Malcolm Slanley - Hallucinations in Auditory Perception

http://videolectures.net/mbc07_slaney_hap/

In this talk I want to review the need for richer architectures for auditory processing. Many experiments point to the tangled web of connections in the perceptual system, yet our engineering solutions remain almost exclusively bottom-up. How is it that we can provide context, so that our systems can solve musical analysis and auditory scene-analysis problems? I'll talk about notable systems that are successful "hallucinators."

Kenji Doya - Computational Models of Basal Ganglia Function

As a mathematical engineer, Kenji Doya approaches the goal of describing the most intricate brain mechanisms from a computational perspective. He constructs models of reinforcement learning involving the networked structures of the basal ganglia. His efforts are captured and expressed quantitatively as probabilities, regressions, and algorithms.

In this presentation, Doya covers basic concepts of reinforcement learning, then surveys the last decade of inquiry into the components of the basal ganglia circuit governing voluntary motion. Among the topics: action values, action candidates, and reward prediction involving the neurotransmitter dopamine; model-free versus model-based learning strategies; and the essential role of serotonin as modulator in the complex information loop.

Doya’s recent research is carried out via robots he calls “cyber rodents.” His dream as an undergraduate was to “build a robot that learns the variety of behaviors on its own.” That is, the computer, not the human engineer, teaches the robot to move. He accomplished this in designing a machine-creature exhibiting emotion-like attributes characterized as “depression,” “impulsivity,” “greed,” and “patience.”

Doya believes the “metaparameters” of reinforcement learning must be “tuned appropriately…Otherwise the performance of your learning is very, very poor.” The iterative process involves three terms -- the reward itself, the expected reward for a new state based on choice of action, and memory of the reward gained in the previous state. In the comparison, any differential greater than zero can be exploited for learning. The tradeoff: “No pain, no gain.”

As research advanced to increasing levels of structural specificity, Doya posited that “there seems to be spatial segregation in the function” of basal ganglia components. Specialization in aspects of reinforcement learning is now seen, for instance, in ventral versus dorsal areas of the striatum.

Differentiation is also found in the cortico-basal ganglia information network: not a simple closed loop, but parallel electrical pathways conducting distinct neural operations. Further, the neuromodulators each have their respective missions. Dopamine encodes the temporal difference error -- the reward learning signal. Acetylcholine affects learning rate through memory updates of actions and rewards. Noradrenaline controls width or randomness of exploration. Serotonin is implicated in “temporal discounting,” evaluating if a given action is worth the expected reward. Doya reminds us that clinically “it is well known that the serotonin function is impaired in the depression patient.”

The system of basal ganglia components and neuromodulators requires dynamic balancing. A delicate interplay determines outcomes for learning, actions, and affective states. Doya’s synthetic models are proxies for human behavior, and his computational framework describing the moving parts ultimately has therapeutic implications for psychiatric and neurological disorders.

Takao K Hensch - Critical Period Mechanisms of Visual Cortical Plasticity

http://videocast.nih.gov/launch.asp?13781

Abstract: (CIT): With interests ranging from child development and human disease to brain circuitry, Dr. Hensch is best known for his studies of the interplay of sensory input and genetics early in mammalian brain development, when the unusual malleability of the nervous system allows experiences to shape the lifelong wiring of the brain. His research has employed techniques from systems and molecular neuroscience to probe the mechanisms of early neural wiring, the limits of early brain plasticity, and how such plasticity might be restored later in life. Such work could have profound implications for developmental disorders as well as learning and education. Dr. Hensch's group made the surprising finding that the maturation of inhibitory circuits - such as the stunted development of wiring in visual cortex from an eye deprived of vision - controls the timing of early brain plasticity. By directly manipulating the onset of such inhibitory transmission within the brain, Dr. Hensch and his colleagues have shown that neural plasticity mirrors this timing, a finding that has had a major impact on developmental neuroscience. He continues to investigate the structural and molecular mechanisms of these phenomena, as well as the role of rhythmic electrical activity that occurs in the brain during sleep, visual experience, and brain plasticity. NIH Neuroscience Seminar Series.

Steve Buck & Scott Murray - Vision and the Brain

Why do we need vision? As it turns out, there are two answers to this question. On the one hand, we need vision to give us detailed knowledge of the world beyond ourselves, knowledge that allows us to recognize things from minute to minute and day to day. On the other hand, we also need vision to guide our actions in that world at the very moment they occur. These are two quite different job descriptions, and nature seems to have given us two different visual systems to carry them out. Dr. Murray explores the problems in the context of object size and brightness perception, and discusses computational challenges in sight that require extensive neural processing.

http://www.researchchannel.org/prog/displayevent.aspx?rid=16249

Oliver Sacks - Seeing Hallucinations while Blind

Pawan Sinha - Project Prakash

http://web.mit.edu/bcs/sinha/prakash.html



‘Prakash’ in Sanskrit means light.
The goal of Project Prakash is to bring light into the lives of curably blind children and, in so doing, illuminate some of the most fundamental scientific questions about how the brain develops and learns to see.

Nanci Bell - The Role of Imagery and Verbal Processing

Nanci Bell, creator of a program which aims to stimulate gestalt imagery in order to aid in language comprehension and analytical thinking, discusses the role imagery plays in comprehension in individuals of all ages. Series: "M.I.N.D. Institute Lecture Series on Neurodevelopmental Disorders"