scholarly journals Dissociation and Brain Rhythms: Pitfalls and Promises

2021 ◽  
Vol 12 ◽  
Author(s):  
Tineke Grent-'t-Jong ◽  
Lucia Melloni ◽  
Peter J. Uhlhaas

Recently, Vesuna et al. proposed a novel circuit mechanism underlying dissociative states using optogenetics and pharmacology in mice in combination with intracranial recordings and electrical stimulation in an epilepsy patient. Specifically, the authors identified a posteromedial cortical delta-rhythm that underlies states of dissociation. In the following, we would like to critically review these findings in the context of the human literature on dissociation as well as highlight the challenges in translational neuroscience to link complex behavioral phenotypes in psychiatric syndromes to circumscribed circuit mechanisms.

2015 ◽  
Vol 114 (2) ◽  
pp. 1248-1254 ◽  
Author(s):  
Robert N. S. Sachdev ◽  
Nicolas Gaspard ◽  
Jason L. Gerrard ◽  
Lawrence J. Hirsch ◽  
Dennis D. Spencer ◽  
...  

A widely accepted view is that wakefulness is a state in which the entire cortical mantle is persistently activated, and therefore desynchronized. Consequently, the EEG is dominated by low-amplitude, high-frequency fluctuations. This view is currently under revision because the 1–4 Hz delta rhythm is often evident during “quiet” wakefulness in rodents and nonhuman primates. Here we used intracranial EEG recordings to assess the occurrence of delta rhythm in 18 awake human beings. Our recordings reveal rhythmic delta during wakefulness at 10% of all recording sites. Delta rhythm could be observed in a single cortical lobe or in multiple lobes. Sites with high delta could flip between high and low delta power or could be in a persistently high delta state. Finally, these sites were rarely identified as the sites of seizure onset. Thus rhythmic delta can dominate the background operation and activity of some neocortical circuits in awake human beings.


Author(s):  
Gonzalo Alarcón ◽  
Antonio Valentín

Around 30% of patients assessed for surgery for the treatment of epilepsy require intracranial electrodes to localize the epileptic focus or to identify functionally relevant cortex. Patients can be very different and the various non-invasive techniques used during presurgical assessment often render conflicting or contradictory results. Deciding the type of electrodes to be used and the sites to be implanted can be puzzling. This chapter describes the electrode types available, their indications, and various implantation strategies. This chapter also summarizes the criteria used to interpret chronic and acute (intraoperative) intracranial recordings, as well at the methods used to carry out and interpret functional mapping with electrical stimulation.


Neurosurgery ◽  
2020 ◽  
Vol 88 (1) ◽  
pp. 15-24
Author(s):  
Jarod L Roland ◽  
Carl D Hacker ◽  
Eric C Leuthardt

Abstract Brain mapping is a quintessential part of neurosurgical practice. Accordingly, much of our understanding of the brain's functional organization, and in particular the motor homunculus, is largely attributable to the clinical investigations of past neurosurgeons. Traditionally mapping was invasive and involved the application of electrical current to the exposed brain to observe focal disruption of function or to elicit overt actions. More recently, a wide variety of techniques have been developed that do not require electrical stimulation and often do not require any explicit participation by the subject. Collectively we refer to these as passive mapping modalities. Here we review the spectrum of passive mapping used by neurosurgeons for mapping and surgical planning that ranges from invasive intracranial recordings to noninvasive imaging as well as regimented task-based protocols to completely task-free paradigms that can be performed intraoperatively while under anesthesia.


Author(s):  
I. Taylor ◽  
P. Ingram ◽  
J.R. Sommer

In studying quick-frozen single intact skeletal muscle fibers for structural and microchemical alterations that occur milliseconds, and fractions thereof, after electrical stimulation, we have developed a method to compare, directly, ice crystal formation in freeze-substituted thin sections adjacent to all, and beneath the last, freeze-dried cryosections. We have observed images in the cryosections that to our knowledge have not been published heretofore (Figs.1-4). The main features are that isolated, sometimes large regions of the sections appear hazy and have much less contrast than adjacent regions. Sometimes within the hazy regions there are smaller areas that appear crinkled and have much more contrast. We have also observed that while the hazy areas remain still, the regions of higher contrast visibly contract in the beam, often causing tears in the sections that are clearly not caused by ice crystals (Fig.3, arrows).


ASHA Leader ◽  
2007 ◽  
Vol 12 (12) ◽  
pp. 3-3 ◽  
Author(s):  
Margaret Rogers

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