Nondeclarative associative learning in Alzheimer's disease: An overview of eyeblink, fear, and other emotion-based conditioning.

Alzheimer's disease is a neurodegenerative disorder that is characterized by progressive cognitive decline, particularly in declarative memory, and the presence of ß-amyloid plaques, neurofibrillary tangles, and cortical atrophy (especially in the temporal lobe). Unlike the relationship between the temporal cortex and declarative memory, nondeclarative memories (e.g., motor, fear, and other emotion-based memories) involve distinct neural structures. The present review investigates nondeclarative associative learning ability in Alzheimer's disease. We discuss eyeblink conditioning, fear conditioning, and other emotion-based learning and present the functions and brain areas that are involved in each type of learning. Evidence suggests that nondeclarative learning is also affected by Alzheimer's disease, although some forms of learning may be relatively preserved. Details about each nondeclarative associative learning process and the implications of these findings are presented.

The impact of a violent community on mental health and the benefits of a sport program for social development.

The aim of the present study was to evaluate the impact of a violent environment on mental health and the impact of a sport for social development (SSD) program on quality of life, mental distress symptoms, and heart rate variability (HRV). HRV and psychometric data were measured from 20 men professional athletes assisted by the SSD and 20 men living in the same violent community. The comparison of groups revealed greater sympathetic parameters of HRV, positive affect, and quality of life in the SSD group. Multiple regression analysis showed that the quality of life in the SSD group was positively predicted by positive affect, while in the control group the quality of life was negatively predicted by their history of traumatic events. Both groups reported high levels of exposure to traumatic events and posttraumatic stress symptoms. However, this study demonstrates the benefits of SSD programs in mental health.

Impact of textual warnings on emotional brain responses to ultra-processed food products.

Background and objectives: Ultra-processed food products (UPF) have been associated with numerous non-communicable diseases. Despite this, the addictive nature of UPF, and the aggressive marketing strategies used to promote them, has created a strong emotional connection between UPF and consumers, and supports their increasing UPF global consumption. In view of the emotional link that consumers often have with UPF, modulating emotional reactions to UPF (by using strategies such as textual warnings) is important in changing consumers' behavior. Since emotions are better understood by assessing individuals' implicit reactions, we conducted an electroencephalographic study applying the event-related potential technique to investigate whether textual warnings were able to modulate the brain responses to UPF stimuli. Materials and methods: Twenty-six participants (19 women) viewed pictures of UPF preceded by a warning sentence about the health risks of consuming UPF or a control sentence while the electroencephalogram was recorded. In addition, the participants rated the picture in respect of pleasantness, arousal, and intention to consume. As emotions are associated with motivational circuits in the brain, we focused on a well-known event-related potential brain marker of the motivational relevance associated with emotional stimuli, namely late positive potential (LPP). Results: The late positive potential amplitude was larger for pictures depicting UPF under the warning condition compared to the control condition, a result that was accompanied by lower pleasantness ratings during the warning condition (compared to the control). Conclusion: Textual warnings about the negative health consequences of consuming UPF changed the emotional responses toward UPF, possibly increasing the motivation to avoid UPF. These results shed new light on the impact of textual warnings on UPF-evoked emotions.

Hidden wounds of violence: Abnormal motor oscillatory brain activity is related to posttraumatic stress symptoms.

Victims of urban violence are at risk of developing Posttraumatic Stress Disorder (PTSD), one of the most debilitating consequences of violence. Considering that PTSD may be associated with inefficient selection of defensive responses, it is important to understand the relation between motor processing and PTSD. The present study aims to investigate the extent to which the severity of posttraumatic stress symptoms (PTSS) is related to motor preparation against visual threat cues in victims of urban violence. Participants performed a choice reaction time task while ignoring a picture that could be threating or neutral. The EEG indices extracted were the motor-related amplitude asymmetry (MRAA) in the alpha frequency range, and the lateralized readiness potential (LRP). We observed a linear relation between longer LRP latency and a slower reaction time, selectively during threat processing (compared to neutral) in low PTSS, but not in high PTSS participants. Alpha MRAA suppression and the PTSS were also linearly related: the smaller the alpha MRAA suppression in the threat condition relative to neutral, the greater the PTSS. These results provide evidence that threatening cues affect motor processing that is modulated by the severity of PTSS in victims of urban violence.

Effects of load and emotional state on EEG alpha-band power and inter-site synchrony during a visual working memory task.

Motivationally/emotionally engaging stimuli are strong competitors for the limited capacity of sensory and cognitive systems. Thus, they often act as distractors, interfering with performance in concurrent primary tasks. Keeping task-relevant information in focus while suppressing the impact of distracting stimuli is one of the functions of working memory (WM). Macroscopic brain oscillations in the alpha band (8-13 Hz) have recently been identified as a neural correlate of WM processing. Using electroencephalography, we examined the extent to which changes in alpha power and inter-site connectivity during a typical WM task are sensitive to load and emotional distraction. Participants performed a lateralized change-detection task with two levels of load (four vs. two items), which was preceded by naturalistic scenes rated either as unpleasant or neutral, acting as distractors. The results showed the expected parieto-occipital alpha reduction in the hemisphere contralateral to the WM task array, compared to the ipsilateral hemisphere, during the retention interval. Selectively heightened oscillatory coupling between frontal and occipital sensors was observed (1) during the retention interval as a function of load, and (2) upon the onset of the memory array, after viewing neutral compared to unpleasant distractors. At the end of the retention interval, we observed greater coupling during the unpleasant compared to the neutral condition. These findings are consistent with the notions that (1) representing more items in WM requires greater interconnectivity across cortical areas, and (2) unpleasant emotional distractors interfere with subsequent WM processing by disrupting processing during the encoding stage.

"Keep That in Mind!" The Role of Positive Affect in Working Memory for Maintaining Goal-Relevant Information.

Some studies have demonstrated a beneficial role of Positive Affect on working memory (WM) by either applying protocols of mood induction or assessing naturally occurring state Positive Affect. However, there are no studies directly linking Positive Affect as a stable personality-like trait with WM. We aimed to address this potential relationship using the Positive and Negative Affect Schedule scale and contra-lateral delay activity (CDA) as measures of trait Positive Affect and WM Capacity, respectively. We also sought to investigate the impact of a neutral or unpleasant emotional state on this relationship. Participants performed a change detection task, while a neutral or an unpleasant emotional state was induced. Our results showed a positive robust correlation between trait Positive Affect and WM Capacity for both neutral and unpleasant emotional states, as revealed by the neuroelectrophysiological gold-standard measure of WM, namely, CDA. These data suggest a tangible role of trait Positive Affect in the cognitive ability of maintaining goal-relevant information in WM, such that even a highly disruptive state is not sufficient to corrupt this relationship.

An unpleasant emotional state reduces working memory capacity: electrophysiological evidence.

Emotional states can guide the actions and decisions we make in our everyday life through their influence on cognitive processes such as working memory (WM). We investigated the long-lasting interference that an unpleasant emotional state had on goal-relevant WM representations from an electrophysiological perspective. Participants performed a change detection task that was preceded by the presentation of unpleasant or neutral task-irrelevant pictures in a blocked fashion. We focused on the contralateral delay activity (CDA), an event-related potential that is sensitive to the number of task-relevant items stored in WM. We found that the asymptotic limit for the CDA amplitude was lower during the unpleasant emotional state than during the neutral one; that is, an emotional state was capable of reducing how many task-relevant items the participants could hold in WM. Furthermore, both the individuals who experienced more intrusive thoughts and those who were dispositionally anxious were more susceptible to the influence of the emotional state. We provide evidence that an unpleasant emotional state diminished visual WM for task-relevant items, particularly in susceptible individuals. These results open new avenues to uncover the emotional-cognitive processing that underlies maladaptive WM representations and the role of such processing in the development of mental illness.

EEG correlates of the severity of posttraumatic stress symptoms: A systematic review of the dimensional PTSD literature.

BACKGROUND: Considering the Research Domain Criteria (RDoC) framework, it is crucial to investigate posttraumatic stress disorder (PTSD) as a spectrum that ranges from normal to pathological. This dimensional approach is especially important to aid early PTSD detection and to guide better treatment options. In recent years, electroencephalography (EEG) has been used to investigate PTSD; however, reviews regarding EEG data related to PTSD are lacking, especially considering the dimensional approach. This systematic review examined the literature regarding EEG alterations in trauma-exposed people with posttraumatic stress symptoms (PTSS) to identify putative EEG biomarkers of PTSS severity. METHOD: A systematic review of EEG studies of trauma-exposed participants with PTSS that reported dimensional analyses (e.g., correlations or regressions) between PTSS and EEG measures was performed. RESULTS: The literature search yielded 1178 references, of which 34 studies were eligible for inclusion. Despite variability among the reviewed studies, the PTSS severity was often associated with P2, P3-family event-related potentials (ERPs) and alpha rhythms. LIMITATIONS: The search was limited to articles published in English; no information about non-published studies or studies reported in other languages was obtained. Another limitation was the heterogeneity of studies, which made meta-analysis challenging. CONCLUSIONS: EEG provides promising candidates to act as biomarkers, although further studies are required to confirm the findings. Thus, EEG, in addition to being cheaper and easier to implement than other central techniques, has the potential to reveal biomarkers of PTSS severity.

Preparing to caress: a neural signature of social bonding.

It is assumed that social bonds in humans have consequences for virtually all aspects of behavior. Social touch-based contact, particularly hand caressing, plays an important role in social bonding. Pre-programmed neural circuits likely support actions (or predispositions to act) toward caressing contacts. We searched for pre-set motor substrates toward caressing by exposing volunteers to bonding cues and having them gently stroke a very soft cloth, a caress-like movement. The bonding cues were pictures with interacting dyads and the control pictures presented non-interacting dyads. We focused on the readiness potential, an electroencephalographic marker of motor preparation that precedes movement execution. The amplitude of the readiness potential preceding the grasping of pleasant emotional-laden stimuli was previously shown to be reduced compared with neutral ones. Fingers flexor electromyography measured action output. The rationale here is that stroking the soft cloth when previously exposed to bonding cues, a compatible context, would result in smaller amplitudes of readiness potentials, as compared to the context with no such cues. Exposure to the bonding pictures increased subjective feelings of sociability and decreased feelings of isolation. Participants who more frequently engage in mutual caress/groom a "significant other" in daily life initiated the motor preparation earlier, reinforcing the caress-like nature of the task. As hypothesized, readiness potentials preceding the caressing of the soft cloth were significantly reduced under exposure to bonding as compared to control pictures. Furthermore, an increased fingers flexor electromyographic activity was identified under exposure to the former as compared to the latter pictures. The facilitatory effects are likely due to the recruitment of pre-set cortical motor repertoires related to caress-like movements, emphasizing the distinctiveness of neural signatures for caress-like movements.

Brain reactivity to unpleasant stimuli is associated with severity of posttraumatic stress symptoms.

Despite the impressive progress in the biological research of posttraumatic stress disorder (PTSD), little is known about the neurobiological correlates of emotional reactions in healthy people with posttraumatic stress symptoms (PTSS). The present study investigated whether PTSS are related to the electrocortical processing of unpleasant pictures in a sample of undergraduate students. Participants were instructed to judge whether images were unpleasant or neutral while an EEG was taken. The late positive potential (LPP) to unpleasant relative to neutral was more positive for people with high PTSS than with low PTSS. Additionally, a temporospatial principal components analysis (PCA) for the whole sample identified positivities that were directly correlated with PTSS. These results provide evidence that brain reactivity to unpleasant cues would predict PTSS intensity and thus be a biomarker of PTSS severity.

Peritraumatic tonic immobility is associated with posttraumatic stress symptoms in undergraduate Brazilian students.

OBJECTIVE: Tonic immobility is a defensive reaction occurring under extreme life threats. Patients with posttraumatic stress disorder (PTSD) reporting peritraumatic tonic immobility show the most severe symptoms and a poorer response to treatment. This study investigated the predictive value of tonic immobility for posttraumatic stress symptoms in a non-clinical sample. METHODS: One hundred and ninety-eight college students exposed to various life threatening events were selected to participate. The Posttraumatic Stress Disorder Checklist - Civilian Version (PCL-C) and tonic immobility questions were used. Linear regression models were fitted to investigate the association between peritraumatic tonic immobility and PCL-C scores. Peritraumatic dissociation, peritraumatic panic reactions, negative affect, gender, type of trauma, and time since trauma were considered as confounding variables. RESULTS: We found significant association between peritraumatic tonic immobility and PTSD symptoms in a non-clinical sample exposed to various traumas, even after regression controlled for confounding variables (ß = 1.99, p = 0.017). CONCLUSIONS: This automatic reaction under extreme life threatening stress, although adaptive for defense, may have pathological consequences as implied by its association with PTSD symptoms.

Peritraumatic tonic immobility is associated with posttraumatic stress symptoms in undergraduate Brazilian students / A imobilidade tônica peritraumática está associada aos sintomas do transtorno de estresse pós-traumático em estudantes brasileiros de graduação

OBJECTIVE: Tonic immobility is a defensive reaction occurring under extreme life threats. Patients with posttraumatic stress disorder (PTSD) reporting peritraumatic tonic immobility show the most severe symptoms and a poorer response to treatment. This study investigated the predictive falue of tonic immobility for posttraumatic stress symptoms in a non-clinical sample. METHODS: One hundred and ninety-eight college students exposed to various life threatening events were selected to participate. The Posttraumatic Stress Disorder Checklist - Civilian Version (PCL-C) and tonic immobility questions were used. Linear regression models were fitted to investigate the association between peritraumatic tonic immobility and PCL-C scores. Peritraumatic dissociation, peritraumatic panic reactions, negative affect, gender, type of trauma, and time since trauma were considered as confounding variables. RESULTS: We found significant association between peritraumatic tonic immobility and PTSD symptoms in a non-clinical sample exposed to various traumas, even after regression controlled for confounding variables (β = 1.99, p = 0.017). CONCLUSIONS: This automatic reaction under extreme life threatening stress, although adaptive for defense, may have pathological consequences as implied by its association with PTSD symptoms.

OBJETIVO: A imobilidade tônica é uma resposta defensiva que ocorre sob ameaça extrema à vida. Pacientes com transtorno de estresse pós-traumático (TEPT) que relatam imobilidade tônica peritraumática são os que apresentam os sintomas mais graves e a pior resposta ao tratamento. Este estudo investigou o valor preditivo da imobilidade tônica para os sintomas de TEPT em uma amostra não clínica. MÉTODOS: Os participantes da pesquisa foram 198 estudantes universitários expostos a traumas diversos. A versão brasileira do Post-Traumatic Stress Disorder Checklist Civilian Version (PCL-C) e questões referentes à imobilidade tônica foram empregadas. Modelos de regressão linear foram utilizados para investigar a associação dos sintomas de estresse pós-traumático com a imobilidade tônica peritraumática. Foram consideradas como variáveis de confusão a dissociação peritraumática, as reações físicas de pânico peritraumática, o traço de afeto negativo, o gênero, o tipo de trauma e o tempo de trauma. RESULTADOS: Encontrou-se uma associação significativa entre a imobilidade tônica peritraumática e os sintomas de TEPT em uma amostra não clínica exposta a traumas diversos mesmo quando controlada por variáveis de confusão (β = 1,99; p = 0,017). CONCLUSÕES: Esta reação defensiva que ocorre sob intensa ameaça, apesar de adaptativa para a defesa, pode ter consequências patológicas como sugere sua associação aos sintomas de TEPT.

The neurobiology of posttraumatic stress disorder: dysfunction in the prefrontal-amygdala circuit?

Posttraumatic stress disorder (PTSD) is an anxiety disorder that can develop following exposure to a traumatic event, including terrifying or life-threatening situations such as sexual assault or natural disasters. The disorder is characterized by a reaction of intense fear, helplessness, or horror when the individual experiences, testifies about, or is faced with one or more events that involve death, severe wounds, or a threat to one's own or another's physical integrity. One of the most important symptoms of PTSD is the revival of the traumatic event, which has been interpreted as an inability to downregulate negative emotions. Neuroimaging studies that probed the ability to regulate emotions in healthy volunteers have found a pattern characterized by activation of the prefrontal cortex associated with a reduction in amygdala activity. This suggests an inhibitory prefrontal cortex-amygdala circuit that underlies emotional regulation. The hypothesis that increased amygdala activation associated with PTSD results from dysfunction in the inhibitory mechanism exerted by the prefrontal cortex has been the topic of debate. The present review investigates the validity of dysfunction in the prefrontal-amygdala pathway in PTSD. The studies provide evidence that the amygdala and prefrontal cortex exhibit distinct activation patterns in PTSD, thus supporting the model of a dysfunctional circuit. Inconsistencies in the literature may be attributable to distinct PTSD subgroups, different experimental approaches, different contrasts employed in neuroimaging studies, and small sample sizes.(AU)

The neurobiology of posttraumatic stress disorder: dysfunction in the prefrontal-amygdala circuit?

Posttraumatic stress disorder (PTSD) is an anxiety disorder that can develop following exposure to a traumatic event, including terrifying or life-threatening situations such as sexual assault or natural disasters. The disorder is characterized by a reaction of intense fear, helplessness, or horror when the individual experiences, testifies about, or is faced with one or more events that involve death, severe wounds, or a threat to one's own or another's physical integrity. One of the most important symptoms of PTSD is the revival of the traumatic event, which has been interpreted as an inability to downregulate negative emotions. Neuroimaging studies that probed the ability to regulate emotions in healthy volunteers have found a pattern characterized by activation of the prefrontal cortex associated with a reduction in amygdala activity. This suggests an inhibitory prefrontal cortex-amygdala circuit that underlies emotional regulation. The hypothesis that increased amygdala activation associated with PTSD results from dysfunction in the inhibitory mechanism exerted by the prefrontal cortex has been the topic of debate. The present review investigates the validity of dysfunction in the prefrontal-amygdala pathway in PTSD. The studies provide evidence that the amygdala and prefrontal cortex exhibit distinct activation patterns in PTSD, thus supporting the model of a dysfunctional circuit. Inconsistencies in the literature may be attributable to distinct PTSD subgroups, different experimental approaches, different contrasts employed in neuroimaging studies, and small sample sizes.