Computational principles underlying the functioning of amygdala in the affective regulation of behaviour

This paper presents a short review, compiled with a computational perspective, of the empirical neuroscientific evidence related to amygdala, a brain complex situated at the core of various brain systems underlying motivations and emotions. The functions of amygdala are fundamental for organisms\u27 adaptive behaviour as they allow them to assign subjective saliency and value to experienced world states, so enhancing the adaptive power of their cognitive processes. In this respect, the major goal of the review is outlining the main computational functionalities of amygdala emerging from the neuroscientific investigations on affective processes so as to contribute to highlight the general architectural and functioning mechanisms underlying organisms\u27 emotional processes. This effort is also expected to fertilise the design of robot controllers exhibiting a flexibility and autonomy comparable to that of real organisms

Backward Masked Snakes and Guns Modulate Spatial Attention

Fearful faces are important social cues that alert others of potential threat. Even backward masked fearful faces facilitate spatial attention. However, visual stimuli other than fearful faces can signal potential threat. Indeed, unmasked snakes and spiders modulate spatial attention. Yet, it is unclear if the rapid threat-related facilitation of spatial attention to backward masked stimuli is elicited by non-face threat cues. Evolutionary theories claim that phylogenetic threats (i.e. snakes and spiders) should preferentially elicit an automatic fear response, but it is untested as to whether this response extends to enhancements in spatial attention under restricted processing conditions. Thirty individuals completed a backward masking dot-probe task with both evolutionary relevant and irrelevant threat cues. The results suggest that backward masked visual fear stimuli modulate spatial attention. Both evolutionary relevant (snake) and irrelevant (gun) threat cues facilitated spatial attention

A Stable Sparse Fear Memory Trace in Human Amygdala

Pavlovian fear conditioning is highly conserved across species, providing a powerful model of aversive learning. In rodents, fear memory is stored and reactivated under the influence of the amygdala. There is no evidence for an equivalent mechanism in primates, and an opposite mechanism is proposed whereby primate amygdala contributes only to an initial phase of aversive learning, subsequently ceding fear memory to extra-amygdalar regions. Here, we reexamine this question by exploiting human high-resolution functional magnetic resonance imaging in conjunction with multivariate methods. By assuming a sparse neural coding, we show it is possible, at an individual subject level, to discriminate responses to conditioned (CS+ and CS-) stimuli in both basolateral and centro-cortical amygdala nuclei. The strength of this discrimination increased over time and was tightly coupled to the behavioral expression of fear, consistent with an expression of a stable fear memory trace. These data highlight that the human basolateral and centro-cortical amygdala support initial learning as well more enduring fear memory storage. A sparse neuronal representation for fear, here revealed by multivariate pattern classification, resolves why an enduring memory trace has proven elusive in previous human studies

Translational neuroscience measures of fear conditioning across development: applications to high-risk children and adolescents

Several mental illnesses, including anxiety, can manifest during development, with onsets in late childhood. Understanding the neurobiological underpinnings of risk for anxiety is of crucial importance for early prevention and intervention approaches. Translational neuroscience offers tools to investigate such mechanisms in human and animal models. The current review describes paradigms derived from neuroscience, such as fear conditioning and extinction and overviews studies that have used these paradigms in animals and humans across development. The review also briefly discusses developmental trajectories of the relevant neural circuits and the emergence of clinical anxiety. Future studies should focus on developmental changes in these paradigms, paying close attention to neurobiological and hormonal changes associated with childhood and adolescence

The uncertain brain: a co-ordinate based meta-analysis of the neural signatures supporting uncertainty during different contexts

Uncertainty is often inevitable in everyday life and can be both stressful and exciting. Given its relevance to psychopathology and wellbeing, recent research has begun to address the brain basis of uncertainty. In the current review we examined whether there are discrete and shared neural signatures for different uncertain contexts. From the literature we identified three broad categories of uncertainty currently empirically studied using functional MRI (fMRI): basic threat and reward uncertainty, decision-making under uncertainty, and associative learning under uncertainty. We examined the neural basis of each category by using a coordinate based metaanalysis, where brain activation foci from previously published fMRI experiments were drawn together (1998-2017; 87 studies). The analyses revealed shared and discrete patterns of neural activation for uncertainty, such as the insula and amygdala, depending on the category. Such findings will have relevance for researchers attempting to conceptualise uncertainty, as well as clinical researchers examining the neural basis of uncertainty in relation to psychopathology

Neural mediators of subjective and autonomic responding during threat learning and regulation

Threat learning elicits robust changes across multiple affective domains, including changes in autonomic indices and subjective reports of fear and anxiety. It has been argued that the underlying causes of such changes may be dissociable at a neural level, but there is currently limited evidence to support this notion. To address this, we examined the neural mediators of trial-by-trial skin conductance responses (SCR), and subjective reports of anxious arousal and valence in participants (n = 27; 17 females) performing a threat reversal task during ultra-high field functional magnetic resonance imaging. This allowed us to identify brain mediators during initial threat learning and subsequent threat reversal. Significant neural mediators of anxious arousal during threat learning included the dorsal anterior cingulate, anterior insula cortex (AIC), and ventromedial prefrontal cortex (vmPFC), subcortical regions including the amygdala, ventral striatum, caudate and putamen, and brain-stem regions including the pons and midbrain. By comparison, autonomic changes (SCR) were mediated by a subset of regions embedded within this broader circuitry that included the caudate, putamen and thalamus, and two distinct clusters within the vmPFC. The neural mediators of subjective negative valence showed prominent effects in posterior cortical regions and, with the exception of the AIC, did not overlap with threat learning task effects. During threat reversal, positive mediators of both subjective anxious arousal and valence mapped to the default mode network; this included the vmPFC, posterior cingulate, temporoparietal junction, and angular gyrus. Decreased SCR during threat reversal was positively mediated by regions including the mid cingulate, AIC, two sub-regions of vmPFC, the thalamus, and the hippocampus. Our findings add novel evidence to support distinct underlying neural processes facilitating autonomic and subjective responding during threat learning and threat reversal. The results suggest that the brain systems engaged in threat learning mostly capture the subjective (anxious arousal) nature of the learning process, and that appropriate responding during threat reversal is facilitated by participants engaging self- and valence-based processes. Autonomic changes (SCR) appear to involve distinct facilitatory and regulatory contributions of vmPFC sub-regions

The Generalization of Fear Condition Between Viewed and Imagined Percepts

Mental images can provoke intense emotional states (Holmes & Matthews, 2010). Imagery and perception have common neural and physiological mechanisms, including activation of the early visual areas (Albers et al., 2013). We tested the prediction that individuals can acquire fear to imagined percepts and if this fear transfers to viewing percepts, using fMRI and self-reported measures to determine participants’ fear. The participants completed a task in which they viewed and imagined two stimuli, and were fear conditioned when imagining the CS+. Participants are only told that mild electrical stimulation will be paired with one of the stimuli, but not which stimulus, viewed or imagined. Participants completed 6 runs of each task after completing 6 runs of a habituation form of each task. Behaviorally, participants report greater fear when imagining the CS+ than imagining the CS-. When acquiring fear to an imagined stimulus, we found significant activation in the right insula. These findings are consistent with previous literature indicating that this regions are involved in processes related to emotional memory, autonomic arousal, and emotion-related motivation. Behaviorally, participants also report greater fear when viewing the CS+ than when viewing the CS-, though neither is ever paired with shock. When fear is generalized from an imagined precept to a viewed one (i.e., CS+ view \u3e CS- view), we found no significant activation. We can conclude that participants generalize the fear acquired when imagining the stimulus to viewing the stimulus. Finally, participants also show a similar level of self-reported fear to fear conditioning acquired to imagining a stimulus as to when fear is acquired to viewing a stimulus. We found insular cortex and precentral gyrus activation when investigating the similarities between these processes. These results indicate: that humans can fear condition to imagined percepts, which involves activation of anterior insula; that this fear conditioning generalizes to instances of viewing the conditioned percept; and that differential conditioning to both imagined and viewed percepts produced a similar magnitude of subjective fear along with activation of the right anterior insula