Human amygdala function has been traditionally associated with processing the affective valence (... more Human amygdala function has been traditionally associated with processing the affective valence (positive versus negative) of an emotionally charged event, especially those that signal fear or threat. However, this account of human amygdala function can be explained by alternative views, which posit that the amygdala might be tuned to either (a) more general emotional arousal (more relevant versus less relevant) or (b) more specific emotion categories (fear versus happy). Delineating the pure effects of valence independent of arousal or emotion category is a challenging task, given that these variables naturally co-vary under many circumstances. To circumvent this issue and test the sensitivity of the human amygdala to valence values specifically, we measured the dimension of valence within the single facial expression category of surprise. Given the inherent valence ambiguity of this category, we show that surprised expression exemplars are attributed valence and arousal values that are uniquely and naturally uncorrelated. We then present functional magnetic resonance imaging data from both sexes showing that the amygdala tracks these consensus valence values. Finally, we provide evidence that these valence values are linked to specific visual features of the mouth region, isolating the signal by which the amygdala detects valence information.
Corticolimbic pathways connecting the amygdala and ventral prefrontal cortex (vPFC) are linked wi... more Corticolimbic pathways connecting the amygdala and ventral prefrontal cortex (vPFC) are linked with trait anxiety, but it remains unclear what potential genetic moderators contribute to this association. We sought to address this by examining the inter-individual variability in neuroplasticity as modeled by a functional polymorphism (rs6265) in the human gene for brain derived neurotrophic factor (BDNF). Amygdala-vPFC pathway fractional anisotropy (FA) from 669 diffusion magnetic resonance images was used to examine associations with trait anxiety as a function of rs6265 genotype. We first replicated the inverse correlation between trait anxiety and amygdala-vPFC pathway FA in women. Furthermore, we found a moderating influence of rs6265 genotype such that the association between trait anxiety and right amygdala-vPFC pathway FA was strongest in women carrying the Met allele, which is linked with decreased activity-dependent neuroplasticity. Results indicate that the microstructural integrity of pathways supporting communication between the amygdala and vPFC help shape the expression of trait anxiety in women, and that this association is further modulated by genetically driven variability in neuroplasticity. Neurobiological theories of anxiety postulate that an interconnected network of brain regions, which typically includes the amygdala 1 , the medial prefrontal cortex 2 , and the bed nucleus of the stria terminalis 3 , are central to the generation and regulation of anxious states. Of particular importance for the experience of anxiety are the dynamic reciprocal interactions between the amygdala and medial prefrontal cortex 4, 5. These brain regions are strongly implicated not only in the normative experience of anxiety but also in its pathological expression as anxiety disorders, which are often associated with structural and functional differences in these regions 6–10. One method of assessing the potential association between the aforementioned neural circuitry and trait anxiety is to determine the degree to which the structural integrity of pathways between the amygdala and medial prefrontal cortex is related to individual differences in trait anxiety. A number of studies have utilized diffusion magnetic resonance imaging (dMRI) – a noninvasive neuroimaging method that measures water diffusivity in brain tissue in vivo – to show that the structural connectivity of the pathways connecting the amygdala and the ventral prefrontal cortex (vPFC) is inversely associated with trait anxiety 11–14. Complementing these structural findings, studies using functional magnetic resonance imaging (fMRI) have demonstrated that the functional connectivity between the amygdala and the vPFC is inversely correlated with self-reported levels of anxiety 15–18. This convergent evidence suggests that increased capacity for efficient communication between the amygdala and vPFC – represented by both greater functional and stronger structural connectivity – is associated with lesser trait anxiety 9. While the inverse association between amygdala-vPFC structural connectivity and anxiety is further supported by studies of clinical populations such as generalized anxiety disorder 19, 20 and social anxiety disorder 21, 22 , comparison of available studies examining trait anxiety in non-clinical samples has been inconsistent, possibly related to inadequate power to detect small effects as well as to explore the influence of potential moderators such as sex and age 23–25. Our recent study 13 aimed to address this issue by examining these links in a relatively large sample (n = 275) comprised of three independent datasets. In addition to observing a significant inverse association between amygdala-vPFC structural connectivity and trait anxiety, our work further revealed sex differences
Oversensitivity to uncertain future threat is usefully conceptualized as intolerance of uncertain... more Oversensitivity to uncertain future threat is usefully conceptualized as intolerance of uncertainty (IU). Neuroimaging studies of IU to date have largely focused on its relationship with brain function, but few studies have documented the association between IU and the quantitative properties of brain structure. Here, we examined potential gray and white-matter brain structural correlates of IU from 61 healthy participants. Voxel-based morphometric analysis highlighted a robust positive correlation between IU and striatal volume, particularly the putamen. Conversely, tract-based spatial statistical analysis showed no evidence for a relationship between IU and the structural integrity of white-matter fiber tracts. Current results converge upon findings from individuals with anxiety disorders such as obsessive-compulsive disorder (OCD) or generalized anxiety disorder (GAD), where abnormally increased IU and striatal volume are consistently reported. They also converge with neurobehavioral data implicating the putamen in predictive coding. Most notably, the relationship between IU and striatal volume is observed at a preclinical level, suggesting that the volumetric properties of the striatum reflect the processing of uncertainty per se as it relates to this dimensional personality characteristic. Such a relationship could then potentially contribute to the onset of OCD or GAD, rather than being unique to their pathophysiology.
The dynamic interactions between the amygdala and the medial prefrontal cortex (mPFC) are usefull... more The dynamic interactions between the amygdala and the medial prefrontal cortex (mPFC) are usefully conceptualized as a circuit that both allows us to react automatically to biologically relevant predictive stimuli as well as regulate these reactions when the situation calls for it. In this review, we will begin by discussing the role of this amygdala-mPFC circuitry in the conditioning and extinction of aversive learning in animals. We will then relate these data to emotional regulation paradigms in humans. Finally, we will consider how these processes are compromised in normal and pathological anxiety. We conclude that the capacity for efficient crosstalk between the amygdala and the mPFC, which is represented as the strength of the amygdala-mPFC circuitry, is crucial to beneficial outcomes in terms of reported anxiety.
Anxiety impacts the quality of everyday life and may facilitate the development of affective diso... more Anxiety impacts the quality of everyday life and may facilitate the development of affective disorders, possibly through concurrent alterations in neural circuitry. Findings from multimodal neuroimaging studies suggest that trait-anxious individuals may have a reduced capacity for efficient communication between the amygdala and the ventral prefrontal cortex (vPFC). A diffusion-weighted imaging protocol with 61 directions was used to identify lateral and medial amygdala-vPFC white matter pathways. The structural integrity of both pathways was inversely correlated with self-reported levels of trait anxiety. When this mask from our first dataset was then applied to an independent validation dataset, both pathways again showed a consistent inverse relationship with trait anxiety. Importantly, a moderating effect of sex was found, demonstrating that the observed brain-anxiety relationship was stronger in females. These data reveal a potential neuroanatomical mediator of previously documented functional alterations in amygdalaprefrontal connectivity that is associated with trait anxiety, which might prove informative for future studies of psychopathology.
Anxiety is linked to compromised interactions between the amygdala and the dorsal and ventral med... more Anxiety is linked to compromised interactions between the amygdala and the dorsal and ventral medial prefrontal cortex (mPFC). While numerous task-based neuroimaging studies show that anxiety levels predict amygdala--mPFC connectivity and response magnitude, here we tested the hypothesis that anxiety would predict functional connectivity between these brain regions even during rest. Resting-state functional magnetic resonance imaging scans and self-reported measures of anxiety were acquired from healthy subjects. At rest, individuals with high anxiety were characterized by negatively correlated amygdala--ventral mPFC functional connectivity, while low anxious subjects showed positively correlated activity. Further, high anxious subjects showed amygdala--dorsal mPFC activity that was uncorrelated, while low anxious subjects showed negatively correlated activity. These data show that amygdala--mPFC connectivity at rest indexes normal individual differences in anxiety.
Here we used diffusion tensor imaging (DTI) and showed that the strength of an axonal pathway ide... more Here we used diffusion tensor imaging (DTI) and showed that the strength of an axonal pathway identified between the amygdala and prefrontal cortex predicted individual differences in trait anxiety. A functional magnetic resonance imaging (fMRI) functional localizer that has been shown to produce reliable amygdala activation was collected in twenty psychiatrically healthy subjects. Voxelwise regression analyses using this fMRI amygdala reactivity as a regressor were performed on fractional anisotropy (FA) images derived from DTI. This analysis identified a white matter pathway between the amygdala and ventromedial prefrontal cortex. Individual differences in the structural integrity of this putative amygdala-prefrontal pathway were inversely correlated with trait anxiety levels (i.e., higher pathway strength predicted lower anxiety). More generally, this study illustrates a strategy for combining fMRI and DTI to identify individual differences in structural pathways that predict behavioral outcomes.
The structure of the mask stimulus is crucial in backward masking studies and we recently demonst... more The structure of the mask stimulus is crucial in backward masking studies and we recently demonstrated such an effect when masking faces. Specifically, we showed that activity of the amygdala is increased to fearful facial expressions masked with neutral faces and decreased to fearful expressions masked with a pattern mask-but critically both masked conditions discriminated fearful expressions from happy expressions. Given this finding, we sought to test whether masked fearful eye whites would produce a similar profile of amygdala response in a face vs non-face context. During functional magnetic resonance imaging scanning sessions, 30 participants viewed fearful or happy eye whites masked with either neutral faces or pattern images. Results indicated amygdala activity was increased to fearful vs happy eye whites in the face mask condition, but decreased to fearful vs happy eye whites in the pattern mask condition-effectively replicating and expanding our previous report. Our data support the idea that the amygdala is responsive to fearful eye whites, but that the nature of this activity observed in a backward masking design depends on the mask stimulus.
In this study, we compared the effects of using neutral face masks vs non-face pattern masks on a... more In this study, we compared the effects of using neutral face masks vs non-face pattern masks on amygdala activity to masked fearful faces. Twenty-seven subjects viewed 18 s blocks of either fearful or happy faces masked with either neutral faces or patterns, while their brain activity was measured using functional magnetic resonance imaging. Results replicated increased amygdala activation to face-masked fearful vs happy faces. In the pattern mask condition, the amygdala discriminated between masked fearful and happy faces, but this effect manifested as a decrease in activation to fearful faces compared to happy faces. This interactive effect between facial expression and mask stimulus shows that amygdala responses to masked fearful faces are influenced by the fearful stimuli per se as well as their interaction with the mask stimulus.
It has long been suggested that feedback signals from facial muscles influence emotional experien... more It has long been suggested that feedback signals from facial muscles influence emotional experience. The recent surge in use of botulinum toxin (BTX) to induce temporary muscle paralysis offers a unique opportunity to directly test this "facial feedback hypothesis." Previous research shows that the lack of facial muscle feedback due to BTX-induced paralysis influences subjective reports of emotional experience, as well as brain activity associated with the imitation of emotional facial expressions. However, it remains to be seen whether facial muscle paralysis affects brain activity, especially the amygdala, which is known to be responsive to the perception of emotion in others. Further, it is unknown whether these neural changes are permanent or whether they revert to their original state after the effects of BTX have subsided. The present study sought to address these questions by using functional magnetic resonance imaging to measure neural responses to angry and happy ...
Unpredictable environments can be anxiety-provoking and elicit exaggerated emotional responses to... more Unpredictable environments can be anxiety-provoking and elicit exaggerated emotional responses to aversive stimuli. Even neutral stimuli, when presented in an unpredictable fashion, prime anxiety-like behavior and elicit heightened amygdala activity. The amygdala plays a key role in initiating responses to biologically relevant information, such as facial expressions of emotion. While some expressions clearly signal negative (anger) or positive (happy) events, other expressions (e.g. surprise) are more ambiguous in that they can predict either valence, depending on the context. Here, we sought to determine whether unpredictable presentations of ambiguous facial expressions would bias participants to interpret them more negatively. We used functional magnetic resonance imaging and facial electromyography (EMG) to characterize responses to predictable vs unpredictable presentations of surprised faces. We observed moderate but sustained increases in amygdala reactivity to predictable presentations of surprised faces, and relatively increased amygdala responses to unpredictable faces that then habituated, similar to previously observed responses to clearly negative (e.g. fearful) faces. We also observed decreased corrugator EMG responses to predictable surprised face presentations, similar to happy faces, and increased responses to unpredictable surprised face presentations, similar to angry faces. Taken together, these data suggest that unpredictability biases people to interpret ambiguous social cues negatively.
Previous brain-imaging studies have reported that major depressive disorder (MDD) is characterize... more Previous brain-imaging studies have reported that major depressive disorder (MDD) is characterized by decreased volumes of several cortical and subcortical structures, including the hippocampus, amygdala, anterior cingulate cortex, and caudate nucleus. The purpose of the present study was to identify structural volumetric differences between MDD and healthy participants using a method that allows a comparison of gray and white matter
Our study aimed to identify gray matter volume differences between panic disorder patients and he... more Our study aimed to identify gray matter volume differences between panic disorder patients and healthy volunteers using optimized voxel-based morphometry. Gray matter volume was compared between 18 panic subjects and 18 healthy volunteers. Panic disorder severity scale (PDSS) and Zung self-rating anxiety scale (Z-SAS) were administered. Gray matter volumes of bilateral putamen were decreased in panic subjects relative to healthy comparison subjects (corrected P < 0.05). Decreased gray matter volume was also observed in the right precuneus, right inferior temporal gyrus, right inferior frontal gyrus, left superior temporal gyrus, and left superior frontal gyrus at a less conservative level of significance. PDSS score negatively correlated with gray matter volume in the left putamen, right putamen, right inferior frontal gyrus, and left superior frontal gyrus in panic subjects. The duration of illness negatively correlated with left putaminal gray matter volume. There was also a negative correlation between gray matter volume in right putamen and Z-SAS score in panic subjects. The current study reports a putaminal gray matter volume decrease in panic subjects, which may be related to the clinical severity of panic disorder.
Human amygdala function has been traditionally associated with processing the affective valence (... more Human amygdala function has been traditionally associated with processing the affective valence (positive versus negative) of an emotionally charged event, especially those that signal fear or threat. However, this account of human amygdala function can be explained by alternative views, which posit that the amygdala might be tuned to either (a) more general emotional arousal (more relevant versus less relevant) or (b) more specific emotion categories (fear versus happy). Delineating the pure effects of valence independent of arousal or emotion category is a challenging task, given that these variables naturally co-vary under many circumstances. To circumvent this issue and test the sensitivity of the human amygdala to valence values specifically, we measured the dimension of valence within the single facial expression category of surprise. Given the inherent valence ambiguity of this category, we show that surprised expression exemplars are attributed valence and arousal values that are uniquely and naturally uncorrelated. We then present functional magnetic resonance imaging data from both sexes showing that the amygdala tracks these consensus valence values. Finally, we provide evidence that these valence values are linked to specific visual features of the mouth region, isolating the signal by which the amygdala detects valence information.
Corticolimbic pathways connecting the amygdala and ventral prefrontal cortex (vPFC) are linked wi... more Corticolimbic pathways connecting the amygdala and ventral prefrontal cortex (vPFC) are linked with trait anxiety, but it remains unclear what potential genetic moderators contribute to this association. We sought to address this by examining the inter-individual variability in neuroplasticity as modeled by a functional polymorphism (rs6265) in the human gene for brain derived neurotrophic factor (BDNF). Amygdala-vPFC pathway fractional anisotropy (FA) from 669 diffusion magnetic resonance images was used to examine associations with trait anxiety as a function of rs6265 genotype. We first replicated the inverse correlation between trait anxiety and amygdala-vPFC pathway FA in women. Furthermore, we found a moderating influence of rs6265 genotype such that the association between trait anxiety and right amygdala-vPFC pathway FA was strongest in women carrying the Met allele, which is linked with decreased activity-dependent neuroplasticity. Results indicate that the microstructural integrity of pathways supporting communication between the amygdala and vPFC help shape the expression of trait anxiety in women, and that this association is further modulated by genetically driven variability in neuroplasticity. Neurobiological theories of anxiety postulate that an interconnected network of brain regions, which typically includes the amygdala 1 , the medial prefrontal cortex 2 , and the bed nucleus of the stria terminalis 3 , are central to the generation and regulation of anxious states. Of particular importance for the experience of anxiety are the dynamic reciprocal interactions between the amygdala and medial prefrontal cortex 4, 5. These brain regions are strongly implicated not only in the normative experience of anxiety but also in its pathological expression as anxiety disorders, which are often associated with structural and functional differences in these regions 6–10. One method of assessing the potential association between the aforementioned neural circuitry and trait anxiety is to determine the degree to which the structural integrity of pathways between the amygdala and medial prefrontal cortex is related to individual differences in trait anxiety. A number of studies have utilized diffusion magnetic resonance imaging (dMRI) – a noninvasive neuroimaging method that measures water diffusivity in brain tissue in vivo – to show that the structural connectivity of the pathways connecting the amygdala and the ventral prefrontal cortex (vPFC) is inversely associated with trait anxiety 11–14. Complementing these structural findings, studies using functional magnetic resonance imaging (fMRI) have demonstrated that the functional connectivity between the amygdala and the vPFC is inversely correlated with self-reported levels of anxiety 15–18. This convergent evidence suggests that increased capacity for efficient communication between the amygdala and vPFC – represented by both greater functional and stronger structural connectivity – is associated with lesser trait anxiety 9. While the inverse association between amygdala-vPFC structural connectivity and anxiety is further supported by studies of clinical populations such as generalized anxiety disorder 19, 20 and social anxiety disorder 21, 22 , comparison of available studies examining trait anxiety in non-clinical samples has been inconsistent, possibly related to inadequate power to detect small effects as well as to explore the influence of potential moderators such as sex and age 23–25. Our recent study 13 aimed to address this issue by examining these links in a relatively large sample (n = 275) comprised of three independent datasets. In addition to observing a significant inverse association between amygdala-vPFC structural connectivity and trait anxiety, our work further revealed sex differences
Oversensitivity to uncertain future threat is usefully conceptualized as intolerance of uncertain... more Oversensitivity to uncertain future threat is usefully conceptualized as intolerance of uncertainty (IU). Neuroimaging studies of IU to date have largely focused on its relationship with brain function, but few studies have documented the association between IU and the quantitative properties of brain structure. Here, we examined potential gray and white-matter brain structural correlates of IU from 61 healthy participants. Voxel-based morphometric analysis highlighted a robust positive correlation between IU and striatal volume, particularly the putamen. Conversely, tract-based spatial statistical analysis showed no evidence for a relationship between IU and the structural integrity of white-matter fiber tracts. Current results converge upon findings from individuals with anxiety disorders such as obsessive-compulsive disorder (OCD) or generalized anxiety disorder (GAD), where abnormally increased IU and striatal volume are consistently reported. They also converge with neurobehavioral data implicating the putamen in predictive coding. Most notably, the relationship between IU and striatal volume is observed at a preclinical level, suggesting that the volumetric properties of the striatum reflect the processing of uncertainty per se as it relates to this dimensional personality characteristic. Such a relationship could then potentially contribute to the onset of OCD or GAD, rather than being unique to their pathophysiology.
The dynamic interactions between the amygdala and the medial prefrontal cortex (mPFC) are usefull... more The dynamic interactions between the amygdala and the medial prefrontal cortex (mPFC) are usefully conceptualized as a circuit that both allows us to react automatically to biologically relevant predictive stimuli as well as regulate these reactions when the situation calls for it. In this review, we will begin by discussing the role of this amygdala-mPFC circuitry in the conditioning and extinction of aversive learning in animals. We will then relate these data to emotional regulation paradigms in humans. Finally, we will consider how these processes are compromised in normal and pathological anxiety. We conclude that the capacity for efficient crosstalk between the amygdala and the mPFC, which is represented as the strength of the amygdala-mPFC circuitry, is crucial to beneficial outcomes in terms of reported anxiety.
Anxiety impacts the quality of everyday life and may facilitate the development of affective diso... more Anxiety impacts the quality of everyday life and may facilitate the development of affective disorders, possibly through concurrent alterations in neural circuitry. Findings from multimodal neuroimaging studies suggest that trait-anxious individuals may have a reduced capacity for efficient communication between the amygdala and the ventral prefrontal cortex (vPFC). A diffusion-weighted imaging protocol with 61 directions was used to identify lateral and medial amygdala-vPFC white matter pathways. The structural integrity of both pathways was inversely correlated with self-reported levels of trait anxiety. When this mask from our first dataset was then applied to an independent validation dataset, both pathways again showed a consistent inverse relationship with trait anxiety. Importantly, a moderating effect of sex was found, demonstrating that the observed brain-anxiety relationship was stronger in females. These data reveal a potential neuroanatomical mediator of previously documented functional alterations in amygdalaprefrontal connectivity that is associated with trait anxiety, which might prove informative for future studies of psychopathology.
Anxiety is linked to compromised interactions between the amygdala and the dorsal and ventral med... more Anxiety is linked to compromised interactions between the amygdala and the dorsal and ventral medial prefrontal cortex (mPFC). While numerous task-based neuroimaging studies show that anxiety levels predict amygdala--mPFC connectivity and response magnitude, here we tested the hypothesis that anxiety would predict functional connectivity between these brain regions even during rest. Resting-state functional magnetic resonance imaging scans and self-reported measures of anxiety were acquired from healthy subjects. At rest, individuals with high anxiety were characterized by negatively correlated amygdala--ventral mPFC functional connectivity, while low anxious subjects showed positively correlated activity. Further, high anxious subjects showed amygdala--dorsal mPFC activity that was uncorrelated, while low anxious subjects showed negatively correlated activity. These data show that amygdala--mPFC connectivity at rest indexes normal individual differences in anxiety.
Here we used diffusion tensor imaging (DTI) and showed that the strength of an axonal pathway ide... more Here we used diffusion tensor imaging (DTI) and showed that the strength of an axonal pathway identified between the amygdala and prefrontal cortex predicted individual differences in trait anxiety. A functional magnetic resonance imaging (fMRI) functional localizer that has been shown to produce reliable amygdala activation was collected in twenty psychiatrically healthy subjects. Voxelwise regression analyses using this fMRI amygdala reactivity as a regressor were performed on fractional anisotropy (FA) images derived from DTI. This analysis identified a white matter pathway between the amygdala and ventromedial prefrontal cortex. Individual differences in the structural integrity of this putative amygdala-prefrontal pathway were inversely correlated with trait anxiety levels (i.e., higher pathway strength predicted lower anxiety). More generally, this study illustrates a strategy for combining fMRI and DTI to identify individual differences in structural pathways that predict behavioral outcomes.
The structure of the mask stimulus is crucial in backward masking studies and we recently demonst... more The structure of the mask stimulus is crucial in backward masking studies and we recently demonstrated such an effect when masking faces. Specifically, we showed that activity of the amygdala is increased to fearful facial expressions masked with neutral faces and decreased to fearful expressions masked with a pattern mask-but critically both masked conditions discriminated fearful expressions from happy expressions. Given this finding, we sought to test whether masked fearful eye whites would produce a similar profile of amygdala response in a face vs non-face context. During functional magnetic resonance imaging scanning sessions, 30 participants viewed fearful or happy eye whites masked with either neutral faces or pattern images. Results indicated amygdala activity was increased to fearful vs happy eye whites in the face mask condition, but decreased to fearful vs happy eye whites in the pattern mask condition-effectively replicating and expanding our previous report. Our data support the idea that the amygdala is responsive to fearful eye whites, but that the nature of this activity observed in a backward masking design depends on the mask stimulus.
In this study, we compared the effects of using neutral face masks vs non-face pattern masks on a... more In this study, we compared the effects of using neutral face masks vs non-face pattern masks on amygdala activity to masked fearful faces. Twenty-seven subjects viewed 18 s blocks of either fearful or happy faces masked with either neutral faces or patterns, while their brain activity was measured using functional magnetic resonance imaging. Results replicated increased amygdala activation to face-masked fearful vs happy faces. In the pattern mask condition, the amygdala discriminated between masked fearful and happy faces, but this effect manifested as a decrease in activation to fearful faces compared to happy faces. This interactive effect between facial expression and mask stimulus shows that amygdala responses to masked fearful faces are influenced by the fearful stimuli per se as well as their interaction with the mask stimulus.
It has long been suggested that feedback signals from facial muscles influence emotional experien... more It has long been suggested that feedback signals from facial muscles influence emotional experience. The recent surge in use of botulinum toxin (BTX) to induce temporary muscle paralysis offers a unique opportunity to directly test this "facial feedback hypothesis." Previous research shows that the lack of facial muscle feedback due to BTX-induced paralysis influences subjective reports of emotional experience, as well as brain activity associated with the imitation of emotional facial expressions. However, it remains to be seen whether facial muscle paralysis affects brain activity, especially the amygdala, which is known to be responsive to the perception of emotion in others. Further, it is unknown whether these neural changes are permanent or whether they revert to their original state after the effects of BTX have subsided. The present study sought to address these questions by using functional magnetic resonance imaging to measure neural responses to angry and happy ...
Unpredictable environments can be anxiety-provoking and elicit exaggerated emotional responses to... more Unpredictable environments can be anxiety-provoking and elicit exaggerated emotional responses to aversive stimuli. Even neutral stimuli, when presented in an unpredictable fashion, prime anxiety-like behavior and elicit heightened amygdala activity. The amygdala plays a key role in initiating responses to biologically relevant information, such as facial expressions of emotion. While some expressions clearly signal negative (anger) or positive (happy) events, other expressions (e.g. surprise) are more ambiguous in that they can predict either valence, depending on the context. Here, we sought to determine whether unpredictable presentations of ambiguous facial expressions would bias participants to interpret them more negatively. We used functional magnetic resonance imaging and facial electromyography (EMG) to characterize responses to predictable vs unpredictable presentations of surprised faces. We observed moderate but sustained increases in amygdala reactivity to predictable presentations of surprised faces, and relatively increased amygdala responses to unpredictable faces that then habituated, similar to previously observed responses to clearly negative (e.g. fearful) faces. We also observed decreased corrugator EMG responses to predictable surprised face presentations, similar to happy faces, and increased responses to unpredictable surprised face presentations, similar to angry faces. Taken together, these data suggest that unpredictability biases people to interpret ambiguous social cues negatively.
Previous brain-imaging studies have reported that major depressive disorder (MDD) is characterize... more Previous brain-imaging studies have reported that major depressive disorder (MDD) is characterized by decreased volumes of several cortical and subcortical structures, including the hippocampus, amygdala, anterior cingulate cortex, and caudate nucleus. The purpose of the present study was to identify structural volumetric differences between MDD and healthy participants using a method that allows a comparison of gray and white matter
Our study aimed to identify gray matter volume differences between panic disorder patients and he... more Our study aimed to identify gray matter volume differences between panic disorder patients and healthy volunteers using optimized voxel-based morphometry. Gray matter volume was compared between 18 panic subjects and 18 healthy volunteers. Panic disorder severity scale (PDSS) and Zung self-rating anxiety scale (Z-SAS) were administered. Gray matter volumes of bilateral putamen were decreased in panic subjects relative to healthy comparison subjects (corrected P < 0.05). Decreased gray matter volume was also observed in the right precuneus, right inferior temporal gyrus, right inferior frontal gyrus, left superior temporal gyrus, and left superior frontal gyrus at a less conservative level of significance. PDSS score negatively correlated with gray matter volume in the left putamen, right putamen, right inferior frontal gyrus, and left superior frontal gyrus in panic subjects. The duration of illness negatively correlated with left putaminal gray matter volume. There was also a negative correlation between gray matter volume in right putamen and Z-SAS score in panic subjects. The current study reports a putaminal gray matter volume decrease in panic subjects, which may be related to the clinical severity of panic disorder.
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Papers by M. Justin Kim