FACILITATION OF PICTURE NAMING BY FOCAL TRANSCRANIAL MAGNETIC STIMULATION OF WERNICKES AREA

On the basis of an evolutionary concept of language it was postulated that activation of the motor systems for arm movements, which are phyl ogenetically older, should facilitate language processes. In aphasic s ubjects picture naming can be improved by a concomitant movement of th e dominant arm. In the present study it was investigated whether a sim ilar facilitation can be observed in normal subjects by studying the e ffects of transcranial magnetic stimulation (TMS) on picture naming la tencies. Suprathreshold focal TMS was applied to the left motor cortex for proximal arm muscles in right-handed subjects. The effects were c ompared with TMS of Wernicke's area. While TMS of the motor cortex and the non-dominant temporal lobe had no facilitatory effects, TMS of We rnicke's area decreased picture naming latencies significantly when TM S preceded picture presentation by 500 or 1000 ms. The observed effect s depended on the intensity of the stimulus used. While clearly presen t with intensities of 35% and 55% of maximum output the facilitation d isappeared with higher stimulation intensities. It is concluded that f ocal magnetic stimulation is able to facilitate lexical processes due to a general preactivation of language-related neuronal networks when delivered over Wernicke's area.