Biology subjects

Manoach, D. S.

Publications and source records attributed to Manoach, D. S..

3 recordsLinked to original sources

bioRxiv2018

The hippocampus is necessary for the sleep-dependent consolidation of a task that does not require the hippocampus for initial learning

During sleep, the hippocampus plays an active role in consolidating memories that depend on it for initial encoding. There are hints in the literature that the hippocampus may have a broader influence, contributing to the consolidation of memories that may not initially require the area. We tested this possibility by evaluating learning and consolidation of the motor sequence task (MST) in hippocampal amnesics and demographically matched control participants. While the groups showed similar initial learning, only controls exhibited evidence of sleep-dependent consolidation. These results demonstrate that the hippocampus can be required for normal consolidation of a task without being required for its acquisition, suggesting that the area plays a broader role in coordinating sleep-dependent memory consolidation than has previously been assumed.

neuroscience↗

bioRxiv2018

Large-Scale Structure and Individual Fingerprints of Locally Coupled Sleep Oscillations

The temporal coordination of slow oscillations and sleep spindles is believed to underlie processes of sleep-dependent memory consolidation and reorganization. Accumulating evidence of the predominantly local expression of these individual oscillatory rhythms suggests that their interaction may have a similar local component. However, it is unclear whether local coupling holds uniformly across the cortex, and whether and how these dynamics differ between fast and slow spindles, and sleep stages. Moreover, substantial individual variability in the expression of both spindles and slow oscillations raise the possibility that their cross-frequency interactions show similar individual differences. Using two nights of multi-channel electroencephalography recordings from 24 healthy individuals, we characterized the topography of slow oscillation-spindle coupling. We found that locally coupled oscillations occur over widespread cortical areas, but that their dynamics vary with spindle class, sleep stage, and location. Moreover, the phase of the slow oscillation cycle at which spindles were expressed differed markedly across individuals but was stable across nights. However, individual variability of coupling phase was not correlated with overnight memory change. These findings both add an important spatial aspect to our understanding of the temporal coupling of sleep oscillations and demonstrate the heterogeneity of coupling dynamics, which must be taken into account when formulating mechanistic accounts of sleep-related memory processing.

neuroscience↗

bioRxiv2017

Individual differences in frequency and topography of slow and fast sleep spindles

Sleep spindles are transient oscillatory waveforms occurring during non-rapid eye movement (NREM) sleep and are implicated in plasticity and memory processes. In humans, spindles can be classified as either slow or fast, but large individual differences in spindle frequency as well as methodological difficulties have hindered progress towards understanding their function. Using two nights of high-density electroencephalography recordings from healthy individuals, we first characterize the individual variability of NREM spectra and demonstrate the difficulty of determining subject-specific spindle frequencies. We then introduce a novel spatial filtering approach that can reliably separate subject-specific spindle activity into slow and fast components that are stable across nights and across N2 and N3 sleep. We then proceed to provide detailed analyses of the topographical expression of individualized slow and fast spindle activity. Group-level analyses conform to known spatial properties of spindles, but also uncover novel differences between sleep stages and spindle classes. Moreover, subject-specific examinations reveal that individual topographies show considerable variability that is stable across nights. Finally, we demonstrate that topographical maps depend nontrivially on the spindle metric employed. In sum, our findings indicate that group-level approaches mask substantial individual variability of spindle dynamics, in both the spectral and spatial domains. We suggest that leveraging, rather than ignoring, such differences may prove useful to further our understanding of the physiology and functional role of sleep spindles.

neuroscience↗