Brain Processes of Relating a Statement to a Previously Read Text: Memory Resonance and Situational Constructions

Brain Processes of Relating a Statement to a Previously Read Text: Memory Resonance and Situational Constructions Franz Schmalhofer, Uwe Friese, Karin Pietruska, Markus Raabe, (FirstName.LastName@uos.de) Institute of Cognitive Science, University of Osnabrueck, Kolpingstr. 7 49069 Osnabrueck, Germany Roland Rutschmann (Roland.Rutschmann@psychologie.uni-regensburg.de) Institute of Experimental Psychology, University of Regensburg, Universitaetsstr. 31 93053 Regensburg, Germany Abstract One of the most fundamental characteristics of texts consists in the coherence among its sentences. We investigated by fMRI where in the brain such coherence relations are established and the relative duration of these processes by a behavioral experiment. In four experimental conditions, the coherence between a sentence and a subsequent test statement ranged from an explicit and a paraphrastic to an implicit and the lack of a precise relation (control condition). The participants had to decide whether the test statement was true with respect to the previously read sentence. For this decision the blood oxygen level dependent (BOLD) response differentially indicated five brain regions (posterior cingulate, STG, left and right IFG, frontal medial gyrus). These results could consistently be interpreted to distinguish two interacting but separate brain processes involved in coherence formation. One of these processes may be termed memory resonance and the other one situational constructions. Introduction A defining characteristic of a text is that its sentences are not unrelated to one another but cohere. To understand a text, a reader must therefore cognitively establish the specific relations between a new statement and a previously read text. The coherence between sentences may be established in different ways: For example, by anaphora resolution (Glenberg, Meyer, and Lindem, 1987), by identifying overlaps in the arguments of different propositions (Kintsch & van Dijk, 1978), by memory processes which resonate for words with closely related meanings (O’Brien, Rizzella, Albrecht & Halleran, 1998) or by more effortful inference processes which are driven by a search for meaning (Graesser, Singer & Trabasso, 1994). O’Brien et al. (1998) postulate the resonance process in memory to be both, autonomous and dumb and to be based on the strengths of preexisting associations in semantic memory. Thus, memory resonance is considered to be a basic bottom-up activation process which may interact with more goal-directed processes of forming a mental model for the here and now description of a situation. Memory resonance is assumed to be passive and in some aspects similar to the bottom-up saliency-based processes of attention (Itti & Koch, 2001). While bottom-up attention processes assist an organism in analyzing a present scene, memory resonance processes assist in a similar manner in analyzing a reader’s past experiences (verbal and non- verbal) as they have become represented in memory. In addition to this passive reactivation mechanism, there may also be a task-dependent and more strategic process which is driven by the reader’s goal of constructing a model of the situation that is described by the text (cf. Graesser et al. 1994). Whereas the postulated memory process would involuntarily reactivate memory contents, the task- dependent process would be more under the control of the reader’s intentions (cf. Calvo et al., in press). Experiments employing brain imaging techniques such as functional magnetic resonance imaging (fMRI) and event- related potentials (ERP) can provide more detailed insights on how text coherence is established (Ferst & von Cramon, 2001; Hagoort et al., 2004). In quite general terms, one would expect that a passive memory resonance process would occur earlier after the presentation of the critical words and more likely in posterior areas of the brain. The more effortful, task dependent processes of situation constructions, on the other hand, should be more likely to involve frontal areas of the brain, and possibly occur later in relation to the onset of the critical words. In agreement with this expectation, Ferstl & von Cramon (2001) have already found that prefrontal midline areas and the left posterior cingulate gyrus (BA 31) together with neighboring inferior precuneal areas (BA 23) are involved for establishing coherence by inferencing. Hagoort et al. (2004) found that the left inferior prefrontal cortex is involved in the integration of newly presented words with both, meaning and world knowledge and that such processes occur in the vicinity of 400 ms after the onset of the critical word. In the current study we investigated the brain processes of relating a statement to a previously read text by more fine- grained experimental contrasts. We employed experimental materials that have been widely used in many behavioral studies as well as for theoretical analyses (cf. Schmalhofer, McDaniel and Keefe, 2002). A small time window of 1.8 seconds was used, where a statement consisting of two or three words had to be related to the previously read sentences by determining whether or not the statement would be true with respect to the described