Proceedings of The Physiological Society
University of Bristol (2005) J Physiol 567P, C129
Cortical representation and lateralization of taste in man
Fabri, Mara; Polonara, Gabriele; Mascioli, Giulia; Tassinari, Giancarlo; Berlucchi, Giovanni; Aglioti, Salvatore; Salvolini, Ugo; Manzoni, Tullio;
1. Dipartimento di Neuroscienze - Sezione di Fisiologia, Universita'Politecnica delle Marche, Ancona, Italy. 2. Dipartimento di Neuroradiologia, Universita' Politecnica delle Marche, Ancona, Italy. 3. Dipartimento di Scienze Neurologiche e della Visione, Universita'di Verona, Verona, Italy. 4. Dipartimento di Psicologia, Universita'di Roma 'La Sapienza', Roma, Italy.
In the human brain taste is represented in the primary gustatory area (GI), a cortical region lying at the transition between the frontoparietal operculum and the insula. This notion has been repeatedly confirmed with MEG, PET and fMRI studies. The latera lization of taste representation, i.e. whether unilateral taste stimuli activate the contralateral or ipsilateral GI, or both areas, is still a controversial issue. The present research was aimed at establishing whether the cortical representation of taste in area GI is mainly ipsilateral as in non-human primates, or bilateral, as suggested by recent neuropsychological studies of patients with callosal resection or cerebral lesions. Six neurologically intact subjects gave their informed consent to participate in the study according to a protocol approved by the Local Ethical Committee and in accord with the Declaration of Helsinki. Functional images were acquired by using a General Electric Signa CV/i-NV/I, with a 1.5 Tesla magnet and 50 mT/M gradients in the three spatial directions. The images of 10 contiguous 5-mm-thick encephalic sections parallel to the axial plane were acquired with an echoplanar sequence. Gustatory stimulation was performed by placing a small cotton pad soaked in 1M NaCl solution on the side of either hemitongue. The stimulation protocol lasted 5 min and consisted of 60 s rest, 30 s stimulation, 90 s rest, 30 s stimulation, 90 s rest. Data were analysed with BrainVoyager and SPM2 software. A statistical value of P < 0.05 was considered to show significant activation. Preliminary results indicate that salty stimulation of the left hemitongue l ed to a clear-cut activation of area GI in the left hemisphere (mean Talairach coordinates: x, -37; y, 21; z, 1) in all subjects, coupled with an activation of the right GI (x, 37; y, 23; z, 5) in 4 of them. Stimulation of the right hemitongue caused a bi lat eral activation of GI (mean Talairach coordinates: right x, 39; y, 14; z, 1; left x, -43; y, 13; z, 0) in 4 subjects, while GI activation was ipsilateral to the stimulus in one of the 2 remaining subjects and contralateral in the other one. The results s uggest that in most neurally intact subjects unilateral taste stimulation evokes bilateral activation of area GI. They are generally compatible with our previous findings in callosotomy patients (Aglioti et al. 2001), according to which 'gustatory pathways from tongue to cortex are bilaterally distributed, with an ipsilateral predominance that may be subject to individual variations'.
Where applicable, experiments conform with Society ethical requirements