Somatotopy of the Anterior Cingulate Cortex and Supplementary Motor Area for tactile stimulation of the hand and the foot D. Arienzo 1,2, T.D. Wager 3, J. Ferrera 4, G.L. Romani 1,2, J. Hirsch 4, 1 Department of Clinical Sciences and Bioimaging, G. D'Annunzio University, Chieti, Italy; 2 Institute for Advanced Biomedical Technologies, G. D'Annunzio University Foundation, Chieti, Italy; 3 Department of Psychology, Columbia University, New York, USA; 4 Department of Radiology, fMRI Center, Columbia University, New York, USA. INTRODUCTION METHODS DISCUSSION REFERENCES Subjects and Stimuli Ten right handed healthy volunteers (19 to 33 years, 5 males, 5 females). Tactile stimulation delivered to either the right hand or the right foot. Data acquisition and analysis BOLD functional imaging was performed with a 1.5T G.E. scanner by means of T2* EPI sequences (TR 2s, TE 52 ms, matrix 64x64, voxel size 4 mm x 4 mm, flip angle 90°, slice thickness 4.5 mm). Functional volumes consisted of 21 slices acquired parallel to the AC-PC line. Each scanning session was composed of two parts: a block design paradigm and an event related design paradigm. The block design paradigm consisted of 3 runs, each presenting an alternating sequence of 13 16s-long blocks of either rest or paint brush stimulation to the hand or the foot. Each run lasted 3 minutes and 34 seconds and, at a TR=2s, yielded 107 volumes. In the event related design there were 8 runs, each consisting of 24 trials, 12 of which lasted 11 s, and 12 lasted 15 s. Each run lasted 5 minutes and 22 seconds and, at TR=2, yielded 161 volumes. Data were analyzed in the general linear model framework with Brain Voyager 4.9. Preprocessed functional images were transformed into the Talairach space. Talairach coordinates of activation were selected at the most significant voxel in each cluster. The difference in the individual Talairach coordinates between median and tibial nerve activation was tested for ACC and SMA with an ANOVA test. We used functional magnetic resonance imaging (fMRI) to test the hypothesis of a somatotopic organization in the anterior cingulate cortex (ACC) and in the supplementary motor area (SMA) for tactile stimulation to the hand and the foot. Individual functional maps showed a clear segregation of activation in the two different paradigms. The preliminary results of the present study support the working hypothesis of a spatial segregation of somatosensory inputs in cognitive-sensorimotor areas such as ACC and SMA. The results demonstrated somatotopic organization of hand and foot within both the ACC and the SMA for both the event related design paradigm and for the block design paradigm. Results from a typical subject are depicted in Figures 1 and 2. These preliminary results confirm the working hypothesis supporting the importance of spatial segregation of somatosensory inputs in cognitive-sensorimotor areas such as ACC and SMA. Figure 1. Results of a typical subject showing the activated areas in the anterior cingulate cortex (ACC) after tactile stimulation to the hand and the foot. Red: activated areas during hand stimulation. Blue: activated areas during foot stimulation. RESULTS 12 TH ANNUAL MEETING OF THE ORGANIZATION FOR HUMAN BRAIN MAPPING, JUNE 11-15, FLORENCE, ITALY Although the somatotopic organization of early sensory and motor–sensitive areas is well established, the somatotopic organization of supplementary and executive regions is an active investigational question. Positron emission tomography (PET) has shown a within-arm somatotopy in ACC and SMA during visuomotor tracking tasks involving the shoulder, the elbow, the wrist, the finger, the thumb and the eye [1]. More recent fMRI evidence has indicated an activation of the ACC and SMA following nonpainful electrical stimulation of the hand and foot [2]. The present study aims at evaluating the working hypothesis that the spatial segregation of somatosensory inputs in cognitive-sensorimotor areas such as ACC and SMA is present with tactile stimulation of the hand and foot. [1]Grafton ST et al. Exp Brain Res. 1993;95:172. [2] Ruben J. et al. Cereb Cortex. 2001;11:463. Figure 2. Results of a typical subject showing the activated areas in the supplementary motor area (SMA) after tactile stimulation to the hand and the foot. Red: activated areas during hand stimulation. Blue: activated areas during foot stimulation. HANDFOOT HAND FOOT ACC SMA 497 TH - AM