CiteULike: briordan meg

The effects of priming on frontal-temporal communication

Avniel Ghuman — 2008-06-17T17:52:59-00:00

Proceedings of the National Academy of Sciences, Vol. 105, No. 24. (17 June 2008), pp. 8405-8409.

Repeated exposure to a stimulus facilitates its processing. This is reflected in faster and more accurate identification, reduced perceptual identification thresholds, and more efficient classifications for repeated compared with novel items. Here, we test a hypothesis that this experience-based behavioral facilitation is a result of enhanced communication between distinct cortical regions, which reduces local processing demands. A magnetoencephalographic investigation revealed that repeated object classification led to decreased neural responses in the prefrontal cortex and temporal cortex. Critically, this decrease in absolute activity was accompanied by greater neural synchrony (a measure of functional connectivity) between these regions with repetition. Additionally, the onset of the enhanced interregional synchrony predicted the degree of behavioral facilitation. These findings suggest that object repetition results in enhanced interactions between brain regions, which facilitates performance and reduces processing demands on the regions involved. 10.1073/pnas.0710674105

Lexical access and selection of contextually appropriate meaning for ambiguous words

Aya Ihara — 2007-12-17T01:49:40-00:00

NeuroImage, Vol. 38, No. 3. (15 November 2007), pp. 576-588.

To clarify the neural mechanisms of lexical access and selection of contextually appropriate meanings for ambiguous words, we investigated the spatio-temporal characteristics of neural activities during silent reading and semantic judgment of lexically ambiguous or unambiguous target words that were preceded by semantically related or unrelated words by using magnetoencephalography. The left posterior superior temporal/inferior parietal area and the left anterior middle/inferior temporal area consistently showed a clear context effect, regardless of the ambiguity: the activities for related words were weaker than those for unrelated words. The activities in the left inferior frontal cortex, in contrast, were influenced by ambiguities. From ~ 200 to 300 ms, the activities in the left anterior inferior frontal cortex (aIFC) were stronger for ambiguous words than for unambiguous words, regardless of context. The stronger activities in the left aIFC, reflecting an increase in controlled semantic retrieval, indicate that multiple meanings for lexically ambiguous words are accessed irrespective of context. At ~ 400 ms, the left posterior inferior frontal cortex (pIFC) showed a clear context effect for unambiguous words but not for ambiguous ones. In addition, the activation in the left pIFC was stronger for related ambiguous words than for related unambiguous ones. These results suggest that in ambiguous words, not only contextually appropriate meanings but also two or more inappropriate meanings would be semantically integrated with a context. We conclude that the left IFC plays an important role in selecting an appropriate meaning from multiple alternatives after the integration of contextual information.

Compound words and structure in the lexicon

Robert Fiorentino — 2007-10-17T02:09:00-00:00

Language and Cognitive Processes, Vol. 22, No. 7. (2007), pp. 1-48.

The structure of lexical entries and the status of lexical decomposition remain controversial. In the psycholinguistic literature, one aspect of this debate concerns the psychological reality of the morphological complexity difference between compound words (<i>teacup</i>) and single words (<i>crescent</i>). The present study investigates morphological decomposition in compound words using visual lexical decision with simultaneous magnetoencephalography (MEG), comparing compounds, single words, and pseudomorphemic foils. The results support an account of lexical processing which includes early decomposition of morphologically complex words into constituents. The behavioural differences suggest internally structured representations for compound words, and the early effects of constituents in the electrophysiological signal support the hypothesis of early morphological parsing. These findings add to a growing literature suggesting that the lexicon includes structured representations, consistent with previous findings supporting early morphological parsing using other tasks. The results do not favour two putative constraints, word length and lexicalisation, on early morphological-structure based computation.