for energy recovery. The study was focused on how to determine each individual component within a locomotor system operates, while at the same time studying how they function collectively as an integrated whole. The paper also mention 4 themes.
1) Spatiotemporal dynamics of locomotion are complicated but understandable on the basis of a few principles. 2) performance of animals in natural habitats reflects trade-off between different ecological important aspects of behavior and is affected by the physical properties of the environment. 3) control of locomotion is not linear, but organized. 4) muscles perform many different functions in locomotion.
So lets compare walking and running. When walking the center mass is much like a pendulum, at mid stance mass is its highest. Running is like that of a spring, compressing and recoiling. A great example to talk about how habitats effect movement is that of a 2 different jellyfish. A bullet shaped jellyfish uses jet propulsion, but vortices produced by a disk jellyfish are more advantangeous for its body shape. Now we can see how things works as a whole and we see that control systems are closely coupled. Both neural and mechanical pathways is integrated with guidance from eyes, ears, ect.. Example central nervous system generates motor commands that activate the musculoskeletal system of the animal, that in turn acts on the external environment, that is sensed by multiple modalities and fed back to the central nervous system. This provides evidence that the different system are coupled and can be broken down to look at individually and coupled to be studied as an integrated whole.

Peer Pressure

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I was surfing the web and decided to check out the website sciencedaily.com to see if there was any interesting news. The title peer pressure? It's hardwired into our brains jumped out at me. I looked up the full article on googlescholar and decided to share the information with everyone else.

The specific interest in mind for the study was to investigate how individuals assess the outcome of their decision in private versus social setting and whether depending on the setting, evaluations of outcomes of risky choices influence later decisions. They hypothesized that in a social environment the participant will be more risky in their decision than in a private setting.Brain activity was determined (using a combination of functional MRI and skin conductance recordings) while participants chose between 2 lotteries. In a private setting the outcome of the unchosen lottery was observed and in a social setting the outcome of a lottery chosen by another person was observed.
The medial prefrontal cortex(associated with social reasoning) had larger activity, during the choice phase, in individuals in a social setting rather than private. Analysis of brain activity and behavior showed that brain activity during choice phase is influenced by outcome-related striatum(associated with rewards) activity and past outcomes in social settings affects later behavior. The results showed that the decision process in a social setting(under peer pressure) is influenced by the interaction of the reward and social reasoning networks and that in a social setting participants engaged in more risky and competitive behavior.

There were many parts of this paper that I didn't understand (even after reading numerous times), and I cant get the MRI photos or any other charts/graphs to show up. So for more understanding on the article I suggesting clicking on the link below.

http://www.pnas.org/content/early/2011/09/01/1100892108.short

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