Using event related brain potentials (ERPs), we examined the neurocognitive basis of phonological discrimination of phoneme /h/ in native English speakers and Francophone late second language (L2) learners, as a function of L2 proficiency and stimulus/task demands. In Experiment 1, native and non-native (L2 only) phonological contrasts were presented as syllables during a task that directed attention to phonological form. Phonological categorization was assessed with MMN, N2b and P3b effects. In Experiment 2, the same contrasts were presented as words/ pseudowords during a task that directed attention to semantics. Phonological discrimination was assessed with N400 pseudoword effects. High proficiency L2 learners displayed similar ERPs as native speakers in both experiments; low proficiency L2 learners showed discrimination of non-native contrasts in Experiment 1 (directed attention task) only. Thus, L2 phonological discrimination by late learners may depend on stimulus/task factors and occurs in a wider range of contexts as L2 proficiency improves.

The role of the basal ganglia in syntactic language processing was investigated with event-related brain potentials in fourteen neurologically impaired patients. Seven of these patients had basal ganglia lesions while 7 other patients primarily had lesions of the left temporo–parietal region excluding the basal ganglia. All patients listened to sentences that were either correct or included a verb argument structure violation. In previous experiments this type of violation elicited a biphasic pattern of an N400–P600 complex in young healthy participants. While the N400 may result from incorrect semantic-thematic role assignment, the P600 reflects the fact that verb information does not license the syntactic structure at present. Results of the patient experiment revealed a double dissociation: patients with left temporo–parietal lesions only show a P600, whereas patients with lesions of the basal ganglia showed no P600, but a negativity with extended duration that resembled an N400. The latter pattern not only confirms previous reports that the basal ganglia modulate the P600 but extends these results by showing that the N400 as a late semantic–thematic integration process appears partially modulated by the basal ganglia. (JINS, 2003, 9, 1053–1060.)

Contralateral-control methods can be applied to psychophysiology and in particular to the study of visual memory. Visual memory possesses some degree of hemispheric organization, so that visual memory traces for laterally presented stimuli are stronger or more durable in the hemisphere contralateral to the hemifield where the stimuli were first presented. I first introduce the concept of hemispheric organization of function. Then I discuss how hemispheric organization can be exploited for obtaining information about the time course and brain localization of psychological processes, using a contralateral-control method. Behavioral and event-related brain potential data support the hemispheric organization view of visual memory, and the contralateral-control method, in conjunction with the recording of the event-related optical signal, can be used to reveal the existence of memory-driven processes in early stations of the visual system.