Gentlemen!

So far, restricting our attention to the area of speech, we have contrasted brain disease and mental illness. Speech pathology is one of the best understood topics amongst brain diseases. Likewise, spoken expressions encompass so many of the symptoms of mental illnesses that by themselves they entitle us to view mental patients from this sole perspective. Nevertheless, I hope that in the following more extensive discussion, your understanding will be aided by starting from the simplified conditions of our example.

As already mentioned when discussing the central projection field, we can take it as established that memory traces and ideas are localized, that is, they are linked, according to their content, with different locations in the cerebral cortex. Apart from such localization in the aphasia schema, one can reasonably regard the receiver and sender of those telegrams as being linked to the notional Conceptualization Centre B, that is, with all the rest of the cerebral cortex and, as we shall see, its system of association connections. This would artificially separate the two projection fields s and m from the totality of all other projection fields. Such separation within the cortex is the basis for differentiating the areas for the two projection fields s and m (whether we stress their subcortical links or their transcortical links beyond the projection fields). In this illustration, the anatomical view was that the aggregate of transcortical pathways sB and mB formed discrete pathways vulnerable to discrete lesions localized to the neighbourhood of the two projection fields, while beyond there the pathways had to be seen as radiating out to many disparate areas of the cerebral cortex. The discovery of the clinical picture of transcortical motor and sensory aphasia seemingly relied by sheer chance on the fact that these lesions appeared to occupy precisely the postulated site. It is easily grasped that these rare cases were initially attributed to focal diseases of the brain. On the other hand, observation of the patient I already introduced to you proved that such clinical pictures can arise during the course of a typical mental illness, thus forming a natural transition to mental illnesses.

It is essential for our purpose that we go beyond such rare occurrences. However, if we stay with that initial example, and hold fast to the principle of localized representation, then we can conveniently split the centre B into two localized representations linked by an association pathway: We shall call them A and Z. A, the source representation [W], is linked with the sensory speech field by an association pathway sA. Z, the destination representation [W], is linked with the motor projection field for speech by an identical pathway Zm. AZ is the association pathway between A and Z. Altering the schema in such a way corresponds to some extent to processing of an arithmetical problem presented to a patient: Understanding the problem takes place as registration, in A; the solution corresponds with the destination representation Z; and only when the solution is found does activation of m take place. Between task and solution, complex thought processes can proceed, from which it becomes clear that the association pathway AZ itself can be regarded as subdivided many times over. We need not assume that the entire process normally follows a set pattern, virtually in preformed pathways, so that the result is predictable. However, we can tentatively assume that it behaves in just this manner in response to any random question; understanding the question is represented in A, the meaning of the answer by Z, and the intermediate in-series pathway AZ makes sense of the case, so that the answer develops from a more or less simple deliberation. If we do not expect a speaker to lead us astray, then we must recognize that in this case, in a normal person, answers will arise in a totally determined manner, to be predicted with approximate accuracy. The regularity hereby observed is based, as we shall see later, on the principle of ‘well-worn pathways’ [Ed].