Essay On The Nervous System

The nervous system includes the brain and spinal cord of the central nervous system and the ganglia of the peripheral nervous system. The functional unit of the nervous system is a neuron. It is estimated 100 billion neurons reside in the brain with some neurons making anywhere between 10,000 to 100,000 connections with other cells! A distinctive class of neurons, mirror neurons discharge both when the individual executes a motor action and when he/she observes another individual performing that same or similar action. These mirror neurons were discovered by neurophysiologists in the 1990s at the University of Parma, Italy. Using macaque monkeys, these researchers found that neurons of the rostral part of the inferior premotor cortex were activated both when the monkey made goal-directed hand movements (grasping, holding, & tearing) and when the monkey observed specific hand movements done by the experimenters (Pellegrino, et al., 1992). In a monkey’s inferior frontal and inferior parietal cortex, it is estimated that about 10% of neurons have “mirror” properties.

Later studies have found that many of these mirror neurons are also activated not only when performing a specific action but when hearing the related sound. For example, neurons responded to the vision and sound of a paper ripping, even when the associated sound was performed out of the monkey’s sight (Kohler, et al., 2002). For these types of studies, specific neurons were recorded using microelectrodes inserted through the dura mater of the monkey’s brain. Obviously, performing similar experiments on humans is not really possible and so most evidence for human mirror neurons is indirect. However, using functional magnetic resonance imaging (fMRI), researchers have fo...

... middle of paper ...

....

Many scientists have argued vehemently against mirror neurons both in their existence and their role in humans and monkeys. For example, an Oxford researcher argues that the mirror neuron system is not an evolutionary adaptation for action-understanding, but a byproduct of social interaction (Heyes, 2009). A neurophilosopher, Patricia Churchland, expresses concern over the role of the function of mirror neurons. She explains that intentions are more than individual neuron recordings. Intentions, she argues, are at a much more complex level of neural activity (Churchland, 2011). Taking into account the many doubts associated with the mirror neuron system, the importance of mirror neurons should not be overestimated and caution should be used. At the same, the mirror neuron research related to empathy, understanding intentions, and autism should not be overlooked.