A fronto-parietal circuit for tactile object discrimination: an event-related fMRI study M. Cornelia Stoeckel, a, * Bruno Weder, b Ferdinand Binkofski, a,c Giovanni Buccino, d N. Jon Shah, e and Ru ¨diger J. Seitz a a Department of Neurology, University Hospital Du ¨sseldorf, Du ¨sseldorf, Germany b Department of Neurology, Kantonsspital St. Gallen, St. Gallen, Switzerland c Department of Neurology, University Hospital Lu ¨beck, Lu ¨beck, Germany d Institute of Human Physiology, University of Parma, Parma, Italy e Institute of Medicine, Research Centre Ju ¨lich, Ju ¨lich, Germany Received 23 August 2002; revised 1 March 2003; accepted 18 March 2003 Abstract Previous studies of somatosensory object discrimination have been focused on the primary and secondary sensorimotor cortices. However, we expected the prefrontal cortex to also become involved in sequential tactile discrimination on the basis of its role in working memory and stimulus discrimination as established in other domains. To investigate the contributions of the different cerebral structures to tactile discrimination of sequentially presented objects, we obtained event-related functional magnetic resonance images from seven healthy volunteers. Our results show that right hand object exploration involved left sensorimotor cortices, bilateral premotor, parietal and temporal cortex, putamen, thalamus, and cerebellum. Tactile exploration of parallelepipeds for subsequent object discrimination activated further areas in the dorsal and ventral portions of the premotor cortex, as well as parietal, midtemporal, and occipital areas of both cerebral hemispheres. Discriminating a parallelepiped from the preceding one involved a bilateral prefrontal–anterior cingulate–superior temporal– posterior parietal circuit. While the prefrontal cortex was active with right hemisphere dominance during discrimination, there was left hemispheric prefrontal activation during the delay period between object presentations. Delay related activity was further seen in the anterior intraparietal area and the fusiform gyrus. The results reveal a prominent role of the human prefrontal cortex for somatosensory object discrimination in correspondence with recent models on stimulus discrimination and working memory. © 2003 Elsevier Science (USA). All rights reserved. Keywords: Somatosensory; Tactile; Working memory; Prefrontal cortex; Event-related functional MRI Introduction The discrimination of objects with respect to their geo- metric characteristics by active touch is more than a simple combination of touch and kinesthesia (Re ´ve ´sz, 1950). In- deed, the tactile exploration of object features is mediated by dedicated finger movements, which have been described in detail by Roland and Mortensen (1987). Recent neuro- imaging studies have shown that different cytoarchitectonic subareas of the somatosensory cortex specifically code roughness, edge, and shape characteristics of objects (Bodegård et al., 2001). The superior parietal lobule and the secondary somatosensory cortex in conjunction with the ventral premotor cortex have been shown to build the basic circuit for tactile object identification (Binkofski et al., 1999). Conversely, well-defined, circumscribed brain lesions of the parietal cortex are known to disturb object exploration and recognition associated with tactile apraxia (Binkofski et al., 2001a). Further, patients with lesions in the dorsal por- tion of the supramarginal gyrus and secondary somatosen- sory cortex may be impaired in identifying objects by tactile * Corresponding author. Moorenstr. 5, 40225 Du ¨sseldorf, Germany. Fax: +49-211-8118485. E-mail address: stoeckco@uni-duesseldorf.de (M.C. Stoeckel). NeuroImage 19 (2003) 1103–1114 www.elsevier.com/locate/ynimg 1053-8119/03/$ – see front matter © 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S1053-8119(03)00182-4