Mode of functional connectivity in amygdala pathways dissociates level of awareness for signals of fear

Westmead Hospital, Sydney, New South Wales, Australia
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.75). 10/2006; 26(36):9264-71. DOI: 10.1523/JNEUROSCI.1016-06.2006
Source: PubMed

ABSTRACT Many of the same regions of the human brain are activated during conscious attention to signals of fear and in the absence of awareness for these signals. The neural mechanisms that dissociate level of awareness from activation in these regions remain unknown. Using functional magnetic resonance imaging with connectivity analysis in healthy human subjects, we demonstrate that level of awareness for signals of fear depends on mode of functional connectivity in amygdala pathways rather than discrete patterns of activation in these pathways. Awareness for fear relied on negative connectivity within both cortical and subcortical pathways to the amygdala, suggesting that reentrant feedback may be necessary to afford such awareness. In contrast, responses to fear in the absence of awareness were supported by positive connections in a direct subcortical pathway to the amygdala, consistent with the view that excitatory feedforward connections along this pathway may be sufficient for automatic responses to "unseen" fear.

Download full-text


Available from: Leanne M Williams, Feb 08, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Emotional scene perception is associated with enhanced activity in ventral occipitotemporal cortex and amygdala. While a growing body of research supports the perspective that emotional perception is organized via amygdala feedback to rostral ventral visual cortex, the contributions of high-order thalamic structures strongly associated with visual attention, specifically the mediodorsal nucleus and pulvinar, have not been well investigated. Here we sample the activity of amygdala, MDN, pulvinar, and extrastriate ventral visual regions with fMRI as a group of participants view a mixed series of pleasant, neutral, and unpleasant natural scenes, balanced for basic perceptual characteristics. The results demonstrate that all regions showed enhanced activity during emotionally arousing relative to neutral scene perception. Consistent with recent research, the latency of emotional discrimination across subcortical and visual cortical regions suggests a role for the amygdala in the early evaluation of scene emotion. These data support the perspective that higher order visual thalamic structures are sensitive to the emotional value of complex scene stimuli, and may serve in concert with amygdala and fusiform gyrus to modulate visual attention toward motivationally relevant cues.
    Brain Research 08/2014; 1587. DOI:10.1016/j.brainres.2014.08.061 · 2.83 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Emotion dysregulation is a key feature of schizophrenia, a brain disorder strongly associated with genetic risk and aberrant dopamine signalling. Dopamine is inactivated by catechol-O-methyltransferase (COMT), whose gene contains a functional polymorphism (COMT Val158Met) associated with differential activity of the enzyme and with brain physiology of emotion processing. The aim of the present study was to investigate whether genetic risk for schizophrenia and COMT Val158Met genotype interact on brain activity during implicit and explicit emotion processing.MethodA total of 25 patients with schizophrenia, 23 healthy siblings of patients and 24 comparison subjects genotyped for COMT Val158Met underwent functional magnetic resonance imaging during implicit and explicit processing of facial stimuli with negative emotional valence. RESULTS: We found a main effect of diagnosis in the right amygdala, with decreased activity in patients and siblings compared with control subjects. Furthermore, a genotype×diagnosis interaction was found in the left middle frontal gyrus, such that the effect of genetic risk for schizophrenia was evident in the context of the Val/Val genotype only, i.e. the phenotype of reduced activity was present especially in Val/Val patients and siblings. Finally, a complete inversion of the COMT effect between patients and healthy subjects was found in the left striatum during explicit processing. CONCLUSIONS: Overall, these results suggest complex interactions between genetically determined dopamine signalling and risk for schizophrenia on brain activity in the prefrontal cortex during emotion processing. On the other hand, the effects in the striatum may represent state-related epiphenomena of the disorder itself.
    Psychological Medicine 05/2012; 43(2):1-14. DOI:10.1017/S0033291712001134 · 5.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To investigate whether the non-conscious processing of fearful faces exist in unattended condition, event-related potentials (ERPs) were recorded in a facial expression detection task. Participants were asked to discriminate the facial expressions (fearful or neutral) at the attended location. Unattended faces were associated with a response that was either congruent or in conflict with the response to the attended face. ERP results showed that the trials with response conflict between attended and unattended faces enhanced the amplitude of the P3 component when the neutral face was presented at attended location and the fearful face was presented at the unattended location. Our findings imply that the non-conscious fearful faces can be processed in the unattended condition.
    Neuroscience Letters 12/2011; 506(2):317-21. DOI:10.1016/j.neulet.2011.11.034 · 2.06 Impact Factor