How does reading direction modulate perceptual asymmetry effects?

Left-side bias effects refer to a bias towards the left side of the stimulus/space in perceptual/visuospatial judgments, and are argued to reflect dominance of right hemisphere processing. It remains unclear whether reading direction can also account for the bias effect. Previous studies comparing readers of languages read from left to right with those read from right to left (e.g., French vs. Hebrew) have obtained inconsistent results. As a language that can be read from left to right or from right to left, Chinese provides a unique opportunity for a within-culture examination of reading direction effects. Chinese participants performed a perceptual judgment task (with both face and Chinese character stimuli; Experiment 1) and two visuospatial attention tasks (the greyscales and line bisection tasks; Experiment 2) once before and once after a reading task, in which they read Chinese passages either from left to right or from right to left for about 20 min. After reading from right to left, participants showed significantly reduced left-side bias in Chinese character perceptual judgments but not in the other three tasks. This effect suggests that the role of reading direction on different forms of left-side bias may differ, and its modulation may be stimulus-specific.     

The advantage of mentally rotating clockwise

The time taken to decide whether a character is shown in its mirror or normal version has been shown to increase approximately linearly with the angular departure from an up-right position. Additionally, in some studies, decisions took longer for clockwise tilted characters than for counterclockwise tilted ones. Other studies do not report the latter effect. We argue that inconsistencies across studies are caused by variance in participants' strategies. The task employed here was specifically designed to bring these strategies and thereby the direction of rotation under experimental control. From the EEG recorded during the rotation period, we extracted an event-related slow potential whose amplitude is sensitive to the amount of mental rotation. In both strategy conditions, the slow potential's amplitude was lower for clockwise than for counterclockwise rotations. We take this as evidence that mental rotation of alphanumeric characters is easier in a clockwise than in a counterclockwise direction.     

Fifty years of dichotic listening research - still going and going and…

This year celebrates 50 years of research in auditory laterality and hemispheric asymmetry, using a dichotic listening approach. The discovery of the "right ear advantage" in 1961 by Doreen Kimura to dichotic presentations of phonetic stimuli paved the way for new studies of how speech perception and related language processes are lateralized in the human brain. The articles in this special issue, celebrating the first 50 years of dichotic listening research, reveal both the breadth and depth of current research, with contributions spanning from basic research to clinical applications, from behavioral studies to studies using advanced neuroimaging techniques, and with contributions from all over the world. It is my hope as Guest Editor that the next 50 years will be as productive as the first 50 years.     

Neuroanatomy of childhood disruptive behavior disorders

Our aims were to (1) examine possible neuroanatomical abnormalities associated with the Disruptive Behavior Disorders (DBDs) as a group and (2) assess neuroanatomical anomalies specific to each DBD (i.e., conduct disorder [CD] and oppositional defiant disorder). Cortical thickness analysis and voxel-based morphometry were analyzed in 47 8-year-old boys (22 DBDs with and without CD and/or ODD and 25 healthy controls) from Magnetic Resonance Imaging brain scans. DBD symptoms were assessed using the Dominic-R. In DBD subjects relative to controls, we found (1) a decreased overall mean cortical thickness; (2) thinning of the cingulate, prefrontal and insular cortices; and (3) decreased gray matter density (GMd) in the same brain regions. We also found that scores on the Dominic-R were negatively correlated with GMd in the prefrontal and precuneus/superior temporal regions. There was a subdiagnostic main effect for CD, related to thinning of the middle/medial frontal, and for ODD in the left rectal/orbitofrontal. Findings suggest that thinning and decreased GMd of the insula disorganizes prefrontal circuits, diminishing the inhibitory influence of the prefrontal cortex on anger, aggression, cruelty, and impulsivity, and increasing a person's likelihood of aggressive behavior. These findings have implications for pathophysiologic models of the DBDs, their diagnostic classification system, and for designing more effective intervention programs.     

Neural correlates of facial emotion processing in infancy

In the present study we examined the neural correlates of facial emotion processing in the first year of life using ERP measures and cortical source analysis. EEG data were collected cross‐sectionally from 5‐ (N = 49), 7‐ (N = 50), and 12‐month‐old (N = 51) infants while they were viewing images of angry, fearful, and happy faces. The N290 component was found to be larger in amplitude in response to fearful and happy than angry faces in all posterior clusters and showed largest response to fear than the other two emotions only over the right occipital area. The P400 and Nc components were found to be larger in amplitude in response to angry than happy and fearful faces over central and frontal scalp. Cortical source analysis of the N290 component revealed greater cortical activation in the right fusiform face area in response to fearful faces. This effect started to emerge at 5 months and became well established at 7 months, but it disappeared at 12 months. The P400 and Nc components were primarily localized to the PCC/Precuneus where heightened responses to angry faces were observed. The current results suggest the detection of a fearful face in infants’ brain can happen shortly (~200–290 ms) after the stimulus onset, and this process may rely on the face network and develop substantially between 5 to 7 months of age. The current findings also suggest the differential processing of angry faces occurred later in the P400/Nc time window, which recruits the PCC/Precuneus and is associated with the allocation of infants’ attention.     

Oppositional Children Differ from Healthy Children in Frontal Brain Activation

An atypical EEG pattern of frontal brain activation, which has been found in children and adults with emotional disorders, also is hypothesized to be present in disruptive behavior disorders. One hundred nineteen children (4 $\frac{1}{2}$ and 8 years of age) were examined with regard to the following questions: (1) Do children who are diagnosed with oppositional defiant disorder (ODD) exhibit an atypical pattern of frontal brain activation? (2) Can this pattern be demonstrated in preschool children (4 $\frac{1}{2}$ years of age) as well as in school children (8 years)? (3) Are there gender differences in these patterns similar to those that have been demonstrated in adults? Spontaneous EEG activity was subjected to power spectral analysis. In oppositional preschool and elementary school girls, the well-known pattern of lower left frontal than right frontal activation emerged that has been found previously in emotionally disordered children. Healthy girls showed no frontal brain asymmetry at 4 $\frac{1}{2}$ years of age, and left frontal activation at 8 years. In contrast, healthy boys demonstrated a greater right than left frontal activation, whereas ODD boys did not display any frontal brain asymmetry. Thus, the pattern of frontal brain activation seems to be gender-specific. The atypical activation pattern in oppositional children is hypothesized to be a biological substrate of negative affective style.     

Extinction-like effects in normals: independence of localization and response selection

An extinction-like effect in normal subjects was previously elicited when a low-salience target in the left was simultaneously presented with a highly salient distractor in the right visual hemifield, but not vice versa (Pollmann, 1996). We investigated in four experiments whether this extinction-like effect depends on (a) explicit localization and (b) response competition. It was found that the extinction-like effect could be replicated in the absence of both. In contradistinction to our previous results, low-salience distractors had no effect on pop-out target search. This showed that explicit spatial localization demands lead to low-salience distractor interference on pop-out search.     

Attention maintains mental extrapolation of target position: irrelevant distractors eliminate forward displacement after implied motion

Observers' judgments of the final position of a moving target are typically shifted in the direction of implied motion ("representational momentum"). The role of attention is unclear: visual attention may be necessary to maintain or halt target displacement. When attention was captured by irrelevant distractors presented during the retention interval, forward displacement after implied target motion disappeared, suggesting that attention may be necessary to maintain mental extrapolation of target motion. In a further corroborative experiment, the deployment of attention was measured after a sequence of implied motion, and faster responses were observed to stimuli appearing in the direction of motion. Thus, attention may guide the mental extrapolation of target motion. Additionally, eye movements were measured during stimulus presentation and retention interval. The results showed that forward displacement with implied motion does not depend on eye movements. Differences between implied and smooth motion are discussed with respect to recent neurophysiological findings.