by Carol A Westbrook

Dementia refers to progressive, irreversible cognitive impairment usually seen in the elderly. The clinical findings of dementia almost always include some degree of memory impairment. We didn’t know much about how memories were formed in the brain until 1953, when the now-famous patient named Henry Molaison, HM, had removal of an area in the temporal lobe of his brain called the “hippocampus”  the operations successfully prevented seizures, but unfortunately HM also lost the ability to form new memories of events, and his recollection of anything that happened in the preceding eleven years was severely impaired. Other types of memories such as learning physical skills were not affected. This was the first step in learning about how and where memories are formed in the human brain.

We now know that the hippocampus plays an important part in the formation of new memories by the physical interaction and modification of neurons, and it also processes short  -term memories into long-term memories, which are then stored in the frontal cortex.  Specific brain structures have other specific tasks in memory development, (see figure 2) such as the amygdala, the area of the brain which adds emotional pertinence to memories such as fear, pleasure or pain, whereas physical skills and movement are dependent on the cerebellum. We are beginning to understand how and why specific brain lesions can lead to different forms of dementia. Read more »