fMRI studies of sensitivity and habituation effects within the auditory cortex at 1.5 T and 3 T

Towards a mechanistic understanding of mindfulness-based stress reduction (MBSR) using an RCT neuroimaging approach: Effects on regulating own stress in social and non-social situations

Although much research has shown that mindfulness-based interventions (MBIs) can reduce psychological stress, it is less clear if effects generalize to everyday social situations, which range among the largest stress triggers. Furthermore, mechanisms of MBIs have not been fully established. Emotion regulation (ER) has been suggested as one key mechanism, yet the role of cognitive reappraisal and acceptance strategies is still under debate. To address these questions, a neuroimaging-based randomized controlled trial (RCT) was performed (n=68), comparing mindfulness-based stress reduction (MBSR) with a reading/listening intervention (READ), using a novel dyadic paradigm for self and other emotion regulation under stress as primary outcome on behavior and brain levels and established empathy measures (clinicatrials.gov NCT03035669). Compared to READ, MBSR led to self-reported stress reduction through both cognitive reappraisal and acceptance only when regulating self and not when regulating others' distress. In addition, MBSR led to increased brain activation over time for regulating own (parietal cortex) and others' (precuneus, TPJ) emotions through cognitive reappraisal and acceptance, albeit this effect was also seen for the reading intervention for regulating own stress via reappraisal. Brain changes did not scale with subjective stress reduction and amount of meditation practice. More distant generalization effects of MBSR on socio-emotional functioning (cognitive empathy and compassion) could also not be shown. This study identified both cognitive reappraisal and acceptance as two ER mechanisms of MBSR, but indicates that effects do not extend to social settings.

Altered auditory processing in patients with panic disorder: a pilot study

OBJECTIVES

Clinical and electrophysiological studies suggest that panic disorder (PD) patients show disturbed response inhibition to sensory stimuli. Thus, habituation of neuronal activation after repeated sine tone stimulation was assessed by functional magnetic resonance imaging (fMRI) in patients with PD.

METHODS

Twenty patients with PD and 20 age- and gender-matched healthy controls were assessed by 3T fMRI for auditory habituation. During three stimulation cycles of digitally generated pulsed (ν=5 Hz) 800-Hz sine tones alternating with silent periods, activation of the auditory cortex and other anxiety- or sensory integration-related regions was assessed. Brain activation was further analyzed dependent on functional serotonin transporter (5-HTT) gene variation (5-HTTLPR).

RESULTS

PD patients demonstrated an extended brain activity in the first stimulation block, which normalized during the second stimulation cycle. A positive correlation with anxiety measures (HAMA) and an increased activity of distinct anxiety- or sensory integration-related areas (e.g., BA 22, BA 10) were seen during the third block of auditory stimulation. There was a significant interaction of left amygdala activation and the 5-HTTLPR S allele.

CONCLUSIONS

Our results support the hypothesis of an aberrant processing of sensory information in PD patients. This phenomenon may underlie an enhanced responsiveness to anxiety-relevant or irrelevant stimuli possibly increasing PD vulnerability.

Smoking-related videos for use in cue-induced craving paradigms

Environmental cues (e.g., the sight of a cigarette) have long been recognized as important triggers for craving in smokers. Available imaging technologies (e.g., fMRI) allow investigation of the neural mechanisms for cue-induced craving, but there stands a need for a cue-delivery system compatible with an MRI environment. We developed a standardized set of 24 high-resolution videos, 12 containing cigarette smoking scenes (e.g., lighting up), and 12 containing neutral scenes (e.g., reading a book), each 30 s long, with comparable lighting, visual complexity, and background filmed by a professional cinematographer. Study participants were 20 smokers (mean age=37.7 years, 50% female). Each was exposed to the 24 videos in a random order under laboratory conditions. Dependent measures included heart rate, blood pressure, skin conductance, skin temperature, and self-reported craving (0-100) following each video. Overall findings indicated that smokers had greater reactivity to the smoking videos than to neutral videos (p<.01). Follow-up univariate analyses revealed significant cue effects on self-reported craving, galvanic skin response, and skin temperature. Interestingly, exploratory examination of gender revealed that men had higher blood pressure and skin temperature responses than women, and that women had higher responses when viewing videos of women smoking than when viewing men smoking. Results support this set of videos as an effective tool for investigation of cue-elicited craving, and raise the possibility of unique gender effects in cue reactivity.

Quantification of fMRI BOLD signal and volume applied to the somatosensory cortex

Functional magnetic resonance imaging based on blood-oxygenation-level-dependent (BOLD) signal variations is clinically used to investigate the impact of neurological disorders on brain function. Such disorders effect not only the localization but also the amplitude and extent of the BOLD signal. Statistical methods are useful to localize the BOLD signal but fail to quantify functional activity because they rely on arbitrary thresholds. This article presents a method that uses a priori defined VOI (volume of interest) and independently quantifies the mean BOLD signal and extent of the activated volume. The technique is based on the separation of the VOI signal difference distribution into a noise and an activation contribution. The technique does not require any threshold and is nearly independent of the preselected VOI size. The technique was verified in a test group of 17 subjects performing bilateral finger tapping. The results were compared with those of conventional analysis based on statistical tools. A standard imaging technique using FID-EPI (free induction decay echo-planar imaging, TR = 4000 ms, TE = 66 ms, 60 images activation, 60 images rest) was employed. The activated volume, V, and signal difference, deltaS, of the motor cortex were determined with an accuracy of sigma(V) = 17.1% and sigma(deltaS) = 3.6%, respectively. The activated volume of the left hemispheric motor area was significantly greater (P = 0.025) then in the right hemispheric, VL = 7.35 +/- 2.29 cm3 versus VR = 6.39 +/- 2.34 cm3. The result is consistent with the findings obtained by other techniques. On the other hand, the statistical methods did not yield any significant difference in activation between both hemispheres. The VOI-based method presented here is an additional tool to study the extent and amplitude of the BOLD signal.

MR-Encephalography: Fast multi-channel monitoring of brain physiology with magnetic resonance

A new approach to measure activation-related changes in the brain by magnetic resonance is described offering high temporal resolution of 10-100 measurements per second. This is achieved by simultaneous multi-channel reception where the spatial resolution during continuous observation is determined by the sensitive volume of each coil alone without any additional spatial encoding gradients. Experimental results demonstrate the very high sensitivity of this approach, which allows to directly measure and monitor the stimulus-dependent hemodynamic response as well as ECG- and breathing-related signal fluctuations. One-dimensional spatial encoding either parallel or orthogonal to the cortex demonstrates that vascular signals can be identified by the pronounced signal variation at the ECG-frequency. Noise analysis at different frequencies reveals regional signal fluctuations in the frequency range between 2 and 10 Hz. Furthermore, initial results show that frequency changes in the order of <0.03 Hz corresponding to <1 nano Tesla can be detected. In addition to its potential use in neuroscientific studies, this new method opens a wide range of applications for fast physiological monitoring and can be easily combined with conventional high-resolution imaging.