Functional differences in cerebral activation between slow wave-coupled and uncoupled sleep spindles

Spindles are often temporally coupled to slow waves (SW). These SW-spindle complexes have been implicated in memory consolidation that involves transfer of information from the hippocampus to the neocortex. However, spindles and SW, which are characteristic of NREM sleep, can occur as part of this complex, or in isolation. It is not clear whether dissociable parts of the brain are recruited when coupled to SW vs. when spindles or SW occur in isolation. Here, we tested differences in cerebral activation time-locked to uncoupled spindles, uncoupled SW and coupled SW-spindle complexes using simultaneous EEG-fMRI. Consistent with the “active system model,” we hypothesized that brain activations time-locked to coupled SW-spindles would preferentially occur in brain areas known to be critical for sleep-dependent memory consolidation. Our results show that coupled spindles and uncoupled spindles recruit distinct parts of the brain. Specifically, we found that hippocampal activation during sleep is not uniquely related to spindles. Rather, this process is primarily driven by SWs and SW-spindle coupling. In addition, we show that SW-spindle coupling is critical in the activation of the putamen. Importantly, SW-spindle coupling specifically recruited frontal areas in comparison to uncoupled spindles, which may be critical for the hippocampal-neocortical dialogue that preferentially occurs during sleep

Does the early bird really get the worm? How chronotype relates to human intelligence

Objectives: Chronotype impacts our state at a given time of day, however, chronotype is also heritable, trait-like, and varies systematically as a function of age and sex. However, only a handful of studies support a relationship between chronotype and trait-like cognitive abilities (i.e., intelligence), and the evidence is sparse and inconsistent between studies. Typically, studies have: (1) focused on limited subjective measures of chronotype, (2) focused on young adults only, and (3) have not considered sex differences. Here, using a combination of cognitive aptitude and ability testing, subjective chronotype, and objective actigraphy, we aimed to explore the relationship between trait-like cognitive abilities and chronotype. Design: Participants (N = 61; 44 females; age = 35.30 ± 18.04 years) completed the Horne-Ostberg Morningness-Eveningness Questionnaire (MEQ) to determine subjective chronotype and wore an activity monitor for 10 days to objectively assess bedtime, rise-time, total sleep time, inter-daily stability, intra-daily variability, and relative amplitude. Cognitive ability (e.g., Verbal, Reasoning and Short-Term Memory) testing took place at the completion of the study. Results: Higher MEQ scores (i.e., more morning) were associated with higher inter-daily stability scores. Superior verbal abilities were associated with later bedtimes, younger age, but paradoxically, higher (i.e., more morning) MEQ scores. Superior STM abilities were associated with younger age only. The relationships between chronotype and trait-like cognitive abilities were similar for both men and women and did not differ between younger and older adults. Conclusions: The present study demonstrates that chronotype, measured by the MEQ, is highly related to inter-daily stability (i.e., the strength of circadian synchronization). Furthermore, although evening types have superior verbal abilities overall, higher (i.e., more morning) MEQ scores were related to superior verbal abilities after controlling for “evening type” behaviours

Noncrossover dither creeping mutation-based genetic algorithm for pipe network optimization

A non-crossover dither creeping mutation-based genetic algorithm (CMBGA) for pipe network optimization has been developed and is analyzed. This CMBGA differs from the classic GA optimization in that it does not utilize the crossover operator, but instead it only uses selection and a proposed dither creeping mutation operator. The creeping mutation rate in the proposed dither creeping mutation operator is randomly generated in a range throughout a GA run rather than being set to a fixed value. In addition, the dither mutation rate is applied at an individual chromosome level rather than at the generation level. The dither creeping mutation probability is set to take values from a small range that is centered about 1/ND (where ND=number of decision variables of the optimization problem being considered). This is motivated by the fact that a mutation probability of approximately 1/ND has been previously demonstrated to be an effective value and is commonly used for the GA. Two case studies are used to investigate the effectiveness of the proposed CMBGA. An objective of this paper is to compare the performance of the proposed CMBGA with four other GA variants, and other published results. The results show that the proposed CMBGA exhibits considerable improvement over the considered GA variants, and comparable performance with respect to other previously published results. A big advantage of CMBGA is its simplicity and that it requires the tuning of fewer parameters compared with other GA variants.Feifei Zheng, Aaron C. Zecchin, Angus R. Simpson and Martin F. Lamber

Hemispheric Asymmetry in White Matter Connectivity of the Temporoparietal Junction with the Insula and Prefrontal Cortex

The temporoparietal junction (TPJ) is a key node in the brain's ventral attention network (VAN) that is involved in spatial awareness and detection of salient sensory stimuli, including pain. The anatomical basis of this network's right-lateralized organization is poorly understood. Here we used diffusion-weighted MRI and probabilistic tractography to compare the strength of white matter connections emanating from the right versus left TPJ to target regions in both hemispheres. Symmetry of structural connectivity was evaluated for connections between TPJ and target regions that are key cortical nodes in the right VAN (insula and inferior frontal gyrus) as well as target regions that are involved in salience and/or pain (putamen, cingulate cortex, thalamus). We found a rightward asymmetry in connectivity strength between the TPJ and insula in healthy human subjects who were scanned with two different sets of diffusion-weighted MRI acquisition parameters. This rightward asymmetry in TPJ-insula connectivity was stronger in females than in males. There was also a leftward asymmetry in connectivity strength between the TPJ and inferior frontal gyrus, consistent with previously described lateralization of language pathways. The rightward lateralization of the pathway between the TPJ and insula supports previous findings on the roles of these regions in stimulus-driven attention, sensory awareness, interoception and pain. The findings also have implications for our understanding of acute and chronic pains and stroke-induced spatial hemineglect

Understanding Northeastern Plains Village sites through archaeological geophysics

The archaeologically defined Northeastern Plains Village Complex (NEPV), centered in the American Great Plains has been a problem for archaeologists because of an inability to recognize buried cultural features, particularly those relating to house structures. Elsewhere in the Great Plains magnetics and earth resistance had been shown effective methods, which was applied at two NEPV sites in North Dakota. Those geophysical methods were combined with down-hole magnetic susceptibility as a way to identify and interpret multiple fortified ditches, circular house structures and a possible bastion at two prehistoric villages dating from ad 1400 to 1500. This information shows that these people occupied these sites seasonally, but were still threatened enough to construct defensive structures during a period of conflict in the area. The geophysical surveys highlight the advantages of combining these techniques in NEPV site discovery and evaluation

Success rate (percentage of subjects that had a connection value >2.0 out of 5000 samples), mean and standard error of connectivity values with the TPJ for each ipsilateral target (non-distance-corrected).

<p>Abbreviations: rTPJ = right temporoparietal junction, lTPJ = left temporoparietal junction, pgACC = pregenual anterior cingulate cortex, MCC = mid-cingulate cortex, IFGt = inferior frontal gyrus (pars triangularis), IFGo = inferior frontal gyrus (pars opercularis).</p

Regions of interest, displayed on the MNI152 stereotaxic brain for A) TPJ seeds where tractography was initiated (top row displays seeds for primary analysis, and bottom row displays seeds for secondary analysis) and B) targets.

<p>For targets, the left image displays perigenual anterior cingulate cortex (pgACC) and mid-cingulate cortex (MCC), the middle image displays bilateral pars triangularis of the inferior frontal gyrus (IFGt), pars opercularis of the inferior frontal gyrus (IFGo), putamen and thalamus, and the right image displays the short gyrus of the insula.</p