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Distribution, Amplitude, Incidence, Co-Occurrence, and Propagation of Human K-Complexes in Focal Transcortical Recordings(1,2,3).

Mak-McCully RA, Rosen BQ, Rolland M, Régis J, Bartolomei F, Rey M, Chauvel P, Cash SS, Halgren E - eNeuro (2015)

Bottom Line: KCs were marked manually on each channel, and local generation was confirmed with decreased gamma power.Locally generated KCs were found in all sampled areas, including cingulate, ventral temporal, and occipital cortices.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurosciences, University of California, San Diego , San Diego, California 92093.

ABSTRACT
K-complexes (KCs) 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 findings is that KCs are primarily generated in medial frontal cortex and propagate parietally, whereas an electrocorticography (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% occurred 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 2 and 3 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.

No MeSH data available.


Related in: MedlinePlus

KC occurrence rates vary across the cortex. A, Manually marked KCs color coded for each subject. The size of the circle indicates the KC occurrence rate at each location, normalized to the maximum KC occurrence rate seen on any channel for that subject. Black circles in the top right indicate this normalized occurrence rate scale. Locations identified by a linear mixed-effects model to have a significantly higher occurrence rate than the orbitofrontal reference are highlighted by pink circles. Locations identified as occurring significantly less frequently are highlighted by blue circles. B, KC-like activity in addition to manually marked KCs. The locations showing a lower occurrence rate are the same as in A. The locations showing a higher occurrence rate differ with the addition of the template-detected KCs.
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Figure 5: KC occurrence rates vary across the cortex. A, Manually marked KCs color coded for each subject. The size of the circle indicates the KC occurrence rate at each location, normalized to the maximum KC occurrence rate seen on any channel for that subject. Black circles in the top right indicate this normalized occurrence rate scale. Locations identified by a linear mixed-effects model to have a significantly higher occurrence rate than the orbitofrontal reference are highlighted by pink circles. Locations identified as occurring significantly less frequently are highlighted by blue circles. B, KC-like activity in addition to manually marked KCs. The locations showing a lower occurrence rate are the same as in A. The locations showing a higher occurrence rate differ with the addition of the template-detected KCs.

Mentions: In Figure 5A, the occurrence rate in each bipolar pair was normalized to the pair with the highest frequency in that subject, resulting in less striking differences between cortical locations. As a measure of occurrence rate, the inter-KC intervals were calculated for each channel. A linear mixed-effects model of these intervals was calculated with location as a fixed effect and patient as a random effect to test for areas with significantly different occurrence rates. Compared with the orbitofrontal reference, KCs occurred 15% more often in the anterior cingulate (p = 0.0051), 48% more often in posterior cingulate (p < 0.00001), 11% more often in posterior prefrontal cortex (p = 0.024), and 14% more often in ventrolateral temporal regions (p = 0.022); these groups are highlighted in pink in Figure 5A. Again, contrary to inferences from scalp EEG findings, KCs occurred 30% less often in the anterior prefrontal cortex (p = 0.0001) compared with the orbitofrontal location. KCs also occurred two times less frequently in the central sulcus (p < 0.00001); these two locations are highlighted in blue in Figure 5A.


Distribution, Amplitude, Incidence, Co-Occurrence, and Propagation of Human K-Complexes in Focal Transcortical Recordings(1,2,3).

Mak-McCully RA, Rosen BQ, Rolland M, Régis J, Bartolomei F, Rey M, Chauvel P, Cash SS, Halgren E - eNeuro (2015)

KC occurrence rates vary across the cortex. A, Manually marked KCs color coded for each subject. The size of the circle indicates the KC occurrence rate at each location, normalized to the maximum KC occurrence rate seen on any channel for that subject. Black circles in the top right indicate this normalized occurrence rate scale. Locations identified by a linear mixed-effects model to have a significantly higher occurrence rate than the orbitofrontal reference are highlighted by pink circles. Locations identified as occurring significantly less frequently are highlighted by blue circles. B, KC-like activity in addition to manually marked KCs. The locations showing a lower occurrence rate are the same as in A. The locations showing a higher occurrence rate differ with the addition of the template-detected KCs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4596022&req=5

Figure 5: KC occurrence rates vary across the cortex. A, Manually marked KCs color coded for each subject. The size of the circle indicates the KC occurrence rate at each location, normalized to the maximum KC occurrence rate seen on any channel for that subject. Black circles in the top right indicate this normalized occurrence rate scale. Locations identified by a linear mixed-effects model to have a significantly higher occurrence rate than the orbitofrontal reference are highlighted by pink circles. Locations identified as occurring significantly less frequently are highlighted by blue circles. B, KC-like activity in addition to manually marked KCs. The locations showing a lower occurrence rate are the same as in A. The locations showing a higher occurrence rate differ with the addition of the template-detected KCs.
Mentions: In Figure 5A, the occurrence rate in each bipolar pair was normalized to the pair with the highest frequency in that subject, resulting in less striking differences between cortical locations. As a measure of occurrence rate, the inter-KC intervals were calculated for each channel. A linear mixed-effects model of these intervals was calculated with location as a fixed effect and patient as a random effect to test for areas with significantly different occurrence rates. Compared with the orbitofrontal reference, KCs occurred 15% more often in the anterior cingulate (p = 0.0051), 48% more often in posterior cingulate (p < 0.00001), 11% more often in posterior prefrontal cortex (p = 0.024), and 14% more often in ventrolateral temporal regions (p = 0.022); these groups are highlighted in pink in Figure 5A. Again, contrary to inferences from scalp EEG findings, KCs occurred 30% less often in the anterior prefrontal cortex (p = 0.0001) compared with the orbitofrontal location. KCs also occurred two times less frequently in the central sulcus (p < 0.00001); these two locations are highlighted in blue in Figure 5A.

Bottom Line: KCs were marked manually on each channel, and local generation was confirmed with decreased gamma power.Locally generated KCs were found in all sampled areas, including cingulate, ventral temporal, and occipital cortices.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurosciences, University of California, San Diego , San Diego, California 92093.

ABSTRACT
K-complexes (KCs) 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 findings is that KCs are primarily generated in medial frontal cortex and propagate parietally, whereas an electrocorticography (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% occurred 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 2 and 3 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.

No MeSH data available.


Related in: MedlinePlus