[Role of the frontal lobes in language. (A neuropsychological and experimental study)]

An experimental study carried out on 30 patients suffering from localised frontal lesions (16 left, 9 right, 5 bilateral lesions) using a battery of twenty tests (17 language tests and 3 visuo-spatial tests) showed: 1) frontal lesions disturb verbal control; 2) these disturbances seem to be proportionate to the extent of the lesion, that is, the area of the frontal lobe put out of action. As a result, there is a diversity of conditions ranging from quasi mutism in the extensive lesions, to an impossibility of producing accurate propositional and appropriate language indicating shades of meaning, in limited lesions; 3) the most frequently encountered disorder is characterised by an elementary level of language being well preserved but with difficulty of even impossibility in producing complex propositional language. This disorder, already obvious in spontaneous language, can be easily shown by means of appropriate verbal tests. 4) It seems to us of the utmost importance to emphasize that this syndrome appears irrespective of the side affected by the lesion. In fact, we have found that in 10 of the tests involved in our study which do in fact require replies which are appropriate to situations of a certain degree of complexity, similar failures were recorded for left frontal lesions (10 cases) and for right frontal lesions (11 cases). These findings prove that both the frontal lobes have a part to play in the exercise of verbal control. 5) It should however be emphasized that, in our group, the most serious deterioration in language was observed in left or bilateral frontal lesions. The same characteristics were found in these cases: elementary language better than propositional language but the level of achievement possible was very low being limited to brief replies which gave little information although they were usually correct. These findings justify the conclusion that a syndrome exists: disturbances in verbal control caused by frontal lesions. The function of the frontal lobes in language and verbal control in normal subjects is discussed.