Aprajita Mohanty

Paying attention to emotion: An fMRI investigation of cognitive and emotional Stroop tasks

In this research, we investigated the degree to which brain systems involved in ignoring emotionally salient information differ from those involved in ignoring nonemotional information. The design allowed examination of regional brain activity, using fMRI during color-word and emotional Stroop tasks. Twelve participants indicated the color of words while ignoring word meaning in conditions in which neutral words were contrasted to emotionally negative, emotionally positive, and incongruent color words. Dorsolateral frontal lobe activity was increased by both negative and incongruent color words, indicating a common system for maintaining an attentional set in the presence of salient distractors. In posterior regions of the brain, activity depended on the nature of the information to be ignored. Ignoring color-incongruent words increased left parietal activity and decreased parahippocampal gyrus activity, whereas ignoring negative emotional words increased bilateral occipito-temporal activity and decreased amygdala activity. The results indicate that emotion and attention are intimately related via a network of regions that monitor for salient information, maintain attention on the task, suppress irrelevant information, and select appropriate responses.

The Spatial Attention Network Interacts with Limbic and Monoaminergic Systems to Modulate Motivation-Induced Attention Shifts

How does the human brain integrate information from multiple domains to guide spatial attention according to motivational needs? To address this question, we measured hemodynamic responses to central cues predicting locations of peripheral attentional targets (food or tool images) in a novel covert spatial attention paradigm. The motivational relevance of food-related attentional targets was experimentally manipulated via hunger and satiety. Amygdala, posterior cingulate, locus coeruleus, and substantia nigra showed selective sensitivity to food-related cues when hungry but not when satiated, an effect that did not generalize to tools. Posterior parietal cortex (PPC), including intraparietal sulcus, posterior cingulate, and the orbitofrontal cortex displayed correlations with the speed of attentional shifts that were sensitive not just to motivational state but also to the motivational value of the target. Stronger functional coupling between PPC and posterior cingulate occurred during attentional biasing toward motivationally relevant food targets. These results reveal conjoint limbic and monoaminergic encoding of motivational salience in spatial attention. They emphasize the interactive role of posterior parietal and cingulate cortices in integrating motivational information with spatial attention, a process that is critical for selective allocation of attentional resources in an environment where target position and relevance can change rapidly.

Cognitive deficits in depression and functional specificity of regional brain activity

The growing literature on cognitive deficits in depression is considered in light of regional brain activity as well as comorbid anxiety and life stressors. Cognitive impairments associated with depression are reviewed, with an emphasis on various aspects of executive function such as memory, attention, and problem-solving. These deficits are related to patterns of brain activity observed in prefrontal, anterior cingulate, and parietal cortices, as well as in subcortical regions. Evidence for the largely unexplored role of environmental stressors in depression and their impact on cognition and brain function is also examined, and promising avenues of additional research are noted. In addition to promoting interdisciplinary research, systematically assessing variables such as cognitive performance, comorbid anxiety, and relevant stressors may elucidate distinct patterns of brain function and cognition that could inform prevention and intervention.

Emotion-Modulated Performance and Activity in Left Dorsolateral Prefrontal Cortex

Functional MRI (fMRI) was used to examine the relationship between processing of pleasant and unpleasant stimuli and activity in prefrontal cortex. Twenty volunteers identified the colors in which pleasant, neutral, and unpleasant words were printed. Pleasant words prompted more activity bilaterally in dorsolateral prefrontal cortex (DLPFC) than did unpleasant words. In addition, pleasant words prompted more activity in left than in right DLPFC. Response speed to pleasant words was correlated with DLPFC activity. These data directly link positive affect, enhanced performance, and prefrontal activity, providing some of the first fMRI evidence supporting models of emotional valence and frontal brain asymmetry based on electroencephalography (EEG).

Localization of asymmetric brain function in emotion and depression

Although numerous EEG studies have shown that depression is associated with abnormal functional asymmetries in frontal cortex, fMRI and PET studies have largely failed to identify specific brain areas showing this effect. The present study tested the hypothesis that emotion processes are related to asymmetric patterns of fMRI activity, particularly within dorsolateral prefrontal cortex (DLPFC). Eleven depressed and 18 control participants identified the color in which pleasant, neutral, and unpleasant words were printed. Both groups showed a leftward lateralization for pleasant words in DLPFC. In a neighboring DLPFC area, the depression group showed more right-lateralized activation than controls, replicating EEG findings. These data confirm that emotional stimulus processing and trait depression are associated with asymmetric brain functions in distinct subregions of the DLPFC that may go undetected unless appropriate analytic procedures are used.

Neural mechanisms of affective interference in schizotypy

Negatively valenced stimuli foster cognitive impairment in schizotypy and schizophrenia. To identify relevant brain mechanisms, the authors had 16 positive-schizotypy and 16 control participants perform an emotional Stroop task, judging the ink color of negative and neutral words during functional magnetic resonance imaging (fMRI) of regional brain activity. Schizotypy individuals showed increased right and decreased left activity in dorsolateral prefrontal cortex, indicating a deficit in maintenance of attentional set in the presence of negative emotional distractors. They also showed abnormal activity in ventral limbic areas, including decreased activity in nucleus accumbens and increased activity in hippocampus and amygdala, a circuit involved in the integration of cognitive and affective processes. These results indicate that aspects of emotion-cognition processes and the brain mechanisms that implement them are similar in schizotypy and schizophrenia.

Effects of lesion variables and emotion type on the perception of facial emotion.

The purpose of this study was to consider the effects of valence, motoric direction (i.e., approach/withdrawal), and arousal on the perception of facial emotion in patients with unilateral cortical lesions. We also examined the influence of lesion side, site, and size on emotional perception. Subjects were 30 right-hemisphere-damaged (RHD) and 30 left-hemisphere-damaged (LHD) male patients with focal lesions restricted primarily to the frontal, temporal, or parietal lobe. Patient groups were comparable on demographic and clinical neurological variables. Subjects were tested for their ability to match photographs of four facial emotional expressions: happiness, sadness, fear, and anger. Overall, RHD patients were significantly more impaired than LHD patients in perceiving facial emotion. Lesion side, but not site, was associated with motoric direction and valence dimensions. RHD patients had specific deficits relative to LHD patients in processing negative and withdrawal emotions; there were no group differences for positive/approach emotions. Lesion size was not significantly correlated with accuracy of emotional perception.

Classification of functional brain images with a spatio-temporal dissimilarity map

Classification of subjects into predefined groups, such as patient vs. control, based on their functional MRI data is a potentially useful procedure for clinical diagnostic purposes. This paper presents an automated method for classifying subjects into groups based on their functional MRI data. The proposed methodology provides general framework using preprocessed time series for the whole brain volume. Using a training set of two groups of subjects, the new methodology identifies spatio-temporal features that distinguish the groups and uses these features to categorize new subjects. We demonstrate the method using simulations and a clinical application that classifies individuals into schizotypy and control groups.

Search for a Threatening Target Triggers Limbic Guidance of Spatial Attention

The ability to actively locate potential threats in our environment is highly adaptive. To investigate mediating neural mechanisms, we designed a visual search task in which central cues signaled future location and emotional expression (angry or neutral) of a target face. Cues predicting angry targets accelerated subsequent attention shifts, indicating that endogenous signals predicting threatening events can prime the spatial attention network. Functional imaging showed that spatially informative cues activated the fusiform gyrus (FG) as well as frontoparietal components of the spatial attention network, including intraparietal sulcus (IPS) and frontal eye field (FEF), whereas cues predicting angry faces also activated limbic areas, including the amygdala. Anatomically overlapping, additive effects of spatial and emotional cuing were identified in the IPS, FEFs, and FG, regions that also displayed augmented connectivity with the amygdala after cues predicting angry faces. These data highlight a key role for the frontoparietal spatial attention network in the compilation of a salience map that combines the spatial coordinates of an event with its motivational relevance. Furthermore, they suggest that active search for a threatening stimulus elicits amygdala input to the spatial attention network and inferotemporal visual areas, facilitating the rapid detection of upcoming motivationally significant events.

Specificity of emotion-related effects on attentional processing in schizotypy.

OBJECTIVES In the schizophrenia spectrum, cognitive functions such as perception, language, and attention have been shown to be adversely influenced by negative affect. The present study addressed three issues of specificity and one issue of mechanism regarding affect-related attentional disruption in schizotypy: (1) Is attentional disturbance from negative affective stimuli specific to positive (PS) but not negative schizotypy (NS)? (2) Do positive affective stimuli also foster attentional disturbance? (3) Are anxiety and depression differentially related to PS and NS? (4) Whatever the degree of specificity in these relationships, does anxiety mediate the relationship between schizotypy and attentional disturbance? METHODS Nonpatient participants (N=162) provided responses on scales of schizotypy, anxiety, and depression and performed an emotional Stroop task, judging the ink color of positive, neutral, and negative words. RESULTS PS but not NS was associated with poorer attentional performance. This attentional disturbance was specific to negative words. PS was associated with anxiety and depression, whereas NS was associated only with depression. Finally, anxiety and depression did not fully mediate the relationship between PS and attentional interference related to negative affective stimuli. CONCLUSIONS Findings of attentional disturbance in the presence of negative affective stimuli, particularly in positive schizotypy, have substantial theoretical implications. They provide a path by which the interplay of cognitive and affective phenomena could lead to the formation, maintenance, and exacerbation of positive symptoms, including delusions and hallucinations. Findings from this study also underscore the importance of examining the differential contribution of comorbid anxiety and depression to cognitive and affective function in the schizophrenia spectrum.