The human brain is bombarded with a cacophony of information from the eyes, ears, nose, mouth and skin. Now a team of scientists at the University of Rochester, Washington University in St. Louis, and Baylor College of Medicine has unraveled how the brain manages to process those complex, rapidly changing, and often conflicting sensory signals to make sense of our world.
The answer lies in a relatively simple computation performed by single nerve cells, an operation that can be described mathematically as a straightforward weighted average. The key is that the neurons have to apply the correct weights to each sensory cue, and the authors reveal how this is done.
The study, to be published online Nov. 20 in Nature Neuroscience, represents the first direct evidence of how the brain combines multiple sources of sensory information to form as accurate a perception as possible of its environment, the researchers report.
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Click on the video above to see how the dots create a sense of moving forward straight ahead, to the right, and to the left. Credit: University of Rochester
The discovery may eventually lead to new therapies for people with Alzheimer's disease and other disorders that impair a person's sense of self-motion, says study coauthor Greg DeAngelis, professor and chair of brain and cognitive sciences at the University of Rochester. This deeper understanding of how brain circuits combine different sensory cues could also help scientists and engineers to design more sophisticated artificial nervous systems such as those used in robots, he adds.
The brain is constantly confronted with changing and conflicting sensory input, says DeAngelis. For example, during IMAX theater footage of an aircraft rolling into a turn "you may find yourself grabbing the seat," he says. The large visual input makes you feel like you are moving, but the balance cues conveyed by sensors in your inner ear indicate that your body is in fact safely glued to the theater seat. So how does your brain decide how to interpret these conflicting inputs?
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This video shows how adding randomly moving dots, or visual “noise,” makes visual motion cues much harder for your brain to interpret, until the noise is removed toward the end of the video. Using segments of these animations, the study found that individual neurons are responsible for the brain’s complex ability to shift between different sensory signals depending on which are more reliable. Credit: University of Rochester
The study shows that the brain does not have to first "decide" which sensory cue is more reliable. "Indeed, this is what's exciting about what we have shown," says DeAngelis. The study demonstrates that the low-level computations performed by single neurons in the brain, when repeated by millions of neurons performing similar computations, accounts for the brain's complex ability to know which sensory signals to weight as more important. "Thus, the brain essentially can break down a seemingly high-level behavioral task into a set of much simpler operations performed simultaneously by many neurons," explains DeAngelis.
The study confirms and extends a computational theory developed earlier by brain and cognitive scientist Alexandre Pouget at the University of Rochester and the University of Geneva, Switzerland and a coauthor on the paper. The theory predicted that neurons fire in a manner predicted by a weighted summation rule, which was largely confirmed by the neural data. Surprisingly, however, the weights that the neurons learned were slightly off target from the theoretical predictions, and the difference could explain why behavior also varies slightly from subject to subject, the authors conclude. "Being able to predict these small discrepancies establishes an exciting connection between computations performed at the level of single neurons and detailed aspects of behavior," says DeAngelis.
To gather the data, the researchers designed a virtual-reality system to present subjects with two directional cues, a visual pattern of moving dots on a computer screen to simulate traveling forward and physical movement of the subject created by a platform. The researchers varied the amount of randomness in the motion of the dots to change how reliable the visual cues were relative to the motion of the platform. At the end of each trial, subjects indicated which direction they were heading, to the right or to the left.
Provided by University of Rochester
"Nerve cells key to making sense of our senses." November 20th, 2011. http://medicalxpress.com/news/2011-11-nerve-cells-key.html
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Robert Karl Stonjek
Robert Karl Stonjek
A shot for high cholesterol: Patients struggling with high cholesterol may soon get just the shot in the arm they need. In the first human test of a new injectable drug designed to target LDL, or "bad" cholesterol, scientists at Amgen laboratories in California found it lowered cholesterol in healthy individuals by almost two-thirds.
“While churning the butter, mother Yashoda was singing about the childhood activities of Krishna. It was formerly a custom that if one wanted to remember something constantly, he would transform it into poetry or have this done by a professional poet. It appears that mother Yashoda did not want to forget Krishna's activities at any time.” (Shrila 
Mother Yashoda, the foster mother of the Supreme Personality of Godhead during His most famous descent to this world, is the songwriter we speak of. When would she compose her songs? Did she write them down on paper, meticulously craft the verses together using intricate meters and other tools of the poetry trade, and then practice them with public performances? On the contrary, in the oddest of settings, while performing menial housework was where this famous mother’s handiwork was born. The world was her studio, for she was always consumed by loving emotions tied to the gift the Supreme Lord had given her: His personal company in the form of a young child.
Do we need guidance? The more appropriate question would be, “when do we not need guidance?” Starting from when we exit the womb of our mother, we need help in doing everything. Even with the so-called self-starters, the people unwilling to ask for directions on how to get some place, who refuse to ask for help in a store when looking for a particular product, there is the reliance on the senses and mind. The mind is aided through experience and personal observation. The brain works off of the information fed to it, which it can then use to formulate conclusions.
Mother Yashoda showed through her behavior that Krishna was God. The Lord’s name says that He is all-attractive. If something has this quality, it must be able to evoke blissful feelings in the people who interact with it. No one has more intimate dealings with a young child than a mother, so Yashoda had to always be happy if Krishna was really all-attractive.
Such were the situations for the residents of Vrindavana. They each had a specific rasa, or transcendental mellow, applied to Krishna. If He were to reveal that He was God, those relationships would change, and thus the happiness derived would be affected. If the same loving emotions weren’t directed to Krishna by the residents, how could He take tremendous pleasure in their association? The Lord is already worshiped reverentially in the minds of those who are in awe of Him. The many temples around the world follow reverential worship as well.
On the flip side, remaining in the company of the Supreme Lord proves to be auspicious. Mother Yashoda, through no extra effort, managed to sing beautifully about her son, whom even meditational yogis, Vedantists and fruitive workers are not able to catch. Only through transcendental love, or prema, can Krishna be brought to one’s heart to stay. He already resides within us in His unmanifested feature of the Paramatma, but through bhakti-yoga, or 
“Seeing that his daughter was unmarried and at an age suitable for marriage, the king spoke with his guru and relatives to see what should be done. They advised him to plan a svayamvara, so the king decided upon a contest, where whoever could lift Lord Shiva’s bow would marry his daughter.” (Janaki Mangala, Svayamvara Ki Taiyari, 8 )
How can a king have all good qualities? Especially in ancient times, were not kings required to fight with enemies? We know that King Yudhishthira, the eldest of the five Pandava brothers, felt tremendous remorse after emerging victorious in the Bharata War. Though he was abiding by dharma, or religiosity, and thus had no sin attached to his killing, he nevertheless felt terrible that millions of soldiers had lost their lives on account of his fighting. Indeed, violence can be so grotesque that many believe that fighting of any kind is sinful, that violence should never be an option.
King Janaka’s dilemma taxing his brain was an example of a situation where there appeared to be duality but the right choice was made regardless. Though a ruler of a country wielding tremendous power, there was not a hint of sin in Janaka, who ruled over the kingdom of Mithila many thousands of years ago. He never did anything wrong, for he followed the advice of his gurus. The kshatriya, or warrior caste, is responsible for protecting; therefore they can use force when necessary. The gurus belong to the brahmana, or priestly class. A bona fide priest is a teacher of spirituality, giving advice to those looking to remain connected with God. The kshatriyas serve the Supreme Lord by protecting the innocent members of society. Through their work coupled with detachment to the outcome, they steadily ascend the planes of consciousness. It is the consciousness that determines one’s disposition; happy or sad, elated or morose, transcendentally situated or materially entangled.
If Janaka did not marry Sita off, he would invite scorn and ridicule from others. No longer would he be the pious king so dedicated to righteousness. Not that he cared himself for the glory, but Janaka knew that if he didn’t follow dharma, then he could not expect the citizens to either. In this way the execution of his duties as a king would be hampered by his transgression of keeping Sita unmarried.
His connection in yoga to Brahman and his love for God’s wife guided Janaka along the proper path. He did not need to explicitly try to develop the qualities of righteousness, for that route is very difficult. Sita is the very embodiment of dharma, so just having love for her is enough to not only get you tremendous fortune, but also to imbibe the divine qualities in you. Worried about facing ridicule from his family and losing Sita as a daughter, Janaka made the right decision by approaching his gurus and relatives. They advised him to hold a svayamvara, or self-choice ceremony. This way the choice wouldn’t necessarily be made by Janaka.Svayamvaras were rarely held, only in those circumstances where the daughters were considered really exceptional by their fathers.
The decision was that the svayamvara would host a contest to lift Lord Shiva’s bow. In this way the ceremony would honor Mahadeva, keep the relatives happy, follow the advice of the gurus, and at the same time make it extremely difficult to find a suitable match. Who in the world was going to lift this bow? Even if everyone from around the world came and couldn’t lift it, at least Janaka would be off the hook. He would know then that no man was worthy of marrying his daughter, which was his inclination anyway.
