Contextual fear conditioning in humans using feature-identical contexts

How fear conditioning affects the visuocortical processing of context cues in humans. Evidence from steady state visual evoked responses

Previous research has focused on how different environments modulate fear learning and the accompanying prioritization of acquired threat cues in sensory cortices. Here, we focus on the other side of the coin and show how the acquisition of threat relevance influences the sensory processing of the environment and an associated context cue. Thereby, we observed that spatial suppression surrounding the focus of threat relevant cues extended by threat learning. By recording frequency-tagged steady-state visual evoked fields (ssVEFs) from 35 healthy participants using Magnetoencephalography (MEG), we replicate earlier findings that centrally presented acquired threat-relevant cues (CS+) evoke greater ssVEF responses, whereas visuocortical engagement during the processing of threat-irrelevant cues (CS-) is inhibited. Critically, as predicted by early computational models of threat learning such as the Rescorla-Wagner model, ssVEF responses to an inter-trial peripheral background flicker (context cue), when no CS was shown, increased linearly during learning. In contrast, visuocortical engagement in the early-tier visual cortex during the processing of the background flicker was strongly reduced during CS presentation in the last learning block. This effect was observed during maximal CS+ and CS- discrimination. However, in more anterior ventral visual cortex, the inhibition of oscillatory responses of the context cue occurred only during CS + trials, whereas during CS- trials, background ssVEF responses were increased. These results are in line with the notion that attentional resources are reallocated flexibly between cues of different threat relevance and that the spatial extension of center surround neuronal competition can be modulated by threat learning.

The impact of the left inferior frontal gyrus on fear extinction: A transcranial direct current stimulation study

INTRODUCTION

Fear extinction is a fundamental component of exposure-based therapies for anxiety-related disorders. The renewal of fear in a different context after extinction highlights the importance of contextual factors. In this study, we aimed to investigate the causal role of the left inferior frontal gyrus (LiFG) in the context-dependency of fear extinction learning via administration of transcranial direct current stimulation (tDCS) over this area.

METHODS

180 healthy subjects were assigned to 9 groups: 3 tDCS conditions (anodal, cathodal, and sham) × 3 context combinations (AAA, ABA, and ABB). The fear conditioning/extinction task was conducted over three consecutive days: acquisition, extinction learning, and extinction recall. tDCS (2 mA, 10min) was administered during the extinction learning phase over the LiFG via a 4-electrode montage. Skin conductance response (SCR) data and self-report assessments were collected.

RESULTS

During the extinction learning phase, groups with excitability-enhancing anodal tDCS showed a significantly higher fear response to the threat cues compared to cathodal and sham stimulation conditions, irrespective of contextual factors. This effect was stable until the extinction recall phase. Additionally, excitability-reducing cathodal tDCS caused a significant decrease of the response difference between the threat and safety cues during the extinction recall phase. The self-report assessments showed no significant differences between the conditions throughout the experiment.

CONCLUSION

Independent of the context, excitability enhancement of the LiFG did impair fear extinction, and led to preservation of fear memory. In contrast, excitability reduction of this area enhanced fear extinction retention. These findings imply that the LiFG plays a role in the fear extinction network, which seems to be however context-independent.

Attenuating human fear memory retention with minocycline: a randomized placebo-controlled trial

Pavlovian fear conditioning is widely used as a pre-clinical model to investigate methods for prevention and treatment of anxiety and stress-related disorders. In this model, fear memory consolidation is thought to require synaptic remodeling, which is induced by signaling cascades involving matrix metalloproteinase 9 (MMP-9). Here we investigated the effect of the tetracycline antibiotic minocycline, an inhibitor of MMP-9, on fear memory retention. We conducted a pre-registered, randomized, double-blind, placebo-controlled trial in N = 105 healthy humans (N = 70 female), using a configural fear conditioning paradigm. We administered a single dose of minocycline before configural fear memory acquisition and assessed fear memory retention seven days later in a recall test. To index memory retention, we pre-registered fear-potentially startle (FPS) as our primary outcome, and pupil dilation as the secondary outcome. As control indices of memory acquisition, we analyzed skin conductance responses (SCR) and pupil dilation. We observed attenuated retention of configural fear memory in individuals treated with minocycline compared to placebo, as measured by our primary outcome. In contrast, minocycline did not affect fear memory acquisition or declarative contingency memory. Our findings provide in-vivo evidence for the inhibition of fear memory consolidation by minocycline. This could motivate further research into primary prevention, and given the short uptake time of minocycline, potentially also secondary prevention of PTSD after trauma.

Default mode network connectivity and social dysfunction in children with Attention Deficit/Hyperactivity Disorder

Objective

Attention Deficit/Hyperactivity Disorder (ADHD) negatively affects social functioning; however, its neurological underpinnings remain unclear. Altered Default Mode Network (DMN) connectivity may contribute to social dysfunction in ADHD. We investigated whether DMN's dynamic functional connectivity (dFC) alterations were associated with social dysfunction in individuals with ADHD.

Methods

Resting-state fMRI was used to examine DMN subsystems (dorsal medial prefrontal cortex (dMPFC), medial temporal lobe (MTL)) and the midline core in 40 male ADHD patients (7-10 years) and 45 healthy controls (HCs). Connectivity correlations with symptoms and demographic data were assessed. Group-based analyses compared rsFC between groups with two-sample t-tests and post-hoc analyses.

Results

Social dysfunction in ADHD patients was related to reduced DMN connectivity, specifically in the MTL subsystem and the midline core. ADHD patients showed decreased dFC between parahippocampal cortex (PHC) and left superior frontal gyrus, and between ventral medial prefrontal cortex (vMPFC) and right middle frontal gyrus compared to HCs (MTL subsystem). Additionally, decreased dFC between posterior cingulate cortex (PCC), anterior medial prefrontal cortex (aMPFC), and right angular gyrus (midline core) was observed in ADHD patients relative to HCs. No abnormal connectivity was found within the dMPFC.

Conclusion

Preliminary findings suggest that DMN connectional abnormalities may contribute to social dysfunction in ADHD, providing insights into the disorder's neurobiology and pathophysiology.

Altered frontolimbic activity during virtual reality-based contextual fear learning in patients with posttraumatic stress disorder

BACKGROUND

Deficiency in contextual and enhanced responding in cued fear learning may contribute to the development of posttraumatic stress disorder (PTSD). We examined the responses to aversive Pavlovian conditioning with an unpredictable spatial context as conditioned stimulus compared to a predictable context. We hypothesized that the PTSD group would demonstrate less hippocampal and ventromedial prefrontal cortex (vmPFC) activation during acquisition and extinction of unpredictable contexts and an over-reactive amygdala response in the predictable contexts compared to controls.

METHODS

A novel combined differential cue-context conditioning paradigm was applied using virtual reality with spatial contexts that required configural and cue processing. We assessed 20 patients with PTSD, 21 healthy trauma-exposed (TC) and 22 non-trauma-exposed (HC) participants using functional magnetic resonance imaging, skin conductance responses, and self-report measures.

RESULTS

During fear acquisition, patients with PTSD compared to TC showed lower activity in the hippocampi in the unpredictable and higher activity in the amygdalae in the predictable context. During fear extinction, TC compared to patients and HC showed higher brain activity in the vmPFC in the predictable context. There were no significant differences in self-report or skin conductance responses.

CONCLUSIONS

Our results suggest that patients with PTSD differ in brain activation from controls in regions such as the hippocampus, the amygdala, and the vmPFC in the processing of unpredictable and predictable contexts. Deficient encoding of more complex configurations might lead to a preponderance of cue-based predictions in PTSD. Exposure-based treatments need to focus on improving predictability of contextual processing and reducing enhanced cue reactivity.

Measuring human context fear conditioning and retention after consolidation

Fear conditioning is a laboratory paradigm commonly used to investigate aversive learning and memory. In context fear conditioning, a configuration of elemental cues (conditioned stimulus [CTX]) predicts an aversive event (unconditioned stimulus [US]). To quantify context fear acquisition in humans, previous work has used startle eyeblink responses (SEBRs), skin conductance responses (SCRs), and verbal reports, but different quantification methods have rarely been compared. Moreover, preclinical intervention studies mandate recall tests several days after acquisition, and it is unclear how to induce and measure context fear memory retention over such a time interval. First, we used a semi-immersive virtual reality paradigm. In two experiments (N = 23 and N = 28), we found successful declarative learning and memory retention over 7 d but no evidence of other conditioned responses. Next, we used a configural fear conditioning paradigm with five static room images as CTXs in two experiments (N = 29 and N = 24). Besides successful declarative learning and memory retention after 7 d, SCR and pupil dilation in response to CTX onset differentiated CTX+/CTX- during acquisition training, and SEBR and pupil dilation differentiated CTX+/CTX- during the recall test, with medium to large effect sizes for the most sensitive indices (SEBR: Hedge's g = 0.56 and g = 0.69; pupil dilation: Hedge's g = 0.99 and g = 0.88). Our results demonstrate that with a configural learning paradigm, context fear memory retention can be demonstrated over 7 d, and we provide robust and replicable measurement methods to this end.

Built environment color modulates autonomic and EEG indices of emotional response

Understanding built environment exposure as a component of environmental enrichment has significant implications for mental health, but little is known about the effects design characteristics have on our emotions and associated neurophysiology. Using a Cave Automatic Virtual Environment while monitoring indoor environmental quality (IEQ), 18 participants were exposed to a resting state (black), and two room scenes, control (white) and condition (blue), to understand if the color of the virtual walls affected self-report, autonomic nervous system, and central nervous system correlates of emotion. Our findings showed that exposure to the chromatic color condition (blue) compared to the achromatic control (white) and resting-state (black, no built environment) significantly increased the range in respiration and skin conductance response. We also detected a significant increase in alpha frontal midline power and frontal hemispheric lateralization relative to blue condition, and increased power spectral density across all electrodes in the blue condition for theta, alpha, and beta bandwidths. The ability for built environment design to modulate emotional response has the potential to deliver significant public health, economic, and social benefits to the entire community. The findings show that blue coloring of the built environment increases autonomic range and is associated with modulations of brain activity linked to emotional processing.

A Biologically Inspired Neural Network Model to Gain Insight Into the Mechanisms of Post-Traumatic Stress Disorder and Eye Movement Desensitization and Reprocessing Therapy

Eye movement desensitization and reprocessing (EMDR) therapy is a well-established therapeutic method to treat post-traumatic stress disorder (PTSD). However, how EMDR exerts its therapeutic action has been studied in many types of research but still needs to be completely understood. This is in part due to limited knowledge of the neurobiological mechanisms underlying EMDR, and in part to our incomplete understanding of PTSD. In order to model PTSD, we used a biologically inspired computational model based on firing rate units, encompassing the cortex, hippocampus, and amygdala. Through the modulation of its parameters, we fitted real data from patients treated with EMDR or classical exposure therapy. This allowed us to gain insights into PTSD mechanisms and to investigate how EMDR achieves trauma remission.

Contextual modulation of conditioned responses in humans: A review on virtual reality studies

Conditioned response (CRs) triggered by stimuli predicting aversive consequences have been confirmed across various species including humans, and were found to be exaggerated in anxious individuals and anxiety disorder patients. Importantly, contextual information may strongly modulate such conditioned responses (CR), however, there are several methodological boundaries in the translation of animal findings to humans, and from healthy individuals to patients. Virtual Reality (VR) is a useful technological tool for overcoming such boundaries. In this review, we summarize and evaluate human VR conditioning studies exploring the role of the context as conditioned stimulus or occasion setter for CRs. We observe that VR allows successful acquisition of conditioned anxiety and conditioned fear in response to virtual contexts and virtual cues, respectively. VR studies also revealed that spatial or temporal contextual information determine whether conditioned anxiety and conditioned fear become extinguished and/or return. Novel contexts resembling the threatening context foster conditioned fear but not conditioned anxiety, suggesting distinct context-related generalization processes. We conclude VR contexts are able to strongly modulate CRs and therefore allow a comprehensive investigation of the modulatory role of the context over CR in humans leading to conclusions relevant for non-VR and clinical studies.

When gut feelings teach the brain to fear pain: Context-dependent activation of the central fear network in a novel interoceptive conditioning paradigm

The relevance of contextual factors in shaping neural mechanisms underlying visceral pain-related fear learning remains elusive. However, benign interoceptive sensations, which shape patients' clinical reality, may context-dependently become conditioned predictors of impending visceral pain. In a novel context-dependent interoceptive conditioning paradigm, we elucidated the putative role of the central fear network in the acquisition and extinction of pain-related fear induced by interoceptive cues and pain-predictive contexts. In this fMRI study involving rectal distensions as a clinically-relevant model of visceroception, N = 27 healthy men and women underwent differential conditioning. During acquisition training, visceral sensations of low intensity as conditioned stimuli (CS) predicted visceral pain as unconditioned stimulus (US) in one context (Con⁺), or safety from pain in another context (Con^-). During extinction training, interoceptive CS remained unpaired in both contexts, which were operationalized as images of different rooms presented in the MRI scanner. Successful contextual conditioning was supported by increased negative valence of Con⁺ compared to Con^- after acquisition training, which resolved after extinction training. Although interoceptive CS were perceived as comparatively pleasant, they induced significantly greater neural activation of the amygdala, ventromedial PFC, and hippocampus when presented in Con⁺, while contexts alone did not elicit differential responses. During extinction training, a shift from CS to context differentiation was observed, with enhanced responses in the amygdala, ventromedial, and ventrolateral PFC to Con⁺ relative to Con^-, whereas no CS-induced differential activation emerged. Context-dependent interoceptive conditioning can turn benign interoceptive cues into predictors of visceral pain that recruit key regions of the fear network. This first evidence expands knowledge about learning and memory mechanisms underlying interoceptive hypervigilance and maladaptive avoidance behavior, with implications for disorders of the gut-brain axis.

Neuroanatomical correlates of apathy and disinhibition in behavioural variant frontotemporal dementia

Neuroanatomical correlates of apathy and disinhibition, behavioral abnormalities in behavioral variant Frontotemporal dementia (bvFTD) remain unclear. In this study 45 participants (25 bvFTD patients and 20 controls) provided data on clinical, neuropsychological, behavioral (on Frontal Systems Behavior (FrSBe) Scale), cortical volume (on voxel-based morphometry (VBM)) and tract based spatial fractional anisotropy ((FA) on magnetic resonance imaging (MRI), allowing examination of the neural correlates of apathy and disinhibition. The patients with bvFTD had predominant grey matter loss and corresponding white matter fractional anisotropy reduction in the frontal and temporal lobe compared to the controls. Grey matter loss in frontal, temporal and limbic structures correlated with apathy and degeneration in temporal limbic brain areas correlated with disinhibition. FA changes in inferior fronto-occipital fasciculus and forceps minor correlated with apathy and fibre integrity changes in the superior longitudinal fasciculus correlated with disinhibition. The current study suggests that apathy and disinhibition arises due to changes in the frontal, temporal and limbic brain areas  in bvFTD.

Roles for the Dorsal Striatum in Aversive Behavior

The ability to identify and avoid environmental stimuli that signal danger is essential to survival. Our understanding of how the brain encodes aversive behaviors has been primarily focused on roles for the amygdala, hippocampus (HIPP), prefrontal cortex, ventral midbrain, and ventral striatum. Relatively little attention has been paid to contributions from the dorsal striatum (DS) to aversive learning, despite its well-established role in stimulus-response learning. Here, we review studies exploring the role of DS in aversive learning, including different roles for the dorsomedial and dorsolateral striatum in Pavlovian fear conditioning as well as innate and inhibitory avoidance (IA) behaviors. We outline how future investigation might determine specific contributions from DS subregions, cell types, and connections that contribute to aversive behavior.

Generalization of Conditioned Contextual Anxiety and the Modulatory Effects of Anxiety Sensitivity

Anxiety patients overgeneralize fear responses, possibly because they cannot distinguish between cues never been associated with a threat (i.e., safe) and threat-associated cues. However, as contexts and not cues are discussed as the relevant triggers for prolonged anxiety responses characterizing many anxiety disorders, we speculated that it is rather overgeneralization of contextual anxiety, which constitutes a risk factor for anxiety disorders. To this end, we investigated generalization of conditioned contextual anxiety and explored modulatory effects of anxiety sensitivity, a risk factor for anxiety disorders. Fifty-five participants underwent context conditioning in a virtual reality paradigm. On Day 1 (acquisition), participants received unpredictable mildly painful electric stimuli (unconditioned stimulus, US) in one virtual office (anxiety context, CTX+), but never in a second office (safety context, CTX-). Successful acquisition of conditioned anxiety was indicated by aversive ratings and defensive physiological responses (i.e., SCR) to CTX+ vs CTX-. On Day 2 (generalization), participants re-visited both the anxiety and the safety contexts plus three generalization contexts (G-CTX), which were gradually dissimilar to CTX+ (from 75 to 25%). Generalization of conditioned anxiety was evident for ratings, but less clear for physiological responses. The observed dissociation between generalization of verbal and physiological responses suggests that these responses depend on two distinct context representations, likely elemental and contextual representations. Importantly, anxiety sensitivity was positively correlated with the generalization of reported contextual anxiety. Thus, this study demonstrates generalization gradients for conditioned contextual anxiety and that anxiety sensitivity facilitates such generalization processes suggesting the importance of generalization of contextual anxiety for the development of anxiety disorders.

Dysregulation of inflammation, neurobiology, and cognitive function in PTSD: an integrative review

Compelling evidence from animal and human research suggest a strong link between inflammation and posttraumatic stress disorder (PTSD). Furthermore, recent findings support compromised neurocognitive function as a key feature of PTSD, particularly with deficits in attention and processing speed, executive function, and memory. These cognitive domains are supported by brain structures and neural pathways that are disrupted in PTSD and which are implicated in fear learning and extinction processes. The disruption of these supporting structures potentially results from their interaction with inflammation. Thus, the converging evidence supports a model of inflammatory dysregulation and cognitive dysfunction as combined mechanisms underpinning PTSD symptomatology. In this review, we summarize evidence of dysregulated inflammation in PTSD and further explore how the neurobiological underpinnings of PTSD, in the context of fear learning and extinction acquisition and recall, may interact with inflammation. We then present evidence for cognitive dysfunction in PTSD, highlighting findings from human work. Potential therapeutic approaches utilizing novel pharmacological and behavioral interventions that target inflammation and cognition also are discussed.

Semantic and attentional networks in bilingual processing: fMRI connectivity signatures of translation directionality

Comparisons between backward and forward translation (BT, FT) have long illuminated the organization of bilingual memory, with neuroscientific evidence indicating that FT would involve greater linguistic and attentional demands. However, no study has directly assessed the functional interaction between relevant mechanisms. Against this background, we conducted the first fMRI investigation of functional connectivity (FC) differences between BT and FT. In addition to yielding lower behavioral outcomes, FT was characterized by increased FC between a core semantic hub (the left anterior temporal lobe, ATL) and key nodes of attentional and vigilance networks (left inferior frontal, left orbitofrontal, and bilateral parietal clusters). Instead, distinct FC patterns for BT emerged only between the left ATL and the right thalamus, a region implicated in automatic relaying of sensory information to cortical regions. Therefore, FT seems to involve enhanced coupling between semantic and attentional mechanisms, suggesting that asymmetries in cross-language processing reflect dynamic interactions between linguistic and domain-general systems.

Conjunctive and Elemental Representations of a Context in Humans

The dual-process theory assumes that contexts are encoded in an elemental and in a conjunctive representation. However, this theory was developed from animal studies, and we still have to explore if and how elemental and conjunctive representations contribute to, for example, contextual anxiety in humans. Therefore, 28 participants underwent differential context conditioning in a newly developed flip-book paradigm. Virtual rooms were presented similar to a flip-book, that is, as a stream of 49 consecutive screenshots creating the impression of walking through the rooms. This allowed registration of event-related brain potentials triggered by specific screenshots. During two acquisition phases, two rooms were shown in this way for six times each. In one room, the anxiety context (CTX+), mildly painful electric stimuli (unconditioned stimuli [USs]) were administered unpredictably after 12 distinct screenshots, which became threat elements, whereas 12 selected comparable screenshots became nonthreat elements (elemental representation); all screenshots represented the anxiety context (conjunctive representation). In the second room, the safety context (CTX-), no USs were applied; thus, all screenshots created the safety context whereby 12 preselected screenshots represented safety elements. Increased US expectancy ratings for threat versus nonthreat or safety elements reflected elemental representation. Conjunctive representation was evident in differential ratings (arousal and contingency) and increased P100 and early posterior negativity amplitudes for threat and nonthreat CTX+ versus safety CTX- screenshots. These differences disappeared during two test phases without US delivery indicating successful extinction. In summary, we revealed the first piece of evidence for the simultaneous contributions of elemental and conjunctive representation during context conditioning in humans.

Characterizing the neural circuitry associated with configural threat learning

Contextual threat learning is often associated with two processes: elemental and configural learning. Few studies have examined configural learning where subjects form a representation of the threat-related context as a gestalt whole from the individual features in the environment. The goal of the current study was to compare and contrast neural circuitry recruited by variation in demands placed on configural threat encoding. Subjects (N = 25) completed a configural threat learning task, where we manipulated the amount of configural encoding required to learn the threat association (low demand: changes to a discrete element of the context; and high demand: rearrangement of elements). US expectancy ratings, skin conductance responses (SCR), and functional magnetic resonance imaging (fMRI) were collected. Subjects successfully learned the configural threat association as measured by US expectancy ratings, SCR, and BOLD activity. Hippocampal and amygdala region of interest analyses indicated differential configural threat learning and predicted SCR measures of learning. Furthermore, whole brain analyses identified four circuits that were impacted by the amount of differential configural encoding required, but none correlated with SCR. These results set the stage for a more detailed understanding of how configural threat learning is instantiated in the brain-an important mechanism associated with PTSD and other fear-related disorders.

The Future of Contextual Fear Learning for PTSD Research: A Methodological Review of Neuroimaging Studies

There has been a great deal of recent interest in human models of contextual fear learning, particularly due to the use of such paradigms for investigating neural mechanisms related to the etiology of posttraumatic stress disorder. However, the construct of "context" in fear conditioning research is broad, and the operational definitions and methods used to investigate contextual fear learning in humans are wide ranging and lack specificity, making it difficult to interpret findings about neural activity. Here we will review neuroimaging studies of contextual fear acquisition in humans. We will discuss the methodology associated with four broad categories of how contextual fear learning is manipulated in imaging studies (colored backgrounds, static picture backgrounds, virtual reality, and configural stimuli) and highlight findings for the primary neural circuitry involved in each paradigm. Additionally, we will offer methodological recommendations for human studies of contextual fear acquisition, including using stimuli that distinguish configural learning from discrete cue associations and clarifying how context is experimentally operationalized.

Default Mode Network Subsystems are Differentially Disrupted in Posttraumatic Stress Disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) is a psychiatric disorder characterized by debilitating re-experiencing, avoidance, and hyperarousal symptoms following trauma exposure. Recent evidence suggests that individuals with PTSD show disrupted functional connectivity in the default mode network, an intrinsic network that consists of a midline core, a medial temporal lobe (MTL) subsystem, and a dorsomedial prefrontal cortex (dMPFC) subsystem. The present study examined whether functional connectivity in these subsystems is differentially disrupted in PTSD.

METHODS

Sixty-nine returning war Veterans with PTSD and 44 trauma-exposed Veterans without PTSD underwent resting state functional MRI (rs-fMRI). To examine functional connectivity, seeds were placed in the core hubs of the default mode network, namely the posterior cingulate cortex (PCC) and anterior medial PFC (aMPFC), and in each subsystem.

RESULTS

Compared to controls, individuals with PTSD had reduced functional connectivity between the PCC and the hippocampus, a region of the MTL subsystem. Groups did not differ in connectivity between the PCC and dMPFC subsystem or between the aMPFC and any region within either subsystem. In the PTSD group, connectivity between the PCC and hippocampus was negatively associated with avoidance/numbing symptoms. Examination of the MTL and dMPFC subsystems revealed reduced anticorrelation between the ventromedial PFC (vMPFC) seed of the MTL subsystem and the dorsal anterior cingulate cortex in the PTSD group.

CONCLUSIONS

Our results suggest that selective alterations in functional connectivity in the MTL subsystem of the default mode network in PTSD may be an important factor in PTSD pathology and symptomatology.

Hippocampal Context Processing during Acquisition of a Predictive Learning Task Is Associated with Renewal in Extinction Recall

Renewal is defined as the recovery of an extinguished response if extinction and retrieval contexts differ. The context dependency of extinction, as demonstrated by renewal, has important implications for extinction-based therapies. Persons showing renewal (REN) exhibit higher hippocampal activation during extinction in associative learning than those without renewal (NOREN), demonstrating hippocampal context processing, and recruit ventromedial pFC in retrieval. Apart from these findings, brain processes generating renewal remain largely unknown. Conceivably, processing differences in task-relevant brain regions that ultimately lead to renewal may occur already in initial acquisition of associations. Therefore, in two fMRI studies, we investigated overall brain activation and hippocampal activation in REN and NOREN during acquisition of an associative learning task in response to presentation of a context alone or combined with a cue. Results of two studies demonstrated significant activation differences between the groups: In Study 1, a support vector machine classifier correctly assigned participants' brain activation patterns to REN and NOREN groups, respectively. In Study 2, REN and NOREN showed similar hippocampal involvement during context-only presentation, suggesting processing of novelty, whereas overall hippocampal activation to the context–cue compound, suggesting compound encoding, was higher in REN. Positive correlations between hippocampal activation and renewal level indicated more prominent hippocampal processing in REN. Results suggest that hippocampal processing of the context–cue compound rather than of context only during initial learning is related to a subsequent renewal effect. Presumably, REN participants use distinct encoding strategies during acquisition of context-related tasks, which reflect in their brain activation patterns and contribute to a renewal effect.

Nociceptive Local Field Potentials Recorded from the Human Insula Are Not Specific for Nociception

The insula, particularly its posterior portion, is often regarded as a primary cortex for pain. However, this interpretation is largely based on reverse inference, and a specific involvement of the insula in pain has never been demonstrated. Taking advantage of the high spatiotemporal resolution of direct intracerebral recordings, we investigated whether the human insula exhibits local field potentials (LFPs) specific for pain. Forty-seven insular sites were investigated. Participants received brief stimuli belonging to four different modalities (nociceptive, vibrotactile, auditory, and visual). Both nociceptive stimuli and non-nociceptive vibrotactile, auditory, and visual stimuli elicited consistent LFPs in the posterior and anterior insula, with matching spatial distributions. Furthermore, a blind source separation procedure showed that nociceptive LFPs are largely explained by multimodal neural activity also contributing to non-nociceptive LFPs. By revealing that LFPs elicited by nociceptive stimuli reflect activity unrelated to nociception and pain, our results confute the widespread assumption that these brain responses are a signature for pain perception and its modulation.

Local field potentials elicited in the human insular cortex by painful stimuli reflect cortical activity that is unrelated to pain perception and so cannot be used as an objective measure of pain.

A widely accepted notion is that the insula, especially its posterior portion, plays a specific role in the perception of pain. This has led a number of researchers to consider activity recorded from this so-called “ouch zone” as an objective correlate of pain perception. We provide compelling evidence to the contrary. Using direct intracerebral recordings, we demonstrate that painful and nonpainful stimuli elicit very similar responses throughout the human insula. This observation argues against the notion that these responses reflect the brain activity through which pain emerges from nociception in the human brain. These findings have implications for basic theories, as well as for the development of diagnostic tests and the identification of therapeutic targets for the treatment of chronic pain. They question the use of these insular responses to assess the effects of pharmacological treatment or to assess pain in patients unable to communicate. Furthermore, they have legal implications, as they contradict the proposal that these responses could be used to determine unequivocally whether plaintiffs are truly experiencing the pain for which they are seeking redress. Finally, they undermine the rationale for neurosurgical procedures aiming at alleviating pain by targeting the posterior insula.

Limbic correlates of fearlessness and disinhibition in incarcerated youth: Exploring the brain-behavior relationship with the Hare Psychopathy Checklist: Youth Version

The purpose of this study was to determine whether scores on two temperament dimensions (fearlessness and disinhibition) correlated differentially with gray matter volumes in two limbic regions (amygdala and hippocampus). It was predicted that the fearlessness dimension would correlate with low gray matter volumes in the amygdala and the disinhibition dimension would correlate with low gray matter volumes in the hippocampus after controlling for age, IQ, regular substance use, and total brain volume. Participants were 191 male adolescents (age range=13-19 years) incarcerated in a maximum-security juvenile facility. Structural magnetic resonance imaging (MRI) analysis of the limbic and paralimbic regions of the brain was conducted. The temperament dimensions were estimated with items from the Psychopathy Checklist: Youth Version (PCL: YV: Forth et al., 2003). Analyses showed that the fearlessness dimension correlated negatively with gray matter volumes in the amygdala and the disinhibition dimension correlated negatively with gray matter volumes in the hippocampus but not vice versa. These findings provide preliminary support for the construct validity of the fearlessness and disinhibition temperament dimensions and offer confirmatory evidence for involvement of the amygdala and hippocampus in fear conditioning and behavioral inhibition, respectively.