Historically, early scholars in neuropsychology argued that cognitive functions are dissociated (i.e., they can be selectively altered by brain damage) and that each of these functions is made up of different elements that, in turn, are also dissociated.

The previous hypothesis, called “of the modularity of the mind” , supports the idea that the neurological system of information processing is formed by an interconnection of several subsystems, each of which includes a number of processing units or modules in charge of supporting the main system.

On the other hand, the fact that any brain damage may selectively alter one of these components also seems to be directed towards another modular organization of the structure and physiological processes of the brain.

Objective of neuroscience in neuropsychological intervention

Thus, the primary objective of neuroscience in this question is to know to what extent biological brain functions are “broken down” in such a way that this division corresponds directly to the breakdown of the processing units that (according to the main postulates of neuropsychology) underlie the performance of a given cognitive function.

In an attempt to achieve the above goal, neuropsychology has tried to advance by leaps and bounds in the knowledge of the structure and functioning of the information processing system by studying and analyzing in detail the behavior of patients with various types of brain damage .

Neurological alterations and disorders

It should be noted that, as the main consequence of a brain injury, a pattern of altered and preserved behaviours can be clearly observed in the patient. Interestingly, the altered behaviors, in addition to being dissociated from the rest of the individual behaviors, may be (in many cases) associated with each other.

If an analysis of the behavioural dissociations derived from brain damage, on the one hand, and an analysis of the associations, on the other, is carried out (the latter aiming to determine whether all the associated symptoms can be explained by virtue of the damage to a single component), the components of each modular subsystem could be identified , within the overall and/or main system, thus facilitating the study of the functioning of each one of them.

Behavioral dissociations

In the 1980’s some authors identified three different types of behavioral dissociations: the classical dissociation, the strong dissociation and the tendency to dissociate .

When classic dissociation occurs, the individual shows no impairment in the performance of various tasks, but performs others quite poorly (compared to his executive skills before the brain injury).

On the other hand, we speak of strong dissociation when the two tasks compared (performed by the patient for assessment) are shown to be deteriorated, but the deterioration observed in one is much greater than that observed in the other , and furthermore the results (measurable and observable) of the two tasks can be quantified and the difference between them expressed. In the opposite case to the one presented above, we talk about “tendency to dissociation” (it is not possible to observe a significant difference between the executive level of both tasks, besides not being able to quantify the results obtained in each of them and explain their differences).

Let us know that the concept of “strong dissociation” is closely related to two independent factors: the (quantifiable) difference between the levels of execution in each of the two tasks, and the magnitude of the executive deterioration presented.The greater the first and the lesser the second, the stronger the dissociation presented.

Symptomatological complexes

Traditionally within our field of study, a set of symptoms (in this case behavioural) that tend to occur together in an individual under various conditions has been called a “syndrome”.

Classifying patients into “syndromes” has a number of advantages for the clinical psychologist . One of them is that, since a syndrome corresponds to a certain location of the lesion produced, this can be determined by observing the execution of the patient in the tasks for their consequent assignment to a specific syndrome.

Another advantage for the therapist is that what we call “syndrome” has a clinical entity, so once it is described, it is considered that the behavior of every patient who has been assigned to it is being described.

It should be stressed that, in fact, rarely does a patient under treatment fit the description of a specific syndrome; moreover, patients assigned to the same syndrome do not usually resemble each other.

The reason for this is that, in the concept of “syndrome” as we know it, there is no restriction on why the symptoms that make up the syndrome tend to occur together, and those reasons can be of at least three types:

1. Modularity

There is a single component and/or biological module altered and all the symptoms presented in the patient’s behaviour are directly derived from this alteration .

2. Proximity

Two or more significantly altered components are present (each of which causes a series of symptoms), but the anatomical structures that keep them functioning and/or support them are very close to each other , so the lesions tend to produce symptoms to all of them together and not to one in particular.

3. Chain effect

The direct modification of a neurological element or module resulting from a brain injury, in addition to directly causing a series of symptoms (known as “primary symptoms”), alters the executive function of another element and/or neurological structure whose anatomical support is originally intact, which causes secondary symptoms even without having been the main target of the injury produced.