Examples of cortical normal modes and coupled state variables for excitatory (\(\bf A,B\)) and inhibitory (\(\bf C,D\)) cell populations. Here, in both cases the normal modes are rapidly decaying underdamped oscillations. In this instance, only about one third of the 208 cortical normal modes have a peak magnitude significantly different from zero; the majority of the modes decay with very small magnitude towards zero. Note that the normal modes shown in (A) and (C) are fundamental modes which cannot be attributed to individual cortical columns. The coupling of the normal modes, however, enables the distinction between the waveforms of individual columns and, thus, between the different cortical fields and areas, respectively. The three blue waveforms with the large peak magnitudes are the waveforms of the coupled state variables of the three input columns, one for each of the three core fields. Subsequently, with increasing distance from the location of the thalamic input columns, the magnitudes of the waveforms decrease, and their peak latencies are shifted to larger values.