Perceptual biases in processing facial identity and emotion

Normal observers demonstrate a bias to process the left sides of faces during perceptual judgments about identity or emotion. This effect suggests a right cerebral hemisphere processing bias. To test the role of the right hemisphere and the involvement of configural processing underlying this effect, young and older control observers and patients with right hemisphere damage completed two chimeric faces tasks (emotion judgment and face identity matching) with both upright and inverted faces. For control observers, the emotion judgment task elicited a strong left-sided perceptual bias that was reduced in young controls and eliminated in older controls by face inversion. Right hemisphere damage reversed the bias, suggesting the right hemisphere was dominant for this task, but that the left hemisphere could be flexibly recruited when right hemisphere mechanisms are not available or dominant. In contrast, face identity judgments were associated most clearly with a vertical bias favouring the uppermost stimuli that was eliminated by face inversion and right hemisphere lesions. The results suggest these tasks involve different neurocognitive mechanisms. The role of the right hemisphere and ventral cortical stream involvement with configural processes in face processing is discussed.     

Cerebral laterality and depression: differences in perceptual asymmetry among diagnostic subtypes

Examined the influence of diagnostic subtype of depression on perceptual asymmetry for dichotic listening and visual tachistoscopic tasks. A total of 65 unmedicated patients with major depressive disorders and 30 normal controls were tested on a verbal and nonverbal task in each modality. Patients diagnosed according to the DSM-III with melancholia had abnormal perceptual asymmetry for dichotic nonsense syllable and complex tone tasks. In contrast, patients having a nonmelancholic "atypical depression" (reactivity of mood with preserved pleasure capacity and associated features) did not differ from normal controls on these tasks, but had an increased incidence of left handedness. Bipolar depression (history of hypomania) differed from unipolar depression in showing abnormal perceptual asymmetry for a tachistoscopic dot enumeration task. Alterations of perceptual asymmetry in melancholia and bipolar depression were consistent with hypothesized right hemisphere dysfunction.     

Perceptual asymmetry for chimeric stimuli in children with early unilateral brain damage

The present study used a chimeric stimuli task to assess the magnitude of the left-hemispace bias in children with congenital unilateral brain damage (n = 46) as compared to typically developing matched controls (n = 46). As would be expected, controls exhibited a significant left-hemispace bias. In the presence of left hemisphere (LH) damage, the left-hemispace preference was found to be present, but attenuated, whereas right hemisphere (RH) damage resulted in a less lateralized process. Examination of lesion severity revealed that large lesions in the RH were associated with a reversal of the typical left-hemispace bias, while small lesions resulted in a left bias approximating that of controls. In contrast, the left-hemispace preference in children with LH damage was similar across lesion size. We conclude that damage to either hemisphere early in brain development may alter hemispheric preference for processing of nonverbal stimuli, and that at least in the case of RH damage, alteration of the normal perceptual asymmetry may depend on the interaction between lesion side and severity.     

Electroencephalographic asymmetries in adolescents with major depression: influence of comorbidity with anxiety disorders

This study examined whether adolescents with major depressive disorder (MDD) display the abnormal electroencephalographic (EEG) alpha asymmetries found in depressed adults. Resting EEG was recorded in 25 right-handed female outpatients (19 with MDD, 11 of whom also had a current anxiety disorder; 6 with anxiety disorders only) and 10 non-ill controls. In contrast to the non-ill controls, adolescents having MDD but no anxiety disorder showed alpha asymmetry indicative of less activation over right than over left posterior sites. Within the MDD patient group, comorbid anxiety disorders reduced the posterior alpha asymmetry, supporting the potential importance of evaluating anxiety in studies of regional brain activation in adolescent MDD. These preliminary findings are similar to those from adult studies that suggest that MDD is associated with right parietotemporal hypoactivation.     

Comorbidity of unipolar depression: I. Major depression with dysthymia

The degree of current and lifetime comorbidity between major depressive disorder (MDD) and dysthymia (DY) was examined in large community samples of older adolescents (n = 1,710) and adults (n = 2,060). DY was highly comorbid with MDD (lifetime odds ratio of 3.4 for adolescents and 1.6 for adults) and was more likely to precede than to follow MDD, especially in persons who became depressed early in life. MDD was by far the more frequent form of depression: Approximately 80% of the depressed persons experienced only MDD, 10% experienced only DY, and 10% experienced both MDD and DY. The large number of persons who had became depressed twice experienced MDD in the 2nd episode, regardless of the nature of the 1st depression. History of depression was associated with a greater probability for other mental disorders in both adolescents and adults; however, the rates of comorbidity for MDD did not differ from rates for DY or for both MDD and DY.     

Right hemisphere sensitivity to arousal and depression.

Several lines of evidence show impaired right hemisphere function in depression. Lateralized simple reaction time tasks show impaired left visual field responses both in normals experiencing a depressed mood and in patients with mild unipolar depression. One interpretation for these findings is that depression impairs right hemisphere function by interfering with right hemisphere arousal and vigilance mechanisms. In order to test this hypothesis, subjects receiving either depression or relaxation mood suggestions performed an uncued reaction time task that has been shown to be sensitive to right posterior brain damage. Level of alertness was varied by contrasting uncued blocks with blocks in which targets were preceded by a warning tone. The results showed the predicted slowing of left visual field responses in the depressed mood, but only in women. The effect was significant only for the uncued blocks. The left visual field impairment was significantly larger during depression than in the relaxation state, but a smaller left visual field slowing was present in women in the relaxed state as well. These results may be consistent with the notion that depression interferes with right hemisphere function in part by influencing right hemisphere arousal mechanisms.     

Recognition of emotional facial expressions in depressed children and adolescents

Of the neurobiological models of children's and adolescents' depression, the neuropsychological one is considered here. Experimental and clinical evidence has allowed us to identify a lateralization of emotional functions from the very beginning of development, and a right hemisphere dominance for emotions is by now well-known. Many studies have also correlated depression with a right hemisphere dysfunction in patients of different ages. The aim of our study was to analyze recognition of different facial emotions by a group of depressed children and adolescents. Patients affected by Major Depressive Disorder recognized less fear in six fundamental emotions than a group of healthy controls, and Dysthymic subjects recognized less anger. The group of patients' failure to recognize negative-aroused facial expressions could indicate a subtle right hemisphere dysfunction in depressed children and adolescents.     

Are temporal features crucial acoustic cues in dog vocal recognition?

To investigate the perceptual mechanisms underlying conspecific vocal recognition in canine species, eighteen dogs were presented with playbacks of normal and reversed versions of typical dog vocalizations. Auditory perception was analysed using the head-turn paradigm, a non-invasive technique extensively employed to study hemispheric specializations for processing conspecific vocalizations in primates. The results revealed that dogs usually turn their heads with the right ear leading (left hemisphere activation) in response to the forward version of their typical calls, and with either no bias and the left ear leading (right hemisphere activation) in response to the reversed call versions. Overall, our findings suggest that temporal features are determinant auditory cues for call sound recognition in dogs, and support earlier findings of the role of the left hemisphere in the analyses of intraspecific communication.     

Major depression, double depression and personality disorders

Personality disorders are much more common among depressive patients than among normal people. Until now, little research has been conducted into the prevalence of personality disorders among patients with both major depression and dysthymia (double depression). The subject of this study is whether depressive patients with dysthymia have more personality disorders than those with no dysthymia. The Vragenlijst voor Kenmerken van de Persoonlijkheid (a Dutch self-report based on the International Personality Disorder Examination) was completed for 211 outpatients with major depression. Approximately 60% of the patients suffer from one or more personality disorders. Depressive patients with dysthymia differ little from the patients without dysthymia, but patients with dysthymia have more cluster A disorders and are more avoidant. Depressive patients without dysthymia do not differ from the patients with dysthymia in terms of symptoms. Depressive patients with personality disorders have significantly more symptoms than the patients without these disorders. There is no interaction between dysthymia and personality disorder.     

Prevention of depression among Icelandic adolescents: a 12-month follow-up

This paper reports the 12-month follow-up results regarding a program designed to prevent the initial episode of depression and/or dysthymia among Icelandic adolescents. This indicated prevention program was implemented in school settings for 14–15 year-old students judged to be “at risk” for depression because of the presence of some depressive symptoms and/or a negative attributional style. We previously reported (Arnarson & Craighead, 2009) that this program, when compared to treatment-as-usual, was effective in preventing the first episode of depression and/or dysthymia at 6-months following completion of the program. Survival analyses of the 12-month follow-up data indicated that the preventive effects were sustained at the end of 1 year following the completion of the prevention program with only 2 of the prevention program participants reporting an initial episode of MDD/DYS versus 13 of the TAU participants (χ² = 5.02, p = .025). Using logistic regression, we also found that initial level of depressive symptoms significantly (p = .0330) predicted the first episode of depression and/or dysthymia among TAU subjects. The limitations of the study were noted, and future directions of research regarding prevention of depression were discussed.     

Ambivalence over emotional expression in major depression

High ambivalence over the expression of emotions (AEE) has consistently been associated with high levels of depression in previous research. However, there is a lack of studies examining this construct and its associations in a clinical sample of patients with major depressive disorder (MDD). Therefore, the present study compared 76 MDD with 77 non-depressed controls (NC) regarding AEE. As expected, MDD reported greater AEE as compared to ND. Furthermore, levels of AEE and levels of depression were positively correlated in the MDD group. These findings extend previous work and underline the importance of AEE as a central construct in depression. Targeting AEE in treatments of depression may help to modify maladaptive interpersonal patterns of emotional expression.     

抑郁症患者工作记忆内情绪刺激加工的特点及其机制

抑郁症患者在工作记忆内情绪刺激加工的特点为倾向于加工与负性心境一致的材料, 被认为是抑郁症认知易感性的核心特征。目前研究者们围绕抑郁症工作记忆中央执行系统三个子功能的情绪刺激加工特点及其作用机制进行了大量研究, 发现在更新功能上, 患者难以移除负性情绪信息, 且在正性信息的加工上存在缺损; 在抑制功能上, 患者难以抑制无关负性情绪信息进入工作记忆; 在转换功能上, 患者情绪材料转换困难的研究证据尚不充分。神经生理与脑成像的研究初步表明, 工作记忆中的情绪刺激加工与抑郁症患者背外侧前额叶和前扣带回的功能激活水平异常有关。未来研究需评估工作记忆三个子功能对抑郁症状的差异性贡献及在情绪刺激加工上的统一性, 并探究其随疾病发生发展变化的轨迹, 谨慎选取并评估不同情绪刺激材料指标的诱发效应及其对工作记忆功能的独特影响。在此基础上, 深入探究工作记忆内情绪刺激加工的神经机制, 为工作记忆偏向矫正干预的临床应用及其预期效果提供理论依据和方向。     

Representational bias does not affect bisection of lines with a pictorially or semantically defined top by patients with left hemispatial neglect

Normal subjects may have both representational and visual-based components determining bias in bisection of horizontal, vertical, and radial lines. The influence of these components is less clear in patients with neglect. We asked 25 patients with right hemisphere stroke and clinical features of neglect to bisect lines oriented horizontally, vertically, and radially above and below eye level. Objects including human silhouette figures, arrowheads, and the words 'TOP' and 'BOTTOM' were placed at either end of each line. These figures were presented either upright or upside down in some orientations, and presented rightward and leftward in other orientations, to pictorially or semantically define a "top" to each line independent of the actual top of the visual field. Patients demonstrated a rightward bias on all horizontal line bisections, with similar bias and greater magnitude than normal subjects. Patients also demonstrated visual-based biases on some of the vertical, radial down, and radial up lines presented. However, patients did not demonstrate a significant representational bias with any of the visual cues presented on any of the line orientations. Patients with acute right hemisphere stroke demonstrate a rightward bias when asked to perform line bisection in the horizontal line orientation, as well as an upward bias in vertical line bisection. The lack of representational bias in patients with neglect may be due to a greater degree of visual-based neglect as compared to representational neglect, or it may be due to an absence of representational bias in patients with right hemisphere stroke.     

Hemispheric lateralization in 47,XXY Klinefelter's syndrome boys

Thirty-two boys with a 47,XXY karyotype were compared with chromosomally normal male controls in their performance on six tasks of hemispheric specialization. The results revealed that the 47,XXY subjects had smaller asymmetries on left hemisphere tasks and larger asymmetries on right hemisphere tasks than controls. Analyses of individual right and left side scores revealed that the atypical lateral asymmetries of the 47,XXYs were due to a shift toward greater right hemisphere involvement on four of the six measures. It was postulated that the slower fetal growth rates of the extra X chromosome group might contribute to their atypical hemispheric specialization and the failure of their left hemisphere to gain dominance over their right in language processing.     

Deficits in temporal sequencing of verbal material: The effect of laterality of lesion

Temporal sequencing of verbal materials (digits, words, and geometric forms) presented in two sensory modalities (auditory and visual) to three groups of subjects (Broca's with left anterior lesions, patients with right hemisphere lesions, and normals) was examined. Each subject was asked to point to a set of stimuli in the same sequence as presented by the examiner. Results indicated that patients with left hemisphere lesions were more impaired on all tasks than the right hemisphere lesioned patients who, in turn, were impaired compared to normal controls. Response to auditory presentation was superior to response to visual presentation. Also, digits were the easiest for all groups, and words were easier than geometric forms. Of special interest was the finding which suggested that right hemisphere lesions are associated with impairment of verbal temporal sequencing under either auditory or visual presentation.     

Impaired social learning in patients with major depressive disorder revealed by a reinforcement learning model

Background/objectivePatients with major depressive disorder (MDD) have altered learning rates for rewards and losses in non-social learning paradigms. However, it is not well understood whether the ability to learn from social interactions is altered in MDD patients. Using reinforcement learning during the repeated Trust Game (rTG), we investigated how MDD patients learn to trust newly-met partners in MDD patients.MethodSixty-eight MDD patients and fifty-four controls each played as ‘investor’ and interacted with ten different partners. We manipulated both the level of trustworthiness by varying the chance of reciprocity (10, 30, 50, 70 and 90%) and reputation disclosure, where partners’ reputation was either pre-disclosed or hidden.ResultsOur reinforcement learning model revealed that MDD patients had significantly higher learning rates for losses than the controls in both the reputation disclosure and non-disclosure condition. The difference was larger when reputation was not disclosed than disclosed. We observed no difference in learning rates for gains in either condition.ConclusionsOur findings highlight that abnormal learning for losses underlies the social learning process in MDD patients. This abnormality is higher when situational unpredictability is high versus low. Our findings provide novel insights into social rehabilitation of MDD.     

阈下抑郁个体对负性情绪刺激的注意解脱困难

本研究拟采用点探测范式及不同情绪内容的面孔刺激（高兴、中性、悲伤和愤怒）考察阈下抑郁个体的负性注意偏向及其内在机制。点探测任务中情绪面孔配对呈现（负性-中性、正性-中性）,配对面孔中的情绪线索位置与靶刺激的位置构成负性一致/不一致和正性一致/不一致条件,同时实验中加入“中性-中性”面孔线索作为一致和不一致条件的对比基线来考察注意偏向的内在机制。结果发现,阈下抑郁个体在负性不一致条件下的反应时显著长于负性一致条件,表明阈下抑郁个体具有对负性刺激的注意偏向;进一步比较发现,阈下抑郁个体在负性不一致条件下的反应时显著的长于“中性-中性”基线条件,而负性一致条件与基线之间差异不显著,表明阈下抑郁个体的负性注意偏向为对负性刺激的注意解脱困难。结果另发现,阈下抑郁个体未能像无抑郁对照组个体表现出对正性刺激的注意偏向。结果表明,处于阈下抑郁状态的个体表现出对负性刺激的注意偏向,具体为对负性刺激的注意解脱困难,其原因可能是由于阈下抑郁个体在注意控制和情绪调节功能上的紊乱。     

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.     

Strategies of semantic categorization in the cerebral hemispheres

Strategies of semantic categorization in intact cerebral hemispheres were studied in two experiments by presenting names of typical and atypical category instances to the left visual field (LVF) (right hemisphere) or to the right visual field (RVF) (left hemisphere). The results revealed that the typicality of instances had a large effect on categorization times in the LVF in both experiments, suggesting that the right hemisphere relies strongly on a holistic, similarity-based comparison strategy. In Experiment 1, the typicality effect was weaker in the RVF than in the LVF. In Experiment 2, a typicality effect in the RVF was observed for the "four-footed animal" category but not for the "bird" category. The hypothesis that the left hemisphere employs a strategy based on defining or necessary features is not supported by the observed typicality effect in the "four-footed animal" category. Instead, it is suggested that the left hemisphere may be able to categorize on the basis of prestored instance-category knowledge. When such knowledge is not available (e.g., as for four-footed animals), a similarity-based comparison strategy is employed by the left hemisphere.