The cerebral cortex is the phylogenetically most advanced part of the central nervous system in mammals. Meaning? It is the "newest" part of the brain in an evolutionary sense. The cerebral cortex is divided into various parts, but before getting into what they do, lets clear up one point about the anatomy of the brain:
The cerebral cortex is not the entire brain, only a large and very prominent structure. When you look a the brain from almost any angle, you see the complex and convoluted folds (sulci and gyri) of the cortical surface. However, the cortical surface itself is only a few millimeters thick -- in fact what looks like a very dense, noddle-y mass is actually a thin sheet of grey matter (neuron cell bodies) which completely covers and conceals from view most of the "lower" structures of the brain* such as the basal ganglia, thalamus, midbrain and spinal chord. Thus, there is much of the brain that is not the cerebral cortex. That being established, lets move on . . .
I must correct ophie's classification of brain parts on two small points above: 1) The insula is anatomically and functionally really a small part of the parietal lobe -- though it is located in a very out-of-the-way spot. 2) The "limbic lobe" is not a well defined set of structures. It would be more precise to say that the brain parts that make up the limbic system are somewhere "in between" the cerebral cortex and lower brain structures. Some limbic structures, such as the entorhinal cortex, are located near to and have functions similar to cerebral cortex proper, while others, like the putamen, are classified as diencephalic (lower) brain centers.
So lets talk about the lobes:
- Occipital lobe: The most well understood part of the cortex. Located at the posterior most area of the cortex, the occipital lobe is responsible for all aspects of visual information processing; detecting edges and borders, depth perception, the processing of color, the processing of motion and the beginnings of object recognition. I will try to treat these in more detail in another WU, but suffice it to say that many of these different activities occur in anatomically distinct areas, and that these areas are organized in a hierarchical fashion. There are two main visual processing "output" pathways, the "dorsal stream", which is concerned with the location of objects in the visual world, and the "ventral stream", which is concerned with the identification of objects in the visual world.
- Parietal lobe: Located in front of the occipital lobe but behind the frontal lobe, the parietal lobe has two main functions that we know of: 1) processing somatasensory (touch) information in much the same way the occipital lobe processes visual information. and 2) forming a 3-D representation of the outside world using somatasensory information as well as the information contained in the dorsal stream (object location) mentioned above.
- Temporal lobe: Located below the frontal and parietal lobes, the temporal lobe has several functions, including auditory information processing, language processing and execution, object recognition and memory encoding. These latter two functions are subserved in great part by the dorsal stream (object recognition) information from the occipital lobe, as the structures of the temporal lobe feed this information into the hippocampus and associated structures.
- Frontal lobe: Located at the front-most part of the cortex, the frontal lobe is the most evolutionarily advanced, highly developed, and complex part of the brain, responsible for personality, decision making, reasoning and higher thought in general. The frontal lobe receives no primary sensory information, but instead receives most of its information from the other three lobes and is responsible for the primary output of the brain -- that is it prepares and executes the neural commands which control voluntary muscle movement. The frontal lobe is the least well understood part of the brain, though some aspects of its function have been mapped out: for instance, it has been shown that specific parts of the frontal lobes communicate heavily with the parts of the parietal lobe that represent the 3-D outer world. It is thought that these lines of communication help update the location of objects in the brain's working memory.
So how, exactly do all of these parts
work? The first person to figure that out gets a
nobel prize = ) However, in general we are able say that the occipital, parietal and temporal lobes receive
primary sensory information and use that information to
discern the nature of the outside world. This information is fed into the frontal lobes, where it is integrated, processed and responded to. Of course, this is a gross
oversimplification: this description ignores the heavy
interconnectivity within and between lobes and the critical role of the many, many, many lower brain centers.
* That is, the diencephalon, the mesencephalon, the metencephalon and the myencephalon. The cerebral cortex itself is considered part of the telencephalon.