Anesthesia and the Thalamocortical System

2009 ◽  
pp. 127-138
Author(s):  
Michael T. Alkire
e-Neuroforum ◽  
2017 ◽  
Vol 23 (3) ◽  
Author(s):  
Alexander Groh ◽  
Rebecca Mease ◽  
Patrik Krieger

AbstractThe transduction of painful stimuli into the experience of pain involves several peripheral and central signaling pathways of the nervous system. The organization of these pathways parallels the main functions of pain: the assessment of noxious stimuli (where, what, how strong), and the negative emotion of unpleasantness. Multiple lines of evidence suggest that the thalamocortical (TC) system, which interprets ascending pain signals, has two main pathways which support these functions. We discuss the structural and functional findings that support the view that the lateral TC pathway is involved in discriminative assessment of pain, while the medial TC pathway gives rise to aversive emotions associated with pain. Our review focuses on acute pain, but we also discuss putative TC maladaptations in humans and animal models of pain that are thought to underlie pathological pain sensations.


2018 ◽  
Vol 120 (2) ◽  
pp. 617-623 ◽  
Author(s):  
Petro Julkunen ◽  
Olli Löfberg ◽  
Elisa Kallioniemi ◽  
Jelena Hyppönen ◽  
Reetta Kälviäinen ◽  
...  

Unverricht-Lundborg disease (EPM1) is associated with progressive functional and anatomic changes in the thalamus and motor cortex. The neurophysiological mechanisms behind the impaired thalamocortical system were studied through short-term adaptation of the motor cortex to transcranial magnetic stimulation (TMS) via repetition suppression (RS) phenomenon. RS is considered to be related to neural processing of external stimuli. We hypothesized that this neural processing is progressively impaired in EPM1 from adolescence to adulthood. Eight adult patients with EPM1 (age: 40 ± 13 yr), six adolescent patients with EPM1 (age: 16 ± 1 yr), and ten adult controls (age: 35 ± 12 yr) were studied using navigated TMS and RS study protocol including trains of four repeated stimuli with intertrain interval of 20 s and interstimulus interval of 1 s. Changes in RS were investigated from adolescence to adulthood in EPM1 by comparing with adult controls. In controls, the RS was seen as 50–55% reduction in motor response amplitudes to TMS after the first stimulus. RS was mild or missing in EPM1. RS from first to second stimulus within the stimulus trains was significantly stronger in adolescent patients than in adult patients ( P = 0.046). Abnormal RS correlated with the myoclonus severity of the patients. In agreement with our hypothesis, neural processing of external stimuli is progressively impaired in EPM1 possibly due to anatomically impaired thalamocortical system or inhibitory tonus preventing sufficient adaptive reactiveness to stimuli. Our results suggest that RS abnormality might be used as a biomarker in the therapeutic trials for myoclonus. NEW & NOTEWORTHY Unverricht-Lundborg disease (EPM1) is associated with impaired thalamocortical function, which we studied in 8 adult and 6 adolescent patients and in 10 adult controls through repetition suppression (RS) of the motor cortex. We hypothesized that neural processing is progressively impaired in EPM1 from adolescence to adulthood. RS was normal in controls, whereas it was mild or missing in EPM1. Stronger RS was seen in adolescent patients than in adult patients correlating with the myoclonus severity.


2000 ◽  
Vol 84 (4) ◽  
pp. 1863-1868 ◽  
Author(s):  
Kyle L. Kirkland ◽  
Adam M. Sillito ◽  
Helen E. Jones ◽  
David C. West ◽  
George L. Gerstein

We have previously developed a model of the corticogeniculate system to explore cortically induced synchronization of lateral geniculate nucleus (LGN) neurons. Our model was based on the experiments of Sillito et al. Recently Brody discovered that the LGN events found by Sillito et al. correlate over a much longer period of time than expected from the stimulus-driven responses and proposed a cortically induced slow covariation in LGN cell membrane potentials to account for this phenomenon. We have examined the data from our model, and we found, to our surprise, that the model shows the same long-term correlation. The model's behavior was the result of a previously unsuspected oscillatory effect, not a slow covariation. The oscillations were in the same frequency range as the well-known spindle oscillations of the thalamocortical system. In the model, the strength of feedback inhibition from the cortex and the presence of low-threshold calcium channels in LGN cells were important. We also found that by making the oscillations more pronounced, we could get a better fit to the experimental data.


2021 ◽  
Vol 15 ◽  
Author(s):  
Jesse J. Winters

In recent years, there has been a proliferation of neuroscientific theories of consciousness. These include theories which explicitly point to EM fields, notably Operational Architectonics and, more recently, the General Resonance Theory. In phenomenological terms, human consciousness is a unified composition of contents. These contents are specific and meaningful, and they exist from a subjective point of view. Human conscious experience is temporally continuous, limited in content, and coherent. Based upon those phenomenal observations, pre-existing theories of consciousness, and a large body of experimental evidence, I derived the Temporally-Integrated Causality Landscape (TICL). In brief, the TICL proposes that the neural correlate of consciousness is a structure of temporally integrated causality occurring over a large portion of the thalamocortical system. This structure is composed of a large, integrated set of neuronal elements (the System), which contains some subsystems, defined as having a higher level of temporally-integrated causality than the System as a whole. Each Subsystem exists from the point of view of the System, in the form of meaningful content. In this article, I review the TICL and consider the importance of EM forces as a mechanism of neural causality. I compare the fundamentals of TICL to those of several other neuroscientific theories. Using five major characteristics of phenomenal consciousness as a standard, I compare the basic tenets of Integrated Information Theory, Global Neuronal Workspace, General Resonance Theory, Operational Architectonics, and the Temporo-spatial Theory of Consciousness with the framework of the TICL. While the literature concerned with these theories tends to focus on different lines of evidence, there are fundamental areas of agreement. This means that, in time, it may be possible for many of them to converge upon the truth. In this analysis, I conclude that a primary distinction which divides these theories is the feature of spatial and temporal nesting. Interestingly, this distinction does not separate along the fault line between theories explicitly concerned with EM fields and those which are not. I believe that reconciliation is possible, at least in principle, among those theories that recognize the following: just as the contents of consciousness are distinctions within consciousness, the neural correlates of conscious content should be distinguishable from but fall within the spatial and temporal boundaries of the full neural correlates of consciousness.


2021 ◽  
Vol 29 (6) ◽  
pp. 927-942
Author(s):  
Nikita Egorov ◽  
◽  
Vladimir Ponomarenko ◽  
Sofia Melnikova ◽  
Ilya Sysoev ◽  
...  

This work aims to show that long transient processes in mesascale models of thalamocortical brain network can appear in very general case, in particular for different number of elements in the ensemble (different level of detalization) and different initial phase of external driving, with these regimes surviving at small variations of number and structure of couplings. Methods. Thalamocortical brain networks are modelled using electronic circuit realized using computer SPICE eluating software. FitzHugh – Nagumo analog generator is used as a single circuit element. Results. Long quasiregular and nonregular oscillation processes with stationary amplitude were shown to occur in ensembles of 14, 28 and 56 model FitzHug – Nagumo generators. The dependency of transient process length on the external driving initial phase and particular coupling matrix structure was studied. Conclusion. The proposed electronic models of thalamocortical system were proved to reproduce the pathological regimes of brain activity in similar way despite the number of elements in the circuit, connectivity matrix and initial driving phase.


Author(s):  
Eric D. Young ◽  
Donata Oertel

Neuronal circuits in the brainstem convert the output of the ear, which carries the acoustic properties of ongoing sound, to a representation of the acoustic environment that can be used by the thalamocortical system. Most important, brainstem circuits reflect the way the brain uses acoustic cues to determine where sounds arise and what they mean. The circuits merge the separate representations of sound in the two ears and stabilize them in the face of disturbances such as loudness fluctuation or background noise. Embedded in these systems are some specialized analyses that are driven by the need to resolve tiny differences in the time and intensity of sounds at the two ears and to resolve rapid temporal fluctuations in sounds like the sequence of notes in music or the sequence of syllables in speech.


2007 ◽  
Vol 18 (2) ◽  
pp. 344-363 ◽  
Author(s):  
Maria J. Galazo ◽  
Verónica Martinez-Cerdeño ◽  
César Porrero ◽  
Francisco Clascá

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