Biology subjects

Paller, K. A.

Publications and source records attributed to Paller, K. A..

3 recordsLinked to original sources

bioRxiv2018

Targeted memory reactivation during sleep elicits neural signals related to learning content

Reactivation of learning-related neural activity patterns is thought to drive memory stabilization. However, finding reliable, non-invasive, content-specific indicators of reactivation remains a central challenge. Here, we attempted to decode the content of reactivated memories in the electroencephalogram (EEG) during sleep. During encoding, human participants learned to associate spatial locations of visual objects with left- or right-hand movements, and each object was accompanied by an inherently related sound. During subsequent slow-wave sleep within an afternoon nap, we presented half of the sound cues that were associated (during wake) with left- and right-hand movements before bringing participants back for a final post-nap test. We trained a classifier on sleep EEG data (focusing on lateralized EEG features that discriminated left- vs. right-sided trials during wake) to predict learning content when we reactivated the memories during sleep. Discrimination performance was significantly above chance and predicted subsequent memory, supporting the idea that reactivation leads to memory stabilization. Moreover, these lateralized signals increased with post-cue spindle power, demonstrating that reactivation has a strong relationship with spindles. These results show that lateralized activity related to individual memories can be decoded from sleep EEG, providing an effective indicator of offline reactivation.

neuroscience↗

bioRxiv2018

Targeted memory reactivation during sleep to strengthen memory for arbitrary pairings

A powerful way to investigate memory consolidation during sleep utilizes acoustic stimulation to reactivate memories. In multiple studies, Targeted Memory Reactivation (TMR) using sounds associated with prior learning improved later memory, as in recalling locations where objects previously appeared. In the present experiment, we examined whether a variant of the same technique could strengthen memory for the locations of pairs of objects. Each sound was naturally connected to one object from each pair, but we hypothesized that both memories could be improved with TMR. We first asked participants to memorize each of 50 pairs of objects by associating the two objects with each other and with the sound of one of the objects (e.g., cat-meow). Next, objects were presented in unique locations on a grid. Participants learned these locations in an adaptive procedure. During an afternoon nap, 25 of the sounds were quietly presented. In memory tests given twice before and twice after the nap, participants heard the sound for each object pair and were asked to recall the name of the second object and the locations of both objects. Forgetting scores were calculated using the mean difference between pre-nap and post-nap spatial recall errors. We found less forgetting after the nap for cued compared to non-cued objects. Additionally, the extent of forgetting tended to be similar for the two members of each pair, but only for cued pairs. Results thus substantiate the potential for sounds to reactivate spatial memories during sleep and thereby improve subsequent recall performance, even for multiple objects associated with a single sound and when participants must learn a novel sound-object association.\n\nHighlightsO_LIMemories can be improved during sleep using arbitrary sounds\nC_LIO_LIParticipants learned a random screen location for each of 100 objects\nC_LIO_LIObjects were learned in pairs with the characteristic sound of one of the objects\nC_LIO_LIHalf of those sounds were presented during a nap that followed learning\nC_LIO_LIAfter sleep, location recall was more accurate for cued than for non-cued objects\nC_LI

neuroscience↗

bioRxiv2017

Sleep spindle refractoriness segregates periods of memory reactivation

The stability of long-term memories is enhanced by reactivation during sleep. Correlative evidence has linked memory reactivation with thalamocortical sleep spindles, although their functional role is poorly understood. Our initial study replicated this correlation but also demonstrated a novel rhythmicity to spindles, such that spindles are less likely to occur immediately following other spindles. We leveraged this rhythmicity to test the role of spindles in memory by using real-time spindle tracking to present cues inside versus outside the presumptive refractory period; as predicted, cues presented in the refractory period led to better memory. Our findings reveal a previously undescribed neural mechanism whereby spindles segment sleep into two distinct substates: prime opportunities for reactivation and gaps that segregate reactivation events.\n\nOne Sentence SummaryThe characteristic timing of sleep spindles regulates when memories can be reactivated during sleep.

neuroscience↗