Aug 31, 2022 10:00 pm

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 into your Glia cells and Hemispheres!

Glia cells

“Glia” literally means “glue” in Greek. The Glia cells in the brain provide the neurons with nourishment, protection, and structural support. Neurons consume a lot of energy, resources and require a lot of maintenance, which explains why Glia cells outnumber neurons in the brain by a factor of 10 to 50. Interestingly, these are also the cells most commonly involved in brain tumors.

Note that for a very long time it was believed that Glia cells were essentially support cells with no influence on cognition, but that this has since been proven to be not completely true. For instance, Oligodendroglia cells influence cognition by slowing down or speeding up specific signals travelling through axons, in effect they act as modulators on the signals involved in cognition. Let’s review some types of Glia cells:

  • Astroglia
  • Oligodendroglia cells
  • Ependymal cells
  • Microglia

Cerebral hemispheres

As has repeatedly been stated, the cerebrum (= telencephalon) is divided into two approximately symmetrical hemispheres. These hemispheres are connected by the Corpus Callosum, a wide and thick bundle of nerves connecting the two hemispheres, but also through a couple of smaller connections and through the midbrain (remember the two “strands” of the midbrain going to each cerebral hemisphere).

Corpus Callosum

The Corpus Callosum looks like a flat ribbon wrapped around the Diencephalon (and more precisely, wrapped around the two thalamuses) in the back-to-front direction, which connects the two cerebral hemispheres as can be seen of figures 15a and 15b. It is made up of about 200–300 million axonal projections linking various neuronal regions of both hemispheres with each other.

Note that the corpus callosum is only found in placental mammals and that if damaged or severed, it doesn’t seem to impair brain function that much. In humans, the corpus callosum is sometimes cut as a last resort against uncontrollable epilepsy attacks. Such attacks consist of an “electrical brainstorm” in the cerebral cortex that suddenly diffuse to the whole brain. By cutting the corpus callosum, attacks are confined to one hemisphere at the time, which greatly increases the quality of life of the patients. These “split-brain” patients don’t report feeling any different from before the surgery, except for the dramatic decrease in epileptic attacks of course. There consciousness doesn’t seem affected at a first glance. In fact, it takes quite intricate psychological experiments to observe the effects of cutting the corpus callosum, but they are fascinating and have greatly contributed to our current understanding of the brain and consciousness.

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

You can find all our stories already published on our blog.

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