TY - JOUR T1 - Distribution, Amplitude, Incidence, Co-occurrence, and Propagation of Human K-Complexes in Focal Transcortical Recordings JF - eneuro JO - eneuro DO - 10.1523/ENEURO.0028-15.2015 SP - ENEURO.0028-15.2015 AU - Rachel A. Mak-McCully AU - Burke Q. Rosen AU - Matthieu Rolland AU - Jean RĂ©gis AU - Fabrice Bartolomei AU - Marc Rey AU - Patrick Chauvel AU - Sydney S. Cash AU - Eric Halgren Y1 - 2015/09/02 UR - http://www.eneuro.org/content/early/2015/09/02/ENEURO.0028-15.2015.abstract N2 - K-complexes are thought to play a key role in sleep homeostasis and memory consolidation; however, their generation and propagation remain unclear. The commonly held view from scalp EEG is that KCs are primarily generated in medial frontal cortex and propagate parietally, whereas an ECOG study suggested dorsolateral prefrontal generators and an absence of KCs in many areas. In order to resolve these differing views, we used unambiguously focal bipolar depth electrode recordings in patients with intractable epilepsy to investigate spatiotemporal relationships of human KCs. KCs were marked manually on each channel and local generation was confirmed with decreased gamma power. In most cases (76%), KCs occurred in a single location, and rarely (1%) in all locations. However, if automatically-detected KC-like phenomena were included, only 15% occurred in a single location and 27% in all recorded locations. Locally-generated KCs were found in all sampled areas, including cingulate, ventral temporal, and occipital cortices. Surprisingly, KCs were smallest and occurred least frequently in anterior prefrontal channels. When KCs occur on two channels, their peak order is consistent in only 13% of cases, usually from prefrontal to lateral temporal. Overall, the anterior-posterior separation of electrode-pairs explained only 2% of the variance in their latencies. KCs in stages two and three had similar characteristics. These results open a novel view where KCs overall are universal cortical phenomena, but each KC may variably involve small or large cortical regions, and spread in variable directions, allowing flexible and heterogeneous contributions to sleep homeostasis and memory consolidation.Significance Statement: This is the first examination of the location of KCs and their temporal relationship across the cortex using such focal measures of brain activity. KCs, along with sleep spindles and slow oscillations, are thought to play important roles in the restorative and memory consolidation processes of non-REM sleep. KCs are unique from these other markers because they indicate isolated periods of cortical silence. We describe here that KCs occur in parts of the brain previously thought not to generate KCs. We show they may co-occur over small or large parts of the cortex, but do not propagate in a systematic way. This variability could reflect and support consolidation processes devoted to memories involving the corresponding cortical areas and sequences. ER -