Risk for depression is associated with neural biases in emotional categorisation

Negative biases in emotional processing are a major characteristic of depression. Recent research has shown that such negative biases are evident in high risk individuals even in the absence of personal history of depression, suggesting that they may serve as key vulnerability markers of depression. However, the neural basis of these behavioural observations has not been fully explored. This study therefore aimed to (1) illustrate the neural processes involved in the categorisation of emotional personality-trait words; and (2) examine whether these neural mechanisms are biased towards negative information in high risk individuals. Risk for depression was defined by high neuroticism (N). We recruited a sample of high risk (high N) and low risk (low N) never-depressed young adults. Functional magnetic resonance imaging (fMRI) was acquired during the categorisation and memory for positive and negative self-referent personality-trait words (e.g. honest, rude). High risk volunteers showed greater responses in the right superior parietal cortex than low risk volunteers specifically during the categorisation of negative words. Moreover, neuroticism score was positively correlated with neural responses in the left anterior cingulate during the categorisation of negative words but negatively correlated within the same region during the retrieval of these words. These results highlight a role of the fronto-parietal circuitry in emotional processing and further suggest that negative biases in these neural processes may be involved in risk for depression.     

Unilateral attention deficits and hemispheric asymmetries in the control of visual attention

The present study sought to determine the roles of the two hemispheres in arousal and the selective components of attention. Ten patients with left and right parietal lesions and ten with left and right temporal lesions participated in the experiment. The hypothesis that posterior parietal lesions, whether left or right, cause two selective attentional deficits, namely, a reduced reactivity to stimuli in the visual field contralateral to the lesion, and a reduced reactivity to any stimulus which occupies a relative contralateral spatial position, was tested by asking the patient to tilt their head either to the left or to the right by 90 degrees and to respond to two stimuli displayed above and on either side of fixation mark. The arousal component of attention was studied by analysing the overall RT to visual stimuli independent of their spatial positions. The results showed that (1) patients with either left or right parietal damage are impaired in shifting attention from the ipsilateral to the contralateral visual field, and, within each visual field, in a direction contraversive to the lesion and (2) these two attentional deficits are more severe after right than after left parietal damage. Furthermore, the results show that the difficulty in maintaining a high level of alertness is a specific deficit of patients with right hemispheric lesion and not of patients with an extinction syndrome, insofar as there is no significant difference in overall RT between patients with parietal and temporal lesions.     

Structural connectivity in spatial attention network: reconstruction from left hemispatial neglect

Left hemispatial neglect (neglect) is an impaired state of spatial attention. We aimed to reconstruct structural connectivity in the spatial attention network and to identify disconnection patterns underlying neglect. We enrolled 59 right-handed patients who had their first-ever infarction in the right hemisphere and classified them into neglect group (34 patients with neglect) and control group (25 patients without neglect). The neglect group was further subcategorized into 6 subgroups based on infarcted vascular territories. Diffusion tensor imaging data were obtained from all patients. Fractional anisotropy maps were compared between neglect group/subgroups and the control group by using non-parametric voxel-based analysis, generating a lesion path mask. Probabilistic tractography analysis using the lesion path mask reconstructed the following structural connectivity in the spatial attention network, which is specifically damaged in neglect patients: (1) superior longitudinal fasciculus (SLF) I connecting the superior parietal lobule/intraparietal sulcus with the superior frontal gyrus/frontal eye field (SFG/FEF) (dorsal attention network); (2) SLF III/the arcuate fasciculus (AF) and the extreme capsule/inferior fronto-occipital fasciculus (IFOF) connecting the right inferior parietal lobule/temporoparietal junction/superior temporal gyrus (IPL/TPJ/STG) with the middle frontal gyrus/inferior frontal gyrus (ventral attention network); (3) the thalamic radiations to the spatial attention-related cortices; and (4) SLF II and IFOF interconnecting dorsal and ventral attention networks. Individual analysis indicated that isolated damage in SLF I, SLF II, SLF III/AF or the thalamic radiations to IPL/TPJ/STG due to posterior cerebral artery infarction, or simultaneous damage in four thalamic radiations due to anterior choroidal artery infarction, underlies different phenotypes of neglect.     

Semantic paralexia: A release of right hemispheric function from left hemispheric control?

In an unselected group of aphasics those patients who produced semantic paralexias had significantly larger lesions than those without semantic paralexias. The possible mechanisms of the release of “alternative” right hemisphere reading from left hemisphere control are discussed.     

Asymmetries in hemispheric control of attention in schizophrenia

Investigators have long suggested that schizophrenia might be related to an impairment in the regulation of attention. In this report, the performance of schizophrenic patients was compared with nonschizophrenic control subjects in their ability to direct visual attention. In the first experiment, patients were distinguished from controls by a slower response to a target in the right visual field than to a target in the left visual field when attention was not first directed to the target location. In the second experiment, patients were distinguished from controls by a stronger bias in favor of symbolic information over language information about spatial direction. In both experiments, the patients demonstrated deficits in attention similar to patients from previous studies who had unilateral lesions of the left hemisphere. The identification of performance abnormalities using tasks that are simple, have dissectable cognitive components, have been related to discrete neural systems, and control for nonspecific variables provide the basis for constructing reasonable hypotheses about the cognitive psychology and functional neuroanatomy of schizophrenia.     

Self-organizing neural network analyses of cardiac data in depression

OBJECTIVE: To determine if an unsupervised self-organizing neural network could create a clinically meaningful distinction of 'depression' versus 'no depression' based on cardiac time-series data. DESIGN: A self-organizing map (SOM) was used to separate the time-series of 84 subjects into groups based on characteristics of the data alone. MATERIALS AND METHODS: Analyses included natural log transformations and two types of filtering to enhance characteristics of the data as well as classifications of unprocessed data. A Pearson chi(2) analysis was performed to determine if the SOM groups bore any relation to the binary clinical groups. RESULTS: Overall correct SOM classifications ranged from 54 to 70.2% with two classifications being clinically meaningful. CONCLUSIONS: SOM classifications of cardiac time-series data with enhanced ultradian variations and cardiac data recorded around the interval when a person was in bed were useful in differentiating clinically meaningful subgroups with and without depression.     

The neural underpinings of simultanagnosia: disconnecting the visuospatial attention network

Because of our limited processing capacity, different elements of the visual scene compete for the allocation of processing resources. One of the most striking deficits in visual selection is simultanagnosia, a rare neuropsychological condition characterized by impaired spatial awareness of more than one object at time. To decompose the neuroanatomical substrates of the syndrome and to gain insights into the structural and functional organization of visuospatial attention, we performed a systematic evaluation of lesion patterns in a group of simultanagnosic patients compared with patients with either (i) unilateral visuospatial deficits (neglect and/or extinction) or (ii) bilateral posterior lesions without visuospatial deficits, using overlap/subtraction analyses, estimation of lesion volume, and a lesion laterality index. We next used voxel-based morphometry to assess the link between different visuospatial deficits and gray matter and white matter (WM) damage. Lesion overlap/subtraction analyses, lesion laterality index, and voxel-based morphometry measures converged to indicate that bilateral parieto-occipital WM disconnections are both distinctive and necessary to create symptoms associated with simultanagnosia. We also found that bilateral gray matter damage within the middle frontal area (BA 46), cuneus, calacarine, and parieto-occipital fissure as well as right hemisphere parietal lesions within intraparietal and postcentral gyri were associated with simultanagnosia. Further analysis of the WM based on tractography revealed associations with bilateral damage to major pathways within the visuospatial attention network, including the superior longitudinal fasciculus, the inferior fronto-occipital fasciculus, and the inferior longitudinal fasciculus. We conclude that damage to the parieto-occipital regions and the intraparietal sulcus, together, with bilateral WM disconnections within the visuosptial attention network, contribute to poor visual processing of multiple objects and the loss of processing speed characteristic of simultanagnosia.     

A neural network elicited by parametric manipulation of the attention load

We used a parametric experimental design to identify the rCBF variations related to a continuous variation of the attention load. The experiment involved goal-directed visual tasks. The length of time during which the subject's attention was engaged toward the external stimulus was taken as the factor of interest. The neural network revealed areas that positively (left cerebellum, bilateral MT/V5 complex and superior parietal lobule, right inferior temporal lobe and dorsolateral prefrontal cortex) or negatively (precuneus, anterior cingulate and medial superior frontal cortex) correlate with the attention load. Results demonstrate that the activity of these areas varies continuously as a function of the variation in the attention load.     

The effects of multi-task learning and time-varying hemispheric asymmetry on lateralisation in a neural network model

While various functional and cognitive capabilities appear to differ in both degree and direction of lateralisation, the factors underlying these differences are poorly understood. It is hypothesised that time-varying asymmetry in plasticity between homologous regions in the cerebral hemispheres, coupled with asynchronous development of capabilities, may account for the lateralisation differences in two ways. First, the lateralisation of an earlier acquired behaviour may influence the lateralisation of a later developing behaviour. Second, temporal changes in the underlying plasticity asymmetry may also result in differences in lateralisation for functions acquired at different times. This study examines the plausibility of these hypotheses using a computational neural network model consisting of two interacting hemispheric regions and capable of learning two tasks. Lateralisation was measured while learning rates for the two hemispheres were changed independently over time to create a time-varying asymmetry in plasticity, and while the initiation of learning for each task was also varied over time. The results suggest that the lateralisation of one behaviour/function can affect the lateralisation of another in a fundamental way, and that experimentally observed temporal differences in hemispheric development can result in functional lateralisation differences, providing support for past theories of lateralisation based on asymmetric hemispheric growth and maturation.     

Modeling cognitive and emotional processes: A novel neural network architecture

In our continuous attempts to model natural intelligence and emotions in machine learning, many research works emerge with different methods that are often driven by engineering concerns and have the common goal of modeling human perception in machines. This paper aims to go further in that direction by investigating the integration of emotion at the structural level of cognitive systems using the novel emotional DuoNeural Network (DuoNN). This network has hidden layer DuoNeurons, where each has two embedded neurons: a dorsal neuron and a ventral neuron for cognitive and emotional data processing, respectively. When input visual stimuli are presented to the DuoNN, the dorsal cognitive neurons process local features while the ventral emotional neurons process the entire pattern. We present the computational model and the learning algorithm of the DuoNN, the input information–cognitive and emotional–parallel streaming method, and a comparison between the DuoNN and a recently developed emotional neural network. Experimental results show that the DuoNN architecture, configuration, and the additional emotional information processing, yield higher recognition rates and faster learning and decision making.     

The callosal dilemma: explaining diaschisis in the context of hemispheric rivalry via a neural network model

It is often suggested that a major factor in diaschisis is the loss of transcallosal excitation to the intact hemisphere from the lesioned one. However, there is long-standing disagreement in the broader experimental literature about whether transcallosal interhemispheric influences in the human brain are primarily excitatory or inhibitory. Some experimental data are apparently better explained by assuming inhibitory callosal influences. Past neural network models attempting to explore this issue have encountered the same dilemma: in intact models, inhibitory callosal influences best explain strong cerebral lateralization like that occurring with language, but in lesioned models, excitatory callosal influences best explain experimentally observed hemispheric activation patterns following brain damage. We have now developed a single neural network model that can account for both types of data, i.e., both diaschisis and strong hemisphere specialization in the normal brain, by combining excitatory callosal influences with subcortical cross-midline inhibitory interactions. The results suggest that subcortical competitive processes may be a more important factor in cerebral specialization than is generally recognized.     

Brain laterality,depression and anxiety disorders: New findings for emotional and verbal dichotic listening in individuals at risk for depression

ABSTRACT

Studies using dichotic listening tests and electroencephalographic (EEG) measures of hemispheric asymmetry have reported evidence of abnormal brain laterality in patients having depressive disorders. We present new findings from a multigenerational study of risk for depression, in which perceptual asymmetry was measured in dichotic listening tests of emotional and verbal processing. Biological offspring and grandchildren of probands with a major depressive disorder (MDD) who were at high risk and those of nondepressed controls who were at low risk were tested on dichotic emotional recognition and consonant–vowel syllable tests. In the emotion test, individuals with a lifetime diagnosis of MDD had a smaller right hemisphere advantage than those without a MDD, but there was no difference between high- and low-risk groups or between those with or without an anxiety disorder. In the syllable test, a smaller left hemisphere advantage was found in individuals with an anxiety disorder compared to those without an anxiety disorder, but there was no difference between high- and low-risk groups or between those with or without a MDD. This double dissociation indicates that lifetime diagnosis of MDD and anxiety disorders have a differential impact on lateralized hemispheric processing of emotional and verbal information.     

Impaired emotional categorisation in young people at increased familial risk of depression

Negative biases in emotional information processing are characteristic of patients with acute depression and may persist after clinical recovery. It is not clear, however, whether such biases are present before the onset of the depressive disorder. The aim of the present study was to examine whether young people at risk of depression, by virtue of having a depressed biological parent (FH+), demonstrate negative biases in tasks of emotional facial recognition and emotional categorization. We also assessed whether task performance and the influence of parental depression are modified by allelic variation in the serotonin transporter (5HTT) gene. We found that the FH+ participants did not show evidence of negative biases relative to matched controls. They were, however, significantly slower to perform a task of emotional categorization. 5HTT genotype did not influence emotional processing significantly. We conclude that negative biases in emotional processing do not appear to be present in people with a family history of depression. However, impairment in emotional categorization could identify a high-risk phenotype and may indicate that people at genetic risk of depression have difficulty in using "mood as information".     

Disengagement of attention from facial emotion in unipolar depression

Abnormal processing of facial expressions is assumed to be an important factor mediating the course of depression. The aim of the present study was to investigate the ability to disengage attention from facial emotion in depressed patients in the course of an inpatient treatment program. It was hypothesized that in depression disengagement of visual attention from negative facial expression is delayed, while disengagement from positive facial expression is facilitated. A face-in-the-crowd task using schematic stimuli and crowds of neutral and emotion faces as 'distractor' stimuli was administered to depressed patients and normal controls matched for age, sex, and education. Patients with major depression (n=15) and normal controls (n=15) were tested twice, about 6 weeks apart. From test 1 to test 2, patients' depressivity decreased significantly. Depressives showed higher response latencies and error rates than control subjects. However, depressed patients exhibited the same scanning pattern for facial emotion as healthy individuals across both test sessions. Participants detected a negative face more rapidly in a crowd of faces than a positive face. When displays consisted of repetitions of the same face, subjects were generally slower (and less accurate) when faces were negative relative to positive or neutral. The present data suggest that the ability to disengage attention from facial emotion in visual search is not impaired in depression.     

Differential right hemispheric memory storage of emotional and non-emotional faces

Seventy-two female subjects memorized two photographed faces and subsequently discriminated these “target” faces from two “non-target” faces. The faces were presented unilaterally for 150 msec, and manual reaction times for the discriminations served as the dependent variable. The face stimuli were either “neutral” or “emotional” in facial expression, these attributes having been shown, by a preliminary study, to be highly reliable. Faster reaction times were obtained for left visual field than for right visual presentation. Subjects (N = 36) who memorized emotional faces showed significantly faster discrimination of faces presented in the left than in the right visual field (25·7 msec); subjects (N = 36) who memorized faces lacking emotional expression also showed significant left visual field superiority (11·6 msec), but this left field superiority was significantly smaller than that of subjects memorizing emotional faces. Results are consistent with previous tachistoscopic evidence of right hemisphere superiority in face recognition speed and with diverse non-tachistoscopic evidence of preferential memory storage of affective material. The pattern of latencies for the different visual field-response hand conditions supported a model of lateral specialization in which the specialized hemisphere normally processes both directly-received and interhemispherically- transferred stimuli.     

Negative ion effects on hemispheric processing and selective attention in the mentally retarded

ABSTRACT. The effect of high concentrations of negative air ions on a dichotic digits task was investigated in 19 mentally retarded individuals. Subjects were assigned randomly to an ion or to an unmodified-air placebo condition under double-blind testing. Left and right ears were precued for report order and this order was reversed for the second set of trials. Negative ions promoted greater left hemisphere lateralization on the first set of trials, and enhanced recall when switching to the opposite channels, in the second set of trials. However, the ion-induced REA occurred at the expense of selective attention to the left channel and superior left ear recall after the right ear first condition is an anomalous dichotic listening pattern. Such paradoxical results suggest that negative ions are not necessarily beneficial or detrimental to processing. Negative ions may increase arousal, in this case amplifying a time-phased, information processing disorder in the retarded characterized by excessive right hemisphere inhibition during early processing of receptive speech and diffuse interhemispheric excitatory activation during later processing.     

Predictors of cognitive level and depression severity are different in patients with left and right hemispheric stroke within the first year of illness

Causes of cognitive impairment after stroke are not yet clear because a large number of sociodemographic and clinical variables complicate the understanding of the phenomenon. We aim to evaluate sociodemographic and clinical predictors of cognitive level and depression in subjects with different lesion laterality. We assessed 153 right (n = 87) and left (n = 66) unilateral first-ever stroke patients within the first year of illness with the Structured Clinical Interview for DSM-IV-Patient Edition, the Hamilton Depression Rating Scale, the Hamilton Anxiety Rating Scale, the State Trait Anger Expression Inventory, the Barthel Index, and the Mini Mental State Examination (MMSE). Sociodemographic variables were also measured. Sixty-two (41 %) patients suffered from Major Depression (MDD), and 26 (17 %) suffered from Minor Depression (MIND). An univariate analysis of variance showed that MMSE scores were different throughout the groups of left and right stroke patients with MDD, MIND and without depression. Left stroke patients with MDD were more cognitively impaired than all the other groups. This result was valid after controlling for the effect of lesion location on cognitive level difference between the groups. A series of stepwise multiple regression analyses indicated that depression severity was a predictor of cognitive level and vice-versa in left hemispheric stroke patients only. Moreover, educational level in right hemispheric stroke patients and state-anger and number of regions affected in left hemispheric stroke patients were other predictors of cognitive level. The study confirms the hypothesis that predictors of cognitive level and depression severity are different in subjects with different laterality of lesion and that MDD is associated with cognitive impairment in left stroke patients. Received: 4 February 2002, Received in revised form: 14 May 2002, Accepted: 22 May 2002 Correspondence to Gianfranco Spaletta, MD     

Amygdala and nucleus accumbens activation to emotional facial expressions in children and adolescents at risk for major depression

OBJECTIVE: Offspring of parents with major depressive disorder face a threefold higher risk for major depression than offspring without such family histories. Although major depression is a significant cause of morbidity and mortality, neural correlates of risk for major depression remain poorly understood. This study compares amygdala and nucleus accumbens activation in children and adolescents at high and low risk for major depression under varying attentional and emotional conditions. METHOD: Thirty-nine juveniles, 17 offspring of parents with major depression (high-risk group) and 22 offspring of parents without histories of major depression, anxiety, or psychotic disorders (low-risk group) completed a functional magnetic resonance imaging study. During imaging, subjects viewed faces that varied in intensity of emotional expressions across blocks of trials while attention was unconstrained (passive viewing) and constrained (rate nose width on face, rate subjective fear while viewing face). RESULTS: When attention was unconstrained, high-risk subjects showed greater amygdala and nucleus accumbens activation to fearful faces and lower nucleus accumbens activation to happy faces (small volume corrected for the amygdala and nucleus accumbens). No group differences emerged in amygdala or nucleus accumbens activation during constrained attention. Exploratory analysis showed that constraining attention was associated with greater medial prefrontal cortex activation in the high-risk than in the low-risk group. CONCLUSIONS: Amygdala and nucleus accumbens responses to affective stimuli may reflect vulnerability for major depression. Constraining attention may normalize emotion-related neural function possibly by engagement of the medial prefrontal cortex; face-viewing with unconstrained attention may engage aberrant processes associated with risk for major depression.