How were Georgopoulos et al. able to predict the direction of movement using only neural activity?
Georgopoulos et al. used standard electrophysiological techniques to collect extracellular recordings of the activity of single neurons in the motor cortex (contralateral to the arm that would be performing the movement). Neurons that changed activity in response to spontaneous activity of the arm or movements directed toward food rewards were selected. Each neuron’s frequency of discharge was used to determine its directional preference. Neurons with direction preferences were represented as vectors that made weighted contributions, based on their changes in activity during the arm movement, along their preferred direction axis. The sum of all neuron vectors and their weighted contributions produced the population vector which aligned closely with the true direction of arm movement, and could then be used to predict the direction of movement.
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Georgopoulos et al. mentions that the population vector can be used to monitor directional processing information of neuron populations over time. Assuming that complex movements are generated from sequencing multiple simple movements together, then this approach’s ability to monitor directional neuron populations over time could be used to predict the direction of complex movements. However, this would require monitoring the response of each neuron’s weighted contribution to the population vector, while also determining the neuron’s activity in relation to each stage of the complex movement. Simple movements would need to be identified and filtered out, once completed, in order to determine the neuron’s weighted contribution throughout each stage of the movement. Thus, the population vector, in 3D space, represented as a function of time that shifts based on the weighted contributions of single neurons, could potentially illustrate/predict complex
Dava Sobel’s novel, Longitude: The True Story Of A Lone Genius Who Solved The Greatest Scientific Problem Of His Time is a history of the scientific battle to obtain a method of finding the exact longitude of a specific location. Knowing the longitude of a location may seem unimportant, but in fact it is vital. To fully understand the work that went into this effort, first, one must understand the basic principles for determining location on Earth.
...e in the brain to deliver electrical stimulation to targeted areas that control movement (mayoclinic.com, 2013).
Neuroscientists claim that due to unconscious brain activity, we are “biochemical puppets” (Nahmias). Through experiments conducted by neuroscientists like Itzhak Fried, neural activity is shown to occur before a conscious decision is made. Fried concluded that this was a predetermined occurrence
The brain receives input and somehow transforms it into output. How does it do it? In part because of the extraordinary technological feats achieved using digital processing computers, the brain has often been interpreted as a symbol manipulator and its cognitive activities as the transformation of symbols according to rules. By contrast, recent successes with parallel distributed processing computers have encouraged a connectionist theory of mind which regards the brain as a pattern recognizer and its cognitive activities as the transformation of neuronal activation patterns; however, these pattern transformations are not rule-governed processes, but straightforwardly causal processes in which networked units (neurons) excite and inhibit each other's activation level.
The widely popular research on mirror neurons and various applications of the research findings began with an important, but unexpected finding in the brains of macaque monkeys. The original studies did not intend to look at mirror neurons and in fact the existence of mirror neurons was found by accident. Neuroscientist Giacomo Rizzolatti and his colleagues found a group of cells that fired whenever a monkey prepared to act on a stimulus as well as when it watched another monkey act on the stimulus (Winerman, 2005). For example, the monkeys showed a similar pattern of activation when they were performing a simple motor action like grasping a peanut and when they watched another monkey perform the same action (Winerman, 2005). In other words, monkey see, monkey fire -- monkey do, monkey fire. This grouping of cells was called "mirror neurons." The ...
rapidly back and forth. This sudden movement can cause the brain to bounce around or twist in
As with the mental map experiments, the fact that reaction time depends directly on the degree of rotation has been taken as evidence that we solve the...
The least invasive method of BCI uses a set of electrodes attached to the scalp (Figure 3) to read brain signals however, to get a higher resolution, a chip can be inserted into the grey matter of the brain. (Grabianowski, n.d.) . The use of BCI has great implications for people with limited mobility and ghpeople who have lost limbs and has been used to control prosthetic arms. (Neurogadget,
The most famous series of experiments to empirically address the problem of free will were those conducted by Benjamin Libet and colleagues (Libet, Gleason, Wright, & Pearl, 1983; Libet, 1985). He analyzed the timing of conscious awareness of movement, and concluded that voluntary action begins with unconscious activity in the brain. Libet’s findings have been replicated in several more recent studies, such as those by Soon, Brass, Heinze, & Haynes (2008) and Bode, He, Soon, Trampel, Turner, Haynes (2011). Collectively, these results have almost conclusively determined that the conscious decision to act is preceded by unconscious neural action; however, the application of these findings to the problem of free will is still a subject of debate. To some experimental neuroscientists (Libet, 1985; Soon et al., 2008; Haggard, 2011; Fried, Mukamel, & Kreiman, 2011), these studies indicate that free will, or the conscious will ...
Prevosto, V., & Sommer, M.A. (2013). Cognitive Control of Movement Via the Cerebellar-Recipient Thalamus. Frontiers in Systems Neuroscience, 7, 1-8.
S.A. Clark, T. A. (1988). Receptive fields in the body-surface map in adult cortex defined by temporally correlated inputs. Nature, 332.
(Scientists have discovered that there are a large number of internal brain structures, which work together with the input and output brain structures to form fleeting images in the mind. Using these images, we learn to interpret input signals, process them, and formulate output responses in a deliberate, conscious, way.)
Motor evoked potentials (MEPs) have widespread use to diagnose and assess the functional integrity of the descending motor path...
Antidepressant drugs are designed to correct the imbalance. Sutton believes that feedback between his brain machine and MRI pictures of the brain at work will provide more insight not only of depression and Alzheimer's, but of stroke, multiple sclerosis, and other disorders that affect large areas of the brain. In one experiment, he and his colleagues looked at pictures of brains while their owners did simple motor tasks, such as tapping their fingers in simple and complex patterns. As expected, they saw activity in small networks of cells located in brain areas that control movements.
Observational learning is a type of learning that is done by observing the actions of others. It describes the process of learning by watching others, retaining what was learned, and