In examining someone who has suffered a broken neck and is therefore paralyzed, we have discussed in class that it is the connection that passes the electrical impulses from the spinal chord to the brain (thalamus, hypothalamus, cortex, etc.) that is severed. This also means that neuronal signals cannot be transmitted from the brain back down the spinal chord either. These people are therefore paralyzed. The signals can travel through the sensory nerves into the spinal chord through the dorsal root but the reciprocating motor nerves will not be activated. We compared this to the studies done on the frog nerves entering the spinal chord, where either one root or the other was severed, thereby severely reducing capabilities while still leaving some functions intact. We could see the frog walking on the leg when he couldn't feel it and reacting to pinches when he shouldn't have been able to move it. Yet a broken neck eliminates all of these avenues. This evidence proves that the brain must still receive input when one of the roots whether it is dorsal or ventral is cut. If the brain can receive input, behavior can occur.

A person who has suffered this injury still performs some of the types of behavior we have discussed. The I function is still present, the personality is totally intact. We debated the idea of personality being in the spinal chord along with the brain but this idea does not stand up against the evidence presented in the case of para- and quadrapalegics. The distinction between action and behavior is an interesting idea which needs to be explored in greater depth.

Indeed we'll want to consider the relation between action and behavior in greater depth ... again and again as we go through course. Careful about use of terms like "paralyzed". Arms and legs CAN move in person with broken neck, and do. Sensory signals entering spinal cord can and do produce motoneuron discharges from spinal cord. What can't happen is sensory signals entering spinal cord producing motoneuron discharge from brain, and sensory signals entering brain producing motoneuron discharge from spinal cord. PG