Alcohol and the effects of alcohol on memory and general cognitive functioning has been the subject of much research over the years.
Alcohol acts as a general central nervous system depressant, but it affects some areas of the brain more than others. Specifically, it leads to distraction and inattention and significantly inhibits neuronal activity in the hippocampus, which impairs memory encoding since the hippocampus plays an important role in the formation of new declarative memories. Because procedural memory functions more or less automatically, retrieval of procedural memory (“remembering how”) is not as severely impaired by alcohol as retrieval of declarative memory (“remembering what”).
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| One-time, or light, use of stimulants, such as cocaine, amphetamines or caffeine can improve memory recall in humans.|
However, heavy or prolonged use of stimulants or marijuana is associated with small but significant impairments in working memory and episodic memory retrieval.
Alcohol particularly impairs the encoding of episodic memory (that part of declarative memory that relates to our personal experiences and specific events in time), especially for certain types of recall, such as cued recall, the recognition of completed word fragments and free recall. A “blackout” is an example of the difficulty in the encoding of episodic memories due to high doses of alcohol. It is caused by a rapid increase in blood alcohol concentration, which in turn distorts the activity of neurons in the hippocampus, thus impairing a person’s ability to form new episodic memories. Alcohol also severely disrupt the encoding and storage process of new semantic memories (our memory of facts, meanings and acquired knowledge about the external world), although apparently not that of previously learned information.
Alcohol also impairs short-term (working) memory, although mainly by affecting certain mnemonic strategies and executive processes rather than by shrinking the basic holding capacity of working memory or by physically altering the structure of those parts of the brain which are critical for working memory function. Although light to moderate drinking does not appear to impair long-term cognitive functioning significantly (and according to some studies, may actually decrease the risk of cognitive decline), heavy drinking and chronic alcoholism are associated with long-term impairment in sustained attention and working memory function, especially visual working memory.
Serious over-consumption of alcohol, especially in comparison with the intake of other foods, can cause a thiamine deficiency, leading to a much more serious form of amnesia known as Korsakoff’s syndrome.