Long-term memory is a neuronal, multimodal function that processes and stores information over the long term.
What is long-term memory?
Long-term memory is understood to be a neural, multimodal function that processes and stores information over the long term. Long-term memory can be divided into declarative and nondeclarative memory. Declarative memory contains concrete knowledge, whereas non-declarative memory stores information that is based on experience. Declarative contents are stored in those cortex regions that were also involved in the processing. The non-declarative long-term memory is assigned rather heterogeneous memory capacities. These include associative and non-associative learning, priming, habits and skills. Non-declarative memory is related to the cerebellum, the amygdala, and the striatum, among others, and is not dependent on conscious memory, whereas declarative knowledge can be consciously remembered and is therefore flexible. Endel Tulving (*1972) also calls these two forms semantic and episodic long-term memory, respectively. Episodic memory encompasses concrete events of a person, whereby spatiotemporal characteristics are also stored. This memory is also known as source memory. Semantic long-term memory includes word meanings, facts, or rule systems. In episodic memory, a single event can be recalled, which is not possible in semantic memory. Another form is procedural memory, which is also called behavioral memory. It stores automated skills such as driving a car or walking. These actions are learned through constant practice and can then be recalled without thinking.
Function and task
In the brain, information is not stored in a specific location, but is found in the overall structure of neurons as well as in their connections. Involved in this process are, for example, the limbic system, the frontal and temporal lobes, and the hippocampus, which transfers content from short-term to long-term memory. Once content enters the long-term memory, it is permanently stored there. For this purpose, so-called engrams are formed (memory traces as a structural change in the brain due to stimulus exposure), through which remembering becomes possible. Examples of long-term memory abilities are remembering a poem, an unpleasant situation or the face of an acquaintance. Information is actively encoded, processed, stored, and reproduced or remembered. An essential function of long-term memory is therefore to provide information in order to be able to make decisions optimally afterwards. In total, four processes of long-term memory are distinguished: learning, retaining, remembering and forgetting. Long-term memory has an almost unlimited capacity. Learning takes place between the motor and sensory neuron (nerve cell). When the sensory neuron is stimulated, increased neurotransmitters are released and strong muscle activation occurs. The learning process takes place first as short-term storage and later as long-term storage, whereby the synapse increases in size and changes its function. By relating the learning material to what is already known, information can be stored in long-term memory. Only extremely rarely, however, are certain facts or events reproduced faithfully. In remembering, prior knowledge apparently plays a significant role, but reflection or certain retrieval processes can also modify or distort content.
Diseases and complaints
One possible disease related to long-term memory is memory problems. Disturbances in memory, poor concentration and forgetfulness, if they do not increase, are often due to exhaustion or stress. However, if the problems increase and normal daily routines become problematic, a doctor should be consulted, as forgetfulness can also conceal a more serious illness. One possible disease is dementia, which impairs the ability to think or the mental performance. Those affected have problems absorbing new content and then reproducing it.In addition, speech, arithmetic and the ability to orient oneself are also affected. The most common form is Alzheimer’s disease, in which brain cells die due to protein clumps that occur outside or inside the nerve cells. Another common form is vascular dementia, which is caused by circulatory disorders in the brain. Less common is a condition called Lewy body dementia. Lewy bodies are spherical structures found in the cerebral cortex or brainstem. Affected individuals experience progressive memory impairment and suffer from movement disorders as well as psychotic symptoms. Dementia can also occur in the context of Pick’s disease. Here, above all, the ability to think abstractly is disturbed and certain brain regions die slowly. In contrast, dementia develops very quickly in Creutzfeldt-Jakob disease. There are mainly disturbances in concentration, attention or memory, the cause being toxic proteins that cause the brain tissue to die. Accompanying dementia is also possible in Parkinson’s disease or HIV. Other diseases in which forgetfulness may occur are:
- Meningitis: Viruses or bacteria can cause confusion, drowsiness or poor concentration.
- Meningitis: Here symptoms such as confusion or impaired consciousness occur.
- Sleep apnea: Since in this disease the night sleep is out of rhythm, there is a lack of concentration, forgetfulness or fatigue during the day.
- Chronic fatigue syndrome: Typical of this is a physical and mental exhaustion, which is accompanied by irritability and poor concentration.
- Depression and anxiety disorders can also affect the brain and lead to forgetfulness.
Other causes can include medications, lack of fluids and nutrition, sleep disorders, stress, alcohol abuse and cancer treatments.
