Biomedical subjects

Uwe Mattler

Publications and source records attributed to Uwe Mattler.

12 recordsLinked to original sources

PubMed2006

Common modules for processing invalidly cued events in the human cortex.

A central question regarding the nature of cognitive control is the extent to which different tasks are controlled by a common system. We addressed this issue by comparing the cortical activation associated with the processing of an invalidly cued event with the activation associated with a validly cued event. In a perceptual cueing task, we cued the likely stimulus modality (visual or auditory), and in a motor cueing task, we cued the likely motor response (left or right hand). Event-related functional MRI revealed increased activation in the anterior cingulate cortex on valid and invalid trials in both tasks. In addition, a network of six regions, including the dorsal medial frontal cortex, showed increased activation on invalid trials irrespective of whether the invalid cue referred to the stimulus modality or response. Findings suggest that dorsal medial frontal cortex rather than the anterior cingulated cortex is involved in conflict monitoring operations. We summarize our findings in a model that links six modules for processing invalidly cued events.

Acoustic Stimulation↗

PubMed2006

Combined expectancies: electrophysiological evidence for the adjustment of expectancy effects.

BACKGROUND: When subjects use cues to prepare for a likely stimulus or a likely response, reaction times are facilitated by valid cues but prolonged by invalid cues. In studies on combined expectancy effects, two cues can independently give information regarding two dimensions of the forthcoming task. In certain situations, cueing effects on one dimension are reduced when the cue on the other dimension is invalid. According to the Adjusted Expectancy Model, cues affect different processing levels and a mechanism is presumed which is sensitive to the validity of early level cues and leads to online adjustment of expectancy effects at later levels. To examine the predictions of this model cueing of stimulus modality was combined with response cueing. RESULTS: Behavioral measures showed the interaction of cueing effects. Electrophysiological measures of the lateralized readiness potential (LRP) and the N200 amplitude confirmed the predictions of the model. The LRP showed larger effects of response cues on response activation when modality cues were valid rather than invalid. N200 amplitude was largest with valid modality cues and invalid response cues, medium with invalid modality cues, and smallest with two valid cues. CONCLUSION: Findings support the view that the validity of early level expectancies modulates the effects of late level expectancies, which included response activation and response conflict in the present study.

Acoustic Stimulation↗

PubMed2006

Distance and ratio effects in the flanker task are due to different mechanisms.

When participants must respond to a relevant central target and ignore irrelevant flanking stimuli the flanking stimuli produce a compatibility effect, with increased response speed and accuracy on compatible as compared to incompatible trials. This flanker effect is larger when compatible trials are more frequent than incompatible trials (the ratio effect). A potential explanation of this ratio effect is that the occurrence of frequent incompatible trials causes the focus of spatial attention to be set narrower than when there are frequent compatible trials. The present investigation tests this hypothesis by comparing the flanker effect with near and far flankers. The hypothesis predicts that the flanker distance should modulate the ratio effect more when incompatible trials are frequent than when compatible trials are frequent. The results, however, show the opposite pattern: Distance effects are larger in conditions with frequent compatible trials. Moreover, the effect of distance but not the ratio effect was eliminated when flanker distance remained fixed across blocks of trials, and also when participants had to attend to flanker stimuli in a go-no-go task. These results suggest that the ratio effect does not result from an adjustment of the focus of spatial attention.

Analysis of Variance↗

PubMed2006

On the locus of priming and inverse priming effects.

Visual stimuli that are made invisible by a following mask can affect overt motor responses and nonmotor processing. Previous studies have compared the effects of primes that were perceptually similar to the subsequent stimulus with those of primes that were perceptually similar to an alternative stimulus. The present study examined the effect of congruent primes that are perceptually dissimilar to the target (or the cue) but are nonetheless associated with the same response (or the same task) as the later stimulus. Positive and inverse priming effects (negative compatibility effects) were studied in a target priming paradigm (Experiments 1 and 2) and in a cue priming paradigm (Experiments 3 and 4). The results showed stronger priming effects with similar primes than with dissimilar congruent primes. However, the effects of perceptually dissimilar congruent primes differed from those of dissimilar incongruent primes. These findings suggest that a substantial part of both positive target and cue priming effects is produced at levels of processing that are not affected by perceptual similarity. The version of inverse priming effects examined in this study, however, seems to arise from perceptual processing that is affected by the similarity between a prime and the stimulus that follows the mask.

Adult↗

PubMed2005

Combined expectancy effects: an accumulator model.

When participants use cues to prepare for a likely stimulus or a likely response, reaction times are facilitated by valid cues but prolonged by invalid cues. In studies on combined expectancy effects, two cues give information regarding two dimensions of the forthcoming task. When the two cues consist of two separable stimuli their effects are approximately additive. When cues are presented as an integrated stimulus, cueing effects interact. A model is presented that simulates effects like these. The model assumes that cues affect different processing stages. When implicit information suggests that expectancies are unrelated, as for instance with separated cues, cueing effects at early and late levels of processing remain independent. When implicit information suggests that expectancies are related, as with integrated cues, however, a mechanism that is sensitive to the validity of the early stage cue, leads to an adjustment of the cueing effect at the late stage. The model is based on neurophysiologically plausible assumptions, it is given explicitly in mathematical terms, and it provides a good fit to a large body of empirical data.

Cues↗

PubMed2005

Flanker effects on motor output and the late-level response activation hypothesis.

When participants must respond to a relevant central target and ignore irrelevant flanking stimuli, the flankers produce a flanker compatibility effect on behavioural measures. Current accounts of the flanker compatibility effect assume that both target and flanker stimuli affect response activation. This idea is supported by electrophysiological studies, which show that irrelevant flanker stimuli can affect the motor system. The present experiments examined the characteristics of flanker effects on the motor system by analysing the details of the motor output with response force measures. A total of 60 participants responded in the flanker task to arrows (Experiment 1) or letters (Experiment 2). Reaction time as well as response force increased on incompatible trials. Analyses of the distribution of incorrect activation revealed that both response times and correct motor output increased with the amount of incorrect activity. However, the flanker compatibility effect was only marginally modulated by incorrect activity. Results suggest that the largest part of the flanker compatibility effect cannot be attributed to response activation and competition at late levels of the response system.

Adult↗

PubMed2005

Inhibition and decay of motor and nonmotor priming.

Motor responses can be facilitated by congruent visual stimuli and prolonged by incongruent visual stimuli that are made invisible by masking (direct motor priming). Recent studies on direct motor priming showed a reversal of these priming effects when a three-stimulus paradigm was used in which a prime was followed by a mask and a target stimulus was presented after a delay. A similar three-stimulus paradigm on nonmotor priming, however, showed no reversal of priming effects when the mask was used as a cue for processing of the following target stimulus (cue priming). Experiment 1 showed that the time interval between mask and target is crucial for the reversal of priming. Therefore, the time interval between mask and target was varied in three experiments to see whether cue priming is also subject to inhibition at a certain time interval. Cues indicated (1) the stimulus modality of the target stimulus, (2) the task to be performed on a multidimensional auditory stimulus, or (3) part of the motor response. Whereas direct motor priming showed the reversal of priming about 100 msec after mask presentation, cue priming effects simply decayed during the 300 msec after mask presentation. These findings provide boundary conditions for accounts of inverse priming effects.

Adult↗

PubMed2004

Combined expectancy effects are modulated by the relation between expectancy cues.

Studies of combined expectancies have shown that spatial cueing effects are reduced on trials on which participants have to respond with an unexpected motor response. In the first two experiments the range of reduced expectancy effects is examined. Advance knowledge of the likely response was combined in a trial-by-trial procedure with modality cueing, object cueing, and task cueing. Effects of modality cueing were reduced on trials on which the target requested an unexpected response. However, effects of object cueing as well as effects of task cueing were unaffected by response cueing. Comparing experiments revealed that different types of cues were used in different experiments. To test the effect of type of cue on the interaction of expectancies the third experiment combined spatial cueing with response cueing. When integrated cues were used that cued the likely target location by an arrow and the likely response by an arrow too, spatial cueing effects were reduced on trials with unexpected responses. However, spatial cueing effects remained unaffected by response cueing when separated cues were used consisting in a word cueing the response and an arrow cueing target location. An account for the modulation of combined expectancies by the relation between cues is suggested in terms of the adjusted expectancy model.

Adult↗

PubMed2003

Delayed flanker effects on lateralized readiness potentials.

When participants were required to respond to a relevant central target and ignore irrelevant flanking stimuli, the flankers produced a response compatibility effect. Electrophysiological studies have shown that irrelevant flanker stimuli can affect the motor system. The present experiments further examined the characteristics of flanker effects on the motor system. Sixty participants responded in the flanker task to arrows (experiment 1) or letters (experiment 2). To examine time and extent of flanker effects on the motor system, target onset was delayed with blocked or random stimulus-onset asynchronies (SOA). With SOA of 0 and 100 ms, flanker effects on behavioral measures were reduced in random as compared to blocked conditions, but enhanced with SOA of 400 ms. With SOA of 400 ms, flanker effects on the early lateralized readiness potentials (LRP) were reduced in blocked as compared to random conditions, indicating that the onset of flanker effects on the LRP was delayed. Response-locked LRPs suggest that flanker and target stimuli activate the motor system successively. Findings challenge current theories of the flanker compatibility effect.

Adult↗

PubMed2003

Different time courses for visual perception and action priming.

Visual stimuli may remain invisible but nevertheless produce strong and reliable effects on subsequent actions. How well features of a masked prime are perceived depends crucially on its physical parameters and those of the mask. We manipulated the visibility of masked stimuli and contrasted it with their influence on the speed of motor actions, comparing the temporal dynamics of visual awareness in metacontrast masking with that of action priming under the same conditions. We observed priming with identical time course for reportable and invisible prime stimuli, despite qualitative changes in the masking time course. Our findings indicate that experimental variations that modify the subjective visual experience of masked stimuli have no effect on motor effects of those stimuli in early processing. We propose a model that provides a quantitative account of priming effects on response speed and accuracy.

Adult↗

PubMed2003

Combined perceptual or motor-related expectancies modulated by type of cue.

The interaction of two expectancies was examined. These were either two perceptual or two response-related expectancies. Perceptual expectancies were induced by combining spatial cuing with feature cuing on a trial-by-trial basis. Cues consisted either of two integrated parts, such as two arrows, or two separated pieces, such as an arrow and a word. Spatial-cuing effects were reduced on trials with invalid feature cues, as compared with valid ones. However, the interaction of spatial cuing and feature cuing was modulated by the type of cue used to induce expectancies. With integrated cues, spatial-cuing effects were reduced about twice as much as with separated cues. The same effect of type of cue was found in Experiment 2, although finger cuing was combined with hand cuing. With integrated cues, finger-cuing effects were much smaller on trials with invalid hand cues, as compared with valid ones. With separated cues, however, finger-cuing effects were additive to hand-cuing effects. The similarity of the results within perceptual- and motor-cuing tasks suggests that a general principle governs the combination of expectancies, such as that outlined in the framework of the proposed adjusted expectancy model.

Adult↗

PubMed2003

Priming of mental operations by masked stimuli.

Motor responses can be affected by visual stimuli that have been made invisible by masking. Can masked visual stimuli also affect nonmotor operations that are necessary to perform the task? Here, I report priming effects of masked stimuli on operations that were cued by masking stimuli. Cues informed participants about operations that had to be executed with a forthcoming target stimulus. In five experiments, cues indicated (1) the required response, (2) part of the motor response, (3) the stimulus modality of the target stimulus, or (4) the task to be performed on a multidimensional stimulus. Motor and nonmotor priming effects followed comparable time courses, which differed from those of prime recognition. Experiment 5 demonstrated nonmotor priming without prime awareness. Results suggest that motor and nonmotor operations are similarly affected by masked stimuli.

Adult↗