(extract from p48 of this ebook : 📖 Ebook: Insights from the brain, the road towards Machine Intelligence )
Even if the different cortical areas support very diverse functions, their anatomical organization is strikingly similar.
Indeed, the whole cortical sheet is made of a collection of anatomical fundamental columnar units called minicolumns (around 50 µm of diameter). Each cortical area is basically a collection of millions of minicolumns (each one being composed of around 100 neurons). Minicolumns are organized in layers (generally 6 layers), with specific neuron types and connection patterns in each layer. This organization is said to be laminated.
Neighboring minicolumns share a same Receptive Field (RF), meaning that they are innervated by the same axonal inputs. Those minicolumns form structures called macrocolumns/hypercolumns (around 500 µm of diameter) that are thought to be functional fundamental units (the hypothetical functional role of macrocolumns remains controversial).