Masked immediate-repetition-priming effect on the early lexical process in the bilateral anterior temporal areas assessed by neuromagnetic responses (original) (raw)
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Neuropsychologia, 2007
In this study the neural substrates of semantic and phonological task priming and task performance were investigated using single word task-primes. Magnetoencephalography (MEG) data were analysed using Synthetic Aperture Magnetometry (SAM) to determine the spatiotemporal and spectral characteristics of cortical responses. Comparisons were made between the task-prime conditions for evidence of differential effects as a function of the nature of the task being primed, and between the task-prime and the task performance responses for evidence of parallels in activation associated with preparation for and completion of a specific task.
Cerebral mechanisms of word masking and unconscious repetition priming
Nature Neuroscience, 2001
nature neuroscience • volume 4 no 7 • july 2001 articles A visual word that is flashed for only a few tens of milliseconds remains readable. However, when the same word is presented in close spatial and temporal proximity with other visual stimuli, it becomes indistinct or even invisible, a perceptual phenomenon called masking. Behavioral evidence indicates that the visual, orthographic and phonological properties of masked words, and even their meaning, can be extracted under masking conditions that do not elicit consciousness of those processing steps 1-6 . This suggests that masked words can unconsciously activate part of the cerebral networks for word processing. However, this hypothetical activation has not been measured directly, not is it understood why it fails to elicit consciousness. Here we demonstrate that unseen masked words activate extrastriate, fusiform and precentral regions, and cause a significant reduction in response time and in brain activity to subsequent conscious words, yet fail to elicit the correlated and distributed pattern of activation observed when the same words are consciously perceived.
Brain Activation during Masked and Unmasked Semantic Priming: Commonalities and Differences
Journal of Cognitive Neuroscience, 2013
Using functional magnetic resonance imaging (fMRI) during a lexical decision task (LDT), we investigated the neural correlates of semantic priming under masked and unmasked prime presentation conditions in a repeated measurement design of the same group of 24 participants (14 female). The task was to discriminate between pseudowords and words. Masked and unmasked prime words differed in their degree of semantic relatedness with target stimuli. Neural correlates of priming were defined as significantly different neural activations upon semantically unrelated minus related trials. Left fusiform gyrus, left posterior inferior frontal gyrus and bilateral pre-supplementary motor area showed priming effects independent of the masking condition. By contrast, bilateral superior temporal gyri, superior parietal lobules and the supplementary motor area proper demonstrated greater neural priming in the unmasked compared to the masked condition. The inverted contrast (masked priming minus unmasked priming) did not show significant differences even at lowered thresholds of significance. The conjoint effects of priming in the left fusiform gyrus suggest its involvement as a direct consequence of the neural organization of semantic memory. Activity in brain regions showing significantly more neural priming in the unmasked condition possibly reflected participants' evaluation of the prime-target relationship, presumably in the context of semantic matching. The present results therefore indicate that masked and unmasked semantic priming partially depend on dissociable mechanisms at the neural and most likely also at the functional level.
Stimulus-driven changes in the direction of neural priming during visual word recognition
NeuroImage, 2015
Visual object recognition is generally known to be facilitated when targets are preceded by the same or relevant stimuli. For written words, however, the beneficial effect of priming can be reversed when primes and targets share initial syllables (e.g., "boca" and "bono"). Using fMRI, the present study explored neuroanatomical correlates of this negative syllabic priming. In each trial, participants made semantic judgment about a centrally presented target, which was preceded by a masked prime flashed either to the left or right visual field. We observed that the inhibitory priming during reading was associated with a left-lateralized effect of repetition enhancement in the inferior frontal gyrus (IFG), rather than repetition suppression in the ventral visual region previously associated with facilitatory behavioral priming. We further performed a second fMRI experiment using a classical whole-word repetition priming paradigm with the same hemifield procedure and...
Implicit phonological priming during visual word recognition
NeuroImage, 2011
Phonology is a lower-level structural aspect of language involving the sounds of a language and their organization in that language. Numerous behavioral studies utilizing priming, which refers to an increased sensitivity to a stimulus following prior experience with that or a related stimulus, have provided evidence for the role of phonology in visual word recognition. However, most language studies utilizing priming in conjunction with functional magnetic resonance imaging (fMRI) have focused on lexical-semantic aspects of language processing. The aim of the present study was to investigate the neurobiological substrates of the automatic, implicit stages of phonological processing. While undergoing fMRI, eighteen individuals performed a lexical decision task (LDT) on prime-target pairs including word-word homophone and pseudowordword pseudohomophone pairs with a prime presentation below perceptual threshold. Whole-brain analyses revealed several cortical regions exhibiting hemodynamic response suppression due to phonological priming including bilateral superior temporal gyri (STG), middle temporal gyri (MTG), and angular gyri (AG) with additional region of interest (ROI) analyses revealing response suppression in left lateralized supramarginal gyrus (SMG). Homophone and pseudohomophone priming also resulted in different patterns of hemodynamic responses relative to one another. These results suggest that phonological processing plays a key role in visual word recognition. Furthermore, enhanced hemodynamic responses for unrelated stimuli relative to primed stimuli were observed in midline cortical regions corresponding to the default-mode network (DMN) suggesting that DMN activity can be modulated by task requirements within the context of an implicit task.
ERP Evidence for an Interaction between Phonological and Semantic Processes in Masked Priming Tasks
Two masked priming experiments investigated the time- course of phonological and semantic processes implicated in visual word recognition as well as their possible interaction, using event-related brain potentials (ERPs). Participants read target words which were phonologically related, semantically related, both phonologically and semantically related or unrelated to a masked prime word. In experiment 1, participants performed a phonological task (decide whether targets rhymed with a previously heard rhyme). The phonological relation elicited a frontal negativity whereas the semantic relation elicited a left anterior negativity, both followed by an N400 at centro-parietal sites. In experiment 2, participants performed a semantic task (decide whether targets belonged to a previously presented semantic category). In contrast to experiment 1, phonological and semantic relations elicited an N400 over frontal sites. Together, these results demonstrate that phonological and semantic proc...
Neuroreport, 2002
Evidence from multiple paradigms has converged on the ¢nding that stimulus repetition most often results in decreases in neural activity.The mechanisms of these decreases, however, are not yet well understood. The current study attempted to determine, through the use of masked word repetition priming, whether decreases in activity levels occur in response to pre-or post-prime identi¢cation processes. fMRI was performed while participants engaged in a lexical decision task where words were primed with a brie£y presented and masked word. Masked word priming resulted in increased fMRI signal in regions of cortex associated with the perceptual identi¢cation of the target words. This ¢nding provides evidence suggesting that the impact of repetition priming on the fMRI signal may depend upon whether or not the prime is identi¢ed. NeuroReport13:281^284
Semantic and phonemic priming in the cerebral hemispheres
Neuropsychologia, 1990
Representation of semantic and phonemic codes in the cerebral hemispheres was investigated in two priming experiments where prime and target words were independently projected to the left or right visual fields. The first experiment, using phonemic primes. confirmed the view that phonological information is not accessible to the right hemisphere. Priming effects were obtained only when the prime and target were both projected to the right visual field. The second experiment. employing category exemplars as primes, again found the left hemisphere to be the prinicipal locus of the priming effects. The right hemisphere was unable, by itself, to activate words related to the exemplar prime. However. projection of the prime to the right visual field significantly facilitated responses to left visual field targets. The present findings support the view advanced by Drews
Is the Masked Priming Same-Different Task a Pure Measure of Prelexical Processing?
PLoS One, 2013
To study prelexical processes involved in visual word recognition a task is needed that only operates at the level of abstract letter identities. The masked priming same-different task has been purported to do this, as the same pattern of priming is shown for words and nonwords. However, studies using this task have consistently found a processing advantage for words over nonwords, indicating a lexicality effect. We investigated the locus of this word advantage. Experiment 1 used conventional visually-presented reference stimuli to test previous accounts of the lexicality effect. Results rule out the use of different strategies, or strength of representations, for words and nonwords. No interaction was shown between prime type and word type, but a consistent word advantage was found. Experiment 2 used novel auditorally-presented reference stimuli to restrict nonword matching to the sublexical level. This abolished scrambled priming for nonwords, but not words. Overall this suggests the processing advantage for words over nonwords results from activation of whole-word, lexical representations. Furthermore, the number of shared open-bigrams between primes and targets could account for scrambled priming effects. These results have important implications for models of orthographic processing and studies that have used this task to investigate prelexical processes.
Neural Interactions at the Core of Phonological and Semantic Priming of Written Words
Word processing is often probed with experiments where a target word is primed by preceding semantically or phonologically related words. Behaviorally, priming results in faster reaction times, interpreted as increased efficiency of cognitive processing. At the neural level, priming reduces the level of neural activation, but the actual neural mechanisms that could account for the increased efficiency have remained unclear. We examined whether enhanced information transfer among functionally relevant brain areas could provide such a mechanism. Neural activity was tracked with magnetoencephalography while subjects read lists of semantically or phonologically related words. Increased priming resulted in reduced cortical activation. In contrast, coherence between brain regions was simultaneously enhanced. Furthermore, while the reduced level of activation was detected in the same area and time window (superior temporal cortex [STC] at 250--650 ms) for both phonological and semantic priming, the spatiospectral connectivity patterns appeared distinct for the 2 processes. Causal interactions further indicated a driving role for the left STC in phonological processing. Our results highlight coherence as a neural mechanism of priming and dissociate semantic and phonological processing via their distinct connectivity profiles.