First off, the (unrolled) length of our cochlea maps out frequencies such that high frequency sounds cause excitation (neural signals) from the front part of the cochlea, and low frequencies result in neural signals from the end part of the cochlea. Thus we can associate the neurons at each position along the cochlea with a specific frequency.
The aspect is that I'm unsure of is whether a sinusoidal wave will cause the neural signals from the regions that correspond to the harmonics of the wave's frequency. I.e. when a person listens to a 440Hz sine wave, the neurons corresponding 880,1320,1760... are activated. I seem to recall this idea from somewhere, and this claim is made in this video, but it is unsubstantiated.
Basically, I'd like to know how (and by whom) this phenomenon has been studied, in order to better understand the physiological basis for the sensations of harmony.