MEG responses to rippled noise and Huggins pitch reveal similar cortical representations

The onset of pitch within an ongoing noise signal evokes a particular brain activity, the pitch onset response (POR). Using whole-head MEG, PORs to iterated rippled noise (IRN) and Huggins pitch (HP), representing prototypical pitch-in-noise signals, were measured in twenty subjects during a pitch identification task (333 Hz, 400 Hz, randomized). HP and IRN yielded similar responses, lateralized to the left hemisphere and peaking about 180 ms after pitch onset. The initial phase (140 ms) showed stronger activations to 400 than to 333 Hz whereas later stages (200-300 ms) showed target vs nontarget effects. These results suggest, first, that different pitches converge into a common cortical representation and, second, that the POR encompasses various successive processing stages.