Neural correlates of derived relational responding on tests of stimulus equivalence

<p>Abstract</p> <p>Background</p> <p>An essential component of cognition and language involves the formation of new conditional relations between stimuli based upon prior experiences. Results of investigations on transitive inference (TI) highlight a prominent role for the medial temporal lobe in maintaining associative relations among sequentially arranged stimuli (A > B > C > D > E). In this investigation, medial temporal lobe activity was assessed while subjects completed "Stimulus Equivalence" (SE) tests that required deriving conditional relations among stimuli within a class (A ≡ B ≡ C).</p> <p>Methods</p> <p>Stimuli consisted of six consonant-vowel-consonant triads divided into two classes (A1, B1, C1; A2, B2, C2). A simultaneous matching-to-sample task and differential reinforcement were employed during pretraining to establish the conditional relations A1:B1 and B1:C1 in class 1 and A2:B2 and B2:C2 in class 2. During functional neuroimaging, recombined stimulus pairs were presented and subjects judged (yes/no) whether stimuli were related. SE tests involved presenting three different types of within-class pairs: Symmetrical (B1 A1; C1 B1; B2 A2; C2 B2), and Transitive (A1 C1; A2 C2) and Equivalence (C1 A1; C2 A2) relations separated by a nodal stimulus. Cross-class 'Foils' consisting of unrelated stimuli (e.g., A1 C2) were also presented.</p> <p>Results</p> <p>Relative to cross-class Foils, Transitive and Equivalence relations requiring inferential judgments elicited bilateral activation in the anterior hippocampus while Symmetrical relations elicited activation in the parahippocampus. Relative to each derived relation, Foils generally elicited bilateral activation in the parahippocampus, as well as in frontal and parietal lobe regions.</p> <p>Conclusion</p> <p>Activation observed in the hippocampus to nodal-dependent derived conditional relations (Transitive and Equivalence relations) highlights its involvement in maintaining relational structure and flexible memory expression among stimuli within a class (A ≡ B ≡ C).</p

Generalized anxiety modulates frontal and limbic activation in major depression

<p>Abstract</p> <p>Background</p> <p>Anxiety is relatively common in depression and capable of modifying the severity and course of depression. Yet our understanding of how anxiety modulates frontal and limbic activation in depression is limited.</p> <p>Methods</p> <p>We used functional magnetic resonance imaging and two emotional information processing tasks to examine frontal and limbic activation in ten patients with major depression and comorbid with preceding generalized anxiety (MDD/GAD) and ten non-depressed controls.</p> <p>Results</p> <p>Consistent with prior studies on depression, MDD/GAD patients showed hypoactivation in medial and middle frontal regions, as well as in the anterior cingulate, cingulate and insula. However, heightened anxiety in MDD/GAD patients was associated with increased activation in middle frontal regions and the insula and the effects varied with the type of emotional information presented.</p> <p>Conclusions</p> <p>Our findings highlight frontal and limbic hypoactivation in patients with depression and comorbid anxiety and indicate that anxiety level may modulate frontal and limbic activation depending upon the emotional context. One implication of this finding is that divergent findings reported in the imaging literature on depression could reflect modulation of activation by anxiety level in response to different types of emotional information.</p

Arousal Modulation in Females with Fragile X or Turner Syndrome

The present study was carried out to examine physiological arousal modulation (heart activity and skin conductance, across baseline and cognitive tasks, in females with fragile X or Turner syndrome and a comparison group of females with neither syndrome. Relative to the comparison group, for whom a greater increase in skin conductance was associated with poor arithmetic performance and less risk taking behavior, females with fragile X displayed a minimal increase in heart activity that was nevertheless associated with poor performance on mental arithmetic. In contrast, no arousal–cognitive performance relationship emerged for the group with Turner syndrome. Taken together, our findings suggest that distinct profiles of arousal modulation might be associated with cognitive deficits in these syndrome populations

A complementary method for detecting qi vacuity

<p>Abstract</p> <p>Background</p> <p>Qi vacuity (QV) is defined by traditional Chinese medicine as a loss of energy in the human body. An objective method for detecting QV was not available until recently, however. The automatic reflective diagnosis system (ARDK) is a device that detects human bioenergy through measuring skin conductance at 24 special acupoints on the wrists and ankles.</p> <p>Methods</p> <p>This study used the ARDK to measure skin conductance on 193 patients with QV and 89 sex- and age-matched healthy controls to investigate whether the device is useful in detecting QV. Patients diagnosed with QV have three or more of five symptoms or signs; symptom severity is measured on 5 levels and scored from 0 to 4 points. We compared the difference in the mean ARDK values between patients with QV and healthy controls, and further used linear regression analysis to investigate the correlation between the mean ARDK values and QV scores in patients diagnosed with QV.</p> <p>Results</p> <p>The mean ARDK values in patients with QV (30.2 ± 16.8 μA) are significantly lower than those of healthy controls (37.7 ± 10.8 μA; <it>P </it>< 0.001). A negative correlation was found between the mean ARDK values and QV scores (<it>r </it>coefficient = -0.61; <it>P </it>< 0.001). After adjusting for age, the decreased mean ARDK values in patients with QV showed a significant correlation with the QV scores.</p> <p>Conclusion</p> <p>These results suggest that the mean ARDK values reflect the severity of QV in patients diagnosed with the disorder. They also suggest that the bioenergy level of the human body can be measured by skin conductance. ARDK is a safe and effective complementary method for detecting and diagnosing QV.</p

False Heart Rate Feedback and the Perception of Heart Symptoms in Patients with Congenital Heart Disease and Anxiety

Background Little is known about the mechanisms explaining an increased perception of heart symptoms in congenital heart disease (ConHD). In the present study, it was suggested that a combination of high trait anxiety and disease history increases the perception of heart symptoms. Purpose It was tested whether false heart cues will result in an increased perception of heart symptoms in patients with ConHD and anxiety. Method Thirty-six patients with ConHD and 44 healthy controls performed two exercise tasks. During one of the exercise tasks, participants were exposed to a false heart cue consisting of false heart rate feedback (regular or irregular). Perceived heart symptoms were assessed and heart rate, arterial partial pressure of CO2, and respirator rate were monitored continuously. Results In line with the predictions, false heart rate feedback resulted in an increased perception of heart symptoms in high trait anxious patients with ConHD that could not be explained by acute heart dysfunction. However, unexpectedly, this effect was not observed immediately after the false heart rate feedback task but after a second exercise task without false feedback. Conclusion The results suggest that not the sole presence of ConHD but ConHD in combination with high trait anxiety results in a vulnerability to overperceive heart symptom

The Impact of Worry on Attention to Threat

Prior research has often linked anxiety to attentional vigilance for threat using the dot probe task, which presents probes in spatial locations that were or were not preceded by a putative threat stimulus. The present study investigated the impact of worry on threat vigilance by administering this task during a worry condition and during a mental arithmetic control condition to 56 undergraduate students scoring in the low normal range on a measure of chronic worry. The worry induction was associated with faster responses than arithmetic to probes in the attended location following threat words, indicating the combined influence of worry and threat in facilitating attention. Within the worry condition, responses to probes in the attended location were faster for trials containing threat words than for trials with only neutral words, whereas the converse pattern was observed for responses to probes in the unattended location. This connection between worry states and attentional capture by threat may be central to understanding the impact of hypervigilance on information processing in anxiety and its disorders

Neurobiological substrates of cognitive rigidity and autonomic inflexibility in generalized anxiety disorder

Generalized anxiety disorder (GAD) is characterized by difficulties in inhibiting both perseverative thoughts (worry and rumination) and autonomic arousal. We investigated the neurobiological substrates of such abnormal inhibitory processes, hypothesizing aberrant functional coupling within ‘default mode’ (DMN) and autonomic brain networks. Functional imaging and heart rate variability (HRV) data were acquired from GAD patients and controls during performance of three tracking tasks interspersed with a perseverative cognition (PC) induction. After detection of infrequent target stimuli, activity within putative DMN hubs was suppressed, consistent with a redirection of attentional resources from internal to external focus. This magnitude of activity change was attenuated in patients and individuals with higher trait PC, but was predicted by individual differences in HRV. Following the induction of PC in controls, this pattern of neural reactivity became closer to that of GAD patients. Results support, at a neural level, the association between cognitive inflexibility and autonomic rigidity

Amygdala functional connectivity as a longitudinal biomarker of symptom changes in generalized anxiety

Generalized anxiety disorder (GAD) is characterized by excessive worry, autonomic dysregulation and functional amygdala dysconnectivity, yet these illness markers have rarely been considered together, nor their interrelationship tested longitudinally. We hypothesized that an individual's capacity for emotion regulation predicts longer-term changes in amygdala functional connectivity, supporting the modification of GAD core symptoms. Sixteen patients with GAD (14 women) and individually matched controls were studied at two time points separated by 1 year. Resting-state fMRI data and concurrent measurement of vagally mediated heart rate variability were obtained before and after the induction of perseverative cognition. A greater rise in levels of worry following the induction predicted a stronger reduction in connectivity between right amygdala and ventromedial prefrontal cortex, and enhanced coupling between left amygdala and ventral tegmental area at follow-up. Similarly, amplified physiological responses to the induction predicted increased connectivity between right amygdala and thalamus. Longitudinal shifts in a distinct set of functional connectivity scores were associated with concomitant changes in GAD symptomatology over the course of the year. Results highlight the prognostic value of indices of emotional dysregulation and emphasize the integral role of the amygdala as a critical hub in functional neural circuitry underlying the progression of GAD symptomatology