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PubMed1981

The influence of low-level transcortical DC-currents on response speed in humans.

Low-level direct currents (DC) are thought to polarize brain tissue and to affect brain processes. The present experiments investigated the effects of low-level transcortical DC-currents on response speed and physiological variables in humans. The DC-currents were applied during the warning interval within a constant foreperiod reaction time paradigm. Currents of less than 0.3 mA were applied between a vertex electrode and a noncephalic reference. The polarity of the electrical source varied randomly across trials within subjects. The first two studies showed that subjects respond fastest when the positive pole is applied to the vertex. Under the same conditions higher skin conductance responses were observed as compared to vertex negative conditions. The dynamics of the observed responses suggest that the brain "learns" to respond differentially to the different current polarities. This was confirmed by the third study, which documented different conditioned electroencephalic responses subsequent to current application.

Cerebral Cortex↗
PubMed1984

A new approach to endogenous event-related potentials in man: relation between EEG and P300-wave.

The family of late positive waves which occur at latencies of 250 to 500 msec (P300) has been the most widely studied endogenous event related potential of the brain. We performed experiments with human subjects by applying repetitive acoustical tone bursts; every third or fourth signal was omitted. The endogenous potential related to the omitted stimulation was first averaged. The averaged record was then transformed to frequency domain with Fourier analysis in order to obtain the frequency characteristics. We observed frequency selectivities between 1-2.5 Hz, 3-8 Hz and between 8-13 Hz. After this procedure, single epochs of prestimulus EEG and endogenous potentials were pass-band filtered in the above frequency ranges. The comparison of filtered prestimulus EEG and of single endogenous responses gave the following results: In delta and theta frequency ranges the EEG prior to omitted stimulation showed in most of the trials a phase-reordering; the P300-wave seems to be a continuation of the ordered and stationary pre-EEG. In some cases the P300-wave depicts an amplitude-enhancement against the delta and theta components of the pre-EEG. Alpha-enhancement and alpha-blocking also make important contributions to the organization of the endogenous event-related potentials.

Adult↗
PubMed1985

CNV and time estimation.

We investigated the hypothesis that the development and resolution of CNV waves may, in part at least, reflect time estimation processes in the nervous system. Specifically, we postulated that subjects with a high degree of accuracy in time estimation tasks will show a fast resolution of the negativity following the imperative stimulus (S2). The results showed that, consistent with the hypothesis, accurate estimators, as a group, show CNVs with faster resolution of negativity after S2. In addition, they have CNVs of lower amplitude and show a slower rise time to peak negativity than subjects with poor time estimation abilities.

Adult↗
PubMed1985

Short-term memory and averaged evoked cortical potentials.

Cortical electrical activity reflected by changes in N1 and CNV evoked potentials was compared to performance on a battery of neuropsychological measures of attention and short-term memory. Results supported the hypothesis that N1 reflects the accuracy of the short term memory image. Attentional processes indexed by CNV also appeared to be involved in establishing the memory trace. The two cortical generators appear to interact in some types of short-term memory tasks, but not in others.

Adult↗
PubMed1997

Electrophysiological analysis of expectancy: P3 in informed guessing.

18 healthy subjects had to guess, which of two nonequiprobable events would occur next. Each trial was preceded by a cue which increased the probability of the corresponding event as compared to its global probability. Event-related potentials (ERPs) were recorded and then classified according to global probability of events, their relation to the preceeding cue (valid versus invalid cues) and to subject's prediction (predicted versus nonpredicted). Two late positive waves (P350 and P550) with parietal maxima were distinguished. Both waves had larger amplitudes in response to improbable events than to highly-probably events. Similarly, both had larger amplitudes following invalid cues than following valid cues, and this difference was larger in those subjects who tended to follow the cue than in those who tended to reject it. No difference in terms of ERP component amplitudes was found between predicted and unpredicted events; however, the latency of the P350 peak was longer following unpredicted events. Taken together with data of the literature, the present results indicate that ERP allow us to distinguish between two meanings of the word "expectancy": (1) the rule-related expectancy as cognitive estimation of the likelihood or "representativeness" of an event (based on grasping event contingencies), and (2) the goal-related expectancy manifested in the subject's overt behavior. Only the former "expectancy" affects the amplitude of the late positive wave ("P3"), while the latter does not.

Adolescent↗
PubMed2006

Multiple sources of positive- and negative-priming effects: an event-related potential study.

Event-related potential correlates of positive priming (PP) and negative priming (NP) were investigated in order to further elucidate the cognitive mechanisms involved. Thirty-six participants performed both an identity- and a location-based priming task. Repeating the target stimulus/location from the immediately preceding display produced behavioral PP. With localization, but not with identification, behavioral NP was observed when the target stimulus/location matched the preceding distractor stimulus/location. Smaller P300 amplitude accompanied identity-based PP, suggesting persisting target-specific activation. The lateralized readiness potential, an index of correct/incorrect response activation, indicated persisting central motor activation as another source of PP. Both location-based PP and NP were accompanied by reduced P1/N1 and P300 amplitudes, pointing to the involvement of inhibition of return in location-based priming. The results support the view that multiple brain processes underlie behavioral priming.

Adult↗
PubMed2002

Functional localization and mechanisms of sequential effects in serial reaction time tasks.

Reaction times (RTs) to randomly ordered stimuli are influenced in various ways by the sequence of preceding events. Depending on the response-stimulus interval and stimulus-response compatibility, cost-only or cost-benefit patterns can be observed. In order to localize these effects within the information-processing system, different sequential patterns were induced in overt performance. RTs and amplitude developments of the lateralized readiness potential (LRP) across several trials indicated the accumulation of residual traces as a possible mechanism underlying sequential effects. Analysis of LRP onsets indicated two possible loci of action of such traces. Whereas in motoric stages trace accumulation appeared to produce processing advantages only for continued event repetitions, without corresponding costs for discontinuations, cost-benefit patterns were consistently observed in premotoric stages.

Adolescent↗
PubMed2004

A clockwork orange: compensation opposing momentum in memory for location.

Libet, Gleason, Wright, and Pearl's (1983; Libet, 1985) influential work using a clock-watching task suggests that voluntary actions are initiated in motor cortex prior to the point where the participant claims to have initiated that action. Joordens, van Duijn, and Spalek (2002) showed that a bias exists in this task with respect to the participants' reports of initiation times. Joordens et al. assumed that this bias was primarily due to motion cues that are very much like those used to elicit phenomena such as representational momentum. In the present Experiment 1, it is demonstrated that this bias disappears when a mouse-click response is used in place of a temporal-order judgment. This finding, however, is actually more confusing than clarifying given that the procedural parallels with representational momentum are still present and should be supporting a bias. In the three subsequent experiments the view that a bias is indeed present, but that it is opposed by an opposite-acting compensation process, is proposed and tested. Implications for both representational momentum and for the general use of clock-watching tasks (e.g., Libet et al., 1983) are highlighted.

Association Learning↗
PubMed2001

Multiple bottlenecks in information processing? An electrophysiological examination.

When two stimuli are to be processed in rapid succession, reaction time (RT) to the second stimulus is delayed. The slowing of RT has been attributed to a single processing bottleneck at response selection (RS) or to a central bottleneck following the initiation of the first response. The hypothesis of a response initiation bottleneck is mainly based on reports of underadditive interactions between stimulus onset asynchrony (SOA) and the number of stimulus-response alternatives (simple vs. two-choice response). The present study tested the hypothesis of a response initiation bottleneck by recording the lateralized readiness potential (LRP), a brain wave, emerging during or immediately following RS. The LRP findings were consistent with a central bottleneck but did not support the late bottleneck hypothesis. Instead, the LRP provided direct evidence that the underadditive interaction of number of alternatives and SOA is due to an increase of response anticipations in the simple response condition.

Adult↗
PubMed2000

Neural representation of consciously imperceptible speech sound differences.

The concept of subliminal perception has been a subject of interest and controversy for decades. Of interest in the present investigation was whether a neurophysiologic index of stimulus change could be elicited to speech sound contrasts that were consciously indiscriminable. The stimuli were chosen on the basis of each individual subject's discrimination threshold. The speech stimuli (which varied along an F3 onset frequency continuum from /da/ to /ga/) were synthesized so that the acoustical properties of the stimuli could be tightly controlled. Subthreshold and suprathreshold stimuli were chosen on the basis of behavioral ability demonstrated during psychophysical testing. A significant neural representation of stimulus change, reflected by the mismatch negativity response, was obtained in all but 1 subject in response to subthreshold stimuli. Grand average responses differed significantly from responses obtained in a control condition consisting of physiologic responses elicited by physically identical stimuli. Furthermore, responses to suprathreshold stimuli (close to threshold) did not differ significantly from subthreshold responses with respect to latency, amplitude, or area. These results suggest that neural representation of consciously imperceptible stimulus differences occurs and that this representation occurs at a preattentive level.

Adult↗
PubMed2004

The effects of age on the neural correlates of successful episodic retrieval: an ERP study.

The neural correlates of successful episodic retrieval (recollection), as reflected in event-related potentials (ERPs), were investigated in young (ca 20 years; n = 18) and older (ca 70 years; n = 16) healthy individuals. Subjects classified a series of pictures according to whether each item was new or had been encountered at study in the context of an animacy or a size judgment task. By manipulating the number of times items were presented for study, subsets of test items were formed for which source accuracy did not differ according to age. Relative to ERPs elicited by unstudied pictures, ERPs elicited by items attracting equivalent levels of source accuracy showed marked age-related differences. Those from younger subjects demonstrated the positive-going left parietal and right frontal old/new effects described in several previous studies of source memory. By contrast, analogous ERPs from older subjects contained a large left-lateralized negative effect that overshadowed the positive-going effects evident in the young. No age-related differences in either parietal or frontal ERP old/new effects were detected at electrode sites overlying the right hemisphere. It is possible that the age-related ERP differences observed in this task primarily reflect the use of different kinds of information as a basis for source judgments.

Adolescent↗
PubMed2005

Effects of visual attentional load on low-level auditory scene analysis.

The sharing of processing resources between the senses was investigated by examining the effects of visual task load on auditory event-related brain potentials (ERPs). In Experiment 1, participants completed both a zero-back and a one-back visual task while a tone pattern or a harmonic series was presented. N1 and P2 waves were modulated by visual task difficulty, but neither mismatch negativity (MMN) elicited by deviant stimuli from the tone pattern nor object-related negativity (ORN) elicited by mistuning from the harmonic series was affected. In Experiment 2, participants responded to identity (what) or location (where) in vision, while ignoring sounds alternating in either pitch (what) or location (where). Auditory ERP modulations were consistent with task difficulty, rather than with task specificity. In Experiment 3, we investigated auditory ERP generation under conditions of no visual task. The results are discussed with respect to a distinction between process-general (N1 and P2) and process-specific (MMN and ORN) auditory ERPs.

Acoustic Stimulation↗
PubMed2005

Neurocognitive effects of phobia-related stimuli in animal-fearful individuals.

Two experiments were conducted to explore neurocognitive effects of phobia-related stimuli. Contingency assessments and event-related potentials (ERPs) were collected from animal-fearful individuals during probabilistic classification learning in diverse motivational-affective contexts. As revealed by ERPs, attentional amplification of cortical sensory processing occurred in response to phobia-related stimuli. In particular, the posterior selection negativity in the ERPs to phobia-related stimuli had its origin in a bottom-up route, probably the amygdaloid-extrastriate cortex path. No evidence for top-down modulation of phobia-related attentional amplification was obtained. The covariation bias occurred only when aversive motivational-affective expectancies prevailed, suggesting a role of retrieval from associative emotional memory. Finally, phobia-related cue competition was probably related to the disruption of elaboration in memory of neutral and aversive stimulus pairings that was induced by belonging pairings of phobia-related and aversive stimuli. The findings have far-reaching implications for the interface between cognition and emotion.

Adolescent↗
PubMed1980

[Analysis of resolution of CNV (author's transl)].

The present study was designed to explore the factor affecting the resolution of CNV by using the paradigm in which the attention was experimentally manipulated. The control group (N=13) was given an instruction for conducting the ordinary CNV task, while the experimental group (N=26) was instructed to direct the attention to the different S2 durations. The results obtained showed that in the control group the CNV resolution occurred after the S2 onset, although in the experimental group the resolution occurred after the S2 offset. Considering the findings of this study and of Kakigi, Matsuda, and Hagino (1978) together, it was suggested that the CNV resolution was initiated by the psychological factor, not depending upon the external stimulus nor the key pressing response.

Adult↗
PubMed1989

[Event-related potentials and cognitive information processing: issues on the studies of selective attention].

Following considerations for some general issues of ERP research on human information processing, recent advances in this field are elaborated by reviewing the literature on selective attention. Sections in this review deal with following subjects: (1) two landmark contributions of Hillyard, Hink, Schwent, & Picton (1973) and Näätänen, Gaillard, & Mäntysalo (1978); (2) the endogenous, attention-related negativity ("Nd" wave), which is considered to consist of three possible components, a modalityspecific Nd, a centrally-maximal, controlled-search negativity, and a frontally-focused Nd; (3) the spatial attention effects on the exogenous components in visual and somatosensory modalities; and (4) the organizations of stimulus selection processes indicated by the latency and interrelations between those ERP components.

Attention↗
PubMed1998

[A study on the response selection and inhibition in a cognitive conflict task using event-related potentials].

This study examined the hypothesis (Eriksen & Schultz, 1979) that a subject checks whether a prepared response is correct or not in the Eriksen and Eriksen (1974) cognitive conflict task, using event-related potentials (ERPs). Fourteen right-handed subjects were required to respond selectively to a central target letter flanked with compatible (e.g., HHHHHHH) or incompatible (e.g., SSSHSSS) noise letters, or not to respond to asterisks (*******). The results showed that the lateralized readiness potential indicating an incorrect preparation and the NO-GO potential reflecting a response inhibition emerged for incompatible stimuli. These findings indicate that a prepared response was recognized as erroneous, and was inhibited. Therefore, it is suggested that the check operation functioned in the cognitive conflict task. Furthermore, the result that the NO-GO potential latency for incompatible stimuli was longer than that for NO-GO stimuli suggests that the timing of NO-GO decision and response inhibition by the check operation influenced the NO-GO potential latency.

Adult↗
PubMed1978

Effects of some psychotropic drugs on M-wave and operant behavior in the squirrel monkey.

The effects of low doses of nabilone, chlorpromazine, pentobarbital, meprobamate, diazepam, chlordiazepoxiOde and d-amphetamine on behavioral responding to cues signalling the availability of food rewards, and on the M-wave, an evoked cortical potential previously reported to reflect the conditioned incentive value of the cues were determined in the squirrel monkey. Nabilone and chlorpromazine simultaneously depressed both the M-wave and behavior. Pentobarbital, meprobamate, diazepam and chlordiazepoxide could depress the M-wave without depressing behavior. This effect was most marked with diazepam. The only augmentation of the M-wave observed was the d-amphetamine, and this occurred in only one of five animals. The benzodiazepines were the only drugs to augment behavioral output. However, diazepam occasionally increased the number of cures responded to while concomitantly decreasing both total behavioral output and the amplitude of the M-wave. It is concluded that the M-wave cannot directly reflect the incentive value of the cue, but must rather reflect something that tends to parallel this value.

Animals↗
PubMed1976

Evoked potential audiometry.

A large number of different components of the auditory evoked potential can be recorded from the human scalp using averaging techniques. It is now possible to evaluate with such evoked potential measurements the functioning of the entire human auditory system from the hair cell receptors to the association areas of cortex. This multiplicity of evoked potential components is important clinically since any one component measurement may be the most appropriate for a certain subject at a certain time, and also because the replication of objective audiological findings using more than one testing method allows greater confidence in the results. As well as providing an accurate means of determining the extent of a hearing loss, evoked potential studies can also provide information concerning the type and location of such a defect.

Adult↗