Posts Tagged ‘frontal’

Brain Anatomy

September 8, 2019

The title of this post is identical to the title of a section in an important book by Scott D. Slotnick titled “Cognitive Neuroscience of Memory.” Brain Anatomy is a difficult topic to cover in a blog. The names can be learned and one can impress one’s friends and neighbors by reciting these names with their associated function. But the brain is a three dimensional structure and it is difficult illustrating these structures in two dimensions, especially since the position from which the brain is viewed is important. What is needed is a three dimensional model that can be rotated. Such a model can be found at http://www.brainfacts.org. Look for 3D Brain and click interact with the brain. It will likely take some practice interacting with the brain, but HM thinks this is the best source for this feature.

The brain is composed of four lobes: occipital, temporal, parietal, and frontal. Each lobe has gray matter on the surface, which primarily consists of cell bodies, and white matter below the surface, which primarily consists of cell axons that connect different cortical regions. The occipital lobe is associated with visual processing. The temporal lobe is associated with visual processing and language processing. The parietal lobe is associated with visual processing and attention, and the frontal lobe is associated with many cognitive processes. You can see that over half of the human brain is associated with visual processing. Obviously we are primarily visual animals.

The regions of the brain that are of relevance to memory include the occipital cortex, the temporal cortex, the parietal cortex, the dorsolateral prefrontal cortex, and the medial temporal lobe. The cortex is folded with gyri protruding out and sulk folding in.

The hippocampus (you can look for this using the link provided above) is a structure central to long-term memory. Its importance was realized when surgery was done on a patient, H.M., done to treat the severe epileptic seizures he was having. The medial temporal lobe, which contains the hippocampus, was removed in both hemispheres. This surgery did not affect his intelligence or personality, but it did cause a severe deficit in long-term memory referred to as amnesia. His semantic memory remained intact. He had almost no memory of events that occurred a few years before the surgery, and had no memory for events that occurred after the surgery. Ten months before the surgery he and his family moved to a new house a few blocks away from their old house. After the surgery he had no memory for his new address, he could not find his way to the new home, and he did not know where objects were kept in the new home. He had no memory of articles he had read before, so he would read the same articles repeatedly. He would eat lunch and a half-hour later could not remember he had eaten. Despite this severe deficit in long-term memory, his working memory appeared intact. He could remember a pair of words or a three-digit number for several minutes as long as he was not distracted. So a reasonable conclusion is that the hippocampus and the surrounding cortical regions are critical for long-term memory.

Dr. Slotnick writes, “Long-term memory typically refers to retrieval of previously presented information, However, the key stages of long-term memory include encoding, storage, and retrieval. The hippocampus has been associated with both long-term memory encoding and long-term memory retrieval. Long-term memory storage depends on a process called memory consolidation, which refers to changes in brain regions, including the hippocampus, underlying long-term memory. Thus, all three stages of long-term memory depend on the hippocampus.”

Sometimes people think of the hippocampus as being the location where long-term memories are stored. Memories are stored throughout the brain, it is the processing of these memories for which the hippocampus is critical.