Neural pathways in tactile object recognition

Objective: To define further the brain regions involved in tactile object r ecognition using functional MRI (fMRI) techniques. Background: The neural s ubstrates involved in tactile object recognition (TOR) have not been elucid ated. Studies of nonhuman primates and humans suggest that basic motor and somatosensory mechanisms are involved at a peripheral level; however, the m echanisms of higher order object recognition have not been determined. Meth ods: The authors investigated 11 normal volunteers utilizing fMRI technique s in an attempt to determine the neural pathways involved in TOR. Each indi vidual performed a behavioral paradigm with the activated condition involvi ng identification of objects by touch, with identification of rough/smooth as the control. Results: Data suggest that in a majority of individuals, TO R involves the calcarine and extrastriatal cortex, inferior parietal lobule , inferior frontal gyrus, and superior frontal gyrus-polar region. Conclusi ons: TOR may utilize visual systems to access an internal object representa tion, The parietal cortices and inferior frontal regions may be involved in a concomitant lexical strategy of naming the object being examined. Fronta l polar activation likely serves a role in visuospatial working memory or i n recognizing unusual representations of objects. Overall, these findings s uggest that TOR could involve a network of cortical regions subserving soma tosensory, motor, visual, and, at times,lexical processing. The primary fin ding suggests that in this normal study population, the visual cortices may be involved in the topographic spatial processing of TOR.