...Donald Hebb * Wanted to be a Writer Unlike Physicist Parents * At 33 was a Fellow at Montreal Neurological Institute * Absent Stimulation Causes Deterioration and Hallucinations * First Non-American to Win APA Distinguished Scientific Contribution Award * Had an Award for Canadian Scientists Named after Himself Donald Hebb decided at an early age he did not want to be a Physicist like his parents. He had other aspirations, he wanted to write and study. At the age of 33, Hebb received a position at the Montreal Neurological Institute as a research fellow (Olson & Hergenhahn, 2009). The research Hebb conducted ultimately contributed greatly to the modern knowledge of the brain. He discovered, when there is an absence of stimulation the resulting product is the brain has more difficulty in its ability to problem solve and even to concentrate (Olson & Hergenhahn, 2009). The absence causes deterioration in the ability to do things quickly and efficiently, causing extreme difficulty. Hebb has even reported a few people who said they had experienced hallucinations from the absence of stimulation (Olson & Hergenhahn, 2009). Hebb’s research was extremely helpful in the studies of airplane pilots and of truck drivers. Many of these workers had reported having hallucinations while on the job. Hebb discovered the hallucinations were due to the fact they were not experiencing enough mental stimulation to keep their brains alert and active. From the age...
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...CHAPTER I INTRODUCTION Background of the Study Structural materials can be categorized in many ways in many different ways. One of the most common is by the nature of their failure. Materials, such as steel, after reaching their elastic limit, deform plastically before failing. Such materials, where reasonably large plastic strains are observed, are broadly categorized as ductile. On the other hand, those materials that exhibit little or no plasticity are in contrast termed brittle. In structural design, ductile materials are usually preferred, because failure is rarely sudden and catastrophic. Once the material has yielded, large observable strains will occur before total collapse of a structure. Steel, the most common primary structural building material, generally behaves in a ductile fashion. However, during the World War II, over 200 steel ships suffered serious brittle fracture, often at relatively low stress levels. It was observed that brittle behavior, in normally ductile materials, almost always occurs in regions of elastic stress concentration, where some constraint exists to prevent plastic stress redistribution (McGuire, 1968) Following these experiences, designers realized that brittle fracture in steel could be avoided by sensible detailing. This is also true of reinforced concrete. Concrete itself, is a brittle composite, but with the addition of reinforcements concrete it behaves in a ductile fashion. In an earthquake-prone areas, where designing for ductility...
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...Theory: Forming process are solid state manufacturing processes involving minimum amount of material wastage and faster production. It does have been one of the common methods in formation of product in multi shape and size. In fact some of casting product will undergoes forming process to achieve more precise shape. In metal forming, transformation to desire shape is done at solid state and usually required high forces. If the temperature is below crystallization temperature, it is called ‘cold work’. Large force is applied such that the material flows and takes the desired shape. These processes are normally used for large scale production rates. It is also generally economical and many cases improve the mechanical properties. Some of the metals forming process are rolling, forging, extrusion, drawing, sheet metal forming and bending. In fabrication of metal dustbin, below process forming process are involved. a. Sheet Metal Cutting -Sheet metal cutting can be done by shearing operation. Shearing is the mechanical cutting of material without the formation of chips or the use of burning or melting. When sheets of metal are to be sheared along a straight line, squaring shears are frequently used. As the upper ram descends, a clamping bar or set of clamping fingers presses the sheet of metal against the machine table to hold firmly in formation. A moving blade then comes down across a fixed blade and shears the metal. On larger shears, the moving blade is often set...
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...be ingested into the body by human beings in order to have a healthy life.Calcium has a role in maintaining the health of the skin, bones and cartilages, muscle coordination and ultimately the central nervous system (CNS).This means that humans cannot live without calcium (Xu, J et al), but it is only needed in small amounts, to the tune of milligrams. A synapse is a space between two neurons in which neurotransmitters are released from the presynaptic neurons to exert an effect on the subsequent postsynaptic neuron.An action potential is generated in the pre-synaptic neuron by generating the influx of Na+ through the sodium channels and an efflux of the K+ ions via the Potassium channels.The action potential at the presynaptic terminal, triggers the influx of calcium into the terminal axon. The influx of calcium plays a functional role in the release of neurotransmitters from the presynaptic vesicles into the synaptic cleft. The experiment performed by Katz and Ricardo Melidi showed that presynaptic terminals that are treated with tetrodotoxin( binds sodium) are still capable of generating prolonged action potentials. The current was flowing through calcium channels instead of sodium. Another experiment by rodolfo llinas indicated presence of voltage gated calcium channels in presynaptic terminals. The experiment was carried out by using giant squid axon, confirmed the presence of voltage gated calcium channels in the presynaptic cell.Neurotransmitter releases right after...
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...Previous research has demonstrated that neuroplasticity is disrupted in mood disorders as well as in animal models of stress. Pittenger and Duman (2008) hypothesize that chronic stress, which typically precipitates or exacerbates depression, disrupts neuroplasticity, where antidepressant treatment can produce the opposite effect and enhance neuroplasticity. There are different levels of neuroplasticity such as structural plasticity, functional synaptic plasticity, as well as the molecular and cellular mechanisms accompanying such changes. In Pittenger and Duman’s (2008) article, meant primarily for the medical community, these factors are discussed in great detail. The last 50 years have seen breakthroughs in the discovery of different categories...
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...Throughout the class we have been asked to identify an aspect of human behavior that interests us and apply knowledge we have acquired through the class. Personally, I am very interested in the aspect of brain plasticity and what aspects of life and psychology play a crucial role in its activity. For this reason, my big question is “What largely impacts brain plasticity?”. However, before I go further into my research about brain plasticity it is important to define what brain plasticity is. Brain plasticity is the brain's ability to alter its structure and function following an experience or changes in the body (Brain Facts). The changes that occur in the brain due to brain plasticity could involve a growing or shrinking in grey matter, neural...
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...Environmental factors tend to modify the inputs received by the sensory pathway. The developing brain is most vulnerable to these alterations and interacts with the environment to modify its neural circuitry. In addition to other sensory stimuli, auditory stimulation can also act as external stimuli to provide enrichment during the perinatal period. There is evidence that suggests that enriched environment in the form of auditory stimulation can play a substantial role in modulating plasticity during the prenatal period. The molecular mechanisms of various changes in the hippocampus following sound stimulation to effect neurogenesis, learning and memory are described. Sound stimulation can also modify neural connectivity in the early postnatal life to enhance higher cognitive function or even repair the secondary damages in various neurological and psychiatric disorders. Thus, it becomes imperative to examine in detail the possible bettering effects of prenatal sound stimulation in various psychiatric disorders, such as...
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...frequencies, producing a discharge deceleration. However, Metzner found different a mechanism for the motor control of the JAR from the one described previously. The involvement of two prepacemaker nuclei, one PPn-G and one sublemniscal prepacemaker nucleus (SPPn) and their effect on JAR was observed by lesion study. Article provides multiple pharmacological experiments to elucidate the transmitter types involved. The results suggest a different hypothesis that the JAR is controlled by two separate motor pathways. One controlling rise in frequency originates in the dorsal substructure of the nucleus electrosensorius. It sends excitatory connections to the PPn-G and finally to the pacemaker nucleus, where AMPA-type receptors mediate the synaptic transmission. The second pathway controlling fall in the frequency originates in the ventral substructure of the nucleus electrosensorius. It provides GABAergic input to the SPPn, which is tonically active controlling the EOD frequency even in the absence of jamming signals. Its projection to the pacemaker nucleus is mediated by NMDA-type receptors. Concluding the paper, Metzner suggested that there is no single population of final, feature-extracting elements or “recognition units” that controls JAR-related shifts of the pacemaker frequency holding the idea that the motor control of the JAR consists of an interaction of two independent pathways according to a “push-pull” principle. Fortune et al in 2006 further delved into the phenomena...
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...information coded in neural connections? How do little spikes of voltage represent what we see, what judgments we make, or our desires for a mate? Another aspect of this brain mystery is storing and retrieving memories or the “theory of Brain Plasticity.”...
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...The role of noradrenaline in retrieval requires signaling through the β1-adrenergic receptor in the hippocampus.27 Regarding its relation with the hippocampus, it is believed that NE is an essential modulator of memory through its ability to regulate synaptic mechanisms in the hippocampal region. This catecholamine activates both pre- and post- synaptic adrenergic receptors, which means an increase of neurogenesis in the hippocampus. It enhances its synaptic plasticity and consequently this neurotransmitter positively affects the memory.28 Dopamine level is also expected to increase. It is thought that DA significantly benefits memory consolidation 29 and it has been shown that dopamine plays a central role in the hippocampus and that its lack can cause several psychiatric...
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...This includes attention and even synaptic plasticity. Since working memory is “vulnerable to distraction and interference,” attention is extremely valuable to the process (33). Attending to the information allows it to be repeated and therefore maintained in within the system. The model of working memory can be seen as a convolution of connections. This relates to synaptic plasticity, which is often described in Hebbian terms, meaning that “neurons that fire together, wire together.” This generalizes a memory by building a network of neurons that fire together, even if only few are activated. In terms of working memory, this allows for activity to be sustained within the network, even after activity ceases. These examples are some of the “building blocks” working memory possesses. Clearly, it is a delicate, yet adaptable system; the memory must be the right size to be recalled, but may end up in any number of regions throughout the...
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...expand our knowledge about the neurochemistry of reward. Natural rewarding activities and artificial chemical rewarding stimuli act at the same locations, but while natural activities are controlled by feedback mechanisms that activate aversive centers, no such restrictions bind the responses to artificial stimuli (Vetulani, 2001). Endocannabinoids are synthesized postsynaptically and act as retrograde signals to regulate presynaptic transmitter release. The receptors, targets for THC, play an important role in use/abuse of marijuana (Everitt & Heberlein, 2013). Addictive drugs alter synaptic plasticity in the VTA through a common mechanism. Addictive drugs such as cocaine induce synaptic plasticity in the ventral tegmental area and its projection areas, which may represent the cellular correlate of an addiction trace. Cocaine induces changes in excitatory transmission primarily in the VTA. Specific synaptic and cellular changes in the NAc persist following prolonged exposure to cocaine, and this remodeling may contribute to altered behavior (Creed & Lüscher,...
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...lack the ability to reuptake the 5-HT that is left in the extracellular space. The monoamine hypothesis was and still is a good starting point for needing to search for the biological basis of depression. It is now understood however, that this theory needs to be broadened and fill in the gaps that have opened up in the literature. It is important to consider an alternative view to this unsolved question. Neurotrophic theory An alternative theory to the monoamine hypothesis is the neurotrophic theory which states that depression could be due to the reduced synthesis of proteins which are involved in neurogenesis and synaptic plasticity. Duman and Li (2012) propose that this hypothesis assumes that the reduction in neurotrophic support which results in the atrophy of neuronal cells and reduction in neurogenesis and abnormalities in the synaptic plasticity pathways; could be the biological basis of depression. Duman and Li (2012) believe the areas of vulnerability are the hippocampal area and prefrontal cortex (PFC). This theory suggests that perhaps certain classes of antidepressants are actually blocking or able to reverse the atrophy of cells and neuronal structures which occurs in chronic stress of MDD. A motion of support for this hypothesis came in the way of ketamine, especially looking at how ketamine can affect BDNF. Duman and Li (2012) describe findings of reduced limbic brain structures in brains of depressed patients in particular a reduction in mass of the hippocampus...
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...nearly every one in three drug related emergency hospital visits, having various personal and social economic impacts (Martell, Orson et al. 2009). Many individuals who suffer have been found to have impaired cognitive functions and manifest a myriad of biological and neurological dysfunctions. The relationship between cocaine and cocaine dependence on brain physiology is its effects on particular brain regions and receptors leading to synaptic plasticity mediating altered ability of learning and consolidation [pic](Martinez, Narendran et al. 2007; Thomas, Kalivas et al. 2008; Mameli, Halbout et al. 2009). I argue that cocaine dependence is the result of such neurological changes which occur in the brain which induce cocaine dependence. To justify this argument, I will demonstrate that the mechanisms governing the issue, which are the result of the reward systems, particularly that of dopamine receptors blunted response after repeated exposure to cocaine and how this system works in concert with white matter integrity and synaptic plasticity of the neuronal circuitry, including that of extracellular signal regulated kinase (ERK) and brain derived neurotropic factors (BDNF) as well as the use of modafanil and methadone as plausible treatments in regards to the issue at hand. The reward system and Cocaine Dependence The concept of the reward system is understood to revolve around basic survival functions such as that of sexual arousal, hunger and thirst, whereby the growth...
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... * Another cells in the nervous system * Outnumber Neurons * Provide Nutrition * Structural Support * Aid in Neural Transmission * Remove Waste * Produce Myelin Sheath * Myelin Sheath * A white fatty covering wrapped around axons of some neurons that increases their communication speed * Damage to the Myelin related to Multiple Sclerosis * Node of Ranvier * The “naked” portion of the axon between myelin sheaths * Communication within Neurons * Action Potential- a brief electrical impulse transmitting information along the axon of a neuron * Action potential travels along axon of presynaptic neuron; triggers release of neurotransmitters from synaptic vesicles * Axon membrane is semi-permeable * The axon membrane opens and closes ion channels that allow ions to flow into and out of the axon * Ions- electrically charged particles * Resting Potential- the state in which the neuron is prepared to activate if given enough stimulation * Neuron is polarized * -70mV * Stimulus Threshold * Minimum level of stimulation required to activate a particular neuron * Communication Between Neurons * Synapse- the point of communication between two neurons...
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