Microsurgical C-2 ganglionectomy for chronic intractable occipital pain

The P300 event-related brain potential (ERP) was elicited with visual stimuli using an oddball task in which the subjects made button press responses to discriminate target and standard stimuli. Each stimulus occurred randomly with a 0.50 probability, and 10 trial blocks were presented at 10-min inter-block-intervals (IBIs). P300 amplitude declined reliably across trial blocks, and an interaction between trial block number and electrode site was observed. No habituation effects were found for P300 latency or for N100, P200, or N200 amplitude. The results suggest that P300 amplitude from visual stimuli habituates when short IBIs and a sufficient number of trial blocks are employed. Theoretical implications are discussed with respect to attentional resource allocation and context updating.     

P300 from a single-stimulus paradigm: auditory intensity and tone frequency effects

The P300 component of the event-related brain potential (ERP) was elicited with auditory stimuli in two different tasks. The oddball paradigm presented both target and standard stimuli; the single-stimulus paradigm presented a target but no standard tone stimulus, with the inter-target interval the same as that for the oddball condition. Experiment 1 manipulated stimulus intensity and Experiment 2 manipulated tone stimulus frequency, with the relative target probability maintained 0.20 for both tasks. P300 amplitude and latency were highly similar for the oddball and single-stimulus procedures in both experiments across independent variables. The findings suggest that the single-stimulus paradigm may prove useful in experimental and applied contexts that require very simple ERP task conditions.     

Sensory integration of auditory and visual information.

In exp. I with 3 male and 1 female o, the bisensory recognition of simultaneously presented auditory and visual verbal information was measured as a function of auditory and visual recognition. It is shown that bisensory performance is superior to performance predicted by a model that assumes the 2 modalities are processing the information independently. Instead integrative processing is suggested. In previous studies using theory of signal detectability (tsd), independent processing of bisensory presentations of mathematically equivalent stimuli has been shown. Present results suggest that the mathematically equated stimuli in those studies were not cognitively equivalent. Exp. Ii with 3 male os lends support to this notion by (a) using verbal information in a tsd paradigm, and (b) showing that when the stimuli are equivalent the results are consistent with a model in which bisensory processing occurs integratively on a common decision axis. However, when the stimuli to each mode are not equivalent, results are consistent with a model in which bisensory processing occurs independently on separate decision axes. (french summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Speech-evoked cognitive P300 potentials in cochlear implant recipients

The cognitive P300 evoked potential was elicited by speech stimuli in successful cochlear implant recipients, and the resulting P300 morphology was remarkably similar to that of normal-hearing individuals. The P300 was elicited by the synthesized speech pair/da/and/di/ presented using an oddball paradigm to nine "good" Nucleus cochlear implant users and nine age-matched normal-hearing subjects (34-81 yr old). There were no significant differences in P300 amplitude and latency between the two groups. Moreover, the N1 and P2 potentials occurred at similar latencies in the two groups, although the N1 amplitude was significantly smaller in the cochlear implant users. The P300 was absent in one "poor" cochlear implant user. The results suggest that the P300 may serve as a useful tool for evaluating the cognitive aspects of auditory processing in cochlear implant recipients, and that it may aid in assessing the success of cochlear implantation.     

Brain evoked potential in schizophrenic patients

The authors reviewed the literature on evoked potentials in mentally ill patients, with particular emphasis on schizphreniacs. The commonly observed abnormalities were as follows: 1) higher SEPs amplitudes with less waveshape variability during first 100 ms in non-depressed chronic, paranoid or undifferentiated patients with florid psychotic symptoms; normal SEPs amplitudes in acute or latent schizophrenics and in chronic depressed schizophrenics but without florid psychotic symptoms; 2) reduced SEPs and VEPs amplitude recovery and faster latency recovery; 3) reduced AEPs amplitude and latency; 4) greater VEPs waveshape variability and tendency to be "reducers" in hallucinating patients; reduced amplitude and latency recovery; prolonged latencies in patients with positive family history (schizophrenia or affective disorders in close relatives); prolonged N2 latency in motor responses to "easy" and "difficult" stimuli; reduced activity of "late potentials"; 5) greater waveshape variability in all modalities in chronic schizophrenics, abnormal P300 (reduced amplitude, lack of P300 or negative "effect of uncertainty") and abnormal CNV (less "readiness" potential, prolonged negativity with motor responses).     

ERP components elicited in response to warning stimuli: the influence of task difficulty

A series of experiments were conducted to systematically evaluate the relative contributions of task difficulty and stimulus probability to P300 amplitudes. Scalp event-related potentials (ERPs) were recorded and the topographic distributions were evaluated during a multi-level cognitive task with an antecedent warning. In three separate studies, task difficulty (five levels), probability or expectedness (10-60%), and randomness (random or blocked presentation) were manipulated. Response accuracy, subjective ratings, and reference-free averages of the P300 components elicited by the warning stimuli were evaluated. Statistical analysis indicated that significantly larger P300s were associated with the more difficult task warnings except when memory tasks were presented in a blocked design, suggesting that neither task difficulty nor probability alone can account for variations in the P300 in a multi-level task scenario. Results are discussed with regard to adaptation-level theory.     

Verbal redundancy in multimedia learning: When reading helps listening.

Three studies investigated whether and under what conditions the addition of on-screen text would facilitate the learning of a narrated scientific multimedia explanation. Students were presented with an explanation about the process of lightning formation in the auditory alone (nonredundant) or auditory and visual (redundant) modalities. In Experiment 1, the effects of preceding the nonredundant or redundant explanation with a corresponding animation were examined. In Experiment 2, the effects of presenting the nonredundant or redundant explanation with a simultaneous or a preceding animation were compared. In Experiment 3, environmental sounds were added to the nonredundant or redundant explanation. Learning was measured by retention, transfer, and matching tests. Students better comprehended the explanation when the words were presented auditorily and visually rather than auditorily only, provided there was no other concurrent visual material. The overall pattern of results can be explained by a dual-processing model of working memory, which has implications for the design of multimedia instruction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Laboratory cost control and financial management software

Event-related potentials (ERPs) evoked by light flashes and auditory tones in a standard odd-ball procedure were recorded from Fz, Cz and Pz scalp sites. Tonic pain was evoked by immersion of the hand in cold water (5 degrees C). Significant effects of pain were found in responses to target stimuli but not in responses to non-target stimuli. P300 wave was affected more than the earlier P200 component. The reduction of P300 amplitude was the strongest effect, both in auditory and visual tests. P300 latency was not significantly affected. Difference curves (target minus non-target ERPs) showed the additional effects: latency of P200 component was elongated and its amplitude enlarged but only in auditory experiments. In control experiments with warm water stimulation no significant alterations of P300 or P200 components were found. The results show that the effect of tonic pain is specific: it predominantly affects the processes that manifest themselves as amplitude changes of P300 components in responses to target stimuli.     

A case report of an epidermal papilloma in Mustelus canis

The performances of 12 EMR and 12 nonretarded sixth-grade children on a perceptual learning task were compared to investigate the information processing of visually presented stimuli in individuals with different intelligence levels. A minicomputer flashed either familiar (lowercase) or unfamiliar letters (Gibson-like figures) in either a stimultaneous or successive mode on a same-different matching task. The computer automatically calculated accuracy and latency data for each subject. Results showed that accuracy was superior in the nonretarded group and that mean latencies for the EMR group was consistently higher than those of the nonretarded group. However, when latencies were corrected for differences in basic reaction time, there were no significant differences between the groups in the speed of processing the information.     

The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies

An experiment was conducted to relate individual components of the event-related brain potential to specific stages of information processing in a two-choice reaction time (RT) task in a group of undergraduate students. Specifically, the latency of the P300 component and the lateralized readiness potential (LRP) were studied as a function of variations in stimulus degradation and response complexity. It was hypothesized that degrading the stimulus would delay the P300 and LRP to the same extent as RT, and that increasing response complexity would affect RT but not P300 latency. The extant literature did not permit any hypothesis regarding the effect of response complexity on LRP latency. The two task variables were found to have additive effects on RT. As predicted, variations in stimulus degradation influenced the latencies of both components, whereas alterations in response complexity had no effect on P300 latency. A significant new finding was that the onset latency of the LRP remained unchanged across levels of response complexity. The overall pattern of results supports the notion of temporal selectivity of stage manipulations that is derived from discrete stage models of human information processing. Furthermore, these results refine the functional interpretation of the LRP by indicating that within the conceptual framework of a stage model the processes this component indexes succeed the start of response choice but preceded the start of motor programming.     

Mental comparison: P300 component of the ERP reflects the symbolic distance effect

The symbolic distance effect was studied in a numerical comparison task by means of behavioural measures and event-related potentials (ERP). Two numbers in the range from 11 to 20 were presented simultaneously and the subjects had to indicate if the right side number was smaller or larger than the left side number. Reaction time, error rate and ERPs were selectively averaged according to the numerical differences between the two numbers. The symbolic distance effect was confirmed: Reaction times and error rates decreased significantly with increasing difference between the two numbers. A significant distance effect was also found for both P300 amplitude and latency. The larger the numerical difference the larger the P300 amplitude and the P300 latency tended to be shorter. This finding suggests that the numerical difference is effective already during stimulus encoding.     

Redundancy gains and costs in cognitive processing: Effects of short stimulus onset asynchronies.

In 7 experiments, the influence of varying stimulus onset asynchronies (SOAs) on the processing of redundant information about words and pseudowords was investigated. All stimuli were visually presented once or twice with 2 copies of the same item flashed either simultaneously or with short SOAs between presentations. The experiments revealed a redundancy gain for words that was absent for pseudowords. Furthermore, the redundancy gain disappeared at an SOA of 50 ms, and them was a gradual performance decline at longer SOAs. However, probing SOAs of 150 and 300 ms revealed that, compared with presentation of 1 target stimulus alone, words were processed significantly faster when target and redundant copy appeared with a 150-ms lag. The results are tentatively explained in a neurocognitive framework (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

P300 habituation from visual stimuli?

The P3(00) event-related brain potential (ERP) was elicited with visual stimuli using an oddball task in which the subject indicated with a finger tap response the occurrence of a target stimulus that occurred randomly on 20% of the trials and refrained from responding to a standard stimulus. A total of six trial blocks were collected, with an equal number of artifact-free epochs averaged for both stimulus types. P3 amplitude from the target stimuli did not decrease across trial blocks; P3 amplitude from the standard stimuli did decrease across trial blocks. P3 latency from both the target and standard stimuli increased across trial blocks. No changes in amplitude or latency independent of the P3 effects were obtained for the other ERP components with trial block. The results suggest that P3 components elicited by visual stimuli do not readily habituate for actively discriminated target stimuli. The theoretical implications are discussed in the context of previous findings.     

Potential pitfalls of initiating a newborn hearing screening program

To compare auditory and visual P300 amplitude and latency magnitudes and topographies in patients with narcolepsy and normal subjects, 20 patients with polysomnographically-confirmed narcolepsy and 40 normal subjects were administered auditory and visual P300 testing using 31 evenly spaced scalp electrodes. Patients with narcolepsy were then administered baseline polysomnograms and objective (MSLT, Maintenance of Wakefulness Test or MWT) and subjective tests (Epworth Sleepiness Scale, Clinical Global Impression) of daytime sleepiness. Patients had longer 31-electrode mean age-adjusted auditory P300 latencies (406.0 +/- 27.8 vs. 385.7 +/- 28.9 ms, p = 0.012) and visual P300 latencies (427.3 +/- 29.0 vs. 411.4 +/- 27.7 ms., p = 0.044) than 40 normal subjects in the same age range. Age-adjusted auditory P300 latency was correlated with MWT (r = -0.49, p = 0.028), but not with any other clinical variable or measure of sleepiness. Age-adjusted visual P300 latency was not correlated with any clinical variable or measure of sleepiness. Patients with narcolepsy had longer auditory and visual P300 latencies than normal subjects.     

Shifting attention between global features and small details: an event-related potential study

In two experiments, large letters H or Z composed of small letters (also H or Z) were presented. Subjects had to make a two-choice motor response (e.g. H--left key, Z--right key). A cue presented 500 ms before the letter indicated which level (global or local) was relevant. In Experiment I, a third letter (T) sometimes appeared either at the cued or the non-cued level; in the former case, subjects had to shift their attention and to respond to stimulus features located at the non-cued level. The interference effect (RT delay in response to incongruent stimuli as compared to congruent ones) was larger when the local, rather than global, level was cued. A slow anterior negativity preceding globally-cued stimuli and shorter N1 and P2 ERP component latencies to these stimuli indicated better preparation for processing of global, as compared to local, stimulus features. The shift from local to global focus yielded a larger increase of RT, error rate, and of the P600 latency than the global-to-local shift. The P600 latency changes were parallel to those of RT. In Experiment II, the attentional shift was provoked by stimulus color red-colored letters meant that the cue was invalid, and thus, subjects had to respond to the non-cued level. Neither the interference nor the attentional shift demonstrated any asymmetry between the global and local levels. ERPs also did not differ substantially after local and global cues. In the condition demanding a shift of focus (invalid cue, incongruent letter), a positive deflection of the lateralized readiness potential indicated the activation of the wrong response channel. The large RT increment in this condition was not accompanied by an increase of the P600 latency. Two possible mechanisms of attentional shift may be proposed, the first related to perceptual processes (e.g. an additional visual search), and the second, to the competition between two response intentions.     

Accidental inhalation of a foreign body. Presentation of 2 cases with atypical symptoms

Nonretarded and mildly retarded adults were compared in two experiments on an 8-choice reaction time (RT) task. Stimulus lights were either distant or close. Both groups responded more slowly when stimuli were distant, this effect being more marked for retarded subjects. Patterns of latencies suggested that, compared with nonretarded subjects, retarded subjects inspected information input for longer periods of time and made more inspections before responding. Faster RTs to stimuli nearest the ends and midline of the display and to stimulus repetitions indicated that retarded subjects were more reliant upon more discriminable cues in the stimulus display.     

Motor coactivation revealed by response force in divided and focused attention.

Four experiments examined effects of bimodal stimulation on response force (RF) in addition to reaction time (RT). In a divided-attention task (Exps 1–3), Ss were asked for a speeded response to either a visual or an auditory signal. In unimodal signal trials, either a visual or auditory signal was presented alone, and in redundant-signals trials, both signals were presented simultaneously. The same stimulus arrangement was used in a focused-attention task (Exp 4), but Ss had to withhold their response when an auditory signal was presented alone. In all experiments, the fastest RTs were attained in redundant-signals trials. In addition, RF was largest in redundant-signals trials, especially in the divided-attention task, suggesting a motor coactivation hypothesis. The results indicate that the type of stimulation influences not only when a response is initiated but also how the response is executed. This finding challenges the view, commonly held in mental chronometry, that late motoric processes remain untouched by experimental manipulations. A detailed analysis of the relationship between RT and RF revealed that these variables are not inherently redundant measures, and therefore, RF recording may supplement the traditional RT measurement in mental chronometry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related potentials (P300) in primary headache in childhood and adolescence

There is strong evidence for a loss of habituation during cognitive processing in migraine as measured by P300 and contingent negative variation in adults. Event-related potentials evoked by an oddball paradigm have not yet been studied in children and adolescents suffering from different primary headache types. We recorded visually evoked event-related potentials (two consecutive trials, 200 stimuli each) in 48 children and adolescents suffering from migraine without or with aura, from episodic tension-type headache, and from ergotamine-induced headache and analyzed the latencies, amplitudes, and reaction times. No statistically significant differences were noted between all headache types and healthy controls analyzing the averaged parameters for the whole measurement. However, a highly significant loss of cortical habituation as measured by P300 amplitude and latency could be observed in migraine without and with aura by analyzing the first and the second trial of measurement separately. This phenomenon increased with age and could not be seen in healthy controls, or patients with tension-type headache or ergotamine-induced headache. Our data suggest a specific cognitive processing in migraine even in children and adolescents. Measurement of the habituation effect in P300 latency and amplitude provides a specific method to differentiate between primary headache types in childhood and adolescence.     

Express saccades elicited during visual scan in the monkey

Monkeys trained to saccade to visual targets can develop separate "express" and "regular" modes in their distribution of saccadic latencies. The purpose of this study was to determine whether this occurs under more natural viewing conditions, when targets are suddenly presented in a structured visual field during visual scan. It was found that scanning saccades stopped appearing 60 msec after a target's onset, and subsequent saccades, which were directed toward the suddenly appearing target, had a bimodal distribution of latencies. Express saccades were more likely to occur as the target was presented later in a fixation. Regular mode saccades were more likely to occur with longer target durations. Scanning saccades made to stimuli of the structured visual field always had unimodal inter-saccadic interval distributions. All these effects were apparent after only 2-3 days of training. These findings, taken together with recent physiological results, suggest that the visuomotor cells of the superior colliculus mediate latency bimodality.     

Discriminative power of visual evoked potential characteristics in multiple sclerosis

To investigate the discriminative power of pattern-reversal visual evoked potential characteristics (peak latencies and amplitude) and to test whether the addition of visual evoked potential amplitude can increase the power of the visual evoked potential in the diagnosis of multiple sclerosis, we retrospectively studied visual evoked potentials in 59 patients with definite multiple sclerosis and 126 control subjects. Two check sizes (17' and 10') were used. Females had significantly higher amplitudes and shorter latencies than males. N80 latency showed a gradual increase and P100 amplitude a decrease with age. P100 latency was stable between the ages of 20 and 55 years but was increased in childhood and the elderly. The significance of visual evoked potential peak latencies and amplitude in separating the two groups was investigated by means of a (multivariate) discriminant analysis. The visual evoked potential with a pattern of 10' could be measured in 58% of patients with multiple sclerosis. The exclusive use of the P100 amplitude in the discriminant analysis resulted in a percentage of correctly classified cases of 84%, whereas for P100 and N80 latency it was 85% and 90%, respectively. With the 17' pattern, the N80 latency yielded also a higher correct percentage than did the P100 latency. Although N80 latency is, to a greater extent than P100 latency, influenced by age, sex and size of stimulus pattern, when these influences are accounted for, the N80 latency is a more sensitive measure than P100 latency in the classification of multiple sclerosis. Combined use of latency and amplitude for discriminant analysis yielded no significant improvement of the percentage of correctly classified cases.