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PubMed2000

Psychophysiological studies of unattended information processing.

The article describes the general methods and some of the results obtained in the Psychophysiology Laboratory of the University of La Coruña. The paper covers our research on the Simon effect and accessory effect, although it is not a review of the literature. The research strategy we followed is built around the use of lateralized motor potentials recorded from scalp. These measures allow observing the way responses are selected and when they are selected, providing an invaluable tool to study response interference and to split reaction time into two halves. The research on the Simon effect concludes that interference during response selection is critical in the Simon effect but it is dubious whether this process should be considered as automatic and stimulus-driven, as is widely accepted. The experiments with the accessory effect indicate that facilitation is produced before response selection is over, which ends a long controversy about the locus of the accessory effect.

Contingent Negative Variation↗
PubMed2002

Information processing difficulty long after self-reported concussion.

Recovery of cognitive function after mild head injury (MHI) is thought to be relatively swift and complete. The present study replicates and extends previous work in which university students with self-reported concussion demonstrated reduced P300 amplitude on a set of easy and difficult attention tasks, in addition to performing more poorly than controls on demanding cognitive tasks many years after injury. In the present study, 13 students with self-reported concussion (MHI group: M time since injury = 8 years) and 10 controls were matched for age, sex, education, and a variety of cognitive, physical and emotional complaints. Controls outperformed the MHI group on the Digit Symbol substitution task and on a difficult dual task involving tone discrimination and visual working memory. Additionally, controls exhibited larger P300 amplitudes on both an easy and a difficult auditory discrimination task. A combination of electrophysiological, neuropsychological and self-report indices predicted group membership (MHI vs. control) with 88% accuracy. The present results, coupled with previous work, offer preliminary evidence that the combination of event-related potentials and demanding behavioral measures might reveal long-lasting, subtle cognitive problems associated with MHI. These findings may challenge existing notions of complete recovery after MHI.

Acoustic Stimulation↗
PubMed1998

Source dipole analysis of the early components of the RREP.

Occlusion of the inspiratory airway produces a series of early RREP components. The predominant early positive and negative peaks are seen over the parietal and frontal scalp respectively and have been hypothesised to represent parallel activation of somatosensory and motor cortices in a manner similar to electrically produced SEP components. An alternative hypothesis is that both components are produced by somatosensory cortex, with the frontally maximal negativity reflecting the activity of a tangential dipole source. Respiratory-related evoked potentials (RREPs) elicited by brief occlusion of the inspiratory airway, were recorded using 29 scalp electrodes from six subjects. Early latency components were analysed using the Electromagnetic Source Estimation (EMSE) program for modelling equivalent electrical dipoles, in order to suggest likely generator sources. Two hypotheses were tested: first, that radial dipoles generated by both pre- (motor cortex) and post-centrally (somatosensory cortex) produce the early components; and second, that generator sources are limited to the somatosensory cortex, with activity recorded as frontally maximal reflecting volume conduction from tangential dipoles. Results were highly consistent between subjects and suggested that Nf-P1 was best accounted for by two post-central and two pre-central radial dipoles supporting the first hypothesis. Locations of generator sources are discussed in relation to anatomical correlates.

Brain Mapping↗
PubMed1999

High resolution DC-EEG analysis of the Bereitschaftspotential and post movement onset potentials accompanying uni- or bilateral voluntary finger movements.

UNLABELLED: Movement-related potentials (MRPs, including Bereitschaftspotential, BP) were recorded using a 64 channel DC-EEG amplifier ("High Resolution DC-EEG", Nunez et al. 1994) in 18 subjects (Ss) to explore functions of the supplementary, the cingulate, and the primary motor area (SMA, CMA and MI). Spatial and temporal resolutions on single trials, single subject and grand average data were evaluated for preparation and execution of self-initiated index finger extensions (bilateral, right and left unilateral). Results showed that [1] MRPs consisted of six waves: Early component (BP1) of the MRPs, late component (BP2) of the MRPs, Motor potential (MP), Post movement positive potential (PMPP), Movement-evoked potential I (MEP I) and Movement-evoked potential II (MEP II). [2] Onset of BP1 was earliest in the mesial wall motor areas, SMA/CMA, then in the contralateral MI (conMI) and latest in the ipsilateral MI (ipsMI). [3] MRP amplitudes were maximum in the SMA/CMA in all three tasks. In the unilateral tasks, MRP amplitudes were higher in the conMI than they were in the ipsMI. [4] The early BP component (BP1) was always localized in the fronto-central midline (overlying the mesial wall motor areas SMA and CMA). BP2, MP, PMPP, MEP1 and MEP II showed clear lateralized distributions (contralaterally larger) for unilateral movement but not for bilateral movement. [5] BP2, MP, PMPP, MEPI and MEPII in bilateral movement are not just the mathematical sum of right and left unilateral movements on both hemispheres. [6] The three tasks influenced all six MRP components. [7] Current source density maps, which were relatively robust between different tasks, further demonstrated that BP1 stemmed from the fronto-central midline (mesial wall motor areas). [8] MANOVA showed that there were several statistically significant differences (p<0.001) across the multiple combinations between time points of the epoch (20), electrodes (56) and tasks (3). CONCLUSIONS: [1] SMA/CMA participates in preparation and initiation of volitional index finger extensions, while MI participates in their execution and performance. [2] BP1 stems primarily from the mesial wall motor areas, SMA and CMA. [3] SMA/CMA subserves the temporal organization of sequential movements and bimanual coordination.

Adult↗
PubMed2003

Cortical control mechanisms in volitional swallowing: the Bereitschaftspotential.

OBJECTIVE: This research sought to identify a well-defined pre-motor potential, the Bereitschaftspotential (BP), as a manifestation of cortical contribution to the pre-motor planning of volitional swallowing. METHODS: EEG data were collected from 20 research participants during volitional execution of swallowing and finger movement tasks. A5 second pre-movement epoch for each task was triggered on EMG identification of movement onset. A grand average for each task representing approximately 2400 trials across all research participants was derived to compare and contrast morphological features of the derived waveform. RESULTS: Volitional pharyngeal swallowing and finger movement generated similar waveform characteristics of duration and slope; however, statistically significant differences were identified in polarity and in amplitude at four points both early and late in the epoch. Additionally, swallowing produced a pre-motor waveform with a rapid declination of EEG activity in the final 500 msec prior to movement onset. CONCLUSIONS: This study demonstrates activation of the supplementary motor cortex preceding the onset of volitional swallowing. However, unlike purely voluntary movements, the volitional pharyngeal swallowing task, as assessed with this methodology, does not appear to recruit the primary motor cortex. Thus engagement of the swallowing response appears to rely on indirect parallel pathways between extrapyramidal cortical motor planning regions and lower motor neurons.

Adolescent↗
PubMed2004

[Neurofeedback for the treatment of attention-deficit/hyperactivity disorder (ADHD) in childhood and adolescence].

INTRODUCTION: A variety of non-pharmacological treatments for ADHD have failed to prove their effectiveness. The basis of evidence for neurofeedback (or EEG-biofeedback) has improved recently. Neurofeedback is aiming at an improvement of ADHD core-symptoms via the voluntary modification of abnormal neurophysiologic parameters, e.g. EEG-frequency spectrum and event-related potentials. METHODS: Our review presents an overview of the current research on neurofeedback for the treatment of ADHD. RESULTS: In three controlled studies short-term effects of feedback matched those of stimulant treatment. Neurofeedback lead to significant improvement of attention, impulsivity and hyperactivity, without adversive side effects. Additionally, there was a persistent amelioration of EEG parameters, while stimulants did not lead to a comparable normalization. Results on the stability of feedback effects are encouraging but are based on small numbers of patients. CONCLUSION: Neurofeedback is a promising approach for the treatment of children with ADHD. However, there is a demand for further controlled studies using standardized diagnostic criteria, sufficient sample sizes and appropriate measures and follow-up.

Adolescent↗
PubMed1995

Strategies and mechanisms in nonselective and selective inhibitory motor control.

Motor inhibition was studied in 3 versions of the stop-signal paradigm, with the stop signal requiring inhibition of any response (stop-all), a fixed alternative response (stop-change), or selective inhibition of only 1 of the responses (selective-stop). The lateralized readiness potential was used in Experiment 1 to distinguish between a selective, central, and a global peripheral inhibition mechanism. Inhibition was found to be effected by the central mechanism in the stop-change condition and by the peripheral mechanism in the other conditions. Manipulation of stimulus discriminability in Experiment 2 strongly affected the speed of selective motor inhibition, confirming that such inhibition was achieved by conditionally engaging the peripheral mechanism. These results support the idea that functionally distinct mechanisms and strategies are involved in inhibitory motor control in different situations.

Adolescent↗
PubMed1996

Partial advance information and response preparation: inferences from the lateralized readiness potential.

Response speed to a signal is faster when advance information about the forthcoming movement is provided before signal onset. Although this precuing effect is well established, the location of this saving in reaction time (RT) in the information-processing system is controversial. Some authors have claimed that the precuing effect resides at a motoric level, whereas others have suggested a nonmotoric locus. The present experiments used onset latencies of the lateralized readiness potential (LRP) to locate the precuing effect. The results of 2 experiments with a highly compatible (Experiment 1) and with an incompatible (Experiment 2) stimulus-response mapping indicate that this effect resides, at least partially, in the motoric portion of RT. In addition, the LRP amplitude before signal appearance increased with the amount of advance information, supporting a muscle-specific preparation hypothesis.

Adult↗
PubMed1996

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

Event-related brain 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.

Adolescent↗
PubMed1996

Temporal structure of syntactic parsing: early and late event-related brain potential effects.

Event-related brain potentials (ERPs) were recorded from participants listening to or reading sentences that were correct, contained a violation of the required syntactic category, or contained a syntactic-category ambiguity. When sentences were presented auditorily (Experiment 1), there was an early left anterior negativity for syntactic-category violations, but not for syntactic-category ambiguities. Both anomaly types elicited a late centroparietally distributed positivity. When sentences were presented visually word by word (Experiment 2), again an early left anterior negativity was found only for syntactic-category violations, and both types of anomalies elicited a late positivity. The combined data are taken to be consistent with a 2-stage model of parsing, including a 1st stage, during which an initial phrase structure is built and a 2nd stage, during which thematic role assignment and, if necessary, reanalysis takes place. Disruptions to the 1st stage of syntactic parsing appear to be correlated with an early left anterior negativity, whereas disruptions to the 2nd stage might be correlated with a late posterior distributed positivity.

Adult↗
PubMed1997

Electrophysiological evidence on the time course of semantic and phonological processes in speech production.

The temporal properties of semantic and phonological processes in speech production were investigated in a new experimental paradigm using movement-related brain potentials. The main experimental task was picture naming. In addition, a 2-choice reaction go/no-go procedure was included, involving a semantic and a phonological categorization of the picture name. Lateralized readiness potentials (LRPs) were derived to test whether semantic and phonological information activated motor processes at separate moments in time. An LRP was only observed on no-go trials when the semantic (not the phonological) decision determined the response hand. Varying the position of the critical phoneme in the picture name did not affect the onset of the LRP but rather influenced when the LRP began to differ on go and no-go trials and allowed the duration of phonological encoding of a word to be estimated. These results provide electrophysiological evidence for early semantic activation and later phonological encoding.

Adult↗
PubMed1995

Sustained potential shifts in the toad tectum reflect prey-catching and avoidance behavior.

Sustained potential shifts (SPS) were recorded for 10 s from the surface of the optic tectum of toads presented with live prey and moving artificial prey stimuli. On the anterior tectal surface, a negative SPS was followed by a positive wave; the converse was true for the posterior tectum. Some animals were immobilized, and they exhibited a monophasic negative SPS in the anterior tectum and a positive wave in more posterior regions. The number of orienting responses made by toads to moving "wormlike" stimuli was reflected in the amplitude of the SPS, as was avoidance to stimuli in an "antiworm" configuration. Behavioral activity was most closely related to the negativity of the SPS recording. The SPS of toads responding to live prey showed no direct time relationship between the SPS and behavior, suggesting that the SPS reflects sensory or decision-making activity rather than the consequent behavior.

Animals↗
PubMed2006

Stereotype activation and control of race bias: cognitive control of inhibition and its impairment by alcohol.

Two experiments tested the hypothesis that alcohol increases race-biased responding via impairment of self-regulatory cognitive control. Participants consumed either a placebo or alcohol and then made speeded responses to stereotypic trait words presented after White and Black face primes while behavioral and event-related brain potential (ERP) data were recorded. Alcohol did not affect stereotype activation in either experiment. Experiment 2 showed that alcohol significantly impaired the ability to inhibit race-biased responses but did not reliably influence control of counterstereotypic responses. This disinhibition appears driven by impairment of regulative cognitive control, as indexed by amplitude of the negative slow wave ERP component. These findings suggest that controlling racial bias can be a function of effective implementation of basic self-regulatory processes in addition to the motivational processes identified in other research.

Adult↗
PubMed2005

Preparation for speeded action as a psychophysiological concept.

Mental preparation aids performance and induces multiple physiological changes that should inform concepts of preparation. To date, however, these changes have been interpreted as being due to a global preparatory process (e.g., attention or alertness). The authors review psychophysiological and performance investigations of preparation. Concepts of the central regulation of action offer an integrative framework for understanding the psychophysiology of preparation. If people process multiple streams of information concurrently, then preparatory processing requires a form of supervisory attention- central regulation to maintain unity of action. This concept is consistent with existing psychophysiological results and links them to current views of information processing. Conversely, psychophysiological measures may provide indices to test concepts within theories of the central regulation of action.

Arousal↗
PubMed2005

Dynamic aspects of stimulus-response correspondence: evidence for two mechanisms involved in the Simon effect.

It has been recently proposed that the time course of the Simon effect may vary across tasks, which might reflect different types of stimulus-response (S-R) transmissions (E. Wascher, U. Schatz, T. Kuder, & R. Verleger, 2001). The authors tested this notion in 4 experiments by comparing Simon effects evoked by horizontal and vertical S-R arrangements. The temporal properties of the effect, as well as lateralized readiness potential-difference waves, indicated a fast and transient influence of the horizontal, but a slow and sustained influence of the vertical spatial stimulus feature on performance. Additional evidence for this temporal dissociation was obtained in experiments that induced a shortening or lengthening of the mean response time. Thus, the data strongly indicate that there are 2 temporally dissociable mechanisms involved in generating the Simon effect for horizontal and vertical S-R relations.

Adolescent↗
PubMed2003

Phonological encoding is not contingent on semantic feature retrieval: an electrophysiological study on object naming.

In the present study, the authors examined with event-related brain potentials whether phonological encoding in picture naming is mediated by basic semantic feature retrieval or proceeds independently. In a manual 2-choice go/no-go task the choice response depended on a semantic classification (animal vs. object) and the execution decision was contingent on a classification of name phonology (vowel vs. consonant). The introduction of a semantic task mixing procedure allowed for selectively manipulating the speed of semantic feature retrieval. Serial and parallel models were tested on the basis of their differential predictions for the effect of this manipulation on the lateralized readiness potential and N200 component. The findings indicate that phonological code retrieval is not strictly contingent on prior basic semantic feature processing.

Adolescent↗
PubMed2006

Fundamental properties of the N2pc as an index of spatial attention: effects of masking.

Masking is an important tool in many paradigms used to study the cognitive architecture. The N2pc is an electrophysiological event-related potential (ERP) that has been used as a tool to study the deployment of visual spatial attention. The aim of this paper was to study the effects of masking on the N2pc. Two stimuli were presented on the screen, one to left and one to right of fixation, and subjects reported the identity of one of them. The targets could be discriminated both by their category (letters vs. digit) and by their colour (pink vs. green). Backward masking was produced by presenting a second pair of bilateral stimuli after the offset of the first pair. The second pair of stimuli consisted of characters of the same colour and category as in the first pair. Forward masking was produced by using the very same stimuli as in the backward masking condition, but by instructing subjects to report the second stimulus. The forward mask trials had longer response times compared to no-mask trials, and backward mask trials had even longer response times, and also a higher error rate. Although the different masking procedures lead to clear behavioural effects, the N2pc was not affected, suggesting that the deployment of visual spatial attention, per se, was not affected by pattern masking. A sustained posterior contralateral negativity (SPCN) following the N2pc was also found (300 ms post-target, and beyond), and the amplitude of the SPCN was strongly modulated by the number of presented stimuli and the duration of the SPCN was positively correlated with RT in the behavioural task. We hypothesize that the SPCN reflects neural activity associated with the passage of information through visual short-term memory.

Adult↗