NEURON mod files from the paper: Cassarà AM, Hagberg GE, Bianciardi M, Migliore M, Maraviglia B. Realistic simulations of neuronal activity: A contribution to the debate on direct detection of neuronal currents by MRI. Neuroimage. 39:87-106 (2008). In this paper, we use a detailed calculation of the magnetic field produced by the neuronal currents propagating over a hippocampal CA1 pyramidal neuron placed inside a cubic MR voxel of length 1.2 mm to estimate the Magnetic Resonance signal. The simulation Neuron1.hoc reproduces traces similar to those in Fig.7 (top two panels) and in Fig.8a of the paper. Under unix systems: to compile the mod files use the command nrnivmodl and run the simulation hoc file with the command nrngui Neuron1.hoc Under Windows systems: to compile the mod files use the "mknrndll" command. A double click on the simulation file Neuron1.hoc will open the simulation window. Questions on how to use this model should be directed to antonio.cassara@roma1.infn.it