"Too Many betas do not Spoil the Broth": The Role of Beta Brain Oscillations in Language Processing

Abstract

Over the past 20 years, brain oscillations have proven to be a gateway to the understanding of cognitive processes. It has been shown that different neurocognitive aspects of language processing are associated with brain oscillations at various frequencies. Frequencies in the beta range (13-30 Hz) turned out to be particularly important with respect to cognitive and linguistic manipulations during language processing. Beta activity has been involved in higher-order linguistic functions such as the discrimination of word categories and the retrieval of action semantics as well as semantic memory, and syntactic binding processes, which support meaning construction during sentence processing. From a neurophysiological point of view, the important role of the beta frequencies for such a complex cognitive task as language processing seems reasonable. Experimental evidence suggests that frequencies in the beta range are ideal for maintaining and preserving the activity of neuronal assemblies over time. In particular, recent computational and experimental evidence suggest that beta frequencies are important for linking past and present input and the detection of novelty of stimuli, which are essential processes for language perception as well as production. In addition, the beta frequency's role in the formation of cell assemblies underlying short-term memory seems indispensable for language analysis. Probably the most important point is the well-known relation of beta oscillations with motor processes. It can be speculated that beta activities reflect the close relationship between language comprehension and motor functions, which is one of the core claims of current theories on embodied cognition. In this article, the importance of beta oscillations for language processing is reviewed based both on findings in psychophysiological and neurophysiological literature.

Keywords: beta; brain oscillations; coherence; frequency; language; power.

Figure 1

Coherence differences for the processing of action and non-action verbs compared to a resting baseline condition. Lines between electrodes mapped on the unfolded schemes of both hemispheres denote significant coherence increases. For the evaluation of significant coherence differences paired Wilcoxon-tests were applied. The rank sums obtained were converted to error probabilities, which were presented in probability maps. Mean coherence at central electrodes (indicated by the shaded square) is significantly higher for action compared to non-action verbs (based on data from Weiss et al., 2001).

Figure 2

Beta1 (13–18 Hz) amplitude (square root of power) differences for incongruent and congruent nouns compared to a pre-sentence baseline. Post hoc paired t-tests at each electrode revealed significant differences based on the data of 29 participants (Weiss et al., submitted).

Figure 3

Significant coherence differences between figurative and literal sentences for the interval before the figurative meaning can be encountered (1), the interval while the figurative meaning was encountered (2) and the interval after the sentence (3). Coherence differences were mapped as lines (Berghoff et al., , modified). Further information, see Figure 1.

Figure 4

(A) Left panel: mean amplitude (square root of power) during memory encoding of later recalled and not recalled nouns (t-test, 2p ≤ 0.000). Right panel: coherence for recalled and not recalled nouns. (B) Left panel: mean amplitude (square root of power) during memory encoding of recalled nouns positioned at the beginning (primacy) and at the end of the word list (recency). Note that each person got a different pseudo-randomized word list. Right panel: mean coherence for “primacy” and “recency” items. Note the different scales. (Data were taken from Weiss and Rappelsberger, 2000).

Figure 5

Functional involvement of beta oscillations in language processing (upper part) and windows for measurement and interpretation (lower part).