Neurons and Intelligence, continued

What if we look at specific brain organization and structure? It is important to note that there are regions in mammals for which there is no corresponding area in non-mammals and vice versa. This may or may not have implications for intelligence. The signifiance of anatomical data depends on the relation of structure to function. Thus, we'll focus on mammalian species predominantly.

What if we made a comparison of the size of brains (brain weight) and brain parts, based on indexes that directly reflect size differences (ratios) in species of equal body weight? Well, since I myself could not do the study, we will look at someone who has.

S. Heinz et al. isolated the following brain structures from three different Families of primates -- Prosimians (e.g., lemurs), Simians (e.g., monkeys), and Tenrecinae: medulla oblongata, mesencephalon, cerebellum, diencephalon, telencephalon, bulbus olfactorius, paleocortex, septum, hippocampus, schizocortex, striatum, neocortex, area striata gray, and the corpus geniculatum laterale. They also found the total brain size of these animals. They found that the relative size of some brain parts shows strong differences between individual primate species. To be specific, "a classification of the various brain components based on the trends and intensities of size modifications from low Insectivora through prosimians, monkeys, and apes to man may be suggested as follows: an extremely strong progressive structure is the neocortex; strongly progressive structures are striatum, cerebellum, and diencephalon; fairly progressive structures are shizocortex, septum, hipocampus, and mesencephalon; conservative structures are medulla oblongata and paleocortex and amygdala; and a regressive structure is the olfactory bulb (Heinz, 15).

Does this give us relevant information about intelligence? What about evolutionary trends? What can we hypothesize about the fact that lower primates have smaller amounts of neocortex than higher primates and man? Perhaps this suggests that human primates are more advanced than lower primates due to their relative brain structure sizes? What about accounting for ecological or behavioral adaptations? Differences in relative size of brains and brain parts may reflect differences in these adpatations. However, simple interrelationships are hard to identify as they can be masked by a wide spectrum of factors.

Why don't we actually look inside the brains of all these animals? Click on the button below to look inside some brains.