Discriminating the Cortical Representation Sites of Tongue and Lip Movement by Functional MRI Volker Hesselmann*, Bettina Sorger*, Kathrin Lasek*, Orlando Guntinas-Lichius + , Barbara Krug*, Volker Sturm^, Rainer Goebel ~ , and Klaus Lackner* Summary: Purpose: The purpose of this study was to investigate the possibility to discriminate the representation sites of lip and tongue movement in the primary motor cortex (PMC). In contrast to preceding studies this research was particularly focused on single subject analysis. Procedures: Six healthy right-handed volunteers underwent functional magnetic resonance imaging (fMRI) by means of a 1.5 tesla scanner. Using a block design the subjects had to perform two different motor tasks: horizontal tongue movement and symmetrical lip pursing. To ensure that only the functional selec- tive cortical representations for each particular motor task were determined, the approach of contrasting both motor paradigms was followed during data analysis. Principle results: Selective cortex activations for both motor tasks were detectable in the motor strips and could be spatially discrimi- nated for the whole group and for the majority of the single subjects in both hemispheres. Furthermore, expanded regions responsive to both motor tasks were found bilaterally. Conclusions: The individually proven possibility to differentiate the cortical representation sites of tongue and lip move- ments opens the chance to monitor therapeutic cortical effects after neuro-reconstructive surgery, e. g. hypoglossal-facial nerve anastomosis (HFA). Key words: Functional magnetic resonance imaging; Cortical representation; Lip movement; Tongue movement; Facial nerve; Hypoglossal nerve. Introduction Functional magnetic resonance imaging (fMRI) is a well established means for investigating cerebral activity in neuroscience and in clinical practice (Cohen et al. 1996). In humans the identification of the hand motor region in the central sulcus can be easily identified by simple hand motor tasks (Rao et al. 1995; Bandettini et al. 1992; Kwong et al. 1992). The somatotopic discrimination of different fingers within the primary motor cortex (PMC) is possible as well (Beisteiner et al. 2001), whereby an extending overlap of activations for neighboring digits was found (Schieber et al. 1999). Detection of tongue or lip move- ment-related activation in the PMC is more demanding, as task-concomitant head motion may cause motion arti- facts (Marquart et al. 2000; Hajnal et al. 1994). Moreover, the movement of tongue and lips themselves can gener- ate artifacts due to changes of the shim of the magnetic field, so that the signal amplitude of the activation can be diminished (Yetkin et al. 1996). Because of these possible stimulus-related artifacts the identification of tongue and lip activity has been less reliable (Marquart et al. 2000). However, recent studies were successful in showing that fMRI is feasible to detect tongue movement-related acti- vation in the motor strips using a block-trial method (Lotze et al. 2000; Wildgruber et al. 1996) as well as using a single event-related paradigm (Marquart et al. 2000; Cor- field et al. 1999). In comparison to the investigations of tongue movement-related activation sites there are only few studies dealing with the cortical representation of the motor component of the facial nerve (VII) (Gosain et al. 2001; Lotze et al. 2000). Lotze and colleagues (2000) inves- tigated the representation of articulation and found acti- vation in the PMC for lip and tongue movements. In contrast to other studies confining to group analysis (Gosain et al. 2001; Lotze et al. 2000) the purpose of this study was to investigate whether a discrimination of the cortical representations of lip and tongue movements is possible within single subjects (Wildgruber et al. 1996). As a practical use, these findings could offer the possibil- ity to track functional changes in cortical plasticity after stroke, injury or neuro-reconstructive surgery in further * Department of Radiology, University of Cologne, Cologne, Ger- many. + Department of Otolaryngology, University of Cologne, Cologne, Germany. ^ Department of Stereotaxy and Functional Neurosurgery, Uni- versity of Cologne, Cologne, Germany. ~ Faculty of Psychology, University of Maastricht, The Nether- lands. Accepted for publication: December 10, 2003. Correspondence and reprint requests should be addressed to Volker Hesselmann, MD, Department of Radiology, University of Co- logne, Joseph-Stelzmann-Strasse 9, 50924 Cologne, Germany. Fax:+49/221/478/2317 E-mail: Volker.Hesselmann@uni-koeln.de Copyright 2004 Human Sciences Press, Inc. Brain Topography, Volume 16, Number 3, Spring 2004 (© 2004) 159