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Neuroscience & Karma
(3) The most influential theory and niain basis for stable memoryrecords, again by Hebb, is that memories are fixed in the nerve pathways the niselves. Everything known about the nervous system suggests tbat its coding depends upon the use ot quite nuine rous distinct channels, each carrying a slightly different feature of the information. New behavior is, therefore, likely to be the result of new connections, not of the forination of specific molecules. Majority of neuroscientists believe that selection of pathways is the basis for the memory mechanism. Hebb suggested self-re-exciting chains, that is, the continuous flow of nerve-impulses along a pathway or loop alters the synaptic connections in some way. When the activity dies down, the new connections remain, creating a nerve network that stores a specific nemory. Activating one or two neurons in the chain will tend to trigger the others and thereby bring the memory back to mind. Yet there is really no single piece of hard evidence for this belief. Electron-microscopy has broughi the possibility of visualizing changed synapses, and hence of changed connections ont has revealed isat there are so many synapses on each cell that looking for those changed by learning is worse than trying to find the needle in a haystack. The concept of a distinction between sbort-and-long-termi niemory has been used extensively by neurologists and psychologists. Its validity is strongly indicated by the results of surgical removal of tissue of the temporal lobes and bippocampus of the brain for the relief of epilepsy. After removal of the hippocampus on both sides there has been found to be a very severe impairment of the capacity to set up long-lasting information stores, short-tenn memory remaining normal. 4. Categories of Memory
Two calegories of memory are : memory for skills and memory for events. A study of the course of acquiring a skill, say to type or to play a musical instrument, reveals that at first, there is little progress, Thea there is advance by jumps to new plateau of achievement and finally achievement of apparently unbelievable feats.
Allaninal memories can be considered as stored information for the performance of skills. Huinans also have the facility to recall single events that occurred both recently and long ago. Capacity to do this may
