In recent years, steady state visual evoked potentials (SSVEPs) became an increasingly valuable tool to investigate neural dynamics of competitive attentional interactions and brain computer interfaces. This is due to their good signal-to-noise ratio, allowing for single trial analysis and their ongoing oscillating nature that enables to analyze temporal dynamics of facilitation and suppression. Given the popularity of SSVEPs, it is surprising that only a few studies looked at the cortical sources of these responses. This is in particular the case when searching for studies that assessed the cortical sources of attentional SSVEP amplitude modulations. To address this issue, we used a typical spatial attention task and recorded neuromagnetic fields (MEG) while presenting frequency-tagged stimuli in the left and right visual field, respectively. Importantly, we controlled for attentional deployment in a baseline period before the shifting cue. Subjects either attended to a central fixation cross or to two peripheral stimuli simultaneously. Results clearly showed that signal sources and attention effects were restricted to early visual cortex: V1, V2, hMT+, precuneus, occipital-parietal and inferior-temporal cortex. When subjects attended to central fixation first, shifting attention to one of the peripheral stimuli resulted in a significant activation increase for the to-be-attended stimulus with no activation decrease for the to-be-ignored stimulus in hMT+ and inferio-temporal cortex, but significant SSVEF decreases from V1 to occipito-parietal cortex. When attention was first deployed to both rings, shifting attention away from one ring basically resulted in a significant activation decrease in all areas for the then to-be-ignored stimulus.
Recent evidence suggests that the autonomic nervous system can contribute to memory consolidation during sleep. Whether fluctuations in cardiac autonomic activity during sleep following physical exercise contribute to the process of memory consolidation has not been studied. We assessed the effects of a non-rapid eye movement (NREM) nap following acute exercise on cardiac autonomic regulation assessed with heart rate variability (HRV) to examine if HRV influences memory processes. Fifty-six (59% female) healthy young adults (23.14 ± 3.74 years) were randomly allocated to either the exercise plus nap (ExNap, n = 27) or nap alone (NoExNap, n = 29) groups. The ExNap group performed a 40-minute moderate-intensity cycling, while the NoExNap group was sedentary prior to learning 45 neutral pictures for a later test. Subsequently, participants underwent a 60-minute NREM nap while measuring EKG, followed by a visual recognition test. Our results indicated that heart rate did not significantly differ between the groups (p = 0.302); whereas vagally-mediated HRV indices were lower in the ExNap group compared to the NoExNap group (p < 0.05). There were no significant differences in sleep variables (p > 0.05). Recognition accuracy was significantly higher in the ExNap group than in the NoExNap group (p = 0.027). In addition, the recognition accuracy of the ExNap group was negatively associated with vagally-mediated HRV (p < 0.05). Pre-nap acute exercise attenuated parasympathetic activity and appears to alter the relationship between memory and cardiac autonomic activity, suggesting that post-exercise memory enhancement may be based on other mechanisms.
We describe methods and software resources for a bioimpedance measurement technique, “trans-radial electrical bioimpedance velocimetry” that allows for the non-invasive monitoring of relative cardiac contractility and stroke volume, proxies of sympathetic cardiac tone. In addition to describing the general recording methodology, which requires impedance measurements of the forearm, we provide open source Jupyter based software (operable on most computers) for deriving cardiac contractility from the impedance measurements. We demonstrate the ability of this bioimpedance measurement for tracking event related contractility in a maximal grip force production task. Critically, the results demonstrate both a reactive increase in cardiosympathetic drive with force production as well as a learned increase in drive prior to grip onset, consistent with allostatic autonomic regulation. The method and software should be of broad utility for investigations of event related cardio-sympathetic regulation in psychophysical studies.
Fear overgeneralization and perceived uncertainty about future outcomes have been suggested as risk factors for clinical anxiety. However, little is known regarding how they influence each other. In this study, we investigated whether different levels of threat uncertainty influence fear generalization. Three groups of healthy participants underwent a differential fear conditioning protocol followed by a generalization test. All groups learned to associate one female face (conditioned stimulus, CS+) with a female scream (unconditioned stimulus, US) while the other face (CS-) was not associated with the scream. In order to manipulate threat uncertainty, one group (low uncertainty, n = 26) received 80%, the second group (moderate uncertainty, n = 32) received 60%, and the third group (high uncertainty, n = 30) 40% CS-US contingency. In the generalization test, all groups saw CS+ and CS- again as well as four morphs that varied in similarity with the CS+ in steps of 20%. Subjective (expectancy, valence, and arousal ratings), psychophysiological (skin conductance response, SCR), and visuocortical (steady-state visual evoked potentials, ssVEPs) indices of fear were registered. Participants expected the US in accordance with their reinforcement schedules but displayed stronger skin conductance with more uncertainty. However, acquisition of conditioned fear was not evident in ssVEPs. During the generalization test, we found no effect of threat uncertainty in any of the measured variables, but the strength of generalization for threat expectancy ratings was positively correlated with dispositional intolerance of uncertainty. This study suggests that mere threat uncertainty does not modulate fear generalization.
Active engagement improves learning and memory, and self- vs. externally generated stimuli are processed differently: perceptual intensity and neural responses are attenuated. Whether the attenuation is linked to memory formation remains to be understood. This study investigates whether active oculomotor control over auditory stimuli – controlling for movement and stimulus predictability – benefits associative learning, and studies the underlying neural mechanisms. Using EEG and eyetracking we explored the impact of control during learning on the processing and memory recall of arbitrary oculomotor-auditory associations. Participants (N=23) learned associations through active exploration or passive observation, using a gaze-controlled interface to generate sounds. Our results show faster learning progress in the active condition. ERPs time-locked to the onset of sound stimuli showed that learning progress was linked to an attenuation of the P3a component. The detection of matching movement-sound pairs triggered a target-matching P3b response. There was no general modulation of ERPs through active learning. However, participants could be divided into different learner types: those who benefited strongly from active control during learning and those who did not. The strength of the N1 attenuation effect for self-generated stimuli was correlated with memory gain in active learning. Our results show that control helps learning and memory and modulates sensory responses. Individual differences during sensory processing predict the strength of the memory benefit. Taken together, these results help to disentangle the effects of agency, unspecific motor-based neuromodulation, and stimulus predictability on ERP components and establish a link between self-generation effects and active learning memory gain.
Working memory (WM) impairment has been well characterized in normal ageing. Various studies have explored changes in either the regional activity or the interregional connectivity underlying the WM ageing process. We proposed that brain activity and connectivity would independently alter with ageing and affect WM performance. WM was assessed with a classical N-back task during functional magnetic resonance imaging in a community-based sample comprising 168 elderly subjects (aged 55 to 86 years old). Following the rationale of background functional connectivity, we assessed age-related alterations in brain activity and seed-based interregional connectivity independently. Analyses revealed age-related decrease in the activity of the inferior parietal lobule (IPL) and an increase in the activity of the ventral anterior cingulate cortex (ACC), and the local functional dysfunctions were accompanied by alterations in their connectivity to other cortical regions. Importantly, regional activity impairments in the IPL and ACC could mediate age-related effects on accuracy rate and reaction time, respectively, and those effects were further counterbalanced by enhancement of their background functional connectivity. We thus claimed that age-induced alterations in regional activity and interregional connectivity occurred independently and contributed to WM changes in ageing. Our findings presented the way brain activity and functional connectivity interact in the late adulthood, thus providing a new perspective for understanding WM and cognitive ageing.
Hypnotizability is a psychophysiological trait measured by scales and associated with several differences including interoceptive accuracy and the morpho-functional characteristics of interoception-related brain regions. The aim of the study was to assess whether the amplitude of the heartbeat evoked cortical potential (HEP), a correlate of interoceptive accuracy, differs in participants with low (lows) and high (highs) hypnotizability scores (assessed by the Stanford Hypnotic Susceptibility Scale, form A) before and after the induction of hypnosis. ECG and EEG were monitored in 16 highs and 15 lows during an experimental session including open eyes baseline (B), closed eyes relaxation (R), hypnotic induction (IND), neutral hypnosis (NH), post session baseline (Post). No significant difference was observed between groups and conditions in autonomic variables. The HEP amplitude was lower in highs than in lows at the right parietal site, likely due to hypnotizability-related differences in the functional connection between the right insula and parietal cortex. It increased in highs and decreased in lows across the session, possibly due to the highs’ preeminently internally directed attention and to the lows’ possible disengagement from the task. Since interoception is involved in several cognitive-emotional functions, its hypnotizability-related differences may contribute to the variability of experience and behavior in daily life.
The tendency to ruminate (i.e., repetitive, self-referential, negative thoughts) is a maladaptive form of emotional regulation and represents a transdiagnostic vulnerability factor for stress-related psychopathology. Vagally-mediated heart rate variability (HRV), reflecting parasympathetic nervous system activity, is commonly used as a physiological marker of stress regulation. Past research has suggested a link between trait rumination and resting HRV at baseline; however, inconsistent results exist in healthy individuals. In this study, we investigated the association between the tendency to ruminate and resting HRV measured at baseline in a healthy population using a large cross-sectional dataset (N = 1189, 88% women; mean age = 21.55, ranging from 17 to 48 years old), which was obtained by combining samples of healthy individuals from different studies from our laboratory. The results showed no cross-sectional correlation between resting baseline HRV and trait rumination (confirmed by Bayesian analyses), even after controlling for important confounders such as gender, age, and depressive symptoms. Also, a nonlinear relationship was rejected. In summary, based on our results in a large sample of healthy individuals, baseline resting HRV is not a trait marker of the tendency to ruminate.
Heightened impulsivity and compulsivity are often found in association with both dysfunctional everyday behavior as well as with psychopathology. Impulsivity and compulsivity are also linked to alterations in behavioral response inhibition and its electrophysiological correlates. However, they are rarely examined jointly and their effect outside of clinical samples is still disputed. This study assesses the influence and interaction of impulsivity and compulsivity as measured by questionnaires on behavioral performance and event-related potentials (N2, P3a and P3b) in a visual Go/Nogo task. Data from 250 participants from the general population (49% female; age M = 25.16, SD = 5.07; education level: 94% high school or higher; self-reported lifetime diagnosis of any mental disorder: 12%) were collected. We used robust linear regression as well as regression tree analyses, a type of machine learning algorithm, to uncover potential non-linear effects. We did not find any significant relationship between the self-report measures and behavioral or neural inhibition effects in either type of analysis, with the exception of a linear effect of the premeditation scale of the UPPS on behavioral performance. The current sample size was large enough to uncover even small effects. We discuss potential explanations for this current null finding. One possibility is that inhibitory performance was unimpaired in the current sample and that associations between inhibitory performance and self-report measures might only be seen in samples with mental disorders.