Figure 5. Young and old mean field model.

Neural field model of a one-dimensional coronal cut through the surface of the cortical representation of the index finger tip in primary somatosensory cortex. (a,c) Interaction arising from each neuron, x, of the modeled dimension (here skin surface) is described by short-range excitatory influences (green) with positive strength (w(x)) and - modulated via the inhibitory layer – broader range inhibition with negative strength w(x) (red). (b) The overlay of these two interaction kernels with Gaussian shape, realized by the excitatory and inhibitory layer, results in a Mexican-hat profile of interaction with sharp inhibition (see blue line for an approximation). (c) For the model of older adults the widths of the excitatory and inhibitory kernels were assumed to be broader, leading to a broader and more distributed form of interaction. (d) The different widths of the interaction kernels result in a different distribution of interaction in the model of older adults characterized by broader excitatory and inhibitory influences (see magenta line for approximation).