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J Hohnsbein

Publications and source records attributed to J Hohnsbein.

At least 19 recordsLinked to original sources
PubMed1998

Performance differences in reaction tasks are reflected in event-related brain potentials (ERPs).

Event-related potentials (ERPs), which can be extracted from the electroencephalogram (EEG), are assumed to reflect distinct cognitive processes in real time. Hence ERP analysis could be used in cognitive ergonomics as a tool to specify, for example, bottlenecks or sources of individual performance differences. Such specific results may be helpful to change the tasks or train the subjects specifically. In the present exploratory study, the authors investigated whether subjects with large spontaneous differences in performance accuracy, as defined by their error rates in a speeded binary choice reaction task, also differ in the structure of their ERPs. The ten subjects were divided post hoc into two groups with relatively low (about 6%) and high (about 20%) error rates. While the reaction times were not significantly different for both groups, the ERPs revealed clear group differences. First, large differences were seen in the late part of the contingent negative variation (late CNV), which is assumed to reflect preparatory processes. Subjects with few errors ('GOOD') had a large late CNV, while subjects with many errors ('POOR') showed virtually no late CNV. Second, the late P300-subcomponent (which is related to response identification) was smaller and delayed for POOR compared to GOOD subjects. Finally, the ERP shows signs of poor movement control in POOR subjects. The high error rate of POOR subjects can hence be explained by: (1) their insufficient preparation for the next trial (small late CNV), which impaired response identification (small and delayed late P300 subcomponent); and (2) their poor movement control. These interpretations have to be regarded as preliminary and should be validated with larger groups of subjects. In conclusion, the main reasons for the profound performance differences between the groups, namely differential preparation and movement control, could be elucidated by ERP analysis. A potential ergonomics application of these results is that they suggest specific strategies (for example, a preparation and motor control training) to improve the performance of POOR subjects in comparable work conditions.

Adult↗
PubMed1997

A method to improve the latency estimation of the frequency-following potential (FFP).

If the latency of a noisy frequency-following potential (FFP) is estimated by determining the shift of the (periodical) cross-correlation function (CCF) between the stimulus and the FFP, the result may be unambiguous only within +/-1 or +/-2 periods of the CCF, because the absolute maximum and adjacent local maxima may not be significantly different. Here we present a method to amplify this difference by applying amplitude modulated stimuli. Using this method we first illustrate the effect of the method by a simulation and then demonstrate its usefulness by measuring real FFPs and estimating their latencies.

Artifacts↗
PubMed1997

[Event-related potential components related to errors].

Event-related potentials (ERPs) of error trials in choice tasks and Go/Nogo tasks are found to be considerably different from the ERPs of the correct trials: In error trial ERPs there is an additional negative (Ne) and an additional positive component (Pe) compared to correct trials. Amplitude and latency variation of both components in different experiments supports the hypothesis that these components reflect different aspects of error processing. The Ne is interpreted as a real-time correlate of error detection, as defined by a mismatch between cognitive representations of the erroneous response and the correct response. The variation of Pe with experimental variables is different from that of the Ne and it also from that of positive components in correct trials, and may therefore reflect an additional aspect of error processing, such as change of response strategies.

Adult↗
PubMed1996

Perception of visual motion with modulated velocity: effects of viewing distance and aperture size.

Subjects observed a random dot pattern that moved horizontally with modulated velocity within an invisible aperture. The velocity contrast, (V2-V1)/V1, was 2/3. Two different percepts occurred while observing this stimulus. At lower modulation frequencies, between 2 and 12 Hz, velocity changes were clearly seen; this percept is called "motion irregularity". At frequencies higher than 20 Hz velocity changes were no longer visible; the moving pattern appeared to be divided into stationary columns of different luminance. We call this percept "pattern irregularity". The critical frequency for detection of motion irregularity was independent of viewing distance; it was an inverted U-shaped function of the linear rather than the angular mean velocity of the pattern. At higher mean velocities the critical frequency increased with increasing aperture size; at lower mean velocities it was not affected by the size of the aperture. It is shown that detection performance is a function of the relative velocity of the pattern, i.e. of the ratio between the mean velocity in deg/sec and the aperture size in deg. Pattern irregularity could be detected at modulation frequencies even above 100 Hz. The critical frequency increased with increasing velocity and with decreasing viewing distance. It is suggested that detection of motion irregularity is determined by two distinct processes that are based on spatial analysis of motion at low relative velocities and temporal analysis at high relative velocities; both processes provide constancy of detection performance regardless of viewing distance. On the other hand, pattern irregularity seems to be detected on the basis of an analysis of the retinal luminance distribution at high modulation frequencies.

Adult↗
PubMed1996

What determines the detection of changes in motion velocity? A comment on Dzhafarov, Sekuler, and Allik (1993)

We comment on a recent model aimed at explaining data on speed of reaction to motion onset and to changes in motion velocity. The model is based on calculating the running variance of the stimulus positions passed during the motion. We show that although the model is successful in explaining data on motion onset and suprathreshold velocity changes, it may not be able to explain data on time of reaction to changes in velocity when these are near the detection threshold.

Acceleration↗
PubMed1995

Late ERP components in visual and auditory Go/Nogo tasks.

In an audio-visual Go/Nogo paradigm we studied whether the Go/Nogo difference, usually found in the time range of the visual N2, is also present after auditory stimuli, which bears on the common response inhibition hypothesis of this N2 effect. Moreover the possible presence and variation of P300 subcomponents were studied with the goal of clarifying the reasons for the commonly observed P300 topography changes between Go and Nogo trials. To disentangle possible P300 subcomponents we applied a crossmodal divided attention (DA) condition, in which the subcomponents are known to be separated after auditory stimuli in choice tasks. An N2 effect was found after visual but not after auditory stimuli, which is evidence against the response-inhibition hypothesis. After visual stimuli a positive complex (P400) was seen, whereas after auditory stimuli two dissociated components (P400 and P507) were found instead. The P507 had a parietal maximum for both Go and Nogo trials. It was larger and it peaked later in Go than in Nogo trials. The P400 showed topographic differences between Go and Nogo trials, which could be explained by the overlap of the two subcomponents. We assume that (i) both subcomponents have a stable topography across response type, and (ii) the first subcomponent is invariant with response type, whereas the second (which overlaps the first one) is larger and peaks later on Go than on Nogo trials.

Acoustic Stimulation↗
PubMed1995

Temporal thresholds and reaction time to changes in velocity of visual motion.

A random dot pattern moved at a velocity V1. The velocity then increased or decreased abruptly to another value V2 for some time and again returned to V1. The temporal threshold, i.e. the duration of V2 that was necessary to detect the change was measured. Thresholds for the detection of the same velocity increment, V2 = 2 x V1, were shorter when the baseline velocity V1 increased from 1 to 8 deg/sec (Expt 1). The temporal threshold decreased as the velocity contrast (V2 - V1)/(V1 + V2) increased from 0.33 to 0.77. The thresholds for the detection of velocity decrements were in general longer than those for the detection of increments (Expt 3). In Expts 2 and 4 the random-dot pattern moved with velocity V1, which abruptly increased or decreased to V2, without returning to V1. The reaction time to the change was measured for the same velocity pairs as those used in the temporal threshold measurements. There was a good correspondence between changes in the reaction times and changes in the thresholds under the various conditions. The data are interpreted on the basis of two hypotheses: higher velocities are detected by mechanisms that respond more rapidly; and integration of velocities occurs when temporally-adjacent motions are presented.

Adult↗
PubMed1995

Effects of attention and time-pressure on P300 subcomponents and implications for mental workload research.

Our approach to objective measures of mental workload is establishing relationships between components of the event-related brain potential (ERP) and information processing stages. These relationships can be used to infer the influence of specific workload conditions on specific processing stages. We recently showed that the ERP component P300 in choice tasks is composed of two subcomponents, P-SR and P-CR, which are time-related to stimulus-evaluation and response-selection. With these relations we could specify which processing stages were affected when certain workload conditions are varied. When attention was divided between the visual and auditory modalities compared to (unimodal) focused attention, the choice reaction time (RT) was prolonged, primarily in the auditory modality. This delay was mainly reflected in the P-CR latency, which shows that the division of attention mainly impairs the response-selection process in the auditory modality due to a bias of attention towards the visual modality. When the time-pressure was increased, the latency of the P-CR (and not of the P-SR) was shortened, but less than the choice RT. This suggests a (limited) acceleration of response-selection but not of stimulus evaluation. Since the response-selection process was accelerated less than the overt choice RT, an increase of the error rate was consequently observed. In summary we showed that increases of mental workload can induce accelerations or decelerations of specific processing stages which can be monitored by observing latency changes of the affiliated ERP components.

Adult↗
PubMed1994

Effect of selective attention on the latency of human frequency-following potentials.

While effects of attention on late and middle latency components of the evoked potential have been demonstrated, similar effects on brain stem evoked potentials--in particular on the human frequency-following potential (FFP)--are controversial. The FFP is a response to tone bursts in the frequency range of human language (optimum approximately 350 Hz). It has a latency of approximately 6.3 ms and is probably generated at a site peripheral to the inferior colliculus. We present data showing that the latency of the FFP can be shortened significantly (45 microseconds) if the subject is required to attend to the evoking auditory tone burst, while the amplitude of the FFP remains unaffected. This indicates an attention-controlled influence on signal processing in the earliest parts of the auditory pathway.

Acoustic Stimulation↗
PubMed1994

Effects of choice complexity on different subcomponents of the late positive complex of the event-related potential.

The effects of choice complexity on different subcomponents of the late positive complex were investigated. In a previous choice reaction study, two subcomponents of this complex were identified, called P-SR and P-CR, which seem to be related to stimulus evaluation and response selection, respectively. The present study attempts to show the dependence of the P-CR (and the independence of the P-SR) on response selection by manipulating response selection complexity. This was done by having the subjects perform either 2-way or 4-way choice reactions to single letter stimuli. To enhance the discriminability of P-SR and P-CR, visual and auditory stimuli were used, since the P-SR is modality-dependent. Moreover, the stimulus modalities were mixed ("divided attention paradigm"), which was expected to lead to a dissociation of P-SR and P-CR, especially after auditory stimuli. The choice reaction times were about 100 msec longer for difficult than for easy choices. The main ERP result was a 65 msec increase of the P-CR latency for the difficult as compared to the easy choice, while the P-SR latency remained constant. The P-CR latency difference precisely matched the onset difference of the lateralized readiness potential. The P-SR showed a modality-dependent latency and topography, while the P-CR did not. The present data confirm the close relation of one subcomponent of the late positive complex, the P-CR, to the cognitive response-selection process.

Acoustic Stimulation↗
PubMed1993

Multi-aperture viewing: perception of figures through very small apertures.

A new phenomenon of viewing objects through multiple apertures is reported. When a solid figure is hidden behind a sieve of very small apertures (pinholes), only its general shape may be perceived. Outline figures may be entirely invisible behind the sieve. Motion of the figure markedly improves the visibility of the outline figures and of the small details and edges of the solid figures. Two experiments are presented. The first demonstrates that the size of a dark stimulus moving behind a rear-illuminated row of holes is perceived with an accuracy that may be considerably better (i.e. the error is smaller) than the interhole distance. The results of the second experiment show that the visibility of an outline figure, a ring, is significantly better when the figure smoothly moves than when presented at random positions behind a two-dimensional sieve. Changing the velocity within the range of 5.18-10.36 deg/sec does not affect the visibility of the figure while it moves; however, a lower rate of discrete presentation leads to significantly better visibility. An explanation of the phenomenon is presented in terms of integration of information about the relative positions of the covered/uncovered holes, with a possible involvement of motion analyzing mechanisms.

Adult↗
PubMed1993

Late visual and auditory ERP components and choice reaction time.

Some relations between different late positive ERP components and choice reaction time (RT) were studied. In order to identify the different components we used visual and auditory stimuli, as well as simple and choice reaction tasks, since one of the components is thought to be modality dependent and the other one task dependent. In the paradigm the stimulus modalities were mixed, which was expected to lead to a maximum dissociation of the components after auditory stimuli (Hohnsbein et al. (1991). Electroencephalography and Clinical Neurophysiology, 78, 438-446). The results demonstrated the overlap of two positive waves in choice reaction tasks: a central one (P-SR), and a parietal one (P-CR). The latency of the P-SR varied greatly across modalities, but did not vary with RT, whereas the latency of the P-CR varied strongly with RT. The different overlap of these components on fast and slow trials caused amplitude and latency variations of the "P300" and the positive slow wave. Our results suggest a relation of the P-SR with stimulus evaluation (identification), and of the P-CR with response selection (stimulus-response mapping).

Adolescent↗
PubMed1992

The human frequency-following response (FFR): normal variability and relation to the click-evoked brainstem response.

The frequency-following response (FFR) was recorded from twenty human subjects (11 female and 9 male) over a frequency range of 128-832 Hz in order to study the normal variability of this evoked potential and its dependence on age and sex. Moreover the relation of the FFR to the click-evoked brain stem response (BER) was analyzed in order to contribute to the FFR source discussion. The FFR had a maximum amplitude of about 400 nV and a latency of about 6.4 ms for stimulus frequencies around 350 Hz; the inter-individual variance of the best frequency and of the shape of the frequency function was considerable. Large second harmonics were seen in the FFR to stimuli below about 200 Hz. The FFR amplitude tended to be larger in younger subjects, whereas no such effect was found for the BER. No significant sex effect was found for the FFR amplitude, whereas the BER waves IV and VI were larger for females than for males. There were no correlations between FFR and BER latencies. Significant correlations were found between the amplitudes of the FFR and BER components II, III and IV, but not of waves V and VI. The results support the notion that the FFR and the BER reflect different mechanisms. Moreover the results do not favor the common hypothesis that the inferior colliculus is the major source of the scalp-recorded human FFR, but rather point to lower brainstem levels.

Acoustic Stimulation↗
PubMed1991

Effects of crossmodal divided attention on late ERP components. I. Simple and choice reaction tasks.

We studied several effects of dividing attention between visual and acoustic inputs on different processing stages. Simple and choice responses were required to single letter stimuli. RTs and P300 latencies were delayed for divided attention (variable stimulus modality) as compared to focused attention (constant stimulus modality). In all but one condition, RT and P300 delays were similar. The exception was choice tasks to auditory stimuli, in which the RT delay was far larger than the P300 delay. Since the amplitude of the late ERP was larger in choice tasks than in simple tasks, the differences between the ERPs of choice and simple tasks were computed. They revealed that an additional late positive wave ("P-CR") occurred in all choice ERPs. In the divided attention condition the auditory (but not the visual) P-CR showed a longer delay compared to focused attention. We interpret the P-CR to be time-related to the response selection process. Our results suggest that the division of attention causes a slight impairment of stimulus evaluation (shown in P300 latency) and, after auditory stimuli only, a strong impairment of response selection (shown in P-CR latency). We therefore conclude that the observed RT effects are due to a bias of processing resources towards the visual modality, which mainly affects response selection. The results are in accordance with the theory of visual dominance.

Adolescent↗
PubMed1991

Effects of crossmodal divided attention on late ERP components. II. Error processing in choice reaction tasks.

Reaction times and event-related potentials in correct and incorrect trials were studied in a bimanual choice reaction task. In a focused attention (FA) condition, the stimulus modality was constant (visual or auditory); in a divided attention (DA) condition, the modality was varied at random from trial to trial. Stimulus- and response-triggered averages were computed from the midline EEG leads. In error trials, the ERP amplitude was reduced in the P300 range (300-500 msec) and enhanced in the slow wave range (500-700 msec) compared to correct reaction trials. Difference plots between the ERPs (incorrect minus correct reaction trials) revealed a large fronto-central negativity ("NE") and a parieto-occipital "slow wave." These components appeared larger in the response-triggered averages. We believe that they reflect two different stages of error processing. After auditory stimuli the NE peaked much later for DA than for FA, which supports the idea of an asymmetrical allocation of processing resources to the disadvantage of the auditory modality in our DA condition.

Adolescent↗