How to produce an absent-advantage in visual search

In a series of four experiments, we investigated the conditions under which target-absent responses are faster than target-present responses in visual search. Previous experiments have shown that such an absent-advantage occurs mainly for homogeneous distractors arranged in a regular pattern. From these results, it has been concluded that the absent-advantage is due to perceptual processes, such as grouping by similarity. Our data show that such processes are not sufficient. Rather, the absent-advantage is the result of interactions between perceptual and decisional processes. Certain perceptual conditions, such as randomizing stimulus patterns, lead to specific criteria settings that produce an absent-advantage. That such an account can explain our main results is demonstrated by modeling our data with a modified version of the Guided Search 2 model.     

Walking or talking? Behavioral and neurophysiological correlates of action verb processing

Brain activity elicited by visually presented words was investigated using behavioral measures and current source densities calculated from high-resolution EEG recordings. Verbs referring to actions usually performed with different body parts were compared. Behavioral data indicated faster processing of verbs referring to actions performed with the face muscles and articulators (face-related words) compared to verbs referring to movements involving the lower half of the body (leg-related words). Significant topographical differences in brain activity elicited by verb types were found starting approximately 250 ms after word onset. Differences were seen at recording sites located over the motor strip and adjacent frontal cortex. At the vertex, close to the cortical representation of the leg, leg-related verbs (for example, to walk) produced strongest in-going currents, whereas for face-related verbs (for example, to talk) the most in-going activity was seen at more lateral electrodes placed over the left Sylvian fissure, close to the representation of the articulators. Thus, action words caused differential activation along the motor strip, with strongest in-going activity occurring close to the cortical representation of the body parts primarily used for carrying out the actions the verbs refer to. Topographically specific physiological signs of word processing started earlier for face-related words and lasted longer for verbs referring to leg movements. We conclude that verb types can differ in their processing speed and can elicit neurophysiological activity with different cortical topographies. These behavioral and physiological differences can be related to cognitive processes, in particular to lexical semantic access. Our results are consistent with associative theories postulating that words are organized in the brain as distributed cell assemblies whose cortical distributions reflect the words' meanings.     

Viewpoint dependence in visual and haptic object recognition

On the whole, people recognize objects best when they see the objects from a familiar view and worse when they see the objects from views that were previously occluded from sight. Unexpectedly, we found haptic object recognition to be viewpoint-specific as well, even though hand movements were unrestricted. This viewpoint dependence was due to the hands preferring the back "view" of the objects. Furthermore, when the sensory modalities (visual vs. haptic) differed between learning an object and recognizing it, recognition performance was best when the objects were rotated back-to-front between learning and recognition. Our data indicate that the visual system recognizes the front view of objects best, whereas the hand recognizes objects best from the back.     

Oscillatory brain dynamics, wavelet analysis, and cognition

On the basis of a systems theoretical approach it was hypothesized that event-related potentials (ERPs) are superpositions of stimulus-evoked and time-locked EEG rhythms reflecting resonance properties of the brain (Ba?ar, 1980). This approach led to frequency analysis of ERPs as a way of analyzing evoked rhythms. The present article outlines the basic features of ERP frequency analysis in comparison to ERP wavelet analysis, a recently introduced method of time-frequency analysis. Both methods were used in an investigation of the functional correlates of evoked rhythms where auditory and visual ERPs were recorded from the cat brain. Intracranial electrodes were located in the primary auditory cortex and in the primary visual cortex thus permitting "cross-modality" experiments. Responses to adequate stimulation (e.g., visual ERP recorded from the visual cortex) were characterized by high amplitude alpha (8-16 Hz) responses which were not observed for inadequate stimulation. This result is interpreted as a hint at a special role of alpha responses in primary sensory processing. The results of frequency analysis and of wavelet analysis were quite similar, with possible advantages of wavelet methods for single-trial analysis. The results of frequency analysis as performed earlier were thus confirmed by wavelet analysis. This supports the view that ERP frequency components correspond to evoked rhythms with a distinct biological significance.     

Change of spatial field effects in 16- to 20-week-old infants

Infants from 16 to 20 weeks were presented with objects moving across a 60-cm distance. Tracking increased between 16 and 18 weeks, reaching increased at 18 weeks, and arm lifts (swipes) showed no age change. A right spatial field bias in tracking disappeared gradually. Swipes occurred most often in front of the object, when it was moving in the center field, presumably as reactions due to spatial proximity. Reaching occurred in the peripheral spatial fields in the younger infants, but in the older infants most often in the center spatial field. Moreover, reaching occurred generally more often toward the left spatial field and predicted the emergence of tracking the left spatial field. Thus, it appeared that a bias in reaching corrected a bias in tracking. Similar effects of limb movements, especially when reaching, were found in the successful treatment of visual neglect patients in neuropsychological research.     

Relative mislocalization of briefly presented stimuli in the retinal periphery

We studied the ability to localize flashed stimuli, using a relative judgment task. When observers are asked to localize the peripheral position of a probe with respect to the midposition of a spatially extended comparison stimulus, they tend to judge the probe as being more toward the periphery than is the midposition of the comparison stimulus. We report seven experiments in which this novel phenomenon was explored. They reveal that the mislocalization occurs only when the probe and the comparison stimulus are presented in succession, independent of whether the probe or the comparison stimulus comes first (Experiment 1). The size of the mislocalization is dependent on the stimulus onset asynchrony (Experiment 2) and on the eccentricity of presentation (Experiment 3). In addition, the illusion also occurs in an absolute judgment task, which links mislocalization with the general tendency to judge peripherally presented stimuli as being more foveal than they actually are (Experiment 4). The last three experiments reveal that relative mislocalization is affected by the amount of spatial extension of the comparison stimulus (Experiment 5) and by its structure (Experiments 6 and 7). This pattern of results allows us to evaluate possible explanations of the illusion and to relate it to comparable tendencies observed in eye movement behavior. It is concluded that the system in charge of the guidance of saccadic eye movements is also the system that provides the metric in perceived visual space.     

Gender differences in a clinical sample of patients with borderline personality disorder

The aim of the study was to investigate gender differences and similarities in patients with borderline personality disorder (BPD) with respect to Axis I comorbidity, Axis II comorbidity, general psychopathology (Symptom Checklist 90-Revised), and dimensional personality traits (NEO-Personality-Inventory Revised [NEO-PI-R] and the Dimensional Assessment of Personality Profile Basic questionnaire [DAPP-BQ]). Fifty-seven men and 114 women with BPD were included in the study. Regarding Axis I and II disorders in an exploratory analysis, men with BPD more often fulfilled the diagnostic criteria for binge eating disorder, antisocial personality disorder, narcissistic personality disorder, and conduct disorder in childhood, whereas women had higher frequencies of bulimia nervosa, posttraumatic stress disorder, and panic disorder with agoraphobia. After correcting for multiple tests, only the gender differences in narcissistic and antisocial personality disorder remained significant. In the SCL-90-R profile, no significant gender differences could be identified. In the exploratory analysis of the dimensional personality traits, women showed higher rates on the NEO-PI-R main factors (Neuroticism and Agreeableness) compared to men. In the DAPP-BQ profile, men reached higher sores on the main factor, Dissocial Behavior. When correcting for multiple tests, gender differences still existed for Neuroticism and Dissocial Behavior. Our results argue for gender differences in Axis I and II comorbidity and dimensional personality traits in BPD. However, in general, more similarities than differences were shown in this study.