Fifth: When the retrocentral region is injured, various aphasic syndromes appear. The retrocentral region is the parietal-temporal lobe except the superior part of the parietal lobe and the anterior part of the temporal lobe, which latter two regions when injured do not allow any marked aphasic disorder. Lesions of the middle or posterior temporal region are particularly important for speech, and produce more marked disorder than lesions of the angular gyrus or the supramarginal gyrus. At first, words cannot be spoken, for a period of a fortnight to three months. Speech returns progressively, with an increased power of comprehension. At the same time, the patients begin to read and write. But there is no further spontaneous progress after a period of six or eight months, and then special reëducation must be started. These speech disorders of retrocentral (parietal-temporal) origin are either aphasic syndromes or slight remains of psychical disorders, or again, a disorder practically limited to alexia. The true aphasic syndromes concern the spoken word, understanding the words, writing, and calculation. The disorder is not especially dysarthric and consists particularly in loss of vocabulary. It might be called an amnestic aphasia (Pitres). These cases have well-marked intellectual disorder and their power of calculation is especially poor. As to the aphasic traces, which are more important to understand than they are extensive in point of fact, they relate particularly to calculating power, to vocabulary (slowness in finding words), and to reading (reading without comprehension). As to the cases of alexia, these are cases of lesions of the posterior part of the parietal-temporal lobe, and are usually accompanied by a hemi- or a quadrantanopsia.
To sum up, cases with central lesions (precentral and postcentral gyrus) have hemiplegia and a Broca aphasia without much tendency to cure. Cases with lesions anterior to the central convolutions have a transient anarthria and their recovery is ordinarily complete. Cases with retrocentral lesions have an aphasia suggestive of Wernicke’s aphasia, and ordinarily leave behind them extensive defects in intelligence and language. These cases should be taken account of from the standpoint of compensation, since they are much worse off for work than many cases with amputations; and though their disorder looks slight, it quite interferes with working at a trade. From the point of view of military effectiveness, the retrocentral cases are not very good soldiers, and especially not good officers, as they do not understand commands completely.