Long-term potentiation in the motor cortex

Article Abstract:

Long-term potentiation (LTP) was investigated as a possible mechanism involved in learning and memory. Previous research suggests that the processes of learning and memory depend on the synapses, or connections between nerve cells, in the central nervous system. LTP is prolonged enhancement of synaptic transmission (transmission of nerve impulses). Fourteen adult cats were studied; electrodes were positioned in different regions of their brains to record nerve impulses. LTP occurred in the nerve cells of the motor cortex of the brain when the sensory cortex was stimulated. Conversely, LTP did not result when the thalamus was stimulated. When both the sensory cortex and ventrolateral nucleus of the thalamus were stimulated simultaneously, LTP in motor cortical neurons was observed. This phenomenon, called associative LTP, only occurred in certain neurons of the motor cortex, those that are in its superficial (upper surface) layer. Associative LTP of the motor cortex could be the mechanism by which motor (movement) skills are retained. A possible scenario for learning a motor skill, such as riding a bicycle, is as follows. During the first stages of the learning process, movements are practiced at a slow rate since the animal requires feedback based on sensation of position and movement. With practice, the movement is carried out more quickly and smoothly and sensory feedback becomes progressively less important. Research has shown that removing the sensory cortex at this point has no adverse effect on performance of the motor skill.

Motor learning

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Visuomotor coordination in reaching and locomotion

Article Abstract:

Locomotion is the most basic movement, requiring synergy or cooperation of bodily functions. Visuomotor coordination, the coordination of seeing and movement, is used to achieve the positioning necessary for more difficult locomotor movements within the environment. The nerve cells of the corticospinal tract, the spinal cord and the cortex or outer layer of the brain, are involved in the locomotor control for the complex visuomotor coordination, as shown in experiments with cats. Increased complexity of visuomotor coordination, such as reaching, is seen throughout the evolutionary scale. Locomotion and reaching have been thought to be separate motor functions. However, reaching appears to have evolved from neural systems developed for locomotion, and also involves the nerve cells of the corticospinal tract. Reaching requires control of positioning, which is also necessary for the more complicated locomotion involving visuomotor coordination. The cerebellum, the part of the brain which coordinates voluntary muscular activity, is also involved in reaching, especially in higher animals such as primates, where the forelimbs are not involved in locomotion. Reaching is coordinated with the fine precision movements of the arms and hands.

Laws, regulations and rules, Spinal cord, Motor cortex, Locomotion

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Unresponsiveness to Cannabinoids and Reduced Addictive Effects of Opiates in [CB.sub.1] Receptor Knockout Mice

Article Abstract:

Experiments on mice on the effects of marijuana and opiates reveal that the CB.sub.1 receptor in the nervous system is the means by which these drugs affect the body. The mice whose CB.sub.1 receptor was removed through genetic mutation felt less effects on drug-like properties of marijuana and opiates than the mice with the CB.sub1 receptor.

Narcotics, Marijuana

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