Mismatch Negativity to Acoustic Differences Not Differentiated Behaviorally

Abstract

Mismatch negativity (MMN) reportedly reflects the neurophysiologic detection of acoustic differences, rather than the phonemic categorization of speech sounds. The purpose of the present study was to determine if it is elicited by speech contrasts that are acoustically different but are not differentiated by listeners in behavioral tasks. Experimental stimuli were drawn from a synthetically generated continuum that varied in place of articulation from /da/ to /ga/. Contrasts used to elicit MMN were (a) the continuum endpoints, (b) the two-step contrast that straddled each listener's categorical boundary, and (c) a within-category contrast that was not behaviorally differentiated by any of the listeners. MMN responses were elicited by all three experimental contrasts. It appears that MMN may be an index of the neurophysiology underlying the ability or inability to discriminate the acoustic parameters necessary for speech perception, rather than a neurophysiologic correlate of behavioral speech discrimination ability. However, limitations involving identification of MMN in the responses of individual listeners confounded this interpretation. Abbreviations: 1–9 contrast = contrast between stimulus continuum endpoints, 7–9 contrast = contrast between steps 7 and 9 on the stimulus continuum, Cz = vertex, F1-F5 = first through fifth formants, Fz = 30 percent of the distance between nasion and inion at the midline, listener MAX = the two-step stimulus contrast that was discriminated best by each listener, MMN = mismatch negativity

Auditory cortical responses to speech are shaped by statistical learning of short-term speech input regularities

“…The P3 is characteristically associated with stimulus evaluation, categorization or decision making. Evoked by speech, it aligns better with category differences than acoustic change (Dalebout & Stack, 1999; Dehaene-Lambertz, 1997; Horev et al, 2007; Maiste et al, 1995; Toscano et al, 2010). We calculated the mean ERPs for the P3 across parietal electrodes (P3, P4, Pz) and over a 300-800 ms window (Toscano et al 2010), separately for Canonical and Reverse contexts.…”

“…Prior studies have associated P3 amplitude with post-perceptual categorization processing whereby P3 amplitude is associated with category differences, rather than acoustic changes (Dalebout & Stack, 1999; Dehaene-Lambertz, 1997; Maiste et al, 1995; Toscano et al, 2010). In general, P3 responses in active speech categorization tasks appear to originate across a network of brain regions involving frontal cortical regions areas including the anterior and posterior portions of inferior frontal gyrus (Toscano et al, 2018).…”