The effect of pain on involuntary and voluntary capture of attention.

BACKGROUND: There is converging evidence for the notion that pain affects a broad range of attentional domains. This study investigated the influence of pain on the involuntary capture of attention as indexed by the P3a component in the event-related potential derived from the electroencephalogram. METHODS: Participants performed in an auditory oddball task in a pain-free and a pain condition during which they submerged a hand in cold water. Novel, infrequent and unexpected auditory stimuli were presented randomly in a series of frequent standard and infrequent target tones. P3a and P3b amplitudes were observed to novel, unexpected and target-related stimuli, respectively. RESULTS: Both electrophysiological components were characterized by reduced amplitudes in the pain compared with the pain-free condition. Hit rate and reaction time to target stimuli did not differ between the two conditions presumably because the experimental task was not difficult enough to exceed attentional capacities under pain conditions. CONCLUSIONS: These results indicate that voluntary attention serving the maintenance and control of ongoing information processing (reflected by the P3b amplitude) is impaired by pain. In addition, the involuntary capture of attention and orientation to novel, unexpected information (measured by the P3a) is also impaired by pain. Thus, neurophysiological measures examined in this study support the theoretical positions proposing that pain can reduce attentional processing capacity. These findings have potentially important implications at the theoretical level for our understanding of the interplay of pain and cognition, and at the therapeutic level for the clinical treatment of individuals experiencing ongoing pain.

Use of event-related brain potentials (ERPs) to assess eyewitness accuracy and deception.

This study investigated eyewitness identification using ERPs. Twenty participants completed two eyewitness lineup tasks (standard and deception conditions). For the standard condition, participants tried to accurately identify the culprit, whereas in the deception condition, they were asked to deceptively conceal their recognition of the culprit. Identification rates based on P300 patterns were calculated using two different individual analysis procedures (A and B) that varied in stringency. Correct identification rates for the standard condition were 100% for both procedures A and B. For the deception condition, correct identification rates of the concealed culprit were 90%, and 70% respectively for procedures A and B. Data from a prior study [the culprit-absent condition from Lefebvre, C.D., Marchand, Y., Smith, S.M. & Connolly, J.F., 2007. Determining eyewitness identification accuracy using event-related brain potentials (ERPs). Psychophysiology, 44, 894-904.] was reanalysed to investigate differences in false identification rates based on procedures A and B. False identifications were substantially higher when using procedure A (29%) versus procedure B (0%). Overall, superiority was found for procedure B compared to procedure A based on Grier's A'.

Electrophysiological markers of pre-lexical speech processing: evidence for bottom-up and top-down effects on spoken word processing.

The present study was designed to investigate the electrophysiological consequences of a mismatch between initial phoneme expectations and the actual spoken input. Participants were presented with a word/nonword prompt with the instruction to delete the initial sound (e.g., snap without the /s/; snoth without the /s/) and determine the resulting segment. Following the prompt, an aurally presented response that matched/mismatched expectations (e.g., nap/tap; noth/toth) was presented. The Phonological Mapping Negativity (PMN), a response associated with phonological processing, was largest to mismatching responses, and was not dependent on the lexical status of response items. An N400-like response was also largest to mismatching responses; however, in contrast to the PMN, the N400-like response differentiated mismatching words from mismatching nonwords. These findings highlight a functional dissociation between the PMN and N400, and establish the PMN as a neural marker representing the goodness-of-fit between initial phoneme expectations and the actual spoken input.

Determining eyewitness identification accuracy using event-related brain potentials (ERPs).

This study investigated the use of event-related brain potentials (ERPs) as a neurophysiological measure of eyewitness identification accuracy during a lineup task (ERP-lineup). Time delay between viewing the crime and completing the ERP-lineup (no-delay, 1-h delay and 1-week delay conditions) and culprit presence or absence were also manipulated. Results demonstrated that a P300 provided a reliable index of recognition of the culprit relative to the other lineup members across all time delay conditions. Although participants' accuracy decreased at the 1-week time delay compared to no delay and the 1-h time delay, the P300 effect remained strong for participants that made correct identifications irrespective of the time delay. In addition, the P300 was attenuated or was not elicited when the culprit was absent from the lineup.

Event-related brain potentials as a measure of performance on WISC-III and WAIS-R NI similarities sub-tests.

Communication difficulties are a common consequence of brain injury and neuropathological processes. Equally common is the inability to assess intellectual functioning in many communication-impaired populations because the aphasia and physical disability of such patients prevents measurable performance on traditionally administered tests of mental functioning. This study demonstrates that concept formation abilities can be assessed using event-related brain potentials. It also provides further evidence for the efficacy of this innovative assessment method in which standardized and validated psychometric tests are formatted for computer presentation and simultaneous recording of neural activity, which serves as the response measure in lieu of verbal/behavioral responses.

Influence of phonological expectations during a phoneme deletion task: evidence from event-related brain potentials.

Several studies have identified a negativity [the phonological mismatch negativity (PMN)] preceding the N400 during auditory sentence comprehension. The present study investigated whether the PMN reflects a prelexical or lexical stage of spoken word recognition. Event-related brain potentials (ERPs) were recorded to investigate phonological processing independently from lexical/semantic influences during a task requiring metalinguistic analysis of speech stimuli. Participants were instructed to omit the initial phoneme from a word ("clap" without the/k/) after which they heard a correct (lap) or incorrect (cap, ap, nose) answer. The PMN (peaking at 270 ms) was largest to incorrect items and did not differentiate between items that shared the same rime and items that were phonologically unrelated to the correct choice. Further, the PMN did not differ between word (cap) and nonword (ap) choices. The P300 was largest to correct items but was also seen to choices that rhymed with the correct answer. It is concluded that the PMN serves as a neural marker for the analysis of acoustic input merging with prelexical phonemic expectations.

The disruptive effect of chronic pain on mismatch negativity.

OBJECTIVE: To investigate the effect of chronic pain on processes that generate the mismatch negativity (MMN). METHODS: Twelve participants with a diagnosis of chronic intractable pain were tested before and after pain treatment. During testing, event-related potentials were recorded while participants performed tasks of varying difficulty. RESULTS: The amplitude of the MMN was found to be greater following a nerve block procedure compared to MMN amplitude when participants were experiencing chronic pain. This effect was found to occur in the MMN for difficult-to-detect tones elicited while participants were performing a simultaneous cognitively demanding visual task. MMN amplitude was found to be greater with attention to difficult-to-detect deviants during pain but not in no pain conditions. CONCLUSIONS: These results provide an electrophysiological correlate of previous findings that high levels of pain disrupt cognition during the performance of demanding tasks.

Effects of dipole position, orientation and noise on the accuracy of EEG source localization.

BACKGROUND: The electroencephalogram (EEG) reflects the electrical activity in the brain on the surface of scalp. A major challenge in this field is the localization of sources in the brain responsible for eliciting the EEG signal measured at the scalp. In order to estimate the location of these sources, one must correctly model the sources, i.e., dipoles, as well as the volume conductor in which the resulting currents flow. In this study, we investigate the effects of dipole depth and orientation on source localization with varying sets of simulated random noise in 4 realistic head models. METHODS: Dipole simulations were performed using realistic head models and using the boundary element method (BEM). In all, 92 dipole locations placed in temporal and parietal regions of the head with varying depth and orientation were investigated along with 6 different levels of simulated random noise. Localization errors due to dipole depth, orientation and noise were investigated. RESULTS: The results indicate that there are no significant differences in localization error due tangential and radial dipoles. With high levels of simulated Gaussian noise, localization errors are depth-dependent. For low levels of added noise, errors are similar for both deep and superficial sources. CONCLUSION: It was found that if the signal-to-noise ratio is above a certain threshold, localization errors in realistic head models are, on average the same for deep and superficial sources. As the noise increases, localization errors increase, particularly for deep sources.

Brain activity and cognitive status in pediatric patients: development of a clinical assessment protocol.

The purpose of this study was to test the validity of a new computerized task to assess children's cognitive problem-solving skills using the brain event-related potentials. This event-related potential-computerized cognitive problem-solving task does not require a child to give a verbal or motor (ie, pointing) response. The event-related potential waveforms were recorded from 20 typically developing children. Two nonverbal, problem-solving tasks (tasks 1 and 2) were developed for each of two age groups (5 and 6 years). For each task, single pictures, taken from an existing standardized test of nonverbal problem solving, were individually and sequentially presented on a computer screen. One of the seven pictures was classified as incongruent or outside category; it did not belong with the other pictures. As predicted, the event-related potential amplitudes were significantly larger to the outside- versus within-category pictures. This effect was found for tasks 1 and 2 for the 5- and 6-year-old children. Children as young as 5 years of age reliably exhibit brain activity, which can be used to infer cognitive problem-solving skill. This assessment paradigm may eventually serve as a clinically useful adjunct to a thorough neurologic and neurodevelopmental assessment of selected pediatric populations, such as those presenting with moderate-severe cerebral palsy whose expressive language and motor skills are notably impaired.

Phonological aspects of word recognition as revealed by high-resolution spatio-temporal brain mapping.

We describe, for the first time, the use of high-resolution event-related brain potentials (hrERP) to identify the spatio-temporal characteristics of neural systems involved in phonological analysis. Subjects studied a visual word/non-word that was followed by the brief presentation of a prime letter (e.g. House, M) with the instruction to anticipate the word/non-word formed by replacing the word's first letter with the prime letter. After the prime letter, an auditory target word/non-word was presented that either matched/mismatched expectations (e.g., Mouse/Barn). ERPs were recorded to the onset of the auditory targets and scalp topographical maps were derived for the phonological mismatch negativity (PMN). The PMN reflected phonological analysis and examination of the peak topography revealed that the response was characterized by a prominent frontal, right-asymmetrical distribution. Spatial de-blurring (using current source density maps) indicated that the PMN scalp topography resulted primarily from an active left anterior source. The current results provide the initial evidence for the localization of the intra-cranial generator(s) involved in phonological analysis.

The application of cognitive event-related brain potentials (ERPs) in language-impaired individuals: review and case studies.

There is a substantial body of basic research that has utilized ERPs to investigate the neurological basis of cognition. This research has, in turn, led to the development of practical applications of cognitive ERPs in patient populations. In particular, recent work has focused on the development of ERP-based assessment measures for the neuropsychological assessment of dyslexia and language impairments secondary to stroke. This review describes the innovative assessment methods program (IAMP), an initiative to utilize ERPs for a neuropsychological assessment of patients who cannot be evaluated by traditional methods. The success of this program has demonstrated that ERPs can be used to reliably evaluate an individual's reading and speech comprehension abilities, independent of behavioral and speech production impediments. In contrast to traditional neuropsychological assessment, these ERP methods can discern the cognitive strategies used by an individual to perform a task.

Evaluation of reading comprehension with neuropsychological and event-related brain potential (ERP) methods.

Evidence is presented for the efficacy of a new method of assessing reading comprehension using a standardized reading test that was formatted for computer presentation with simultaneous event-related brain potential (ERP) recordings. Reading comprehension abilities of 23 healthy undergraduate students were evaluated using ERPs. The results revealed a differential ERP response pattern for correct and incorrect test items. These response patterns were observed at individual participant levels. The findings provided further support for the use of ERPs in the neuropsychological assessment of patients who are difficult or impossible to assess using behavioral responses because of concomitant motoric and/or communicative limitations.

Innovations in neuropsychological assessment using event-related brain potentials.

Historically, clinicians have utilized evoked potentials for evaluating sensory functions and neuropsychological tests for evaluating cognitive functions. However, the clinical implementation of event-related brain potentials (ERPs), an on-line index of cognitive processing, remains to be developed fully. We describe a new method for assessing language functions using neuropsychological tests that are formatted for computer presentation with simultaneous ERP recordings. From its inception, there have been two major objectives of this ERP language assessment research. Practically, we have sought to develop assessment techniques that would enable clinicians to evaluate the language functions of individuals with limited behavioral and communicative abilities. Conceptually, we have endeavored to increase the precision of neuropsychological testing through the development of measures that are sensitive to readily identifiable and objective neural responses. This article summarizes the issues central to the development of ERP assessment techniques, reviews recent normative studies with healthy individuals, and suggests some future avenues of research in this area.

Osteogenic growth peptide normally stimulated by blood loss and marrow ablation has local and systemic effects on fracture healing in rats.

Osteogenic growth peptide, a histone H4-related, 14-amino-acid peptide, is an active mediator of local, as well as systemic, osteogenic activity in response to marrow ablation, trauma, and blood loss. In this study, the effect of exogenous osteogenic growth peptide on the healing of femoral fractures in rats was investigated. A fracture at the midshaft of the femur was created in 50 rats. Half of the rats were injected subcutaneously with 25 ng of osteogenic growth peptide per rat per day for the first 7 days after fracture. Radiographs were taken each week, and the diameter of the callus was measured. The femurs of four animals from each group were harvested 1, 2, 3, and 4 weeks after fracture. Two femurs from each group were sectioned for histologic examination, and two were sectioned for measurement of density and mineral content. Marrow was aspirated from the contralateral femurs to establish adhering cell cultures, which were examined for osteogenicity. At 2 weeks, a large increase in mitogenicity and osteogenicity was seen in the marrow-derived cultures from the rats treated with osteogenic growth peptide; this increase was sustained through 4 weeks. Extraction of RNA from the contralateral marrow (systemic expression) and callus (local expression) for amplification with reverse transcription-polymerase chain reaction revealed greater systemic expression of transforming growth factors beta1, beta2, and beta3, fibroblast growth factor-2, insulin-like growth factor-1, and aggrecan throughout the 4 weeks after fracture, whereas types IIA and IIB collagen, link protein, and fibroblast growth factor receptor-3 had a greater local expression. The specimens treated with osteogenic growth peptide had a stronger expression of transforming growth factor-beta1, both locally and systemically. The average diameter of the callus was greater for the treated rats at all time intervals, and peak diameters were 7.58 mm at 3 weeks for the treated rats and 6.64 mm at 2 weeks and 6.63 mm at 3 weeks for the controls. Histological study revealed an earlier organization and faster healing of the treated fractures, as evidenced by the larger, earlier appearance of cartilaginous soft callus and the more rapid organization of bridging trabecular bone. No statistical significance was obtained when these comparisons were made between the groups. These results suggest that osteogenic growth peptide can be used to promote earlier proliferation and differentiation of osteogenic cells in marrow and bone-repair callus, possibly through its effect on the transforming growth factor-beta family.

Latency shifts in the N2b component track phonological deviations in spoken words.

OBJECTIVE: We investigated event-related brain potentials (ERPs) elicited by a novel speech comprehension paradigm modelled after the neuropsychological Token Test. The objective of the study was to determine whether the ERPs were sensitive to differences in the initial phonemes of the speech stimuli. METHODS: Twenty-seven healthy subjects identified incorrect spoken sentences on the computerised Token Test (CTT). The incorrect spoken sentences contained one word that did not match the previously studied animations. The initial phonemes of these words were either different than or similar to the initial phonemes of their correct counterparts. RESULTS: Different initial phonemes were associated with an early N2b, while words having similar initial phonemes resulted in a substantially delayed N2b. CONCLUSION: The delayed latency effect was due to whether the incorrect word's initial phoneme matched or mismatched that of the expected word. In both cases, this component reflected a mismatch with an existing cognitive template maintained in phonological working memory. The results indicate that this mismatching effect reflected primarily attentional detection rather than language processing.

Brain activity and language assessment using event-related potentials: development of a clinical protocol.

To test the validity of a new computerized task to assess children's receptive vocabulary, event-related potentials (ERPs) were recorded from 56 typically developing children ranging in age from 5 to 12 years. This ERP-computerized vocabulary task does not require a child to give a verbal or motor (i.e. pointing) response. Single pictures, from an existing standardized test of receptive vocabulary, were presented on a computer screen and simultaneously named either correctly (congruent) or incorrectly (incongruent) via a computer. As predicted, the N400 amplitude was found to be significantly higher to the incongruent picture-word pair (i.e. the child knew it was an incorrect pairing) than to the congruent picture-word pair (i.e. the child knew it was a correct pairing). This effect was found for each of the four age groups (5 to 6 years, 7 to 8 years, 9 to 10 years, 11 to 12 years). This task accurately estimated current receptive vocabulary in typically developing children. Although still in the development stage, it may eventually serve as an adjunct to a thorough neurological and neurodevelopmental assessment of some children presenting with moderate to severe cerebral palsy.

Performance on WISC-III and WAIS-R NI vocabulary subtests assessed with event-related brain potentials: an innovative method of assessment.

Assessment of intellectual functions is essential for rehabilitative interventions with traumatic brain injury and stroke patients. However, many of these patients are difficult or impossible to assess because of aphasia and physical disabilities that prevent their performance on traditionally administered tests of mental functioning. We present normative evidence obtained from healthy individuals for the efficacy of a new method of assessing such patients using standardized and validated tests formatted for computer presentation and using direct measures of brain activity (event-related brain potentials, ERP) as the measurable response instead of verbal or motor behavior.