Neural Indices Research Articles

Interference Suppression in EEG Dipole Source Localization through Reduced-Rank Beamforming

In this paper, we propose new neural activity indices for the solution of the inverse problem of localizing sources of cortical activity from electroencephalography (EEG) measurements. Such indices are based on reduced-rank beamformers, specifically the generalized sidelobe canceler (GSC), and with the purpose of suppressing the contribution of interfering sources and noise. Here, the GSC is modified with an adaptive blocking matrix (ABM) to optimally estimate and later suppress unwanted brain sources. With respect to the rank-reduction, this is achieved through the cross-spectral metrics (CSM) as they give a sense of the affinity of the beamformers’ eigenstructure to the orthogonal subspace of noise an interference. Based on that, two different neural indices are proposed for the assessment of brain activation. Our realistic simulations show that a more consistent source localization is achieved through the proposed indices in comparison to the use of the traditional full-rank approach, specifically for brain sources embedded in high background activity that originates at the brain cortex and thalamus. We also prove the applicability of our methods on the localization of sources on the visual cortex produced by steady-state visual-evoked potentials.

Differentiating Between Us & Them: Reduced In-Group Bias as a Novel Mechanism Linking Childhood Violence Exposure with Internalizing Psychopathology.

Strong in-group bonds, facilitated by implicit favoritism for in-group members (i.e., in-group bias), promote mental health across development. Yet, we know little about how the development of in-group bias is shaped by early-life experiences. Childhood violence exposure is known to alter social information processing biases. Violence exposure may also influence social categorization processes, including in-group biases, in ways that influence risk for psychopathology. We examined associations of childhood violence exposure with psychopathology and behavioral and neural indices of implicit and explicit bias for novel groups in children followed longitudinally across three time points from age 5 to 10years old (n = 101 at baseline;n = 58 at wave 3). To instantiate in-group and out-group affiliations, youths underwent a minimal group assignment induction procedure, in which they were randomly assigned to one of two groups. Youth were told that members of their assigned group shared common interests (in-group) and members of the other group did not (out-group). In pre-registered analyses, violence exposure was associated with lower implicit in-group bias, which in turn was associated prospectively with higher internalizing symptoms and mediated the longitudinal association between violence exposure and internalizing symptoms. During an fMRI task examining neural responses while classifying in-group and out-group members, violence-exposed children did not exhibit the negative functional coupling between vmPFC and amygdala to in-group vs. out-group members that was observed in children without violence exposure. Reduced implicit in-group bias may represent a novel mechanism linking violence exposure with the development of internalizing symptoms.

From scanner to court: A neuroscientifically informed "reasonable person" test of trademark infringement.

Many legal decisions center on the thoughts or perceptions of some idealized group of individuals, referred to variously as the "average person," "the typical consumer," or the "reasonable person." Substantial concerns exist, however, regarding the subjectivity and vulnerability to biases inherent in conventional means of assessing such responses, particularly the use of self-report evidence. Here, we addressed these concerns by complementing self-report evidence with neural data to inform the mental representations in question. Using an example from intellectual property law, we demonstrate that it is possible to construct a parsimonious neural index of visual similarity that can inform the reasonable person test of trademark infringement. Moreover, when aggregated across multiple participants, this index was able to detect experimenter-induced biases in self-report surveys in a sensitive and replicable fashion. Together, these findings potentially broaden the possibilities for neuroscientific data to inform legal decision-making across a range of settings.

Altered hierarchical organization between empathy and gambling networks in disordered gamblers.

Despite the demonstrated association between empathy and gambling at the behavioral level, limited neuroimaging research on empathy and gambling disorder (GD) has been conducted. Whether and how the brain network of empathy and that of gambling interact in disordered gamblers has not been investigated. This study aimed to address this research gap by examining the hierarchical organizational patterns, in which the differences of causal interactions of these networks between disordered gamblers and healthy controls were revealed. Resting-state functional magnetic resonance imaging (fMRI) data of 32 disordered gamblers and 56 healthy controls were included in the formal analysis. Dynamic causal modeling was used to examine the effective connectivity within and between empathy and gambling networks among all participants. All participants showed significant effective connectivity within and between empathy and gambling networks. However, compared with healthy controls, disordered gamblers displayed more excitatory effective connectivity within the gambling network, the tendency to display more excitatory effective connectivity from the empathy network to the gambling network, and reduced inhibitory effective connectivity from the gambling network to the empathy network. The exploratory study was the first to examine the effective connectivity within and between empathy and gambling networks among disordered gamblers and healthy controls. These results provided insights into the causal relationship between empathy and gambling from the neuroscientific perspective and further confirmed that disordered gamblers show altered effective connectivity within and between these two brain networks, which may be considered to be a potential neural index for GD identification. In addition, the altered interactions between empathy and gambling networks may also indicate the potential targets for the neuro-stimulation intervention approach (e.g., transcranial magnetic stimulation).

Vocal Emotion Recognition in Autism: Behavioral Performance and Event-Related Potential (ERP) Response.

Autistic youth display difficulties in emotion recognition, yet little research has examined behavioral and neural indices of vocal emotion recognition (VER). The current study examines behavioral and event-related potential (N100, P200, Late Positive Potential [LPP]) indices of VER in autistic and non-autistic youth. Participants (N=164) completed an emotion recognition task, the Diagnostic Analyses of Nonverbal Accuracy (DANVA-2) which includedVER, during EEG recording. The LPP amplitude was larger in response to high intensity VER, and social cognition predicted VER errors. Verbal IQ, not autism, was related to VER errors. An interaction between VER intensity and social communication impairments revealed these impairments were related to larger LPP amplitudes during low intensity VER. Taken together, differences in VER may be due to higher order cognitive processes, not basic, early perception (N100, P200), and verbal cognitive abilities may underlie behavioral, yet occlude neural, differences in VER processing.

The unique face of comorbid anxiety and depression: increased interoceptive fearfulness and reactivity.

Anxiety and depression commonly co-occur, yet the underlying brain and behavioral processes are poorly understood. Here we examined the hypothesis that individuals with comorbid anxiety and depression would show increased fearful reactivity to an aversive interoceptive perturbation relative to depressed-only individuals. One-hundred and eighty anxious and/or depressed participants from the Tulsa 1000 study completed multi-level behavioral or functional magnetic resonance imaging assessments of interoception and nociception including breath-hold and cold-pressor challenges, and heartbeat perception and interoceptive attention tasks. One-hundred and four individuals with comorbid depression and anxiety disorders (Dep+Anx) were propensity matched with 52 individuals with depression-only (Dep). Data were analyzed using mixed-effects linear regression. The Dep+Anx group showed significantly greater self-reported fear of suffocation during breath holding (Wilcoxon r = 0.23) and reduced cold pain tolerance (R 2 = 0.027) signified by hand removal during immersion. However, these groups did not differ with respect to neutrally-valenced behavioral indices of heartbeat perception or neural indices of interoceptive attention. Individuals with comorbid depression and anxiety, vs. those with only depression, show increased respiratory fearfulness and nociceptive reactivity during perturbations of these signals, whilst showing similar interoceptive awareness in the absence of perturbation. Our findings suggest that individuals with comorbid anxiety and depression process aversive interoceptive and nociceptive signals differently than those with depression alone, providing support for a process model of increased threat sensitivity and hyperarousal in anxious depression.

Evaluating the Evidence for Brain-Based Biotypes of Psychiatric Vulnerability in the Acute Aftermath of Trauma.

The weak link between subjective symptom-based diagnostic methods for posttraumatic psychopathology and objectively measured neurobiological indices forms a barrier to the development of effective personalized treatments. To overcome this problem, recent studies have aimed to stratify psychiatric disorders by identifying consistent subgroups based on objective neural markers. Along these lines, a promising 2021 study by Stevens et al. identified distinct brain-based biotypes associated with different longitudinal patterns of posttraumatic symptoms. Here, the authors conducted a conceptual nonexact replication of that study using a comparable data set from a multimodal longitudinal study of recent trauma survivors. A total of 130 participants (mean age, 33.61 years, SD=11.21; 48% women) admitted to a general hospital emergency department following trauma exposure underwent demographic, clinical, and neuroimaging assessments 1, 6, and 14 months after trauma. All analyses followed the pipeline outlined in the original study and were conducted in collaboration with its authors. Task-based functional MRI conducted 1 month posttrauma was used to identify four clusters of individuals based on profiles of neural activity reflecting threat and reward reactivity. These clusters were not identical to the previously identified brain-based biotypes and were not associated with prospective symptoms of posttraumatic psychopathology. Overall, these findings suggest that the original brain-based biotypes of trauma resilience and psychopathology may not generalize to other populations. Thus, caution is warranted when attempting to define subtypes of psychiatric vulnerability using neural indices before treatment implications can be fully realized. Additional replication studies are needed to identify more stable and generalizable neuroimaging-based biotypes of posttraumatic psychopathology.

Effects of iron supplementation on neural indices of habituation in Bangladeshi children

BackgroundIron deficiency and anemia have been associated with poor cognition in children, yet the effects of iron supplementation on neurocognition remain unclear. ObjectiveWe aimed to examine the effects of supplementation with iron on neural indices of habituation using auditory event-related brain potentials (ERPs). MethodsThis substudy was nested within a 3-arm, double-blind, double-dummy, individual randomized trial in Bangladesh, in which 3300 8-mo-old children were randomly selected to receive 3 mo of daily iron syrup (12.5 mg iron), multiple micronutrient powders (MNPs) (including 12.5 mg iron), or placebo. Children were assessed after 3 mo of intervention (mo 3) and 9 mo thereafter (mo 12). The neurocognitive substudy comprised a randomly selected subset of children from the main trial. Brain activity elicited during an auditory roving oddball task was recorded using electroencephalography to provide an index of habituation. The differential response to a novel (deviant) compared with a repeated (standard) sound was examined. The primary outcome was the amplitude of the mismatch response (deviant minusstandard tone waveforms) at mo 3. Secondary outcomes included the deviant and standard tone-evoked amplitudes, N2 amplitude differences, and differences in mean amplitudes evoked by deviant tones presented in the second compared with first half of the oddball sequence at mo 3 and 12. ResultsData were analyzed from 329 children at month 3 and 363 at mo 12. Analyses indicated no treatment effects of iron interventions compared with placebo on the amplitude of the mismatch response (iron syrup compared with placebo: mean difference (MD) = 0.07μV [95% CI: −1.22, 1.37]; MNPs compared with placebo: MD = 0.58μV [95% CI: −0.74, 1.90]) nor any secondary ERP outcomes at mo 3 or 12, despite improvements in hemoglobin and ferritin concentrations from iron syrup and MNPs in this nested substudy. ConclusionIn Bangladeshi children with >40% anemia prevalence, iron or MNP interventions alone are insufficient to improve neural indices of habituation.This trial was registered at the Australian New Zealand Clinical Trials Registry as ACTRN12617000660381.

Randomized controlled trial of computerized approach/avoidance training in social anxiety disorder: Neural and symptom outcomes

Social anxiety is associated with diminished automatic approach toward positive social cues that may limit the ability to connect with others. This diminished approach bias may be a modifiable treatment target. We evaluated the effects of an approach avoidance training procedure on positive emotions, social relationship outcomes, clinical symptoms, and neural indices of social approach and reward processing.Forty-five individuals with social anxiety disorder were randomized (parallel 1:1 randomization) to complete computerized Approach Positive training (n = 21) or Balanced training(n = 24). Sessions included a standardized social interaction task. Participants were blind to training group. Participants completed clinical outcome measures and functional magnetic resonance imaging at baseline and post intervention with an MRI-compatible AAT and the social incentive delay task (SID).Both groups displayed significant improvements of similar magnitude on the primary outcome of social connectedness (between group post-treatment d = −0.21) but not positive affect (d = −0.09), from before to after treatment, persisting through follow-up. Groups demonstrated significant improvements on additional outcomes including anxiety, depression, and anhedonia symptoms. Participants in Approach Positive AAT demonstrated increased activation in the thalamus and medial prefrontal cortex during social versus neutral- approach relative to Balanced AAT during the fMRI AAT. Participants in Balanced AAT showed increased activation in regions within an a priori-defined striatum region of interest mask during anticipation of social reward (vs. baseline) in the SID relative to Approach Positive AAT.At a neural processing level AAT may influence the valuation and motivations associated with positive social cues regulated by the mPFC and thalamus. NCT02136212, NIMH R00MH090243.

Children’s inhibition skills are associated with their P3a latency—results from an exploratory study

BackgroundThe P3a response is thought to reflect involuntary orienting to an unexpected stimulus and has been connected with set-shifting and inhibition in some studies. In our exploratory study, we investigated if the amplitude and the latency of the P3a response were associated with the performance in a modified flanker task measuring inhibition and set-shifting in 10-year-old children (N = 42). Children participated in electroencephalography (EEG) measurement with an auditory multifeature paradigm including standard, deviating, and novel sounds. In addition, they performed a separate flanker task requiring inhibition and set-shifting skills.ResultsThe P3a latencies for deviant sounds were associated with the reaction time reflecting inhibition: the shorter the response latencies were, the faster the reaction time was. The P3a latencies for novel sounds were not linked to the reaction times reflecting either inhibition or set-shifting. In addition, the magnitude of the P3a response was not associated with the performance in the flanker task.ConclusionsOur results suggest that P3a response latency and reaction speed reflecting inhibitory skills are based on shared neural mechanism. Thus, the present study brings new insight to the field investigating the associations between behavior and its neural indices.

Impact of acute stress on neural indices of positive and negative reinforcement processing in cannabis users.

Chronic cannabis use is maintained in part through dysregulated stress and reward response systems. Specifically, stress-related negative affect is thought to act as a salient motivator for chronic substance use. Models of addiction posit that the transition from positive to negative reinforcement motives for substance use is a key mechanism of disordered use. However, research in substance-using samples has not assessed stress-related neural processing of both positive and negative reinforcement. Therefore, the present study utilized laboratory stress induction to examine how stress affects the reward positivity, an event-related potential sensitive to both positive (RewP) and negative (relief-RewP) reinforcement, in 87 cannabis users (58.10% female, Mage = 19.40) varying in cannabis use disorder (CUD) severity and, as part of larger study aims, history of traumatic brain injury (TBI). We predicted greater CUD severity would be associated with a blunted RewP and enhanced relief-RewP, particularly after stress induction, independent of TBI status. Findings indicated that CUD severity was not associated with RewP/relief-RewP amplitude regardless of acute stress. Exploratory analyses revealed, however, that among those with history of TBI +, CUD severity was associated with greater stress-elicited blunting of the RewP and enhancement of the relief-RewP. Although initial findings contradict current allostatic models of addiction, exploratory findings suggest that history of TBI, and potentially other confounding variables related to increased risk of TBI experience, may influence the extent to which stressful experiences modulate the neurophysiology of both positive and negative reinforcement reward processing in CUD. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A Self-Controlled Mind Is Reflected by Stable Mental Processing

Self-control—the ability to inhibit inappropriate impulses—predicts economic, physical, and psychological well-being. However, recent findings demonstrate low correlations among self-control measures, raising the question of what self-control actually is. Here, we examined the idea that people high in self-control show more stable mental processing, characterized by processing steps that are fewer in number but longer lasting because of fewer interruptions by distracting impulses. To test this hypothesis, we relied on resting electroencephalography microstate analysis, a method that provides access to the stream of mental processing by assessing the sequential activation of neural networks. Across two samples (Study 1: N = 58 male adults from Germany; Study 2: N = 101 adults from Canada, 58 females), the temporal stability of resting networks (i.e., longer durations and fewer occurrences) was positively associated with self-reported self-control and a neural index of inhibitory control, and it was negatively associated with risk-taking behavior. These findings suggest that stable mental processing represents a core feature of a self-controlled mind.

The neural basis of smile authenticity judgments and the potential modulatory role of the oxytocin receptor gene (OXTR)

Accurate perception of genuine vs. posed smiles is crucial for successful social navigation in humans. While people vary in their ability to assess the authenticity of smiles, little is known about the specific biological mechanisms underlying this variation. We investigated the neural substrates of smile authenticity judgments using functional magnetic resonance imaging (fMRI). We also tested a preliminary hypothesis that a common polymorphism in the oxytocin receptor gene (OXTR) rs53576 would modulate the behavioral and neural indices of accurate smile authenticity judgments. A total of 185 healthy adult participants (Neuroimaging arm: N = 44, Behavioral arm: N = 141) determined the authenticity of dynamic facial expressions of genuine and posed smiles either with or without fMRI scanning. Correctly identified genuine vs. posed smiles activated brain areas involved with reward processing, facial mimicry, and mentalizing. Activation within the inferior frontal gyrus and dorsomedial prefrontal cortex correlated with individual differences in sensitivity (d’) and response criterion (C), respectively. Our exploratory genetic analysis revealed that rs53576 G homozygotes in the neuroimaging arm had a stronger tendency to judge posed smiles as genuine than did A allele carriers and showed decreased activation in the medial prefrontal cortex when viewing genuine vs. posed smiles. Yet, OXTR rs53576 did not modulate task performance in the behavioral arm, which calls for further studies to evaluate the legitimacy of this result. Our findings extend previous literature on the biological foundations of smile authenticity judgments, particularly emphasizing the involvement of brain regions implicated in reward, facial mimicry, and mentalizing.

The Average Reward Rate Modulates Behavioral and Neural Indices of Effortful Control Allocation.

People tend to avoid exerting cognitive effort, and findings from recent behavioral studies suggest that effort allocation is in part determined by the opportunity cost of slothful responding-operationalized as the average reward rate per unit time. When the average rate of reward is high, individuals make more errors in cognitive control tasks, presumably owing to a withdrawal of costly cognitive processing. An open question remains whether the presumed modulations of cognitively effortful control processes are observable at the neural level. Here, we measured EEG while participants completed the Simon task, a well-known response conflict task, while the experienced average reward rate fluctuated across trials. We examined neural activity associated with the opportunity cost of time by applying generalized eigendecomposition, a hypothesis-driven source separation technique, to identify a midfrontal component associated with the average reward rate. Fluctuations in average reward rate modulated not only component amplitude but also, most importantly, component theta power (4-8 Hz). Higher average reward rate was associated with reduced theta power, suggesting that the opportunity of time modulates effort allocation. These neural results provide evidence for the idea that people strategically modulate the amount of cognitive effort they exert based on the opportunity cost of time.

Discrimination Without Intoxication: The Role of Controlled Processes in the Promotion of Racial Bias After Viewing Alcohol-Related Cues

Viewing alcohol-related cues (e.g., advertisements) is known to promote expressions of racial bias and aggression through the temporary promotion of reflexive or impulsive responding. However, this increased automaticity may be inhibited by thoughtful control of behavior. We examined the role of controlled processes in the suppression of racial bias following alcohol cue exposure across two experiments. Experiment 1 (N = 125) indicated reduced control of behavior promoted greater expressions of racial bias after viewing alcohol-related cues. Experiment 2 (N = 71) replicated these effects, suggesting individuals with lower neural indices of control, indexed by reduced amplitudes of the error-related negativity (ERN), similarly express greater racial bias after viewing alcohol-related cues. These findings replicate previous work suggesting alcohol-related cues promote impulsivity and application of negative racial stereotypes. Yet, whether this automaticity manifests into behavioral expressions of racial bias depends on the availability to engage self-control to inhibit these socially undesirable responses.

The late positive potential during affective picture processing: Associations with daily life emotional functioning among adolescents with anxiety disorders

Pediatric anxiety disorders are characterized by potentiated threat responses and maladaptive emotion regulation (ER). The Late Positive Potential (LPP) is a neural index of heightened attention to emotional stimuli. Anxious individuals typically exhibit a larger LPP to unpleasant stimuli, but the LPP may also be blunted to unpleasant and pleasant stimuli for those with co-morbid depression. While a larger LPP is thought to reflect greater emotional reactivity, it is unknown to what extent variation in the LPP to laboratory stimuli corresponds to daily emotional functioning. We assessed the LPP in the laboratory in response to unpleasant, pleasant, and neutral images in combination with ecological momentary assessment of emotional reactivity and regulation in daily life among youth (9–14 years old; 55 % female) with anxiety disorders (ANX, N = 130) and no psychiatric diagnoses (ND, N = 47). We tested whether LPP amplitudes to unpleasant and pleasant stimuli (vs. neutral) are greater in ANX (vs. ND) youth and whether LPP amplitudes inversely correlate with co-morbid depression symptoms. We also examined associations between the LPP and daily life emotional functioning among ANX and ND youth. We found no group-by-valence effects on LPP amplitudes. Within ANX youth, higher depression symptoms were associated with smaller LPP amplitudes to unpleasant, but not pleasant, stimuli relative to neutral stimuli. Larger LPP amplitudes to emotional (relative to neutral) stimuli were correlated with use of specific ER strategies among ANX and ND youth but not emotional reactivity. While the LPP may reflect initial emotional reactivity to laboratory stimuli, it is associated with ER behaviors, and not emotional reactivity, in daily life.

The electrophysiological correlates of word pre-activation during associative word learning

Human beings continuously make use of learned associations to generate predictions about future occurrences in the environment. Such memory-related predictive processes provide a scaffold for learning in that mental representations of foreseeable events can be adjusted or strengthened based on a specific outcome. Learning the meaning of novel words through picture-word associations constitutes a prime example of associative learning because pictures preceding words can trigger word prediction through the pre-activation of the related mnemonic representations. In the present electroencephalography (EEG) study, we used event-related potentials (ERPs) to compare neural indices of word pre-activation between a word learning condition with maximal prediction likelihood and a non-learning control condition with low prediction. Results revealed that prediction-related N400 amplitudes in response to pictures decreased over time at central electrodes as a function of word learning, whereas late positive component (LPC) amplitudes increased. Notably, N400 but not LPC changes were also predictive of word learning performance, suggesting that the N400 component constitutes a sensitive marker of word pre-activation during associative word learning.

More than words: Neurophysiological correlates of semantic dissimilarity depend on comprehension of the speech narrative.

Speech comprehension relies on the ability to understand words within a coherent context. Recent studies have attempted to obtain electrophysiological indices of this process by modelling how brain activity is affected by a word's semantic dissimilarity to preceding words. Although the resulting indices appear robust and are strongly modulated by attention, it remains possible that, rather than capturing the contextual understanding of words, they may actually reflect word-to-word changes in semantic content without the need for a narrative-level understanding on the part of the listener. To test this, we recorded electroencephalography from subjects who listened to speech presented in either its original, narrative form, or after scrambling the word order by varying amounts. This manipulation affected the ability of subjects to comprehend the speech narrative but not the ability to recognise individual words. Neural indices of semantic understanding and low-level acoustic processing were derived for each scrambling condition using the temporal response function. Signatures of semantic processing were observed when speech was unscrambled or minimally scrambled and subjects understood the speech. The same markers were absent for higher scrambling levels as speech comprehension dropped. In contrast, word recognition remained high and neural measures related to envelope tracking did not vary significantly across scrambling conditions. This supports the previous claim that electrophysiological indices based on the semantic dissimilarity of words to their context reflect a listener's understanding of those words relative to that context. It also highlights the relative insensitivity of neural measures of low-level speech processing to speech comprehension.

Working memory dysfunction in fibromyalgia is associated with genotypes of the catechol- O-methyltransferase gene: an event-related potential study

Recent findings have associated different COMT genotypes with working memory capacity in patients with fibromyalgia. Although it is thought that the COMT gene may influence neural correlates (P2 and P3 ERP components) underlying working memory impairment in this chronic-pain syndrome, it has not yet been explored. Therefore, the aim of the present research was to investigate the potential effect of the COMT gene in fibromyalgia patients on ERP working memory indices (P2 and P3 components). For this purpose, 102 participants (51 patients and 51 healthy control participants) took part in the experiment. Event-related potentials and behavioral responses were recorded while participants performed a spatial n-back task. Participants had to decide if the stimulus coincided or not in the same location as the one presented one (1-back condition) or two (2-back condition) trials before. Genotypes of the COMT gene were determined through a saliva sample from all participants. Present results significantly showed lower working memory performance (p < 0.05) in patients with fibromyalgia as compared to control participants (higher rate of errors and slower reaction times). At neural level, we found that patients exhibited enhanced frontocentral and parieto-occipital P2 amplitudes compared to control participants (p < 0.05). Interestingly, we also observed that only fibromyalgia patients carrying the Val/Val genotype of the COMT gene showed higher frontocentral P2 amplitudes than control participants (p < 0.05). Current results (behavioral outcomes and P2 amplitudes) confirmed the presence of an alteration in working memory functioning in fibromyalgia. The enhancement of frontocentral P2 could be reflecting that these patients would manifest an inefficient way of activating executive attention processes, in carriers of the Val/Val genotype of COMT. To our knowledge, the present findings are the first linking neural indices of working memory dysfunctions and COMT genotypes in fibromyalgia. Applying a subgroup of patient’s strategy based on this genetic marker could be useful to establish more tailored therapeutical approaches.

Natural Contrast Statistics Facilitate Human Face Categorization.

The ability to detect faces in the environment is of utmost ecological importance for human social adaptation. While face categorization is efficient, fast and robust to sensory degradation, it is massively impaired when the facial stimulus does not match the natural contrast statistics of this visual category, i.e., the typically experienced ordered alternation of relatively darker and lighter regions of the face. To clarify this phenomenon, we characterized the contribution of natural contrast statistics to face categorization. Specifically, 31 human adults viewed various natural images of nonface categories at a rate of 12 Hz, with highly variable images of faces occurring every eight stimuli (1.5 Hz). As in previous studies, neural responses at 1.5 Hz as measured with high-density electroencephalography (EEG) provided an objective neural index of face categorization. Here, when face images were shown in their naturally experienced contrast statistics, the 1.5-Hz face categorization response emerged over occipito-temporal electrodes at very low contrast [5.1%, or 0.009 root-mean-square (RMS) contrast], quickly reaching optimal amplitude at 22.6% of contrast (i.e., RMS contrast of 0.041). Despite contrast negation preserving an image’s spectral and geometrical properties, negative contrast images required twice as much contrast to trigger a face categorization response, and three times as much to reach optimum. These observations characterize how the internally stored natural contrast statistics of the face category facilitate visual processing for the sake of fast and efficient face categorization.