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.

Individuals with posttraumatic stress disorder (PTSD) have been found to show several event-related brain potential (ERP) abnormalities including reduced target P3b amplitude, P50 suppression, and P2 amplitude/intensity slope. Female Vietnam nurse veterans with (n = 29) and without (n = 38) current PTSD completed P50 paired-click, three-tone “oddball” and four-tone stimulus-intensity modulation procedures. Opposite to previous findings, the current PTSD group had larger target P3b amplitudes and increased P2 amplitude/intensity slopes. Reduced P50 suppression was associated with increased severity of general psychopathology, but not with PTSD diagnosis. Findings suggest that target P3b amplitude and P2 amplitude/intensity slope abnormalities reflect different pathophysiological processes. Future research is needed to determine whether the opposite ERP abnormalities observed in this PTSD sample reflect gender-, trauma-, or sample-specific findings.

Speed-accuracy instructions were manipulated in two symbolic stimulus-response compatibility tasks in an event-related potential study with young adults. For both tasks, the stimuli were the words left and right written in upper and lower case. Three late positive peaks (early P3, P3b, and P4) were seen in one task (with compatibility type blocked) with an additional peak (P3c) in the task that required identifying two stimulus attributes (compatibility type signaled by case). In both tasks, stimulus-response incompatibility and an emphasis on accuracy increased reaction time, made the P4 more prominent and increased its latency. With very rapid responding, P4 was not prominent because of overlap with the preceding peak. Functional characteristics of the peaks are discussed as well as potential sources of latency and amplitude measurement error when P3b is measured in a temporal window broad enough to include the P4.

In a within-subjects design, event-related potentials were compared for two types of sentence-final syntactic errors: Incorrect verb inflection and incorrect word category (phrase structure). In a grammatical judgment task, these errors triggered robust N400 and P600 components. To assess the degree of automaticity of the underlying linguistic processes, the N400 and P600 effects were measured in a task for which the participants judged whether a word in a sentence was printed in upper case. In this physical judgment task, the N400 and P600 following verb inflection errors were greatly attenuated or absent, whereas those elicited by word category violation were only slightly diminished in amplitude. The data suggest that word category information is processed more automatically than inflectional information. The P600 appears to reflect a relatively controlled language-related process.

Event-related potentials were recorded from 80 participants ranging in age from 7 to 24 years while they attended selectively to stimuli with a specified color (red or blue) in an attempt to detect the occurrence of target stimuli. Color attention effects were identified as frontal selection positivity (FSP; 140–275 ms), selection negativity (SN; 150–300 ms), and N2b (200–450 ms), whereas target detection was reflected in P3b (300–700 ms). There were age-related decreases in the latencies of FSP, N2b, and P3b that paralleled decreases in reaction time and error rates. Also, the SN amplitude increased with advancing age, whereas both N2b and P3b showed changes in scalp topography. These results represent neurophysiological evidence that the efficiency of visual selective processes increases during childhood and adolescence. Developmental growth may take place at both relatively early and late levels of visual selective information processing.

Event-related potentials were recorded from 80 participants ranging in age from 7 to 24 years while they attended selectively to stimuli with a specified color (red or blue) in an attempt to detect the occurrence of target stimuli. Color attention effects were identified as frontal selection positivity (FSP; 140–275 ms), selection negativity (SN; 150–300 ms), and N2b (200–450 ms), whereas target detection was reflected in P3b (300–700 ms). There were age-related decreases in the latencies of FSP, N2b, and P3b that paralleled decreases in reaction time and error rates. Also, the SN amplitude increased with advancing age, whereas both N2b and P3b showed changes in scalp topography. These results represent neurophysiological evidence that the efficiency of visual selective processes increases during childhood and adolescence. Developmental growth may take place at both relatively early and late levels of visual selective information processing.

P300 differences for target (.10), nontarget (.10), and standard tones (.80) were assessed using a three-stimulus oddball paradigm in which participants responded only to the target (n = 12). Target/standard (easy or difficult) and nontarget/standard (large or small) pitch differences were manipulated orthogonally. In all conditions, target tones elicited a parietal P300, which was affected only by the target/standard discrimination ease. Nontarget in the easy/large and difficult/small conditions elicited a parietal but smaller P300 than the target but in the easy/small condition elicited similar ERPs to the standard. However, nontarget stimuli in the difficult/large condition elicited an anterior maximum and earlier P300 (P3a) component. The findings suggest that target P300s are not influenced by the nontarget stimulus configuration, whereas the nontarget P300 outcomes are determined directly by the stimulus context. The theoretical implications are discussed.

The effects of methylphenidate (0.3 mg/kg) on young adults' paired-associate learning (PAL) of consonant–vowel–consonant (CVC) pairs and concomitant event-related potentials were assessed. The stimulant elevated mood and heart rate but did not affect PAL performance. For the first CVC, there were amplitude increases with learning for P3b at Pz, P2 at midline sites, and for a negative slow wave at Cz. For the second CVC, P3b and positive slow wave amplitude declined with learning. Increases in P3b amplitude to the first CVC were attributed to increments in stimulus meaningfulness. Decreases in P3b amplitude to the second CVC were interpreted as resulting from fewer disconfirmed expectations of feedback. The negative slow wave following the first CVC was viewed as a contingent negative variation. Methylphenidate increased parietal P3b amplitude for CVC 2, averaged over learning phases.