Development of Spatiotemporal Population Receptive Field Models (pRF) for the Somatosensory Cortex: an fMRI study

Abstract

Understanding the topographic organization of the somatosensory cortex is essential in broadening our knowledge on tactile processing. The current study extends the population Receptive Field (pRF) approach first used in visual field mapping studies to create detailed topographic maps of the somatosensory cortex. Specifically, we investigated the receptive fields on the skin of neuronal populations in Brodmann areas 3b, 1 and 2 of the primary somatosensory cortex (S1) to produce such maps. We therefore developed a model that predicted neuronal responses to vibrotactile stimulation of the fingertips. The model was fit on data obtained by functional magnetic resonance imaging (fMRI). We report pRF estimates in the location of the cortical hand area of S1 along the postcentral gyrus corresponding to locations on the skin to which a neuronal population responds. A somatotopic organization of the finger digits was found in BA 3b and 1, but not in B2. We also found that pRFs were larger in BA 2 in comparison to BA 3b and 1. Additionally, we investigated whether a frequency dependency on neuronal responses existed in S1 by running three experiments which differed in frequency. No effect of frequency on neural responses could be found. Nevertheless, our results show that using pRF models can result in detailed maps of the somatosensory cortex including underlying characteristics