Taxonomy of Subjective Phenomena: a Neuropsychological Basis of Functional Assessment of Ischemic or Traumatic Brain Lesions

Abstract

A proper evaluation of functional competence after central lesions has to be based on a classification of functions that one can agree upon. It is a sad fact in neuropsychology that such a classification is not available. An attempt will be made to discuss such a classification (or taxonomy) that might be useful.

The basic idea is that elementary psychological functions are evolutionary products whose availability is dependent on the functional integrity of neuronal modules. Such modules are embedded neuronal mechanisms that are linked to localized structures or distributed neuronal algorithms. Constancy of interindividual loss of psychological functions associated with lesions of modules can be used to define a catalogue of functions. Using this principle one can differentiate four areas of psychological functions that are represented in a modular fashion. These areas are stimulus representations (“perception”), processing of information (“learning and memory”), evaluation of information (for instance by emotions), and finally action or reaction. Functional competence is, however, not only described by the potential availability of elementary psychological functions, but also by formal aspects, i.e. how functions are made available. Such formal aspects refer to activation and in particular to temporal problems of neuronal processing. A particular “time machine” will be discussed which is essential for functional competence.

Central lesions may either effect the what of functions or the how of functions. A differentiation between these material and formal aspects of functional competence are essential with respect to recovery or restitution of function.