Strength of Word-Specific Neural Memory Traces Assessed Electrophysiologically

Abstract

Memory traces for words are frequently conceptualized neurobiologically as networks of neurons interconnected via reciprocal links developed through associative learning in the process of language acquisition. Neurophysiological reflection of activation of such memory traces has been reported using the mismatch negativity brain potential (MMN), which demonstrates an enhanced response to meaningful words over meaningless items. This enhancement is believed to be generated by the activation of strongly intraconnected long-term memory circuits for words that can be automatically triggered by spoken linguistic input and that are absent for unfamiliar phonological stimuli. This conceptual framework critically predicts different amounts of activation depending on the strength of the word's lexical representation in the brain. The frequent use of words should lead to more strongly connected representations, whereas less frequent items would be associated with more weakly linked circuits. A word with higher frequency of occurrence in the subject's language should therefore lead to a more pronounced lexical MMN response than its low-frequency counterpart. We tested this prediction by comparing the event-related potentials elicited by low- and high-frequency words in a passive oddball paradigm; physical stimulus contrasts were kept identical. We found that, consistent with our prediction, presenting the high-frequency stimulus led to a significantly more pronounced MMN response relative to the low-frequency one, a finding that is highly similar to previously reported MMN enhancement to words over meaningless pseudowords. Furthermore, activation elicited by the higher-frequency word peaked earlier relative to low-frequency one, suggesting more rapid access to frequently used lexical entries. These results lend further support to the above view on word memory traces as strongly connected assemblies of neurons. The speed and magnitude of their activation appears to be linked to the strength of internal connections in a memory circuit, which is in turn determined by the everyday use of language elements.

Neurophysiological evidence for whole form retrieval of complex derived words: a mismatch negativity study

“…It is therefore noteworthy that, consistent with previous results (Alexandrov et al, 2011; Shtyrov et al, 2011), a stronger MMN emerged for the more frequent item (“Sicherheit”). The frequency sensitivity of the MMN suggested by the present data provides a further indication that we measured a whole-form retrieval process and not a combinatorial one.…”

Automatic ultrarapid activation and inhibition of cortical motor systems in spoken word comprehension

“…The word stimuli were all frequent words of Russian well-known to all volunteers. Still, even if there were any lexical frequency-driven effects, they have been shown to influence the response amplitude in core language areas in similar paradigms (36,37), but are not known and not predicted to elicit somatotopic distinctions in the motor strip.…”

Linguistic category structure influences early auditory processing: Converging evidence from mismatch responses and cortical oscillations

“…In these studies, the MMN (amplitude and/or latency) is influenced by linguistic information beyond mere acoustic contrasts. Further research has revealed that the MMN is not only sensitive to the statistics of sound sequences (Alexandrov et al, 2011; Bonte et al, 2005), but also to the abstract linguistic structure of the speech sounds themselves (Cornell et al, 2011, 2013; Eulitz and Lahiri, 2004; Scharinger et al, 2012a; Scharinger et al, 2012b). In particular, Scharinger et al (2012b) set out to test the claim that the mid vowel [ε] is less specified than either [ɪ] or [æ] with regard to the vowel’s tongue height.…”