Open Access

People often remember visual information over brief delays while actively engaging with ongoing inputs from the surrounding visual environment. Depending on the situation, one might prioritize mnemonic contents (i.e., remembering details of a past event), or preferentially attend sensory inputs (i.e., minding traffic while crossing a street). Previous fMRI work has shown that early sensory regions can simultaneously represent both mnemonic and passively viewed sensory information. Here we test the limits of such simultaneity by manipulating attention towards sensory distractors during a working memory task performed by human subjects during fMRI scanning. Participants remembered the orientation of a target grating while a distractor grating was shown during the middle portion of the memory delay. Critically, there were several subtle changes in the contrast and the orientation of the distractor, and participants were cued to either ignore the distractor, detect a change in contrast, or detect a change in orientation. Despite sensory stimulation being matched in all three conditions, the fidelity of memory representations in early visual cortex was highest when the distractor was ignored, intermediate when participants attended distractor contrast, and lowest when participants attended the orientation of the distractor during the delay. In contrast, the fidelity of distractor representations was lowest when ignoring the distractor, intermediate when attending distractor-contrast, and highest when attending distractor-orientation. These data suggest a trade-off in early sensory representations when engaging top-down feedback to attend both seen and remembered features and may partially explain memory failures that occur when subjects are distracted by external events.

There is an ongoing debate about whether working memory (WM) maintenance relies on persistent activity and/or short-term synaptic plasticity. This is a challenging question, because neuroimaging techniques in cognitive neuroscience measure activity only. Recently, neural perturbation techniques have been developed to tackle this issue, such as visual impulse perturbation or “pinging”, which reveals (un)attended WM content during maintenance. There are contrasting explanations of how pinging reveals WM content, which is central to the debate. Pinging could reveal mnemonic representations by perturbing content-specific networks or by increasing the neural signal-to-noise ratio of active neural states. Here we tested the extent to which the neural impulse response is patterned by the WM network, by presenting two different impulse stimuli. If the impulse interacts with WM networks, the WM-specific impulse response should be enhanced by physical overlap between the initial memory item and the subsequent external perturbation stimulus. This prediction was tested in a delayed orientation match-to-sample task by matching or mismatching task-irrelevant spatial frequencies between memory items and impulse stimuli, as well as probes. Matching probe spatial frequency with memory items resulted in faster behavioral response times and matching impulse spatial frequency with memory items increased the specificity of the neural impulse response as measured from EEG. Matching spatial frequencies did neither result in globally stronger neural responses nor in a larger decrease in trial-to-trial variability compared to mismatching spatial frequencies. The improved neural and behavioural readout of irrelevant feature matching provide evidence that impulse perturbation interacts directly with the memory representations.

The activity-silent framework of working memory (WM) posits that the neural activity during object perception and encoding leaves behind patterned, “activity-silent” neural traces that enable WM maintenance without the need for continuous, memory-specific neural activity. The presence of such traces in the memory network subsequently patterns its responses to external stimulation, which can be used to readout the contents of WM using an impulse perturbation or “pinging” approach. The extent to which the neural impulse response is patterned by the WM network should be modulated by the physical overlap between the initial memory item and the subsequent external perturbation stimulus, with higher overlap increasing WM readout. Here we tested this prediction in a delayed orientation match-to-sample task, by either matching or mismatching task-irrelevant spatial frequencies between memory items and impulse stimuli, and between memory items and probes. Matching frequencies resulted in faster behavioral response times, and increased the WM-specificity of the neural impulse response as measured from the EEG signal. We found no evidence that matching spatial frequencies resulted in globally stronger or different neural responses, but rather in distinct neural activation patterns. The beneficial effects of feature matching in our task support the tenets of the activity-silent framework of WM, and confirm that impulse perturbation interacts directly with the representations that are held in memory.

The present study examined the impact of the COVID-19 pandemic on the emotional quality of dreams, the incorporation of pandemic-related themes, and the occurrence of lucid dreaming. Dream reports and lucidity ratings of psychiatric outpatients (n = 30) and healthy controls (n = 81) during two lockdowns in Germany were compared to those of healthy controls (n = 33) before the pandemic. Results confirmed previous reports that pandemic-specific themes were incorporated into dreams. Overall, however, incorporation into dreams was rare. Contrary to expectations, psychiatric outpatients did not differ from controls in the frequency of dream incorporation of pandemic-related content. Moreover, incorporation was independent of psychiatric symptoms and loneliness. Loneliness was, however, associated with threat-related content, suggesting that it represents a risk for bad dreams but not for crisis-specific dream incorporation. Regarding lucid dreaming, both groups had similar scores for its underlying core dimensions, i.e., insight, control, and dissociation, during the two lockdowns. Scores for control and dissociation but not insight were lower compared to the pre-pandemic sample. Our working hypothesis is that REM sleep during lockdowns intensified as a means of increased emotional consolidation, rendering the associated mental state less hybrid and thereby less lucid.

Background: There is growing evidence that Internet-based cognitive behavioral therapy (ICBT) is as effective as a stand-alone treatment and helps facilitating access to treatment. Given the complexity of the treatment, we argue that the effect of ICBT could be even greater if guided by a therapist, as this could increase treatment adherence. We modified an established and well-evaluated treatment approach and developed a mobile application for treating social anxiety disorder (SAD). In the present study, we compare the efficacy of app use alone (APP) with video-based, therapist-guided app use (TG-APP) and with a wait-list control group (WLC) in terms of symptom reduction, and various secondary outcomes such as increase in quality of life or decrease of general psychological distress. Methods/design: A within-between interaction design with randomization to one of three conditions will be used. In the APP condition, patients receive only the app without any additional contact with therapists, while in the TG-APP condition, therapists provide 8 sessions of video-based treatment in addition to using the app. The study will be conducted in two university outpatient treatment centers with reliably diagnosed SAD patients. The primary outcome will be defined as change in SAD symptoms, as measured by the Liebowitz Social Anxiety Scale (expert rating). Furthermore, a wide range of self-reports and clinician ratings for other symptoms (depression, general psychopathology) or quality of life will be used. A simulation-based power analysis for a 3 × 2 interaction effect (group × time) on the primary outcome in a linear mixed model resulted in a total sample size of N = 165. Discussion: The present study will be one of the first to examine the additional benefit of therapist-guided video sessions regarding the use of an app treating SAD. Study results are pivotal to future treatment application in SAD.