Notetaking here so I don’t forget to follow trails: N1 is definitely the zone I’m looking at and not MMN,
Auditory feature encoding and sound representation
ERPs generated in auditory cortex during the latency range 20-120 ms reflect the encoding of a variety of acous- tic features. The neural generators of the early 20-50 ms positivity and the Nl component (80-120ms) both show a tonotopic organization in supratemporal auditory cortex [65,66], and Nl shows additional sensitivity to virtual or perceived pitch derived from harmonics in complex tones or vowel sounds [67*,68,69*,70]. Nl also reflects the binaural fusion of harmonics (67.1, the spatial locus of sound origin [71*], and the integration of signal energy over time [72*]. ERPs in the Nl latency range, however, do not reflect the detailed encoding of stimulus features or of complex sound patterns [73*].
A more elaborate and precise encoding of auditory inputs is reflected in a later negative component in the 140~200ms range that is specifically triggered by any discriminable change in ongoing sound stimulation. This ‘mismatch negativity’ (MMN) can be elicited by sounds that deviate from an ongoing sequence in frequency, intensity, duration, rise time, spatial location or timing [73*]. …
REFERENCES REFERENCED FOR FOLLOWUP:
65. Pantev C, Bertrand 0, Eulitz C, Verkindt C, Hampson S, Schuirer G, Elberf T: Specific tonotopic organizations of different areas of the human auditory cortex revealed by simultaneous magnetic and electric recordings. flectroencephalogr C/in Neurophysiol 1995, 94:26-40.
66. Eulitz C, Diesch E, Pantev C, Hampson S, Elberf T: Magnetic and electric brain activity evoked by the processing of tone and vowel stimuli. J Neurosci 1995, 15:2748-2755.
67. Pantev C, Elberl T, Ross 8, Eulitz C, Terhardt E: Binaural fusion . and the representation of virtual pitch in the human auditory cortex. /-/ear Res 1996, 100:164-l 70.
Neuromagnetic recordings indicated that the center of activation within the cortical tonotopic map corresponds to the location of perceived pitch and not to the locations that are activated when single-frequency constituents are presented.
68. Ragot R, LepauCErcole R: Brain potentials as objective indexes of auditory pitch extraction from harmonics. Neuroreport 1996, 7:905-909.
69. Diesch E, Lute T: Magnetic fields elicited by tones and vowel . formants reveal tonotopy and nonlinear summation of cortical activation. Psychophysiology 1997, 34:501-510.
Neuromagnetic responses elicited by two composite stimuli (a two-tone combination and a two-format vowel) and by their individually presented constituents were recorded. The evoked response to the composite stimuli differed from the linear sum of the constituents in latency, dipole moment, and location, with the sources for the formant being situated more laterally than those for the tones.
70. Winkler I, Tervaniemi M, N%itPnen R: Two separate codes for missing-fundamental pitch in the human auditory cortex. J Acoust Sot Am 1997, 102:1072-l 082.
This study demonstrated a temporal advantage in the pre-attentive process- ing of location information relative to frequency information. The MMN re- sponses to changes in location were shorter in latency than those elicited by changes in frequency, suggesting that spatial information is encoded faster than spectral information.
71. SchrBger E, Wolff C: Fast preattentive processing of location: a . functional basis for selective listening in humans. Neurosci Lett 1997, 232:5-E.
72. Alain C, Woods DL, Covarrubias D: Activation of duration- . sensitive auditory cortical fields in humans. Electroencephalogr C/in Neurophysiol 1997, 104:531-539.
This study showed varying temporal integration functions for different Nl subcomponents, which varied as a function of tone frequency. The results suggest that different auditory cortical areas may have different temporal integration times.
73. N%itPnen R, Alho K: Mismatch negativity-the measure for . central sound representation accuracy. Audio/ Neuro-Otol 1997, 2:341-352.
A comprehensive review of recent findings of MMN studies with emphasis on accuracy of representation of feature-specific and discriminative information in audition.
Temporal dynamics of early perceptual processing Steven A Hillyard*t, Wolfgang A Teder-%lejkvi* and Thomas F Mijntet