Cognitive Neuroscience NeuroReport 0959-4965 # Lippincott Williams & Wilkins The representation of pleasant touch in the brain and its relationship with taste and olfactory areas S. Francis, E. T. Rolls, 1,CA R. Bowtell, F. McGlone, 2 J. O'Doherty, 1 A. Browning, 1 2 S. Clare and E. Smith 2 Magnetic Resonance Centre, University of Nottingham, Nottingham NG7 2RD; 1 Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD; 2 Unilever Research, Port Sunlight Laboratory, Wirral L63 3JW, UK CA Corresponding Author ALTHOUGH there has been much investigation of brain pathways involved in pain, little is known about the brain mechanisms involved in processing somatosensory stimuli which feel pleasant. Employing fMRI it was shown that pleasant touch to the hand with velvet produced stronger activation of the orbitofrontal cortex than affectively neutral touch of the hand with wood. In contrast, the affectively neutral but more intense touch produced more activation of the primary soma- tosensory cortex than the pleasant stimulus. This indicates that part of the orbitofrontal cortex is con- cerned with representing the positively affective aspects of somatosensory stimuli, and in further experiments it was shown that this orbitofrontal area is different from that activated by taste and smell. The ®nding that three different primary or unlearned types of reinforcer (touch, taste, and smell) are represented in the orbito- frontal cortex helps to provide a ®rm foundation for understanding the neural basis of emotions, which can be understood in terms of states elicited by stimuli which are rewarding or punishing. NeuroReport 10:453± 459 # 1999 Lippincott Williams & Wilkins. Key words: Cingulate cortex; Emotion; Orbitofrontal cor- tex; Pleasure; Smell; Somatosensory cortex; Taste; Touch Introduction The aim of this study was to investigate in humans whether brain regions activated by the affective aspects of touch could be found. It is known that after the primary somatosensory cortical area (SI), the somatosensory pathways continue to the insula and orbitofrontal cortex, and via both these struc- tures to the amygdala [1±4]. It is not known where in this pathway positively affective, that is pleasant, aspects of touch are represented. In the taste system of primates, it is known that there is segregation of function, with the primary taste cortex representing the identity and intensity of the taste, whilst the secondary taste cortex, in the orbitofrontal region, represents the reward-related or affective aspect of taste (in that neurons in it only respond to the taste of food when hunger is present) [5±8]. If there is such a segregation in the touch system, it is likely to be found in the outputs of the ventral somato- sensory pathway to the orbitofrontal cortex and amygdala, for the ventral visual pathway provides a representation of objects in the inferior temporal visual cortex, and reward associations of visual stimuli are presented in the orbitofrontal cortex and amygdala [6]. A representation of the positively affective components of touch is more likely in the output of this ventral touch system than the somatosensory projections to the parietal cortex, for this dorsal somatosensory system is more likely to be involved in spatial aspects of somatosensory representation, such as the position of the limbs [9]. The design of the experiment was to compare the activations of different brain regions to a pleasant but soft touch to the hand (using velvet) with an affectively neutral hard tough to the hand produced by the end of a wood dowel. The rationale of this choice of stimulus was that the more intense but neutral stimulus would relatively strongly activate parts of the somatosensory system concerned with the intensity and identi®cation of a somatosensory stimulus, whereas the soft pleasant tactile stimulus would relatively strongly activate parts of the brain concerned with representing the pleasantness of the touch. The level of activation in different brain areas was measured using functional magnetic resonance imaging (fMRI) [10,11]. In order to assess whether any activation related to the affectively pleasant aspects of the tactile stimuli were modality-speci®c or were related to a general change in affect, brain activation was also measured to positively affective stimuli in two other sensory modalities, taste and smell. The taste stimu- NeuroReport 10, 453±459 (1999) Vol 10 No 3 25 February 1999 453