Recent data  suggest that different regions in the brain may exhibit distinct rhythms when perturbed by Transcranial Magnetic Stimulation (TMS). Knowledge of these rhythms may be of value to understand how the brain realizes its functions and to assess brain connectivity. In this work we implemented a neural mass model  of three interconnected cortical regions (Brodmann Area (BA) 19 (occipital lobe), BA 7 (parietal lobe) and BA 6 (frontal lobe)) to fit the impulse responses in three ROIs during an experiment of TMS stimulation on a single subject. First, the natural rhythm of each region was mimicked acting on the local parameters, which reproduce the number of synaptic contacts among neural populations. Then, rhythm propagation from one region to another was simulated (at three different intensities of TMS stimulation) acting on infra-region connectivity parameters. Results show that the model can reproduce the natural rhythms of the three regions, and most rhythm changes induced by stimulation of another region, by using quite a simple connectivity pattern. This pattern is scarcely affected by the stimulus intensity.