Changes In Amygdala Activity Research Articles

Cortical-subcortical structural connections support transcranial magnetic stimulation engagement of the amygdala.

The amygdala processes valenced stimuli, influences emotion, and exhibits aberrant activity across anxiety disorders, depression, and PTSD. Interventions modulating amygdala activity hold promise as transdiagnostic psychiatric treatments. In 45 healthy participants, we investigated whether transcranial magnetic stimulation (TMS) elicits indirect changes in amygdala activity when applied to ventrolateral prefrontal cortex (vlPFC), a region important for emotion regulation. Harnessing in-scanner interleaved TMS/functional MRI (fMRI), we reveal that vlPFC neurostimulation evoked acute and focal modulations of amygdala fMRI BOLD signal. Larger TMS-evoked changes in the amygdala were associated with higher fiber density in a vlPFC–amygdala white matter pathway when stimulating vlPFC but not an anatomical control, suggesting this pathway facilitated stimulation-induced communication between cortex and subcortex. This work provides evidence of amygdala engagement by TMS, highlighting stimulation of vlPFC–amygdala circuits as a candidate treatment for transdiagnostic psychopathology. More broadly, it indicates that targeting cortical-subcortical structural connections may enhance the impact of TMS on subcortical neural activity and, by extension, subcortex-subserved behaviors.

Neural responses to threat and reward and changes in inflammation following a mindfulness intervention

ObjectiveMindfulness meditation has been shown to reduce distress and increase well-being among individuals with chronic disease, including breast cancer survivors. However, the neural correlates of these changes and their links with inflammatory biology are not yet known. The present study examined whether a mindfulness meditation intervention was associated with changes in neural responses to threat and reward from pre- to post-intervention, and whether those neural changes were associated with changes in markers of inflammation in breast cancer survivors. MethodsThis was a single-arm trial of a standardized, validated 6-week mindfulness meditation intervention. Participants were 20 women who had been diagnosed and treated for early-stage breast cancer. Participants provided peripheral blood samples and underwent a 90-minute neuroimaging scan before and after the intervention, with a focus on tasks known to elicit activity in threat- and reward-related neural regions. ResultsThere were significant changes in neural responses to the two tasks of interest from pre to post-intervention (ps < 0.042). Participants showed significant reductions in amygdala activity in response to threatening images and significant increases in ventral striatum activity to rewarding images from pre- to post-intervention. Although changes in amygdala activity were not correlated with inflammatory markers, increases in ventral striatum activity were correlated with decreases in circulating concentrations of the proinflammatory cytokine IL-6 and the inflammatory marker CRP. ConclusionsThese results, while preliminary, suggest that while a mindfulness meditation intervention can alter neural responses to both threat and nonsocial reward-related stimuli, changes in neural reward activity may be more closely linked to changes in circulating levels of inflammation.

Meditation-induced neuroplastic changes in amygdala activity during negative affective processing

ABSTRACTRecent evidence suggests that the effects of meditation practice on affective processing and resilience have the potential to induce neuroplastic changes within the amygdala. Notably, literature speculates that meditation training may reduce amygdala activity during negative affective processing. Nonetheless, studies have thus far not verified this speculation. In this longitudinal study, participants (N = 21, 9 men) were trained in awareness-based compassion meditation (ABCM) or matched relaxation training. The effects of meditation training on amygdala activity were examined during passive viewing of affective and neutral stimuli in a non-meditative state. We found that the ABCM group exhibited significantly reduced anxiety and right amygdala activity during negative emotion processing than the relaxation group. Furthermore, ABCM participants who performed more compassion practice had stronger right amygdala activity reduction during negative emotion processing. The lower right amygdala activity after ABCM training may be associated with a general reduction in reactivity and distress. As all participants performed the emotion processing task in a non-meditative state, it appears likely that the changes in right amygdala activity are carried over from the meditation practice into the non-meditative state. These findings suggest that the distress-reducing effects of meditation practice on affective processing may transfer to ordinary states, which have important implications on stress management.

Sleepiness induced by sleep-debt enhanced amygdala activity for subliminal signals of fear.

BackgroundEmotional information is frequently processed below the level of consciousness, where subcortical regions of the brain are thought to play an important role. In the absence of conscious visual experience, patients with visual cortex damage discriminate the valence of emotional expression. Even in healthy individuals, a subliminal mechanism can be utilized to compensate for a functional decline in visual cognition of various causes such as strong sleepiness. In this study, sleep deprivation was simulated in healthy individuals to investigate functional alterations in the subliminal processing of emotional information caused by reduced conscious visual cognition and attention due to an increase in subjective sleepiness. Fourteen healthy adult men participated in a within-subject crossover study consisting of a 5-day session of sleep debt (SD, 4-h sleep) and a 5-day session of sleep control (SC, 8-h sleep). On the last day of each session, participants performed an emotional face-viewing task that included backward masking of nonconscious presentations during magnetic resonance scanning.ResultsFinally, data from eleven participants who were unaware of nonconscious face presentations were analyzed. In fear contrasts, subjective sleepiness was significantly positively correlated with activity in the amygdala, ventromedial prefrontal cortex, hippocampus, and insular cortex, and was significantly negatively correlated with the secondary and tertiary visual areas and the fusiform face area. In fear-neutral contrasts, subjective sleepiness was significantly positively correlated with activity of the bilateral amygdala. Further, changes in subjective sleepiness (the difference between the SC and SD sessions) were correlated with both changes in amygdala activity and functional connectivity between the amygdala and superior colliculus in response to subliminal fearful faces.ConclusionSleepiness induced functional decline in the brain areas involved in conscious visual cognition of facial expressions, but also enhanced subliminal emotional processing via superior colliculus as represented by activity in the amygdala. These findings suggest that an evolutionally old and auxiliary subliminal hazard perception system is activated as a compensatory mechanism when conscious visual cognition is impaired. In addition, enhancement of subliminal emotional processing might cause involuntary emotional instability during sleep debt through changes in emotional response to or emotional evaluation of external stimuli.

The impact of 5-HTTLPR on acute serotonin transporter blockade by escitalopram on emotion processing: preliminary findings from a randomised, crossover fMRI study.

Benefit from antidepressant treatment such as selective serotonin reuptake inhibitors (SSRIs) may depend on individual differences in acute effects on neural emotion processing. The short ('S') allele of the serotonin transporter (5-HTT)-linked polymorphic region (5-HTTLPR) is associated with both negative emotion processing biases and poorer treatment outcomes. Therefore, the aim of the present study was to explore the effects of 5-HTTLPR on the impact of the SSRI escitalopram during processing of positive and negative emotional images, as well as neutral stimuli. The study employed a double-blind, randomised, placebo-controlled crossover design on 36 healthy Caucasian female participants who underwent functional magnetic resonance imaging (fMRI) scanning following placebo or escitalopram treatment, separated by a 7-day washout period. Changes in the left amygdala signal with escitalopram treatment during processing of emotional stimuli were linearly related to the 5-HTTLPR 'S' allele load such that the signal to positive stimuli decreased and the signal to negative stimuli increased with an increasing number of low-expressing 'S' alleles. While 5-HTTLPR subgroups were small in size, individual subject changes with treatment and task condition increase confidence in the findings. While preliminary, our findings comprise the first pharmacogenetic study demonstrating an effect of the 5-HTTLPR 'S' allele load on escitalopram-induced changes in amygdala activity during emotional processing, consistent with a 5-HTT expression dosage model. The present findings have implications for the impact of this polymorphism on antidepressant efficacy in patients with mood and anxiety disorders.

Amygdala response to mother

In altricial species, like the human, the caregiver, very often the mother, is one of the most potent stimuli during development. The distinction between mothers and other adults is learned early in life and results in numerous behaviors in the child, most notably mother-approach and stranger wariness. The current study examined the influence of the maternal stimulus on amygdala activity and related circuitry in 25 developing children (n = 13) and adolescents (n = 12), and how this circuitry was associated with attachment-related behaviors. Results indicated that maternal stimuli were especially effective in recruiting activity in the left dorsal amygdala, and activity in this amygdala region showed increased functional connectivity with evaluative and motor regions during viewing of maternal stimuli. Increases in this left dorsal amygdala activity and related amygdala-cortical functional connectivity were associated with increased mother-approach behaviors as measured by in-scanner behavioral responding and out-of-scanner child-report. Moreover, age-related changes in amygdala activity to strangers statistically mediated the developmentally typical decline in stranger wariness seen across this period. These results suggest that mother-induced behaviors are enacted by maternal influence on amygdala-cortical circuitry during childhood and adolescence.

Differential patterns of initial and sustained responses in amygdala and cortical regions to emotional stimuli in schizophrenia patients and healthy participants

We sought to investigate the altered brain responses to emotional stimuli in patients with schizophrenia. We analyzed data from 14 patients with schizophrenia and 14 healthy controls who performed an emotional face matching task. We evaluated brain activity and connectivity in the amygdala and cortical regions during the initial (first 21 seconds of each stimulation block) and sustained (last 21 seconds) stages of an emotional processing task, and we determined changes in amygdala activity across the emotional processing task. The patients with schizophrenia showed similar amygdala activation to the controls during the initial stage of processing, but their activation decreased during the sustained stage. The controls showed increasing amygdala activity across the emotional blocks, whereas activity progressively decreased in the schizophrenia group. The patients with schizophrenia showed increased cortical activity and interconnectivity in the medial frontal and inferior parietal cortex in the initial stage of emotional processing.There was increased activity in the superior temporal cortex and greater connectivity with the inferior parietal cortex in the sustained stage. Performance accuracy was lower in the schizophrenia group in the first part of the block, while their reaction time was longer in the latter part of the block. It was not possible to specify the moment at which the switch in amygdala response occurred. Our findings suggest that patients with schizophrenia have an initial automatic emotional response but that they need to switch to a compensatory cognitive strategy to solve the task.