event-related brain potentials during picture naming, using early and late acquired words

background naming is a simple and basic skill of the language which involves semantic, lexical, and phonological levels. there are many different factors affecting the speed and convenience of naming. one of these factors is the word age of acquisition (aoa) and since language processing occurs at an extremely fast rate, psycholinguistics needs a method that has very good temporal resolution. the event-related brain potentials (erp) method is almost ideal among the imaging techniques of studying a language. objectives the current study aimed to investigate the electroencephalograph signals related to the time period of phonological encoding during immediate picture naming through the analysis of aoa effect. patients and methods in this cross-sectional study 15 male, native farsi speakers, aged 18 - 25 years participated. the test involved naming 80 pictures including 40 early-acquired words and 40 late-acquired words, presented by a monitor screen. eeg (electroencephalogram) was recorded continuously from 64 electrodes mounted on an electrode cap. the waves related to early and late-acquired groups were investigated in terms of amplitude, latency, and scalp distribution within a 300 millisecond time range linked to phonological encoding process. results the results showed that the pictures of the early-acquired words were named 40 millisecond faster than those of late-acquired words (p = 0.022). the difference between the two groups was significant on the latency and scalp distribution, but not significant on amplitude. conclusions according to the results of the study, aoa modulated response latencies (early acquired words were produced faster than late-acquired ones), indicating increased processing time-cost for late acquired words, which happens during the phonological encoding period (phonological code retrieval and syllabification). furthermore, the results seem to support a phonological encoding locus for the main aoa effects.