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cheffernan's picture


The idea of reafferent loops at first was counter-intuitive, however, when I left class this week thinking about how an output could also be an input, I thought about it and how when we move our hand, there is a whole new set of sensory inputs that need to account for the change in location of your hand. This need for accounting is important especially when considering a fear response. Let’s say that you burn yourself, your nervous system quickly gets the sensory input to move your hand, and produces an output to move your hand, but without the reafferent loop, the nervous system would not know whether the hand needs to be moved more or if the hand was safe.

Central pattern generation (CPG) is a genetic or learned behavior that requires coordination of various parts of the nervous system, and this coordination would not be capable if it were not for reafferent loops. In the example that Prof. Grobstein gave in class, the crayfish has a nervous system produces swimming behaviors, which requires the coordination of movement of many legs. Reafferent behavior feeds into this because before CPG can occur to tell another leg to begin its swimming movement, the sensory neuron sends a signal back to the nervous system informing it of the leg’s new location. Once this information is received, the next leg moves and allows for coordination to occur.

I am now able to understand how the coordination of the nervous system translates into the coordination of the organism, but how does the nervous system establish CPGs? Is it like conditioning, where once a behavior is reinforced enough the neurons become connected to produce the behavior without thought?


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