Answer: Chronic alcohol abuse may lead to damage of memory centers of the brain.
One of the consequences of chronic alcohol abuse is a difficulty in recalling memories, which is also called amnesia. Amnesia can either be an inability to create new memories, which neuroscientists and psychologists call anterograde amnesia. On the other hand, an amnesia that results in a failure in the capacity to recall memories from long ago is called retrograde amnesia. People who chronically abuse alcohol may have both types of amnesia.
Alcohol is a very small molecule, and is able to affect several cell populations. After chronic alcohol abuse, the drug is able to damage many cells of the brain by depleting the brain of the vitamin thiamine, sometimes also called vitamin B1. In humans, dietary thiamine generally comes from whole grains (such as wheat, rice, rye, maize, barley, quinoa, or wild rice), legumes (such as alfalfa, peas, chickpeas, lentils, soybeans, or peanuts), and certain meats and fishes, particularly lean meats such as chicken, pork, and eggs.
If chronic alcohol abuse leads to the thiamine deficiency that injures the memory centers of the brain, then thiamine supplements may be effective at reversing some of the deficits. Thiamine is a water soluble vitamin. In the case of thiamine deficiency, supplements are very well tolerated. Dietary thiamine is absorbed by the intestine, but when a person consumes a supplement, this is usually taken up largely by passive diffusion. There are a few conditions where a person would regularly take thiamine supplements, namely if they are diagnosed with beriberi or Wernicke encephalopathy.
Memory deficits in alcohol abuse
The thiamine related deficiency that can result in amnesia is called Korsakoff syndrome. Korsakoff syndrome was named after the Russian psychiatrist Sergei Korsakoff who first described the disorder near the end of the 19th century. The patients described by Korsakoff presented with very serious difficulty with learning new tasks as well as difficulty in recalling events from a person’s past. Korsakoff’s syndrome is sometimes also called wet-brain syndrome. It sometimes appears alongside a language and comprehension disorder called Wernicke’s aphasia. When chronic alcoholics present with both memory disorders and language difficulties, they are diagnosed with Wernicke-Korsakoff syndrome.
The memory deficits in Korsakoff’s syndrome are characterized by several traits.
1 Anterograde amnesia
Anterograde amnesia is the loss of the ability to form new memories after the onset of the disorder. For example, if a severe alcoholic was asked what he had just done one hour earlier before a psychological examination, he might not be able to reliably and accurately answer the question. Failure to properly answer this question would be an example of a deficit in their explicit memory, more specifically, their autobiographical memory.
2 Retrograde amnesia
Retrograde amnesia is the inability to recall memories from long before the onset of the disorder. In many cases, severe retrograde amnesia may extend backwards into a person’s childhood. They have difficulty remembering even the most significant events from their school days, for example. They often lose their autobiographical memories and other semantic memories, but generally do not lose their implicit memories (for example, remembering how to ride a bike or rollerskate.)
3 Fixation amnesia
Severe alcoholics who develop Korsakoff’s syndrome may experience a fixation amnesia. In a chronic alcohol abuser, fixation amnesia results in losing track of events that very recently happened, such as in the minute or two before asking a question. A fixation amnesia is often seen as a loss in short term memory formation. In fixation amnesia, a person with Korsakoff’s syndrome may lose either semantic memories or autobiographical memories.
Confabulation is a speech and language disorder. Confabulation is the production of false memories that are not actually true or words that are not logical or fitting. For the patient with Korsakoff’s syndrome, they may forget their train of thought or lose words in the middle of their sentences. In these cases, when they forget, they will say words to fill the empty space. Confabulation can also be seen in patients with other types of dementia, such as in Alzheimer’s dementia or frontotemporal dementia. In most cases, a person who is confabulating will not be aware of their language deficits.
5 Hollow, pointless conversation
In addition to the above symptoms, chronic alcohol abusers oftentimes have difficulty with communication. They may have difficulty holding conversations with others, partially due to the amnesia and memory problems. The alcoholic may forget the beginning of the conversation as they continue talking, so they lose track of the end of their sentences. In order to compensate, they may try their best to keep the conversations simple, using simple words and avoiding complicated or in-depth talks.
There are many regions of the brain that are affected by chronic alcohol abuse that may contribute to memory deficits. Primarily, these brain structures are part of the Papez circuit and may also include the medial temporal lobes. These structures are essential to memory functions. The two structures that are most sensitive to thiamine deficiency are the mammillary bodies of the thalamus and the anterior thalamus. Because of their sensitivity to thiamine deficiency, these structures tend to deteriorate first in chronic alcohol abusers. They are both involved in memory related functions, which explains why some alcoholics may experience amnesia or other deficits in memory.
The hippocampus has been thoroughly researched in respect to memory formation, particularly because of Patient HM, the man who had his hippocampi and bilateral temporal lobes removed to cure his epilepsy. When Dr. Brenda Milner and other neuropsychiatrists did their examination on Patient HM following the removal of his temporal lobes, they observed that he lost the ability to make new memories - the same anterograde amnesia that is observed in some alcoholics after chronic drug abuse.
Mammillary bodies of the hypothalamus
The mammillary bodies are two small protruberances on the ventral side of the brain. They are part of the Papez circuit. The mammillary bodies are injured in patients who are chronic alcohol abuser or those who have Korsakoff’s syndrome, for example. There are several other disorders that show injuries in the mammillary bodies, for example schizophrenia, heart failure, sleep apnea, and Alzheimer’s disease.