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Pernet C, Uusvuori J, and Salmelin R: Parafoveal-on-foveal and foveal word priming are different processes: Behavioral and neurophysiological evidence. NeuroImage 2007, 38: 321–330.
Parafoveal-on-foveal priming refers to the presentation of an item (the prime) in parafoveal vision followed by the presentation of an item (the target) in foveal vision. In natural reading, the 'parafoveal preview benefit' subserves fluent reading as, e.g., reading times increase when such information is not available. Yet, the neural correlates of reading are mostly studied with foveally presented stimuli and little is known of this parafoveal influence. Here, we used complementary information from a behavioral study and a magnetoencephalography experiment to clarify the relationship between parafoveal-on-foveal and foveal priming. Unlike foveal priming, parafoveal-on-foveal priming was present only at short prime-to-target delay (<100 ms). Behaviorally, the parafoveal priming effect was influenced by the prime visual field (left/right) and target lexical type (word/non-word), suggesting emphasis on perceptual analysis for LVF primes and on conceptual analysis for RVF primes. At the neural level, the overall sequence of activation was similar for foveal and parafoveal primes followed by foveal word targets, but the priming effects were bilateral for foveal primes versus left-lateralized for RVF primes. No neural effects of priming appeared for LVF primes, in line with the RVF preference imposed by the Western writing system. These results highlight the role of the left hemisphere in linguistic analysis and point out possible limitations of foveal stimulus presentation for drawing conclusions about natural reading.
Salmelin R: Clinical neurophysiology of language: the MEG approach. Clin Neurophysiol 2007, 118: 237–254.
Clinical evaluation of language function and basic neuroscience research into the neurophysiology of language are tied together. Whole-head MEG systems readily facilitate detailed spatiotemporal characterization of language processes. A fair amount of information is available about the cortical sequence of word perception and comprehension in the auditory and visual domain, which can be applied for clinical use. Language production remains, at present, somewhat less well charted. In clinical practice, the most obvious needs are noninvasive evaluation of the language-dominant hemisphere and mapping of areas involved in language performance to assist surgery. Multiple experimental designs and analysis approaches have been proposed for estimation of language lateralization. Some of them have been compared with the invasive Wada test and need to be tested further. Development of approaches for more comprehensive pre-surgical characterization of language cortex should build on basic neuroscience research, making use of parametric designs that allow functional mapping. Studies of the neural basis of developmental and acquired language disorders, such as dyslexia, stuttering, and aphasia can currently be regarded more as clinical or basic neuroscience research rather than as clinical routine. Such investigations may eventually provide tools for development of individually targeted training procedures and their objective evaluation.
Service E, Helenius P, Maury S, and Salmelin R: Localization of syntactic and semantic brain responses using magnetoencephalography. J Cogn Neurosci 2007, 19: 1193-1205.
Annual Report 2007