Effects of second language study of phonemic discrimination and auditory event-related potentials in adults

This study was designed to investigate the effects of acquisition of a second language on auditory even-related brain potentials and discrimination of foreign language phonemes by 36 women (ages 18 to 47 years), and 25 men (ages 18 to 36 years) and of varying linguistic background, in response to synthetic versions of Japanese phonemes. Subjects were subsequently tested on discrimination between spoken Japanese phonemes. Analysis indicated that the men and women differed in phonological processing and in the way acquisition of the second language affected phonological processing.     

Bottom–up and top–down influences on auditory scene analysis: Evidence from event-related brain potentials.

The physiological processes underlying the segregation of concurrent sounds were investigated through the use of event-related brain potentials. The stimuli were complex sounds containing multiple harmonics, one of which could be mistuned so that it was no longer an integer multiple of the fundamental. Perception of concurrent auditory objects increased with degree of mistuning and was accompanied by negative and positive waves that peaked at 180 and 400 ms poststimulus, respectively. The negative wave, referred to as object-related negativity, was present during passive listening, but the positive wave was not. These findings indicate bottom–up and top–down influences during auditory scene analysis. Brain electrical source analyses showed that distinguishing simultaneous auditory objects involved a widely distributed neural network that included auditory cortices, the medial temporal lobe, and posterior association cortices. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stages of auditory feature conjunction: An event-related brain potential study.

Auditory event-related brain potentials (ERPs) were recorded to tones of different frequencies and locations in a dichotic selective attention task in which Ss responded to occasional deviant tones of a prespecified location and frequency. Attention effects were isolated as negative difference (Nd) waves by subtracting ERPs to tones with no attended features from ERPs to the same tones when they shared target frequency, location, or both cues. The N1/P90 (latency 80–200 msec), originating in a tonotopically organized generator, was enhanced for all tones in the attended ear. Nd waves, beginning at 80 msec and lasting up to 700 ms, were seen to tones with either attended feature. Nd waves to frequency and location features had different scalp distributions consistent with generation in different cortical fields. Conjunction-specific Nds began 30–50 msec after Nds to individual features. The relative timing suggests that feature conjunction began before the analysis of individual features was complete. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Children's performance on pseudoword repetition depends on auditory trace quality: Evidence from event-related potentials.

This study explored the relation between phonological short-term memory and auditory-sensory processing in 7–9-year-old children. Twenty-four participants performed a pseudoword repetition test. The mismatch-negativity (MMN) component of auditory event-related brain potentials was obtained from 9 participants with the highest and 9 participants with the lowest scores on the test. The MMN indexes short-term auditory-sensory memory, including auditory-sensory representations for speech. It was recorded to just perceptible /baga/–/baka/ bisyllabic and easily discriminable 1000/1100-Hz tone contrasts with interstimulus intervals of 350 and 2,000 ms. The high and low repeaters differed significantly in MMN amplitude to speech stimuli at the shorter interstimulus interval. Thus, the accuracy of auditory-sensory processing seems to affect phonological short-term representations in school-age children and therefore may play a role in vocabulary development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alcohol abuse and traumatic brain injury: effect on event-related potentials

OBJECTIVE: To examine the individual and combined impact that traumatic brain injury (TBI) and heavy social use of alcohol have on electrophysiologic correlates of working memory and evaluation of task-relevant information. DESIGN: Case-control study. SETTING: University hospital brain injury rehabilitation unit. PARTICIPANTS: Forty male volunteers divided into four groups on the basis of their history of TBI and alcohol intake. Subjects with TBI had experienced a severe closed head injury at least 1 year before testing. MAIN OUTCOME MEASURE: Event-related potentials (ERPs) and neuropsychometric tests. RESULTS: Groups showed no significant differences in average age or neuropsychological tests. TBI groups did not differ in time postinjury or on severity measures. Alcohol use measures were significantly greater in the two alcohol groups. N200 latency and P300 amplitude were impaired in heavy social drinkers and in nondrinking subjects with TBI relative to controls, but were significantly impaired in subjects with TBI who were also heavy social drinkers. CONCLUSION: The results indicate that although alcohol use and TBI independently produce mile alterations in some aspects of late ERP components, the ERP changes are significantly greater when alcohol use and TBI are combined. This study provides evidence that heavy social drinking after TBI has a measurable impact on electrophysiologic correlates of cognition.     

Explicit and implicit learning of event sequences: Evidence from event-related brain potentials.

Event-related potentials (ERPs) were recorded during a serial reaction time (RT) task, where single deviant items seldom (Experiment 1) or frequently (Experiment 2) replaced 1 item of a repeatedly presented 10-item standard sequence. Acquisition of sequence knowledge was reflected in faster RTs for standard as compared with deviant items and in an enhanced negativity (N2 component) of the ERP for deviant items. Effects were larger for participants showing explicit knowledge in their verbal reports and in a recognition test. The lateralized readiness potential indicated that correct responses were activated with shorter latencies after training. For deviant items, participants with explicit knowledge showed an initial activation of the incorrect but expected response. These findings suggest that the acquisition of explicit and implicit knowledge is reflected in different electrophysiological correlates and that sequence learning may involve the anticipatory preparation of responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response preparation begins before mental rotation is finished: evidence from event-related brain potentials

Behavioral data (response time (RT) and accuracy) and psychophysiological data (event-related brain potentials of ERPs, and lateralized readiness potential or LRP) were studied in an experiment in which rotated alphanumeric characters were presented normally or mirror-reversed. In half of the trials, character classification (letter versus digit) determined whether or not the response was to be executed (go versus nogo) and parity determined the responding hand. In the other half, classification determined the responding hand and parity determined go versus nogo. LRP data indicated that response preparation occurred before mental rotation was finished. These data contradict strictly sequential discrete models of information processing and suggest continuous flow of information.     

Age-related slowing in face and name recognition: Evidence from event-related brain potentials.

Age-related slowing in recognizing famous names and faces was investigated with event-related brain potentials (ERPs). In a group of young adults, item repetition induced early (220-340 ms) and late (400-700 ms) ERP modulations, apparently signaling the access to, respectively, domain-specific representations of faces and names and domain-general semantic knowledge about the persons. These repetition effects and other ERP components were then used as process-specific time markers in middle-aged and elderly participants. For both faces and names, the elderly participants' responses were slowed, but repetition priming in reaction times was not. The ERP latencies suggested that most of the age-related slowing occurred in the access to domain-specific representations and during response decision, whereas sensory and perceptual processing was largely spared. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interactions of focal cortical lesions with error processing: Evidence from event-related brain potentials.

Electrophysiological and hemodynamic studies have suggested that structures in the vicinity of the anterior cingulate cortex are involved in performance monitoring, particularly in detection of errors. Bidirectional interactions between the frontomedian system involved in performance monitoring and the lateral prefrontal cortex as well as the orbitofrontal cortex have been proposed, but few studies have directly addressed this issue. The authors used a speeded flankers task to investigate error-related event-related potentials in 3 patient groups with different focal cortical lesions. Whereas bilateral frontopolar lesions involving the orbitofrontal cortex as well as temporal lesions did not alter the error-related negativity (ERN), lesions of the lateral frontal cortex resulted in an abolition of the ERN and in a reduction of the error positivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of stimulus variability on speech perception in listeners with hearing impairment

Traditional word-recognition tests typically use phonetically balanced (PB) word lists produced by one talker at one speaking rate. Intelligibility measures based on these tests may not adequately evaluate the perceptual processes used to perceive speech under more natural listening conditions involving many sources of stimulus variability. The purpose of this study was to examine the influence of stimulus variability and lexical difficulty on the speech-perception abilities of 17 adults with mild-to-moderate hearing loss. The effects of stimulus variability were studied by comparing word-identification performance in single-talker versus multiple-talker conditions and at different speaking rates. Lexical difficulty was assessed by comparing recognition of "easy" words (i.e., words that occur frequently and have few phonemically similar neighbors) with "hard" words (i.e., words that occur infrequently and have many similar neighbors). Subjects also completed a 20-item questionnaire to rate their speech understanding abilities in daily listening situations. Both sources of stimulus variability produced significant effects on speech intelligibility. Identification scores were poorer in the multiple-talker condition than in the single-talker condition, and word-recognition performance decreased as speaking rate increased. Lexical effects on speech intelligibility were also observed. Word-recognition performance was significantly higher for lexically easy words than lexically hard words. Finally, word-recognition performance was correlated with scores on the self-report questionnaire rating speech understanding under natural listening conditions. The pattern of results suggest that perceptually robust speech-discrimination tests are able to assess several underlying aspects of speech perception in the laboratory and clinic that appear to generalize to conditions encountered in natural listening situations where the listener is faced with many different sources of stimulus variability. That is, word-recognition performance measured under conditions where the talker varied from trial to trial was better correlated with self-reports of listening ability than was performance in a single-talker condition where variability was constrained.     

Stimulus probability and event-related potentials of the brain in 6-month-old human infants: a parametric study

The effects of a priori stimulus probability and local-stimulus sequences on the Nc, NSW and Pc components of the event-related brain potentials were studied in six groups of 6-month-old human infants. Predictions from memory, expectancy and attentional accounts of the Nc, NSW and Pc components were examined using an infant-control oddball paradigm in which visual stimuli were presented across groups, at 0.90/0.10, 0.80/0.20, 0.70/0.30, 0.60/0.40, 0.50/0.50 (alternation) and 0.50/0.50 (random) probabilities. The main results indicated that stimulus probabilities and local-stimulus sequences affected Nc amplitude and latency, NSW amplitude but not the Pc component. Concurrent visual fixation performance was also found to be influenced by stimulus probabilities. The results were discussed in terms of the predictions from memory, expectancy and attentional accounts of the infant late components.     

Structure and process in semantic memory: Evidence from event-related brain potentials and reaction times.

Through scalp measurements of the electrical activity of the brain (ERPs) recorded while Ss verified the truth of sentences relating exemplars and categories (e.g., all dogs are animals), inferences were made about aspects of semantic processing that were not directly reflected by overt responses. In particular, it is suggested that a negative ERP component that peaks about 400 msec after the onset of the sentence predicate (i.e., N400) is sensitive to structural aspects of semantic memory. The amplitude of this component was modulated by the relatedness of the subject and predicate terms, as well as the hierarchical level of both these terms, but was not sensitive to the truth value of a sentence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of caffeine on event-related potentials: comparison of oddball with single-tone paradigms

A report is given of the 1st confirmed outbreak of Albizia versicolor poisoning in Malawi and the 1st natural outbreak reported in sheep and goats. Approximately 800 animals are estimated to have died over a 9-year period on a government farm near Lake Malawi. Deaths occurred exclusively from August to December when ripe dry pods that fell to the ground were ingested. The major clinical signs were hyperaesthesia, wild running, lateral recumbency with rapid leg movements, nystagmus and rapid blinking. Approximately 75% of clinical cases made a full and rapid recovery. Sheep more often showed signs of poisoning than goats which was attributed to inherent susceptibility rather than selective feeding. The majority of animals affected were under 1 year of age. A series of experiments was conducted and all animals dosed with 6.4 g/kg or more of dry pods died with typical clinical signs. Although A. versicolor is well known to the local population there appeared to be no appreciation of its toxicity. Poisonings are probably rare under traditional management systems.     

The influence of acetylsalicylic acid on cognitive processing: an event-related potentials study

The central effects of acetylsalicylic acid (ASA) are discussed controversially. In animal models, it has been shown that ASA can interact with the central serotonergic and catecholaminergic neuronal system. However, the relevance of this interaction for humans is still unknown. We performed a study on the influence of ASA on central cognitive processing. In 25 healthy subjects (age 21-56 years), visually evoked event-related potentials (ERP) and reaction time under IV ASA medication were recorded. ERP were evoked by an oddball paradigm. As compared to placebo, ASA decreased the latency of the P3 component significantly in a time interval of 20-40 min after administration. The latency of the N2 component was significantly decreased about 25 min after administration; the latency of the exogenous P2 component was not influenced by ASA. The mean choice reaction time was significantly decreased by ASA 35 min after administration. At this time point, there was a significant correlation between decrease in reaction time and increase in ASA plasma level. The data show that IV administration of ASA has an accelerating effect on the endogenous components of visual ERP and on reaction time. This finding suggests that ASA can influence central cognitive processing, possibly by ASA induced changes of neurotransmitters. Since serotonin can be released by ASA and serotonin release leads to a decrease of ERP latencies. we assume that ASA most likely influences cognitive processing via the central serotonergic transmitter system.     

Effects of appetitive drive on auditory evoked potentials: A replication.

Reexamined click-evoked potentials in 6 female cats during periods of increased food deprivation under 3 experimental procedures. The amplitudes of click-evoked potentials recorded from the round window, cochlear nucleus, and auditory cortex remained constant as deprivation time increased from 0 to 24 hr regardless of the experimental procedures used. Increased food-deprivation time had no systematic effect on EEG activity recorded from the auditory cortex under the 3 procedures. It is suggested that since increased food-deprivation time under the experimental procedures did not produce a state of heightened EEG arousal, the lack of effect on auditory evoked potentials is related to the amount of environmental stimulation an animal receives during food deprivation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of postinatal stress on visual and auditory evoked potentials

Maturation of visual and auditory evoked potentials (mainly the P3 wave) of 10 controls and of 10 infants exposed to recurrent postnatal stressful events (crying spells lacking organic basis) have been compared. The sourse of maturation of P3 waves may serve as indicator of growth and nature of cognitive processes (including perception). Recurrent srying spells seemed to delay appearance of visual P3 wave, prolonged its latency, and delayed appearance of visible differences in the shape of visual P3 wave upon exposure of the subjects to different visual experiences. A compensatory increase of maturation of the auditory P3 wave appeared. The results suggest that recurrent exposure to stressful events during the early postnatal period may delay the ability of the memory banks of auditory engrams with unusual contents (including memory traces of stresses), a potential basis for future auditory hallucinations.     

Effects of age on working memory: an event-related potential study

The effects of age on behavioural performance and event-related potentials recorded during a working memory task using digits presented either acoustically or visually, were studied in 37 healthy subjects with an age range from 19 to 71 years. With increasing age, psychological tests showed a progressive decline in visuo-spatial performance and both auditory and visual reaction times (RT) increased. There were multiple and varying effects of age on both early and late ERP components. For both auditory and visual responses, increasing age was associated with an increased amplitude of early positive waves (auditory P100 and visual P145) and, in the oldest subjects, significant delays of the major late positive waves. Other changes were modality-specific with a progressive shift of amplitude maxima in the early negative waves of the visual ERPs (from an N190 peak maximal at Pz in the young, to an N270 peak maximal at Cz in the older subjects) and an altered amplitude distribution of late potentials (after the P250 wave) in the auditory responses. The age at which ERP changes occurred varied-significant latency prolongations and increases in the amplitude of the major frontal positive waves occurred only in the oldest subjects, whereas a redistribution of late auditory ERPs also occurred in the intermediate age group. There was no interaction between age and increasing memory load, suggesting that there is no specific effect of age on memory scanning in this age range for these levels of task difficulty. Thus, although performance in working memory was apparently unaffected by age, as judged by behavioural parameters (apart from slowing of the reaction times), ERPs revealed significant changes in both early and late electrical brain processes associated with working memory as age increases. These changes which were not symptomatically manifest and only revealed by sensitive tests, may represent subtle dysfunction of working memory (or associated processes) which does not prevent the successful completion of our task, compensatory mechanisms (which are essential to successfully complete the task), or a combination of both age-induced dysfunction and compensatory mechanisms.     

The gradient of spatial auditory attention in free field: an event-related potential study

Young adult subjects attended selectively to brief noise bursts delivered in free field via a horizontal array of seven loudspeakers spaced apart by 9 degrees of angle. Frequent "standard" stimuli (90%) and infrequent "target/deviant" stimuli (10%) of increased bandwidth were delivered at a fast rate in a random sequence equiprobably from each speaker. In separate runs, the subjects' task was to selectively attend to the leftmost, center, or rightmost speaker and to press a button to the infrequent "target" stimuli occurring at the designated spatial location. Behavioral detection rates and concurrently recorded event-related potentials (ERPs) indicated that auditory attention was deployed as a finely tuned gradient around the attended sound source, thus providing support for gradient models of auditory spatial attention. Furthermore, the ERP data suggested that the spatial focusing of attention was achieved in two distinct stages, with an early more broadly tuned filtering of inputs occurring over the first 80-200 msec after stimulus onset, followed by a more narrowly focused selection of attended-location deviants that began at around 250 msec and closely resembled the behavioral gradient of target detections.     

The time course of brain activations during response inhibition: evidence from event-related potentials in a go/no go task

The cortical organization of executive control was investigated using event-related potentials (ERPs). ERPs were collected while subjects performed a go/no go task that required response inhibition. First, around 260 ms after stimulus onset, an effect of response inhibition on ERPs was observed over inferior prefrontal areas. Generators in these regions were confirmed by source analysis. Later, between 300-600 ms after stimulus onset, a left lateralized fronto-central ERP effect was found which differed in topography from a non-specific effect of task difficulty. Source analysis indicated that generators in anterior cingulate and left premotor areas also contributed to this effect. Orchestrated activation of prefrontal areas and the anterior cingulate subserves executive function whereas relatively late activity of the left premotor cortex is involved in motor control.     

Effects of pemoline on spontaneous and event-related electrical activity of the brain

The effect of pemoline on the electrical activity of the brain (electroencephalogram, EEG) was studied in relation to time since sleep and time of day in 6 healthy subjects carrying out periods of work lasting 18 h. Power of the spontaneous EEG increased with time since sleep and amplitude of the P3 event-related response decreased. The changes may be interpreted as the reduction in alertness with time awake. In contrast, pemoline decreased power of the spontaneous EEG and increased the amplitude the P3 response, effects that are consistent with improved alertness. The changes in brain activity were paralleled by effects on performance, in terms of percentage of correct responses and reaction time. Performance decreased with time awake, and was improved by pemoline compared with placebo. The drug counteracted the adverse effects of time since sleep, with the beneficial effect of the drug persisting over the 18-hour period of work. The findings emphasise that spontaneous and event-related activity of the EEG may be used both to complement measures of performance in the laboratory and to assess behaviour in occupational situations where performance testing is impractical.