PROCEDURAL MEMORY: TYPES, FUNCTIONING AND PHYSIOLOGY - NEUROPSYCHOLOGY - 2025

The procedural memory or instrumental is storing procedures, skills or motor or cognitive skills that allow people to interact with the environment.

It is a type of unconscious long-term memory, and reflects the way of doing things (motor skills). For example: writing, riding a bicycle, driving a car, playing an instrument, among others.

Memory systems are generally divided into two types: declarative memory and non-declarative or implicit memory. The first is that which stores information that can be communicated verbally, consisting of conscious learning.

On the other hand, the second type is a memory that is difficult to verbalize or transform into images. Within it is procedural memory. This is activated when you need to perform a task, and the learned functions are usually skills that are automated.

The main brain substrate for procedural memory is the striatum, basal ganglia, premotor cortex, and cerebellum.

The development of procedural memory occurs to a greater extent in childhood. And it is continually modified by daily experiences and practices. It is true that in adulthood it is more difficult to acquire these types of skills than in childhood, since it requires an extra effort.

Procedural memory concept

Procedural memory consists of habits, skills, and motor skills that the motor system acquires and incorporates into its own circuits. For this type of memory to be acquired, it is necessary to give several training trials that allow the skill to be automated.

Knowledge progresses unconsciously, and is continually modulated by experience. Thus, they adjust throughout their lives to repeated practice.

In more advanced stages, practice makes cognitive or motor skills more precise and faster. This becomes a habit, a behavior that runs automatically.

Procedural memory types

There appear to be two types of procedural memory, with different major locations in the brain.

The first refers to the acquisition of habits and skills. That is, the ability to develop stereotyped behavioral repertoires such as writing, cooking, playing the piano… This type of procedural memory is about goal-directed behaviors, and is housed in the brain's striated system.

The second is a much simpler system. It refers to specific sensorimotor adaptations, that is, adjusting our reflexes or developing conditioned reflexes.

These are body adjustments, allowing the execution of fine and precise movements, as well as conditioned reflexes. It is located in the cerebellar system.

How does procedural memory work?

Procedural memory begins to form early as you learn to walk, talk, or eat. Such skills are repeated and ingrained in such a way that they are done automatically. It is not necessary to consciously think about how to perform such motor activities.

It's hard to tell when you learned to do these kinds of actions. They are generally learned during early childhood and continue to be performed unconsciously.

Acquiring these skills requires training, although it is true that training does not always ensure that the skill is developed. We can say that procedural learning has been acquired when behavior changes thanks to training.

Apparently, there are structures in our brain that control the initial learning of procedural memories, their late learning and their automation.

Brain substrate

When we learn a habit, an area of ​​our brain called the basal ganglia is activated. The basal ganglia are subcortical structures that have multiple connections to the entire brain.

Specifically, they allow the exchange of information between lower brain areas (such as the brain stem) and higher areas (such as the cortex).

This structure appears to play a selective role in procedural learning of habits and skills. It also participates in other non-declarative memory systems, such as classical or operant conditioning.

Within the basal ganglia, a region called the striated nucleus stands out in the acquisition of habits. It receives information from most of the cerebral cortex, in addition to other parts of the basal ganglia.

The striatum is divided into associative striatum and sensorimotor striatum. Both have different functions in learning and automaticity of skills.

Early stages of procedural learning: associative striatum

When we are in the early stages of procedural learning, the associative striatum is activated. Interestingly, as the activity is training and learning, this area decreases its activity. Thus, when we are learning to drive, the associative striatum is activated.

For example, in a study by Miyachi et al. (2002), it was found that, if the associative striatum was temporarily inactivated, new sequences of movements could not be learned. However, the subjects could perform already learned motor patterns.

Late stages of procedural learning: sensorimotor striatum

In later stages of procedural learning, another structure becomes activated: the sensorimotor striatum. This area has an activity pattern opposite to the associative striatum, that is, it is activated when the skill has already been acquired and is automatic.

In this way, once the ability to drive has been sufficiently trained and is already something automatic, the associative striatum reduces its activity while the activation of the sensorimotor striatum increases.

Furthermore, it has been found that a temporary blockage of the sensorimotor striatum prevents the execution of the learned sequences. Although it does not interrupt the learning of new skills.

However, there seems to be one more step. It has been observed that when a task is already very well learned and automated, the neurons of the sensorimotor striatum also stop responding.

Cerebral cortex and procedural memory

What happens then? Apparently, when a behavior is very well learned, the cerebral cortex (cortex) is mostly activated. More specifically the motor and premotor areas.

Although this also seems to depend on how complex the sequence of movements learned is. Thus, if the movements are simple, the cortex is predominantly activated.

On the other hand, if the sequence is very complex, some neurons of the sensorimotor striatum continue to activate. In addition to activating the motor and premotor regions of the cerebral cortex as support.

On the other hand, it has been shown that there is a decrease in the activity of the brain areas that control attention (prefrontal and parietal) when we perform highly automated tasks. While, as mentioned, the activity increases in the motor and premotor areas.

Cerebellum and procedural memory

Cerebellum (blue)

The cerebellum also appears to participate in procedural memory. Specifically, it participates by refining and making the learned movements more precise. That is, it gives us more agility when executing our motor skills.

In addition, it helps to learn new motor skills and consolidate them through the Purkinje cells.

Limbic system and procedural memory

As in other memory systems, the limbic system plays an important role in procedural learning. This is because it is related to processes of motivation and emotion.

For this reason, when we are motivated or interested in learning a task, we learn it more easily and it remains in our memory longer.

Physiological mechanisms

It has been shown that, when we acquire learning, the connections and structures of the neurons involved change.

In this way, through a series of processes, the learned skills begin to form part of long-term memory, reflected in a reorganization of neural circuits.

Certain synapses (connections between neurons) are strengthened and others are weakened, at the same time that the dendritic spines of neurons change in size, lengthening.

On the other hand, the presence of dopamine is essential for procedural memory. Dopamine is a neurotransmitter in the nervous system that has multiple functions, including increasing motivation and feelings of reward. In addition to allowing movement, and of course, learning.

It mainly facilitates the learning that occurs thanks to rewards, for example, learning to press a certain button to get food.

Evaluation

There are various tests with which to evaluate procedural memory capacity in humans. Studies often use such tests comparing performance between patients with memory problems and healthy people.

The most used tasks to evaluate procedural memory are:

Probabilistic weather forecasting task

In this task, procedural cognitive learning is measured. The participant is presented with four different types of cards where different geometric figures appear. Each card represents a certain probability that it will rain or shine.

In the next step, the subject is presented with three grouped cards. This will have to find out if, taking the data together, it is more likely to be sunny or rainy.

After your answer, the examiner will tell you if the answer was correct or not. Therefore, the participant in each trial gradually learns to identify which cards are associated with more probability of sun or rain.

Patients with altered basal ganglia, such as those with Parkinson's disease, fail to gradually learn this task, even though their explicit memory is intact.

Sequential reaction time test

This task assesses the learning of sequences. In it, visual stimuli are presented on a screen, usually letters (ABCD…) The participant is instructed to look at the position of one of them (for example, B).

The participant must press one of four keys depending on where the target stimulus is, as quickly as possible. The left middle and index fingers and the right index and middle fingers are used.

At first the positions are random, but in the next phase they follow a certain pattern. For example: DBCACBDCBA… So, after several trials, the patient should learn the necessary movements and automate them.

Rotating chase task

This task is carried out with a special device that has a rotating plate. In one part of the plate there is a metal point. The participant must place a rod in the metal point for as long as possible, without forgetting that the plate performs circular movements that must be followed.

Mirror test

Good hand-eye coordination is required in this task. Assesses the ability to learn a specific motor skill, such as tracing the outline of a star. However, for this task the participant can only see the reflection of the image he draws in a mirror.

At first mistakes are common, but after several repetitions, movements are controlled by observing the hand itself and the drawing in the mirror. In healthy patients, fewer and fewer mistakes are made.

Sleep and procedural memory

It has been widely demonstrated that procedural memory is consolidated through an off-line process. That is, we fix our instrumental memories in periods of rest between motor training, especially during sleep.

Thus, it has been observed that motor tasks appear to improve markedly when assessed after a rest interval.

This happens with any type of memory. After a period of practice, it has been found beneficial to rest so that what you have learned takes hold. These effects are enhanced by resting just after the training period.

Procedural memory and awareness

Procedural memory has complex relationships with consciousness. We traditionally refer to this type of memory as an unconscious memory that does not involve effort.

However, experimental studies have shown that neuronal activation occurs before conscious planning of the movement to be carried out arises.

That is, the conscious desire to execute a movement is actually an "illusion". In fact, according to different studies, sometimes “being aware” of our automatic movements can negatively affect the execution of the task.

In this way, when we become aware of our sequence of movements, we sometimes deteriorate in performance and make more mistakes. For this reason, many authors emphasize above all that procedural memory, when it is already well established, does not require attention or supervision of the actions themselves to do them well.

Disorders that affect procedural memory

There is a set of both cortical and subcortical structures that intervene in different functions of procedural memory. A selective lesion of any of them produces various disorders in motor functions, such as paralysis, apraxia, ataxia, tremors, choreic movements, or dystonias.

Basal ganglia

Many studies have analyzed the pathologies that affect memory with the aim of knowing the types of existing memories and how they work.

In this case, the possible consequences that a malfunction of the basal ganglia or other structures may have on learning and performing tasks have been examined.

For this, in the various studies different evaluation tests are used comparing healthy people and others with some impairment of procedural memory. Or, patients with procedural memory impairments and other patients with impairments in another type of memory.

For example, in Parkinson's disease there is a deficit of dopamine in the striatum and abnormalities in the performance of certain memory tasks have been observed. Problems can also appear in Huntington's disease, where there is damage to the connections between the basal ganglia and the cerebral cortex.

Difficulties will also arise in patients with brain damage to some of the brain structures involved (for example, that produced by a stroke).

However, today the exact role of the basal ganglia in learning to move is somewhat controversial.

It has been found that, during motor learning, certain brain areas are activated in healthy participants. Some of them were the dorsolateral prefrontal cortex, the supplementary motor area, the anterior cingulate cortex… as well as the basal ganglia.

However, in Parkinson's patients other different areas were activated (such as the cerebellum). Additionally, the striatum and basal ganglia were inactive. It appears that compensation occurs through the cortico-cerebellar system, since the cortico-striatal pathway is damaged.

In patients with this disease and with Huntington's, a greater activation of the hippocampus and the thalamic-cortical pathways has also been observed.

In another study, they evaluated patients who had suffered a stroke affecting the basal ganglia and compared them with healthy participants.

They found that affected patients learn motor sequences more slowly, take longer to provide responses, and responses are less accurate than those of healthy participants.

Apparently, the explanations given by the authors are that these individuals have problems dividing the motor sequence into organized and coordinated elements. Thus, their responses are disorganized and take longer to elaborate.

References

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