While the dynamics of lexical-semantic and lexical-phonological encoding in word production have been investigated in several event-related potential (ERP) studies, the estimated time course of phonological-phonetic encoding is the result of rather indirect evidence. We investigated the dynamics of phonological-phonetic encoding combining ERP analyses covering the entire encoding process in picture naming and word reading tasks by comparing ERP modulations in eight brain-damaged speakers presenting impaired phonological-phonetic encoding relative to 16 healthy controls. ERPs diverged between groups in terms of local waveform amplitude and global topography at ~400ms after stimulus onset in the picture naming task and at ~320-350ms in word reading and sustained until 100ms before articulation onset. These divergences appeared in later time windows than those found in patients with underlying lexical-semantic and lexical-phonological impairment in previous studies, providing evidence that phonological-phonetic encoding is engaged around 400ms in picture naming and around 330ms in word reading.Time-course of phonetic encoding 3

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Background: Producing a word in referential naming requires to select the right word in our mental lexicon among co-activated semantically related words. The mechanisms underlying semantic context effects during speech planning are still controversial, particularly for semantic facilitation which investigation remains under-represented in contrast to the plethora of studies dealing with interference. Our aim is to study the time-course of semantic facilitation in picture naming, using a picture-word “interference” paradigm and event-related potentials (ERPs).Methods: We compared two different types of semantic relationships, associative and categorical, in a single word priming and a double word priming paradigm. The primes were presented visually with a long negative Stimulus Onset Asynchrony (SOA), which is expected to cause facilitation.Results: Shorter naming latencies were observed after both associative and categorical primes, as compared to unrelated primes, and even shorter latencies after two primes. Electrophysiological results showed relatively late modulations of waveform amplitudes for both types of primes (beginning ~330 ms post picture onset with a single prime and ~275 ms post picture onset with two primes), corresponding to a shift in latency of similar topographic maps across conditions.Conclusion: The present results are in favor of a post-lexical locus of semantic facilitation for associative and categorical priming in picture naming and confirm that semantic facilitation is as relevant as semantic interference to inform on word production. The post-lexical locus argued here might be related to self-monitoting or/and to modulations at the level of word-form planning, without excluding the participation of strategic processes.

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