The Cortex Machina project has its origins in a deeply rooted fascination with neurobiology in general, and the biological origins of consciousness in particular. Unfortunately, it can often be very challenging to discuss and share these fascinating concepts, simply because they generally require a lot of prior knowledge which is, to say the least, quite unfamiliar to most people. That’s why we have started this series of short columns: to kindle interest in the fields of neuroscience and neurobiology and to provide my readers with enough general knowledge on the human brain and cognition to start exploring and sharing these fascinating concepts themselves. We will start with a series of articles on brain anatomy, to provide the reader with an understanding of brain architecture and nomenclature, which will be helpful later on when we discuss other topics. So without further ado, let’s enter now into the divisions of the Cerebrum!

Divisions of the Cerebrum

Let’s focus again on the Cerebrum (= telencephalon, which together with the diencephalon forms the forebrain). It consists of two hemispheres separated by a deep longitudinal fissure which contains the corpus callosum. Each hemisphere is divided into five lobes: frontal, parietal, temporal, occipital, insular (see Fig. 1). This division into lobes was originally a purely anatomical classification, but they have been shown to also be related to different brain functions. Each lobe may be divided, once again, into areas that serve very specific functions. An example is Broca’s area, located in the frontal lobe of the dominant hemisphere, usually the left, which has functions specifically linked to the motor aspects of speech production.

Another way to divide the Cerebrum is histologically by its cellular organization. Histologically means “by analyzing the microscopic anatomy of tissues”, usually through a variety of microscopes. The cellular organization just refers to how the neurons from different locations in the brain are interconnected. In 1909, Korbinian Brodmann, a German neurologist, discovered that he could map which cortical tissues were connected with each other by a clever way of dyeing relevant tissues (literally with blue dye), the Nissl method. With this information he produced the first map of the cerebrum based on the underlying neuro-architecture, consisting of 52 so-called “Brodmann areas”. Note that these Brodmann areas overlap with the previous classification into lobes, it is just another way to classify parts of the cerebrum. Often, specific areas can be found back in both classification systems. Wernicke’s area (functions linked to speech fluency) in the lobe system for instance corresponds to Brodmann areas 22, 39 and 40.

Figure 1: Lobes of the Cerebrum.

As the Brodmann system is far too detailed for what we need here, we’ll continue primarily with the lobes classification system. It’s important to understand that each lobe of the brain does not function alone. There are very complex relationships between the lobes of the brain and between 

the right and left hemispheres. As has been stated, each lobe can be further divided into areas linked to very specific functions, like the Broca area and motor strip in the frontal lobe, the sensory strip in the parietal lobe and the Wernicke area in the temporal lobe (see Fig. 1).

Figure 2: Lobes of the brain and specific cortical areas.

A big thanks for your reading from the entire Cortex Machina team!

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