The Role of Beta Oscillations in Mental Time Travel

The role of vmPFC in accessing the temporality of life events for mental time travel

Mental time travel (MTT) refers to the ability to project oneself backward in time, toward past events, and forward in time, toward future events. This study investigates the role of the ventromedial prefrontal cortex (vmPFC) in orienting toward past and future events during MTT. Patients with lesion to the vmPFC (vmPFC patients), control patients, and healthy participants completed a MTT task requiring to orient in time towards the past and the future to estimate the likelihood of typical life events, and a timeline task requiring to place events coherently on a line representing the lifespan. The results showed that vmPFC-but not control-patients systematically anticipated the timing of events, associating them with earlier than typical ages during both past and future MTT, as well as in the timeline task, possibly due to a shortened time perspective or to the systematic devaluation of events. These findings highlight the critical role of vmPFC in activating temporal schemata and supporting temporal orientation during MTT, enabling the construction of coherent life narratives.

Theta Transcranial Alternating Current Stimulation Is Not Effective in Improving Working Memory Performance

There is an extensive body of research showing a significant relationship between frontal midline theta activity in the 4- to 8-Hz range and working memory (WM) performance. Transcranial alternating current stimulation (tACS) is recognized for inducing lasting changes in brain oscillatory activity. Across two experiments, we tested whether WM could be improved through tACS of dorsomedial PFC and ACC, by affecting executive control networks associated with frontal midline theta. In Experiment 1, after either a 20-min verum or sham stimulation applied to Fpz-CPz at 1 mA and 6 Hz, 31 participants performed WM tasks, while EEG was recorded. The tasks required participants to either mentally manipulate memory items or retain them in memory as they were originally presented. No significant effects were observed in behavioral performance, and we found no change in theta activity during rest and task after stimulation. However, alpha activity during retention or manipulation of information in WM was less strongly enhanced during the delay period after verum stimulation as compared with sham. In Experiment 2 (n = 25), tACS was administered during the task in two separate sessions. Here, we changed the order of the stimulation blocks: A 25-min task block was either accompanied first by sham stimulation and then by verum stimulation, or vice versa. Again, we found no improvements in WM through either tACS after-effects or online stimulation. Taken together, our results demonstrate that theta frequency tACS applied at the midline is not an effective method for enhancing WM.

Mental Time Travel as Self-Affirmation

ACADEMIC ABSTRACT

This article integrates and advances the scope of research on the role of mental time travel in bolstering the self. We propose that imagining the self in the future (prospection) or in the past (retrospection) highlights central and positive self-aspects. Thus, bringing to mind one's future or past broadens the perceived bases of self-integrity and offers a route to self-affirmation. In reviewing corresponding research programs on self-prospection and nostalgia, we illustrate that mental time travel serves to affirm the self in terms of self-esteem, coherence, and control. Mental time travel could be implemented as a source of self-affirmation for facilitating coping and behavior change in several domains such as relationships, health, education, and organizational contexts.

PUBLIC ABSTRACT

People can mentally travel to their future or to their past. When people imagine what they will be like in the future, or what they were like in the past, they tend to think about themselves in terms of the important and positive attributes that they possess. Thinking about themselves in such an affirming way expands and consolidates their self-views. This broader image of themselves can increase self-esteem (the extent to which one likes who they are), coherence (the extent to which one perceives life as meaningful), and control (the extent to which one feels capable of initiating and pursuing goals or effecting desirable outcomes). Mental time travel, then, has favorable or affirming consequences for one's self-views. These consequences can be harnessed to modify one's behavior in such life domains as relationships, health, education, and work.

Keeping time and rhythm by internal simulation of sensory stimuli and behavioral actions

Effective behavior often requires synchronizing our actions with changes in the environment. Rhythmic changes in the environment are easy to predict, and we can readily time our actions to them. Yet, how the brain encodes and maintains rhythms is not known. Here, we trained primates to internally maintain rhythms of different tempos and performed large-scale recordings of neuronal activity across the sensory-motor hierarchy. Results show that maintaining rhythms engages multiple brain areas, including visual, parietal, premotor, prefrontal, and hippocampal regions. Each recorded area displayed oscillations in firing rates and oscillations in broadband local field potential power that reflected the temporal and spatial characteristics of an internal metronome, which flexibly encoded fast, medium, and slow tempos. The presence of widespread metronome-related activity, in the absence of stimuli and motor activity, suggests that internal simulation of stimuli and actions underlies timekeeping and rhythm maintenance.