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Neurolinguistic and psycholinguistic studies suggest that grammatical (gender) and phonological information are retrieved independently and that gender can be accessed before phonological information. This study investigated the relative time courses of gender and phonological encoding using topographic evoked potentials mapping methods. Event-related brain potentials (ERPs) were recorded using a high resolution electroencephalogram (EEG) system (128 channels) during gender and phoneme monitoring in silent picture naming. Behavioural results showed similar reaction times (RT) between gender and word onset (first phoneme) monitoring, and longer RT when monitoring the second syllable onset. Temporal segmentation analysis (defining dominant map topographies using cluster analysis) revealed no timing difference between gender monitoring and word onset monitoring: both effects fall within the same time window at about 270-290 ms after picture presentation. Monitoring a second syllable onset generated a later effect at about 480 ms. Direct comparison between gender and first phoneme monitoring revealed a difference of only 10 ms between tasks at approximately 200 ms. Taken together, these results suggest that lemma retrieval and phonological encoding may proceed in parallel or overlap. Word onset is retrieved simultaneously with gender, while the longer RT and the later ERP effect for second syllable onset reflect that segmental encoding continues incrementally to the following phonemes.

Electrical neuroimaging in humans identified the speed and spatiotemporal brain mechanism whereby sounds of living and man-made objects are discriminated. Subjects performed an "oddbal" target detection task, selectively responding to sounds of either living or man-made objects on alternating blocks, which were controlled for in their spectrogram and harmonics-to-noise ratios between categories. Analyses were conducted on 64-channel auditory evoked potentials (AEPs) from nontarget trials. Comparing responses to sounds of living versus man-made objects, these analyses tested for modulations in local AEP waveforms, global response strength, and the topography of the electric field at the scalp. In addition, the local autoregressive average distributed linear inverse solution was applied to periods of observed modulations. Just 70 ms after stimulus onset, a common network of brain regions within the auditory "what" processing stream responded more strongly to sounds of man-made versus living objects, with differential activity within the right temporal and left inferior frontal cortices. Over the 155-257 ms period, the duration of activity of a brain network, including bilateral temporal and premotor cortices, differed between categories of sounds. Responses to sounds of living objects peaked ∼12 ms later and the activity of the brain network active over this period was prolonged relative to that in response to sounds of man-made objects. The earliest task-related effects were observed at ∼100 ms poststimulus onset, placing an upper limit on the speed of cortical auditory object discrimination. These results provide critical temporal constraints on human auditory object recognition and semantic discrimination processes. [ABSTRACT FROM AUTHOR]