Biomedical subjects

Maarten Milders

Publications and source records attributed to Maarten Milders.

9 recordsLinked to original sources

PubMed2006

ERPs predict the appearance of visual stimuli in a temporal selection task.

In contrast to the visual spatial domain, the effect of attention on sensory processing and stimulus appearance in temporal selection tasks is still controversial. Using a rapid serial visual presentation (RSVP) procedure, we examined whether the stimulus onset asynchrony (SOA) between a color cue and a motion target affects the appearance of the latter. Event-related brain potentials (ERPs) recorded simultaneously allowed us to test whether a change in the targets' appearance is associated with a modulation of the sensory ERP components. In the experimental condition 'SOA', the temporal interval between the cue and the target was varied between 0 and 300 ms. In a control condition, the physical appearance of the motion target was varied (level of coherence: 25-100%) while holding the cue-target SOA constant (300 ms). In trials when the participant detected the target motion, his/her task was to report the strength of the perceived motion on a 5-point scale. In both conditions, the mean rating of the target's appearance increased monotonically with increasing SOA and the level of coherence, respectively. The psychophysical ratings were associated with an increase of a negative deflection about 200 ms (N200) related to the sensory processing of visual motion. The physical variation of motion coherence and the variation of the cue-target SOA affected the N200 response in similar fashion. These results indicate that sensory processing is also modulated by attentional resources in temporal selection tasks which - in turn - affect the appearance of the relevant target stimulus.

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PubMed2006

Impairments in theory of mind shortly after traumatic brain injury and at 1-year follow-up.

Most studies into acquired theory of mind (ToM) deficits assessed patients once, long after the onset of brain injury. As a result, the time course of acquired ToM impairments is largely unknown. The present study examined whether ToM impairments following traumatic brain injury (TBI) recover, remain stable, or worsen over time. Because of the alleged association between ToM and social communication, ToM impairments may deteriorate because of changes in patients' social environment following injury. ToM ability and executive functioning were assessed shortly after injury and at 1-year follow-up. Compared with the orthopedic control group, the TBI group was impaired on ToM and executive functioning tasks at both assessments. Furthermore, the ToM impairments in the TBI group remained stable over time.

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PubMed2006

Awareness of faces is modulated by their emotional meaning.

A central question in perception is how stimuli are selected for access to awareness. This study investigated the impact of emotional meaning on detection of faces using the attention blink paradigm. Experiment 1 showed that fearful faces were detected more frequently than neutral faces, and Experiment 2 revealed preferential detection of fearful faces compared with happy faces. To rule out image artifacts as a cause for these results, Experiment 3 manipulated the emotional meaning of neutral faces through fear conditioning and showed a selective increase in detection of conditioned faces. These results extend previous reports of preferential detection of emotional words or schematic objects and suggest that fear conditioning can modulate detection of formerly neutral stimuli.

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PubMed2005

Specifying the distractor inhibition account of attention-induced motion blindness.

There is growing evidence that motion perception is modulated by visual selective attention. In the 'attention-induced motion blindness' paradigm the detection of coherent motion in a random dot kinematogram (RDK) is impaired in a rapid serial presentation task [Sahraie, A., Milders, M., & Niedeggen, M. (2001). Attention induced motion blindness. Vision Research, 41, 1613-1617]. The effect depends on irrelevant motion episodes (distractors) prior to the target. In this study, we show that both the number and timing of distractors affect detection performance, allowing for implications on the build-up and release of inhibition. Furthermore, we rule out the possibility that subjects falsely classify targets as distractors due to uncertainty of temporal order.

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PubMed2004

Depression biases the recognition of emotionally neutral faces.

Functional abnormalities in emotion-related brain systems have been implicated in depression, and depressed patients may therefore attribute emotional valence to stimuli that are normally interpreted as emotionally neutral. The present study examined this hypothesis by comparing recognition of different facial expressions in patients with moderate to severe depression. Eighteen depressed patients and 18 matched healthy controls made a forced-choice response to briefly presented neutral, happy, and sad faces. Recognition accuracy and response time were measured. Twelve patients were retested after showing signs of symptom remission. Depressed patients and controls were equally accurate at recognizing happy and sad faces. Controls also recognized neutral faces as accurately as happy and sad faces, but depressed patients recognized neutral faces less accurately than either happy or sad faces. Depressed patients were also particularly slow to recognize neutral faces. The impairment in processing of neutral faces was still evident after symptom remission. Error analyses showed that depressed patients attributed not only sadness, but also happiness (in remission), to neutral faces. These results suggest that, unlike healthy subjects, depression-prone individuals do not seem to perceive neutral faces as unambiguous signals of emotional neutrality.

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PubMed2004

Central inhibition ability modulates attention-induced motion blindness.

Impaired motion perception can be induced in normal observers in a rapid serial visual presentation task. Essential for this effect is the presence of motion distractors prior to the motion target, and we proposed that this attention-induced motion blindness results from high-level inhibition produced by the distractors. To investigate this, we compared the extent of the attention-induced motion blindness effect with performance on central inhibition tasks: Stroop colour naming and negative priming. A negative correlation between Stroop interference and motion performance reflected that low Stroop scores, indicative of strong inhibition ability, was associated with more severe impairments in motion perception. This association could not be explained by individual differences in fluid intelligence, task switching or response speed. Negative priming was not specifically associated with attention-induced motion blindness. The results confirm that attention can modulate motion perception and suggest that the processes involved may be shared with high-level cognitive abilities.

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PubMed2004

Probing the prerequisites for motion blindness.

Neurobiological studies of visual awareness usually focus on the neural events elicited by perceived or nonperceived stimuli but neglect the preexisting conditions that allow (or prevent) conscious perception. We have examined the conditions that lead to temporary motion blindness in a rapid serial visual presentation paradigm, in which subjects have to detect coherent motion in the peripheral stream after a cue (a red fixation point) in the central stream. The failure of awareness depends critically on the occurrence of similar coherent motion events (probes) before the cue. Event-related brain potentials (ERPs) were recorded to track the processing of motion distractors, which determine the prerequisites for this transient deficit. Analysis of motion-evoked responses revealed that there is no progressive reduction in sensitivity in early visual processing. There is, however, a progressive increase in amplitude of a negative wave over the frontal cortex at approximately 250 msec after motion onset and a corresponding reduction of a centro-parietal positivity at approximately 350 msec with an increasing number of distractors. We propose that these nonsensory ERP components reflect a postperceptual frontal gating mechanism that controls the access of visual stimuli to higher order evaluation and conscious detection.

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PubMed2003

Neuropsychological impairments and changes in emotional and social behaviour following severe traumatic brain injury.

Changes in emotional and social behaviour are relatively common following severe traumatic brain injury (TBI). Despite the serious consequences of these changes, little is known about the underlying neuropsychological deficits. In this study, we investigated which deficits might underlie these behavioural changes. The emotional and social behaviour of 17 patients with severe TBI was assessed with questionnaires, completed by the patient and a relative. Neuropsychological tests assessed recognition of emotional expressions, understanding of other people's mental states and cognitive fluency. Ratings from patients and relatives revealed changes in emotional and social behaviour after injury. Compared to matched healthy controls, the patients were impaired at recognising facial and vocal expressions of emotions, detecting social faux pas and nonverbal fluency. None of these impairments was significantly associated with the relatives' ratings of behavioural problems following TBI, although the correlation with detecting social faux pas was relatively high (r=-.61).

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PubMed2002

Is experimental motion blindness due to sensory suppression? An ERP approach.

Recent psychophysical studies have revealed attentional modulation of visual motion perception and interest now focuses on the locus of this interaction. Using event-related brain potentials (ERPs) we examined whether transient motion blindness evoked in a dual task [Vision Res. 41 (2001) 1613-1617] is related to a selection process occurring at the stage of sensory processing or at a higher level. In our paradigm, a particular change of colour of the fixation point cued the subject to detect a brief episode of coherent random dot motion embedded in a succession of episodes of incoherent motion. Detection of the coherent motion was significantly impaired when it occurred simultaneously with the colour cue, and recovered over the subsequent 300 ms. This functional relationship was reflected in the amplitude of a sensory, motion-evoked component (N200), and in a late positive complex (P300). However, a direct comparison of ERPs produced by stimuli that were detected or missed revealed differences only in the P300 component. These results indicate that attenuation of sensory motion processing does not account for this transient, attention-induced deficit in visual motion perception.

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