Entrainment enhances theta oscillations and improves episodic memory

Abstract

Neural oscillations in the theta band have been linked to episodic memory, but it is unclear whether activity patterns that give rise to theta play a causal role in episodic retrieval. Here, we used rhythmic auditory and visual stimulation to entrain neural oscillations to assess whether theta activity contributes to successful memory retrieval. In two separate experiments, human subjects studied words and were subsequently tested on memory for the words ('item recognition') and the context in which each had been previously studied ('source memory'). Between study and test, subjects in the entrainment groups were exposed to audiovisual stimuli designed to enhance activity at 5.5 Hz, whereas subjects in the control groups were exposed to white noise (Expt. 1) or 14 Hz entrainment (Expt. 2). Theta entrainment selectively increased source memory performance in both studies. Electroencephalography (EEG) data in Expt. 2 revealed that theta entrainment resulted in band-specific enhancement of theta power during the entrainment period and during post-entrainment memory retrieval. These results demonstrate a direct link between theta activity and episodic memory retrieval. Targeted manipulation of theta activity could be a promising new approach to enhance theta activity and memory performance in healthy individuals and in patients with memory disorders.

Site-specific effects of online rTMS during a working memory task in healthy older adults

“…One possible explanation for this discrepancy is that while rTMS may engender certain oscillatory patterns at the site of stimulation, there exists some general latency after the end of the last TMS pulse for that entrainment to emerge. Thus, rTMS applied to a region during the time it is engaging in task-essential processing will disrupt performance, while stimulation trains of appropriate frequency applied prior to that processing can enhance performance, possibly due to entrainment of functional oscillations prior to the essential cortical activity (Hanslmayr et al, 2014;Roberts et al, 2018). The fMRI evidence suggests the essential processing in parietal cortex needed for the DRAT occurred during the delay period, with rTMS applied in that period injecting random noise that disturbed performance, while delay period 5 Hz rTMS to DLPFC may result in pre-processing activity-possibly through entrainment of theta frequency-that may enhance processing there during the subsequent probe period.…”

Neurophysiological Correlates of the Dunning-Kruger Effect

“…Overall, these findings converge to reveal that the larger LPC magnitudes were related to higher proportions of hits on the memory test and with faster response times for recollection-related items of high confidence hits with correct source memory (Addante et al, 2011;Addante et al, 2012a;Roberts et al, 2018). Hence, the LPC was related to recollection, and the more recollection signal (LPC) a subject had predicted the more likely they were to under-estimate their memory performance via their average DK responses in the metacognitive judgments ( Figure 9); recollection thus led people to exhibit more humble metacognitive self-awareness.…”

“…Source memory response distributions for recognition of old and new items are displayed in Table 2. Source memory accuracy values were collapsed to include high and low source confidence responses which were then divided by the sum of items receiving a correct and incorrect source response to calculate the proportion (Addante et al, 2012a(Addante et al, , 2012bRoberts et al, 2018). Mean accuracy for source memory was .30 (SD = .19) and was reliably greater than chance, t(55) = 11.78, p < .001.…”

“…Participants were told to choose the response that gave us the most accurate reflection of their memory, and to respond as quickly and accurately as possible. Immediately after the item recognition judgment, participants were asked to answer a source memory confidence test about if the word came from the animacy decision task or the manmade decision task during encoding on a scale of 1 to 5 (Addante et al, 2011;2012a;2012b;Roberts et al, 2018). Participants were instructed to blink only during this blank screen and avoid blinking during the screens with a small cross or stimuli.…”

Modulation of human intracranial theta oscillations during freely moving spatial navigation and memory

“…We then sought to determine whether memory performance was related to the prevalence of theta oscillations given prior findings showing links between theta and memory 22,23 . To investigate this, we computed the difference in theta prevalence during encoding and retrieval for each recording contact in each participant, and during each block (henceforth referred to as "theta difference"; Methods).…”