The present study establishes an electrophysiological index of lexical access in speech production by exploring the locus of the frequency and cognate effects during overt naming. We conducted 2 event-related potential (ERP) studies with 16 Spanish-Catalan bilinguals performing a picture naming task in Spanish (L1) and 16 Catalan-Spanish bilinguals performing a picture naming task in Spanish (L2). Behavioral results showed a clear frequency effect and an interaction between frequency and cognate status. The ERP elicited during the production of high-frequency words diverged from the low-frequency ERP between 150 and 200 ms post-target presentation and kept diverging until voice onset. The same results were obtained when comparing cognate and noncognate conditions. Positive correlations were observed between naming latencies and mean amplitude of the P2 component following the divergence, for both the lexical frequency and the cognate effects. We conclude that lexical access during picture naming begins approximately 180 ms after picture presentation. Furthermore, these results offer direct electrophysiological evidence for an early influence of frequency and cognate status in speech production. The theoretical implications of these findings for models of speech production are discussed.

Speech production is one of the most fundamental activities of humans. A core cognitive operation involved in this skill is the retrieval of words from long-term memory, that is, from the mental lexicon. In this article, we establish the time course of lexical access by recording the brain electrical activity of participants while they named pictures aloud. By manipulating the ordinal position of pictures belonging to the same semantic categories, the cumulative semantic interference effect, we were able to measure the exact time at which lexical access takes place. We found significant correlations between naming latencies, ordinal position of pictures, and event-related potential mean amplitudes starting 200 ms after picture presentation and lasting for 180 ms. The study reveals that the brain engages extremely fast in the retrieval of words one wishes to utter and offers a clear time frame of how long it takes for the competitive process of activating and selecting words in the course of speech to be resolved.electrophysiology ͉ lexical access ͉ speech production W ord selection is a crucial step in speech production. Considering that the average lexicon contains Ϸ50,000 lexical entries and that an average speaker utters approximately three words per second, the process of lexical retrieval needs to proceed at high speed and with great accuracy. Failures of this process result in speech errors or anomia, which limit communication, as acutely demonstrated in production aphasia, for instance. Although our understanding of how speakers retrieve words from the lexicon has considerably increased in recent years (1-4), the neural implementation of this process remains poorly understood. In particular, insights regarding the time course of word retrieval in speech production are sparse, and most of the chronometric evidence available is derived from event-related potential (ERP) studies relying on button-press responses rather than in actual overt speech production (5-9). This strategy was adopted because EEG is highly susceptible to mouth movements that could possibly mask the cognitive components of interest. However, at least one EEG study and several MEG studies have shown that artifact-free brain responses can be measured up to at least 400 ms after picture onset (10-13), and a few recent ERP studies demonstrated that classical ERP components can be replicated during overt picture naming (14-17).Although these latter studies reveal the validity of ERPs for studying overt naming, they have not directly investigated the issue of the time course of lexical selection, but rather other aspects of word production (e.g., morphological processing, bilingual language control, etc.). It is the goal of the present study to identify the time course of word selection during overt naming, capitalizing on the fine temporal resolution of ERPs. In this study, we directly measure the time course of word retrieval during overt naming. Such temporal information is invaluable for understanding brain mechanisms underlying speech pro...