Faculty Opinions recommendation of Low-frequency theta oscillations in the human hippocampus during real-world and virtual navigation.

Expectations run high for software that makes real-world decisions, particularly when money hangs in the balance. This third episode of the Drill Bits column shows how well-designed software can effectively create wealth by optimizing gains from trade in combinatorial auctions. We'll unveil a deep connection between auctions and a classic textbook problem, we'll see that clearing an auction resembles a high-stakes mutant Tetris, we'll learn to stop worrying and love an NP-hard problem that's far from intractable in practice, and we'll contrast the deliberative business of combinatorial auctions with the near-real-time hustle of high-frequency trading. The example software that accompanies this installment of Drill Bits implements two algorithms that clear combinatorial auctions.

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Electric Vehicle Battery Performance Investigation Based on Real World Current Harmonics

Energies ◽

10.3390/en13020489 ◽

2020 ◽

Vol 13 (2) ◽

pp. 489 ◽

Cited By ~ 2

Author(s):

Sid-Ali Amamra ◽

Yashraj Tripathy ◽

Anup Barai ◽

Andrew D. Moore ◽

James Marco

Keyword(s):

Electric Vehicle ◽

Real World ◽

Low Frequency ◽

Single Frequency ◽

Current Harmonics ◽

Battery Systems ◽

Electric Vehicle Battery ◽

Dc Bus ◽

Dc Current ◽

The Impact

Electric vehicle (EV) powertrains consist of power electronic components as well as electric machines to manage the energy flow between different powertrain subsystems and to deliver the necessary torque and power requirements at the wheels. These power subsystems can generate undesired electrical harmonics on the direct current (DC) bus of the powertrain. This may lead to the on-board battery being subjected to DC current superposed with undesirable high- and low- frequency current oscillations, known as ripples. From real-world measurements, significant current harmonics perturbations within the range of 50 Hz to 4 kHz have been observed on the high voltage DC bus of the EV. In the limited literature, investigations into the impact of these harmonics on the degradation of battery systems have been conducted. In these studies, the battery systems were supplied by superposed current signals i.e., DC superposed by a single frequency alternating current (AC). None of these studies considered applying the entire spectrum of the ripple current measured in the real-world scenario, which is focused on in this research. The preliminary results indicate that there is no difference concerning capacity fade or impedance rise between the cells subjected to just DC current and those subjected additionally to a superposed AC ripple current.

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The Role of Low-frequency Neural Oscillations in Speech Processing: Revisiting Delta Entrainment

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01410 ◽

2019 ◽

Vol 31 (8) ◽

pp. 1205-1215 ◽

Cited By ~ 2

Author(s):

Victor J. Boucher ◽

Annie C. Gilbert ◽

Boutheina Jemel

Keyword(s):

Speech Processing ◽

Low Frequency ◽

Phase Coherence ◽

Theta Oscillations ◽

Neural Oscillations ◽

Acoustic Cues ◽

Low Frequency Oscillations ◽

Temporal Grouping ◽

Delta Oscillations

Studies that use measures of cerebro-acoustic coherence have shown that theta oscillations (3–10 Hz) entrain to syllable-size modulations in the energy envelope of speech. This entrainment creates sensory windows in processing acoustic cues. Recent reports submit that delta oscillations (<3 Hz) can be entrained by nonsensory content units like phrases and serve to process meaning—though such views face fundamental problems. Other studies suggest that delta underlies a sensory chunking linked to the processing of sequential attributes of speech sounds. This chunking associated with the “focus of attention” is commonly manifested by the temporal grouping of items in sequence recall. Similar grouping in speech may entrain delta. We investigate this view by examining how low-frequency oscillations entrain to three types of stimuli (tones, nonsense syllables, and utterances) having similar timing, pitch, and energy contours. Entrainment was indexed by “intertrial phase coherence” in the EEGs of 18 listeners. The results show that theta oscillations at central sites entrain to syllable-size elements in speech and tones. However, delta oscillations at frontotemporal sites specifically entrain to temporal groups in both meaningful utterances and meaningless syllables, which indicates that delta may support but does not directly bear on a processing of content. The findings overall suggest that, although theta entrainment relates to a processing of acoustic attributes, delta entrainment links to a sensory chunking that relates to a processing of properties of articulated sounds. The results also show that measures of intertrial phase coherence can be better suited than cerebro-acoustic coherence in revealing delta entrainment.

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Driving Simulators for Human Vehicle Interaction Design

Balkan Region Conference on Engineering and Business Education ◽

10.1515/cplbu-2015-0034 ◽

2015 ◽

Vol 1 (1) ◽

pp. 297-306

Author(s):

Alexandra Tucă ◽

Valerian Croitorescu ◽

Mircea Oprean ◽

Thomas Brandemeir

Keyword(s):

Real World ◽

Input Signal ◽

Interaction Design ◽

High Frequency ◽

Driver Behavior ◽

Low Frequency ◽

Driving Simulators ◽

Sensory Inputs ◽

Frequency Information ◽

Busy Road

AbstractThe interaction human-vehicle, as well as driver’s behavior are subject long debated in the automotive engineering domain. Driving simulators have an extraordinary important role allowing research that would not be possible to study in real world scenarios.A driver uses his sensory inputs to obtain the required input to base his decision on. The bandwidth of the required input signal should be in accordance to the driver’s task. For simple tasks, like turning on the screen wipers or direction indicator, low frequency information is sufficient. High frequency information is required when cornering on a busy road or when driving in relatively limit situations.The optimal configuration of each sub-system remains a significant cause for debate and still poses a major challenge when considering the ability of simulators to extract realistic driver behavior. If a difference is observed between real and virtual conditions, the factors specifically cause these differences are very difficult to be explained.

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A Direct Comparison of Real-World and Virtual Navigation Performance in Chronic Stroke Patients

Journal of the International Neuropsychological Society ◽

10.1017/s1355617715001228 ◽

2016 ◽

Vol 22 (4) ◽

pp. 467-477 ◽

Cited By ~ 21

Author(s):

Michiel H.G. Claessen ◽

Johanna M.A. Visser-Meily ◽

Nicolien K. de Rooij ◽

Albert Postma ◽

Ineke J.M. van der Ham

Keyword(s):

Real World ◽

Convergent Validity ◽

Geographical Location ◽

Chronic Stroke ◽

Stroke Patients ◽

Virtual Navigation ◽

Survey Knowledge ◽

Patient Groups ◽

Navigation Test ◽

Composite Scores

AbstractObjectives: An increasing number of studies have presented evidence that various patient groups with acquired brain injury suffer from navigation problems in daily life. This skill is, however, scarcely addressed in current clinical neuropsychological practice and suitable diagnostic instruments are lacking. Real-world navigation tests are limited by geographical location and associated with practical constraints. It was, therefore, investigated whether virtual navigation might serve as a useful alternative. Methods: To investigate the convergent validity of virtual navigation testing, performance on the Virtual Tübingen test was compared to that on an analogous real-world navigation test in 68 chronic stroke patients. The same eight subtasks, addressing route and survey knowledge aspects, were assessed in both tests. In addition, navigation performance of stroke patients was compared to that of 44 healthy controls. Results: A correlation analysis showed moderate overlap (r=.535) between composite scores of overall real-world and virtual navigation performance in stroke patients. Route knowledge composite scores correlated somewhat stronger (r=.523) than survey knowledge composite scores (r=.442). When comparing group performances, patients obtained lower scores than controls on seven subtasks. Whereas the real-world test was found to be easier than its virtual counterpart, no significant interaction-effects were found between group and environment. Conclusions: Given moderate overlap of the total scores between the two navigation tests, we conclude that virtual testing of navigation ability is a valid alternative to navigation tests that rely on real-world route exposure. (JINS, 2016, 22, 467–477)

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High-gamma activity in the human hippocampus and parahippocampus during inter-trial rest periods of a virtual navigation task

NeuroImage ◽

10.1016/j.neuroimage.2018.05.029 ◽

2018 ◽

Vol 178 ◽

pp. 92-103 ◽

Cited By ~ 7

Author(s):

Yi Pu ◽

Brian R. Cornwell ◽

Douglas Cheyne ◽

Blake W. Johnson

Keyword(s):

Gamma Activity ◽

Virtual Navigation ◽

Navigation Task ◽

Human Hippocampus ◽

Rest Periods ◽

High Gamma

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Spatial mnemonic encoding: Theta power decreases co-occur with medial temporal lobe BOLD increases during the usage of the Method of Loci

10.1101/052720 ◽

2016 ◽

Cited By ~ 1

Author(s):

M.-C. Fellner ◽

G. Volberg ◽

M. Wimber ◽

M. Goldhacker ◽

M. W. Greenlee ◽

...

Keyword(s):

Temporal Lobe ◽

Medial Temporal Lobe ◽

Negative Relationship ◽

Low Frequency ◽

Theta Oscillations ◽

Oscillatory Activity ◽

Bold Signal ◽

Memory Processes ◽

Theta Power ◽

Method Of Loci

AbstractThe Method of Loci is one, if not the most, efficient mnemonic encoding strategy. This strategy combines the core cognitive processes commonly linked to medial temporal lobe (MTL) activity: spatial processing and associative memory processes. During such tasks fMRI studies consistently demonstrate increases in medial temporal lobe (MTL) activity, while electrophysiological studies have emphasized the important role of theta oscillations (3-8 Hz) in the MTL. How MTL activity is linked to theta oscillatory EEG power, however, is unknown. Specifically, it is not known whether increases or decreases in MTL theta power are associated with increased BOLD signal. To investigate this question we recorded EEG and fMRI while participants used the spatial Method of Loci contrasted to the Pegword Method, a similarly associative but non spatial mnemonic. Surprisingly, the more effective spatial mnemonic induced a pronounced theta power decrease in the left MTL compared to the non-spatial associative mnemonic strategy. This effect was mirrored by BOLD signal increases in the MTL. This pattern of results suggests that theta oscillations in the MTL are negatively related to BOLD signal increases. These findings extend the well-known negative relation of alpha/beta oscillations and BOLD signals in the cortex to theta oscillations in the MTL. The results also demonstrate that decreases in theta power can index MTL involvement during encoding.Significance StatementStudies investigating the oscillatory correlates of memory encoding largely focus on activity in the theta frequency and often implicitly assume that increases in theta activity reflect similar processes as typically reported increases MTL activity changes in fMRI studies. The presented study found decreases in theta power, not increases, closely mapping to MTL BOLD signal increases during the same paradigm. This finding is in line with studies showing a negative relationship between low frequency power and BOLD changes in the cortex, but challenges the assumption that theta power increases reflect MTL activity. The reported findings importantly contribute to answer the question of how and which oscillatory activity indexes MTL memory processes.

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