Defective recognition and naming of famous people from voice in patients with unilateral temporal lobe tumours.

Twenty-nine patients who underwent surgery for a temporal glioma, either in the left (16 patients) or right (13 patients) hemisphere, were administered standardized tests of unknown voice discrimination (UVD) and of famous voice recognition (VO-REC), which included tasks of familiarity evaluation, semantic identification and naming of famous voices. The UVD consisted of twenty stimuli, in which two audio files were consecutively presented; the subject was requested to judge whether the voices belonged to the same or different persons. In the VO-REC, patients were requested to recognize the voices of 40 very well known people; these voices were intermingled with the voices of 20 unknown people for a familiarity check, followed by identification and naming of persons recognized as familiar. We aimed at verifying the effect of laterality and intra-temporal site of lesion on familiarity assessment, false alarms, identification and naming of familiar people. As for the effect of lesion side, our results showed that patients with right temporal gliomas were significantly more impaired in voices discrimination and produced more false alarms than patients with a left glioma, who, in turn, were significantly more impaired in name retrieval than patients with a right temporal glioma. The high number of false alarms in patients with a right temporal glioma suggests that familiarity judgment was impaired. Regarding the neuroanatomical correlates of these different patterns of impairment, MRI data suggested that: (a) UVD disorders are due to lesions involving the whole right anterior temporal lobe and extending to lateral portions of the temporal and frontal lobes; (b) familiarity judgments (testified by an increased number of false alarms) are impaired in lesions restricted to the right anterior temporal lobe; (c) name retrieval deficits are found only in patients with left temporal lesions. UVD disorders were interpreted, at least in part, as due to an impairment of executive functions, resulting from a disconnection of the right temporal lobe from the frontal lobe control. A partly unexpected finding was that some patients with a right temporal tumour had a normal performance in famous voice recognition and identification, in spite of having severe voice discrimination disturbances. These unexpected results, in agreement with previous observation made in the visual (face) modality, are inconsistent with strictly hierarchical models of voice processing.

Transcranial magnetic stimulation of medial prefrontal cortex modulates face expressions processing in a priming task.

The medial prefrontal cortex (mPFC) and the right somatosensory cortex (rSC) are known to be involved in emotion processing and face expression recognition, although the possibility of segregated circuits for specific emotions in these regions remains unclear. To investigate this issue, we used transcranial magnetic stimulation (TMS) together with a priming paradigm to modulate the activation state of the mPFC and the rSC during emotional expressions discrimination. This novel paradigm allows analyzing how TMS interacts with the ongoing activity of different neuronal populations following prime processing. Participants were asked to discriminate between angry and happy faces that were preceded by a congruent prime (a word expressing the same emotion), an incongruent prime (a word expressing the opposite emotion) or a neutral prime. In TMS trials, a single pulse was delivered over the mPFC, rSC or Vertex (control site) between prime and target presentation. TMS applied over the mPFC significantly affected the priming effect, by selectively increasing response latencies in congruent trials. This indicates that the mPFC contains different neural representations for angry and happy expressions. TMS over rSC did not significantly affect the priming effect, suggesting that rSC is not involved in processing verbal emotional stimuli.