Interactions of the hippocampal system and the prefrontal cortex in learning language-like rules

Abstract

One of the most influential views on the hippocampal function suggests that this brain region is critically involved in relational memory processing, that is, binding converging inputs to mediate the representation of relationships among the constituents of episodes. It has been proposed that this binding is automatic and obligatory during learning and remembering In addition, neuroimaging studies have highlighted the importance of the prefrontal cortex, in learning, memory, and language processing. However, the posited importance of hippocampalprefrontal interaction remains to be empirically tested. In the present study we used functional magnetic resonance imaging to examine in detail this interaction by assessing learning-related changes in hemodynamic activity during artificial language acquisition. It has been shown previously that artificial grammar systems might be learned by evaluating pattern-based relations in word sequences and generalizing beyond specific word order, that is, rule abstraction. During scanning, participants learned an artificial language whose miniature grammar meets the universal principles of a natural language. Increased proficiency level of the artificial language is associated with decreased left hippocampal activity. In contrast, we observed an increased recruitment of the left inferior frontal gyrus (Broca's area), a region that contributes to syntax processing in natural language. The present results, therefore, indicate a learning-related change in brain circuitry underlying relational processes of language learning, with a transition from a similarity-based learning system in the medial temporal lobes to a language-related processing system in the left prefrontal cortex.

Rule and similarity in grammar: Their interplay and individual differences in the brain

“…High similarity estimates were related to a greater sensitivity to ungrammatical items. This finding is in a good agreement with previous studies reporting a decreasing activity in the left posterior hippocampus with longer exposure to BROCANTO (Opitz and Friederici, 2003). This decrease in activity was argued to represent decrease in importance of relational processing (Opitz & Friederici, 2004;.…”

“…The artificial language BROCANTO (Opitz & Friederici, 2003) was used to generate the stimulus material. In this artificial grammar system with a total vocabulary of 14 words (e.g., "trul" or "rix") from five word categories: nouns (N), verbs (v), determiners (D, d), adjectives (M) and adverbs (m).…”

“…aaf gum *aaf trul pel rüfi). The reader is referred to previous studies (Opitz & Friederici, 2003;2004) employing this artificial language for further examples and a schematic presentation of the underlying grammar system.…”

Separate influences in learning: Evidence from artificial grammar learning with traumatic brain injury patients

“…Note that Friederici and colleagues have explored artificial grammars in a series of experiments, with a view to understand language processing (e.g., Friederici et al, 2006;Opitz & Friederici, 2003. For example, Opitz and Friederici (2003) reported that improved performance in an artificial language led to increased activation of the left inferior frontal gyrus (Broca's area) and decreased activation in the left hippocampal area.…”

“…For example, Opitz and Friederici (2003) reported that improved performance in an artificial language led to increased activation of the left inferior frontal gyrus (Broca's area) and decreased activation in the left hippocampal area. Some caution is needed before extrapolating such conclusions to AGL.…”