Procedural Memory: Function, Tasks, Role & Diseases

Procedural memory, together with declarative memory, constitutes long-term memory. The information stored in procedural memory is not accessible to consciousness and is referred to as action information, so procedural memory is sometimes referred to as behavioral memory. In people with degenerative diseases, procedural memory is often damaged.

What is procedural memory?

Procedural memory, together with declarative memory, makes up long-term memory. Human long-term memory consists of two distinct parts of memory. One is the declarative memory. The contents stored in it are facts about the world and one’s own life that can be consciously reproduced. Procedural knowledge differs from declarative knowledge in that it escapes consciousness. For this reason, what has been stored in procedural memory cannot be consciously reproduced. Nevertheless, the contents of procedural memory are also knowledge contents in the broadest sense. Procedural memory is also called behavioral memory and thus comprises the implicit knowledge that a person has acquired about automated action sequences. In this context, for example, the movement sequences for dancing, running, cycling or driving a car are anchored in procedural memory, even though the contents cannot be verbalized. All human skills are accordingly stored in this type of long-term memory. In this context, the term skills refers primarily to practically learned and complex movements whose sequence was practiced until it could be recalled without conscious thought about it.

Function and task

While declarative long-term memory contains theoretical information, the procedural part of long-term memory stores only practical information. In connection with procedural memory, there is often talk of implicit learning. This is referred to as ‘learning in the situation’. A person learns structures of a complex stimulus environment without necessarily intending it. The knowledge learned in the situation is sometimes difficult to verbalize and often enters memory as an unconscious learning process. Procedural learning occurs primarily in the cerebellum, subcortical motor centers, and basal ganglia. This distinguishes the learning processes from declarative learning of all facts, which are stored with the involvement of the entire neocortex. Procedural knowledge is not conscious knowledge. Nonetheless, it is the most useful type of knowledge because it refers to unconscious processing and action routines. Walking is a form of procedural knowledge that humans learn in the early infant stage. The nature of learning in this context corresponds to “learning by doing”. After a certain age or a certain repetition rate of the walking movement, the toddler no longer has to concentrate or spend any thought on the movement process. An adult will not be able to say at all what individual movements running consists of. He is hardly consciously aware of himself while running, but automatically recalls the stored sequence of movements from his procedural memory. As soon as movement sequences no longer have to be consciously thought about, they are permanently stored. Memory contents of the long-term memory are based on a special wiring pattern of individual synapses. These connections are built on the basis of neuronal plasticity, but can also be degraded again if they are not recalled often enough. While repetitive motor activities, such as riding a bicycle, are retained well even if the respective person has not practiced them for a long time, synaptic circuits for more complex movements are released more easily. This applies, for example, to rehearsed choreographies to certain dance rhythms. In addition to motor skills and behaviors, procedural memory also encompasses cognitive skills and algorithms for automatic and unconscious application.

Diseases and disorders

Disorders of memory can be of various natures.The best-known memory disorders are various types of amnesia, as they occur after damage to declarative memory. Procedural memory disorders are to be distinguished from this. In severe deficits of declarative memory, the functions and contents of procedural memory are preserved in most cases, since declarative and procedural memory are located in different sections of the brain. For this reason, procedural memory disorders occur almost exclusively after damage to the basal ganglia, cerebellum, or supplementary motor regions. The most frequent cause of this type of lesions is not trauma, as it is relevant for declarative memory disorders, but degenerative diseases. Among the most common, procedural memory disorders and impairments are observed in patients with Parkinson’s disease. Diseases such as Huntington’s disease can also be the cause of procedurally impaired memory. More rarely, procedural memory impairment presents with loss of learned automaticity following lesions in the basal ganglia, such as those that may be caused by inflammatory processes, hypoxia, hemorrhage, or trauma. In isolated cases, procedural memory dysfunction has also been associated with depression. The suspicion of a disorder in procedural memory exists especially for persons who lose learned skills such as the ability to write or to play a certain musical instrument. Under certain circumstances, the impairment of procedural memory is reversible, for example, by relearning the old skills in the course of rehabilitation and training their procedural memory in this way. In degenerative diseases, however, the process can only be delayed by rehabilitation, not halted.