The frontal lobe contains most of the dopamine-sensitive neurons in the cerebral cortex. The dopamine system is associated with reward, attention, short-term memory tasks, planning, and motivation. Dopamine tends to limit and select sensory information arriving from the thalamus to the forebrain.
Na + concentration is lowered, indicating that Na + in-flux is responsible for the rising phase of the action po-tential. Their data also suggested that the falling phaseof the action potential was caused by a later increase inK+ permeability.
Na + is critical for the action potential in nerve cells. As shown in Figure 2.1, action potentials are repeatedly initiated as the extracellular concentration of Na + is modified. As the concentration of sodium in the extracellular solution is reduced, the action potentials become smaller.