Neuron All neurons are electrically excitable, maintaining voltage gradients across their membranes by means of metabolically driven ion pumps, which combine with ion channels embedded in the membrane to generate intracellular-versus-extracellular concentration differences of ions such as sodium, potassium, chloride, and calcium. Changes in the cross-membrane voltage can alter the function of voltage-dependent ion channels. If the voltage changes by a large enough amount, an all-or-none electrochemical pulse called an action potential is generated, which travels rapidly along the cell's axon, and activates synaptic connections with other cells when it arrives. Neurons do not undergo cell division. In most cases, neurons are generated by special types of stem cells. A type of glial cell, called astrocytes (named for being somewhat star-shaped), have also been observed to turn into neurons by virtue of the stem cell characteristic pluripotency. Overview[edit] Anatomy and histology[edit]
Feedforward Neural Networks 2.5.1 Feedforward Neural Networks Feedforward neural networks (FF networks) are the most popular and most widely used models in many practical applications. They are known by many different names, such as "multi-layer perceptrons." Figure 2.5 illustrates a one-hidden-layer FF network with inputs and output . , also called the neuron function. Figure 2.5. Mathematically the functionality of a hidden neuron is described by where the weights { } are symbolized with the arrows feeding into the neuron. The network output is formed by another weighted summation of the outputs of the neurons in the hidden layer. The neurons in the hidden layer of the network in Figure 2.5 are similar in structure to those of the perceptron, with the exception that their activation functions can be any differential function. where n is the number of inputs and nh is the number of neurons in the hidden layer. } are the parameters of the network model that are represented collectively by the parameter vector . In[1]:=
Brain Atlas - Introduction The central nervous system (CNS) consists of the brain and the spinal cord, immersed in the cerebrospinal fluid (CSF). Weighing about 3 pounds (1.4 kilograms), the brain consists of three main structures: the cerebrum, the cerebellum and the brainstem. Cerebrum - divided into two hemispheres (left and right), each consists of four lobes (frontal, parietal, occipital and temporal). – closely packed neuron cell bodies form the grey matter of the brain. Cerebellum – responsible for psychomotor function, the cerebellum co-ordinates sensory input from the inner ear and the muscles to provide accurate control of position and movement. Brainstem – found at the base of the brain, it forms the link between the cerebral cortex, white matter and the spinal cord. Other important areas in the brain include the basal ganglia, thalamus, hypothalamus, ventricles, limbic system, and the reticular activating system. Basal Ganglia Thalamus and Hypothalamus Ventricles Limbic System Reticular Activating System Glia
Introduction to Feedforward Neural Networks - EmilStefanov.net Introduction Neural networks are a very popular data mining and image processing tool. Their origin stems from the attempt to model the human thought process as a an algorithm which can be efficiently run on a computer. The human brain consists of neurons that send activation signals to each other (figure on the left) thereby creating intelligent thoughts. The algorithmic version of a neural network (called an artificial neural network) also consists of neurons which send activation signals to one another (figure below). Because the breadth of neural networks is very large, this project focuses on feed-forward neural networks, perhaps the most common type. Algorithm Description Artificial neural networks (the ones that run on a computer as opposed to a brain) can be thought of as a model which approximates a function of multiple continuous inputs and outputs. Computing Output We will now see how to compute the output of a single neuron N_i. Learning the Weights and Biases
UCSB scientists discover how the brain encodes memories at a cellular level (Santa Barbara, Calif.) –– Scientists at UC Santa Barbara have made a major discovery in how the brain encodes memories. The finding, published in the December 24 issue of the journal Neuron, could eventually lead to the development of new drugs to aid memory. The team of scientists is the first to uncover a central process in encoding memories that occurs at the level of the synapse, where neurons connect with each other. "When we learn new things, when we store memories, there are a number of things that have to happen," said senior author Kenneth S. "One of the most important processes is that the synapses –– which cement those memories into place –– have to be strengthened," said Kosik. This is a neuron. (Photo Credit: Sourav Banerjee) Part of strengthening a synapse involves making new proteins. The production of new proteins can only occur when the RNA that will make the required proteins is turned on. When the signal comes in, the wrapping protein degrades or gets fragmented.
List all the essential neurotransmitters Acetylcholine - synthesized from Choline, Lecithin, and panthothenic acid (B5), or Diethylaminoethanol (DMAE) - Arousal and orgasm - voluntary muscular control and proper tone - enhance energy and stamina - memory - long-term planning - mental focus Dopamine - synthesized from amino acid Levodopa - Alertness - Motivation - motor control - immune function - Ego hardening, confidence, optimism - Sexual Desire - Fat gain and loss - lean muscle gain - Bone density - ability to sleep soundly - Inhibits prolactin - thinking, planning, and problem solving - Aggression - Increase psychic and creative ability - Reduction of compulsivety - Salience and paranoia - Processing of pain - Increase sociability Serotonin (5-HT) - Synthesized from amino acid L-tryptophan with co-factor Niacin (B3), through the intermediate 5-hydroxytryptophan (5-HTP) Norepinephrine - Synthesized from Dopamine with co-factor of vitamin C through the intermediate DOPAC. Vasopressin - Yan Niemczycki
The Learning Brain Gets Bigger--Then Smaller With age and enough experience, we all become connoisseurs of a sort. After years of hearing a favorite song, you might notice a subtle effect that’s lost on greener ears. Perhaps you’re a keen judge of character after a long stint working in sales. Or maybe you’re one of the supremely practiced few who tastes his money’s worth in a wine. Whatever your hard-learned skill is, your ability to hear, see, feel, or taste with more nuance than a less practiced friend is written in your brain. One classical line of work has tackled these questions by mapping out changes in brain organization following intense and prolonged sensory experience. But don’t adopt that slogan quite yet. If you were to look at the side of someone’s brain, focusing on the thin sliver of auditory cortex, it would seem fairly uniform, with only a few blood vessels to provide some bearing. And yet, some aspects of this theory invited skepticism. So what does change? Still, there’s a big question lurking here.
neurotransmitters and neuromodulators The soft warm living substance of the brain and nervous system stands in stark contrast to the rigid metal and plastic hardware of a modern day computer, but at the fundamental level there are clear similarities between these two apparently disparate organizational systems and, of course, one is a product of the other. Not only are the nerve cell units (neurons) self-repairing and self-wiring under the grand design built into our genes, but they can also promote, amplify, block, inhibit, or attenuate the micro-electric signals which are passed to them, and through them. In this way they give rise to signalling patterns of myriad complexity between networks of cerebral neurons, and this provides the physical substrate of mind. These key processes of signalling by one group, or family, of neurons to another is achieved largely by the secretion of tiny quantities of potent chemical substances by neuronal fibre terminals. In this way, the nerve impulses are passed on from cell to cell. 1.
Meditation found to increase brain size Kris Snibbe/Harvard News Office Sara Lazar (center) talks to research assistant Michael Treadway and technologist Shruthi Chakrapami about the results of experiments showing that meditation can increase brain size. People who meditate grow bigger brains than those who don’t. Researchers at Harvard, Yale, and the Massachusetts Institute of Technology have found the first evidence that meditation can alter the physical structure of our brains. Brain scans they conducted reveal that experienced meditators boasted increased thickness in parts of the brain that deal with attention and processing sensory input. In one area of gray matter, the thickening turns out to be more pronounced in older than in younger people. “Our data suggest that meditation practice can promote cortical plasticity in adults in areas important for cognitive and emotional processing and well-being,” says Sara Lazar, leader of the study and a psychologist at Harvard Medical School. Controlling random thoughts
BrainConnection.com - The Anatomy of Movement Susan Schwerin, PhD | March 5, 2013 Almost all of behavior involves motor function, from talking to gesturing to walking. But even a simple movement like reaching out to pick up a glass of water can be a complex motor task to study. Not only does your brain have to figure out which muscles to contract and in which order to steer your hand to the glass, it also has to estimate the force needed to pick up the glass. Figure 1a: Principal cortical domains of the motor system. The primary motor cortex (M1) lies along the precentral gyrus, and generates the signals that control the execution of movement. The primary motor cortex, or M1, is one of the principal brain areas involved in motor function. Figure 1b: The motor homunculus in primary motor cortex. A figurative representation of the body map encoded in primary motor cortex. Other regions of the cortex involved in motor function are called the secondary motor cortices. The spinal cord is comprised of both white and gray matter.
Imagining the Future Invokes Your Memory I REMEMBER my retirement like it was yesterday. As I recall, I am still working, though not as hard as I did when I was younger. My wife and I still live in the city, where we bicycle a fair amount and stay fit. We have a favorite coffee shop where we read the morning papers and say hello to the other regulars. In reality, I’m not even close to retirement. A new study from the January issue of Psychological Science may explain why we are all so optimistic about what’s to come. Cognitive scientists are very interested in people’s “remembered futures.” Still, very little was known until recently about how these simulations work. These are very difficult questions to study in a laboratory—or at least they were until now. Recalling Tomorrow Szpunar and his colleagues began by collecting a lot of biographical detail from volunteers’ actual memories.
Brain Map Robert P. Lehr Jr., Ph.D. Professor Emeritus, Department of Anatomy, School of Medicine, Southern Illinois University Español Brain Function and Deficits In traumatic brain injury the brain may be injured in a specific location or the injury may be diffused to many different parts of the brain. The brain has many parts including the cerebral cortex, brain stem, and cerebellum. Frontal Lobes: Most anterior, right under the forehead. Functions How we know what we are doing within our environment (Consciousness) How we initiate activity in response to our environment Judgments we make about what occurs in our daily activities Controls our emotional response Controls our expressive language Assigns meaning to the words we choose Involves word associations Memory for habits and motor activities Observed Problems Parietal Lobes: near the back and top of the head. Occipital Lobes: Most posterior, at the back of the head. Vision Temporal Lobes: Side of head above ears.
The Brain May Disassemble Itself in Sleep Compared with the hustle and bustle of waking life, sleep looks dull and unworkmanlike. Except for in its dreams, a sleeping brain doesn’t misbehave or find a job. It also doesn’t love, scheme, aspire or really do much we would be proud to take credit for. In a provocative new theory about the purpose of sleep, neuroscientist Giulio Tononi of the University of Wisconsin–Madison has proposed that slumber, to cement what we have learned, must also spur the brain’s undoing. Select an option below: Customer Sign In *You must have purchased this issue or have a qualifying subscription to access this content
Parietal Lobe Function The parietal lobes can be divided into two functional regions. One involves sensation and perception and the other is concerned with integrating sensory input, primarily with the visual system. The first function integrates sensory information to form a single perception (cognition). The second function constructs a spatial coordinate system to represent the world around us. Individuals with damage to the parietal lobes often show striking deficits, such as abnormalities in body image and spatial relations (Kandel, Schwartz & Jessel, 1991). Damage to the left parietal lobe can result in what is called "Gerstmann's Syndrome." Damage to the right parietal lobe can result in neglecting part of the body or space (contralateral neglect), which can impair many self-care skills such as dressing and washing. Bi-lateral damage (large lesions to both sides) can cause "Balint's Syndrome," a visual attention and motor syndrome. References: Kandel, J., Schwartz, J., & Jessell, T. Kimura, D. (1977).