Although all brains share certain features, they also differ in a number of important ways. First of all, some brains contain a great many more nerve cells than others. Also, the more highly developed brains have many more connections between cells. In simple nervous system, a given neuron may directly receive signals from only a few other cells. In man some cells are believed to receive signals directly from thousands of other cells.
Brain size is an important difference. So is the size of individual neurons. The entire brain of some insects is so small that it could fit inside a single large neuron, such as the giant neurons found in the sea slug (these are about 1/25 of an inch in diameter). One of the largest brains belongs to the elephant, and it weighs more than 10 pounds.
The thickness of axons also differs greatly. This is important. The larger the diameter of the axon is, the faster impulses can be sent along it. Therefore, thicker axons mean that different parts of the brain can communicate faster with one another.
Temperature is another factor. The warmer the body is, the faster most nerve activity is. This gives the warm-blooded animal an advantage over his colder and more sluggish competitors.
Some animals have brains with sensory systems not possessed by others. The rattlesnake, for instance, has highly specialized and sensitive receptors in his face for detecting warm objects. With these receptors, he can detect warm-blooded prey, such as mice, many feet away. Relying on the receptors, he can hunt in total darkness.
Bats have specially adapted vocal organs for producing very high-pitched sounds -far too high for our own ears to hear. The bat, however, can detect the echo of its own voice bouncing off distant objects. That is why a bat can fly in the dark without bumping into things and why a bat can pick out tiny insects as prey. This bat system is very much like radar and is of great interest to scientists.
ref: Bojo Loro, Didi Kempot, "Our Brain", Solo Publisher, 1988