Similar Neural Correlates for Language and Sequential Learning: Evidence from Event-Related Brain Potentials

Abstract

We used event-related potentials (ERPs) to investigate the time course and distribution of brain activity while adults performed (a) a sequential learning task involving complex structured sequences, and (b) a language processing task. The same positive ERP deflection, the P600 effect, typically linked to difficult or ungrammatical syntactic processing, was found for structural incongruencies in both sequential learning as well as natural language, and with similar topographical distributions. Additionally, a left anterior negativity (LAN) was observed for language but not for sequential learning. These results are interpreted as an indication that the P600 provides an index of violations and the cost of integration of expectations for upcoming material when processing complex sequential structure. We conclude that the same neural mechanisms may be recruited for both syntactic processing of linguistic stimuli and sequential learning of structured sequence patterns more generally.

Keywords: Event-Related Potentials (ERP); Implicit Learning; LAN; Language Processing; P600; Prediction; Sequential Learning.

Figure 1

a) The artificial grammar used to generate the sequences used in the sequential learning task. The nodes denote stimulus categories and the arrows indicate valid transitions from the beginning node to the end node. b) An example sequence of nonword tokens with its associated visual scene shown here in grey scale (the list of stimulus categories in the square brackets below the nonword sequence is for illustrative purposes only and was not shown to the participants).

Figure 2

Schematic representation of the 128 electrode positions in the Geodesic Nets used to record EEG activity (front is up). The six electrode regions used in the analyses are indicated in grey and the six representative electrodes used in Figures 3 and 4 are indicated by their respective numbers. Adapted from Barber and Carreiras (2005).

Figure 3

Grand average ERPs elicited for target words for grammatical (solid black) and ungrammatical (dashed grey) continuations in the language (left) and sequential learning (right) tasks. The vertical lines mark the onset of the target word. Six electrodes are shown, representative of the left-anterior (25), right-anterior (124), left-central (37), right-central (105), left-posterior (60), and right-posterior (86) regions. Negative voltage is plotted up.

Figure 4

Difference waves (ungrammatical minus grammatical) for language (green) and sequential learning (black) are shown on the left for the six representative electrodes. The corresponding topographic maps for the difference waves are shown on the right, averaged within each of the three latency windows. The grey dots show the location of the 128 electrodes with the black dots indicating the six representative electrodes.