Early and Sustained Supramarginal Gyrus Contributions to Phonological Processing

Reading is a difficult task that, at a minimum, requires recognizing a visual stimulus and linking it with its corresponding sound and meaning. Neurologically, this involves an anatomically distributed set of brain regions cooperating to solve the problem. It has been hypothesized that the supramarginal gyrus (SMG) contributes preferentially to phonological aspects of word processing and thus plays an important role in visual word recognition. Here, we used chronometric transcranial magnetic stimulation (TMS) to investigate the functional specificity and timing of SMG involvement in reading visually presented words. Participants performed tasks designed to focus on either the phonological, semantic, or visual aspects of written words while double pulses of TMS (delivered 40 ms apart) were used to temporarily interfere with neural information processing in the left SMG at five different time windows. Stimulation at 80/120, 120/160, and 160/200 ms post-stimulus onset significantly slowed subjects’ reaction times in the phonological task. This inhibitory effect was specific to the phonological condition, with no effect of TMS in the semantic or visual tasks, consistent with claims that SMG contributes preferentially to phonological aspects of word processing. The fact that the effect began within 80–120 ms of the onset of the stimulus and continued for approximately 100 ms, indicates that phonological processing initiates early and is sustained over time. These findings are consistent with accounts of visual word recognition that posit parallel activation of orthographic, phonological, and semantic information that interact over time to settle into a distributed, but stable, representation of a word

Retrieval-induced forgetting in educational contexts: Monitoring, expertise, text integration, and test format

Retrieval practice leads to the impaired recall of related but unpractised items, an effect termed retrieval-induced forgetting (RIF). Two experiments showed that RIF occurred with "real world" educational material, and isolated several boundary conditions for the phenomenon. Experiment 1 showed that integration of material available to experts but not to novices in a domain of knowledge, protected against RIF, which disappeared after a 24 hours. Experiment 2 examined the impact on RIF of the degree of coherence or integration of the text material itself and the type of test format administered. Text coherence did not influence RIF, which occurred for the short answer and essay tests, but not for the multiple choice test. In both experiments, those participants who demonstrated RIF were able to monitor accurately the likelihood of recall impairment, suggesting that RIF may not be an unconscious process. Results are discussed in relation to exam preparation strategies