scholarly journals Levels of biological plausibility

2020 ◽  
Vol 376 (1815) ◽  
pp. 20190632
Author(s):  
Bradley C. Love
Keyword(s):  
Model Selection ◽  
Functional Neuroimaging ◽  
Scientific Progress ◽  
Blood Oxygen Level Dependent ◽  
Levels Of Analysis ◽  
Biological Plausibility ◽  
Blood Oxygen Level ◽  
Selection Procedures ◽  
Non Invasive ◽  
The Relationship

Notions of mechanism, emergence, reduction and explanation are all tied to levels of analysis. I cover the relationship between lower and higher levels, suggest a level of mechanism approach for neuroscience in which the components of a mechanism can themselves be further decomposed and argue that scientists' goals are best realized by focusing on pragmatic concerns rather than on metaphysical claims about what is ‘real'. Inexplicably, neuroscientists are enchanted by both reduction and emergence. A fascination with reduction is misplaced given that theory is neither sufficiently developed nor formal to allow it, whereas metaphysical claims of emergence bring physicalism into question. Moreover, neuroscience's existence as a discipline is owed to higher-level concepts that prove useful in practice. Claims of biological plausibility are shown to be incoherent from a level of mechanism view and more generally are vacuous. Instead, the relevant findings to address should be specified so that model selection procedures can adjudicate between competing accounts. Model selection can help reduce theoretical confusions and direct empirical investigations. Although measures themselves, such as behaviour, blood-oxygen-level-dependent (BOLD) and single-unit recordings, are not levels of analysis, like levels, no measure is fundamental and understanding how measures relate can hasten scientific progress. This article is part of the theme issue ‘Key relationships between non-invasive functional neuroimaging and the underlying neuronal activity'.

scholarly journals Levels of Biological Plausibility

2019 ◽  
Author(s):  
Bradley C. Love
Keyword(s):  
Model Selection ◽  
Single Unit ◽  
Scientific Progress ◽  
Levels Of Analysis ◽  
Biological Plausibility ◽  
Selection Procedures ◽  
Single Unit Recordings ◽  
The Relationship ◽  
Empirical Investigations

Notions of mechanism, emergence, reduction, and explanation are all tied to levels of analysis. I cover the relationship between lower and higher levels, suggest a levels of mechanism approach for neuroscience in which the components of a mechanism can themselves be further decomposed, and argue that scientists' goals are best realised by focusing on pragmatic concerns rather than on metaphysical claims about what is "real". Inexplicably, neuroscientists are enchanted by both reduction and emergence. A fascination with reduction is misplaced given that theory is not sufficiently developed nor formal to allow it, whereas metaphysical claims of emergence bring physicalism into question. Moreover, neuroscience’s existence as a discipline is owed to higher-level concepts that prove useful in practice. Claims of biological plausibility are shown to be incoherent from a levels of mechanism view and more generally are vacuous. Instead, the relevant findings to address should be specified so that model selection procedures can adjudicate between competing accounts. Model selection can help reduce theoretical confusions and direct empirical investigations. Although measures themselves, such as behaviour, BOLD, and single-unit recordings, are not levels of analysis, like levels, no measure is fundamental and understanding how measures relate can hasten scientific progress.

Functional Magnetic Resonance Imaging

2014 ◽  
Author(s):  
Emmanuel A. Stamatakis ◽  
Eleni Orfanidou ◽  
Andrew C. Papanicolaou
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Functional Magnetic Resonance Imaging ◽  
Functional Neuroimaging ◽  
Blood Oxygen Level Dependent ◽  
Brain Regions ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Blood Oxygen Level ◽  
The One

Functional magnetic resonance imaging (fMRI) is the most frequently used functional neuroimaging method and the one that accounts for most of the neuroimaging literature. It measures the blood oxygen level-dependent (BOLD) signal in different parts of the brain during rest and during task-induced activation of functional networks mediating basic and higher functions. A basic understanding of the various instruments and techniques of recording the hemodynamic responses of different brain regions and the manner in which we establish activation and connectivity patterns out of these responses is necessary for an appreciation of the contemporary functional neuroimaging literature. To facilitate such an understanding is the purpose of this chapter.

scholarly journals Pathway-Specific Variations in Neurovascular and Neurometabolic Coupling in Rat Primary Somatosensory Cortex

2009 ◽  
Vol 29 (5) ◽  
pp. 976-986 ◽  
Author(s):  
Pia Enager ◽  
Henning Piilgaard ◽  
Nikolas Offenhauser ◽  
Ara Kocharyan ◽  
Priscilla Fernandes ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Cortical Area ◽  
Functional Neuroimaging ◽  
Brain Area ◽  
Pyramidal Cells ◽  
Blood Oxygen Level Dependent ◽  
Synaptic Activity ◽  
Inhibitory Interneurons ◽  
Blood Oxygen Level ◽  
Evoked Activity

Functional neuroimaging signals are generated, in part, by increases in cerebral blood flow (CBF) evoked by mediators, such as nitric oxide and arachidonic acid derivatives that are released in response to increased neurotransmission. However, it is unknown whether the vascular and metabolic responses within a given brain area differ when local neuronal activity is evoked by an activity in the distinct neuronal networks. In this study we assessed, for the first time, the differences in neuronal responses and changes in CBF and oxygen consumption that are evoked after the activation of two different inputs to a single cortical area. We show that, for a given level of glutamatergic synaptic activity, corticocortical and thalamocortical inputs evoked activity in pyramidal cells and different classes of interneurons, and produced different changes in oxygen consumption and CBF. Furthermore, increases in stimulation intensities either turned off or activated additional classes of inhibitory interneurons immunoreactive for different vasoactive molecules, which may contribute to increases in CBF. Our data imply that for a given cortical area, the amplitude of vascular signals will depend critically on the type of input, and that a positive blood oxygen level-dependent (BOLD) signal may be a consequence of the activation of both pyramidal cells and inhibitory interneurons.

scholarly journals Altered Task-Evoked Corticolimbic Responsivity in Generalized Anxiety Disorder

2021 ◽  
Vol 22 (7) ◽  
pp. 3630
Author(s):  
Nayoung Kim ◽  
M. Justin Kim
Keyword(s):  
Anxiety Disorder ◽  
Generalized Anxiety Disorder ◽  
Functional Neuroimaging ◽  
A Priori ◽  
Blood Oxygen Level Dependent ◽  
Brain Regions ◽  
Anterior Cingulate ◽  
Generalized Anxiety ◽  
Blood Oxygen Level ◽  
Size Limits

Generalized anxiety disorder (GAD) is marked by uncontrollable, persistent worry and exaggerated response to uncertainty. Here, we review and summarize the findings from the GAD literature that employs functional neuroimaging methods. In particular, the present review focuses on task-based blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) studies. We find that select brain regions often regarded as a part of a corticolimbic circuit (e.g., amygdala, anterior cingulate cortex, prefrontal cortex) are consistently targeted for a priori hypothesis-driven analyses, which, in turn, shows varying degrees of abnormal BOLD responsivity in GAD. Data-driven whole-brain analyses show the insula and the hippocampus, among other regions, to be affected by GAD, depending on the task used in each individual study. Overall, while the heterogeneity of the tasks and sample size limits the generalizability of the findings thus far, some promising convergence can be observed in the form of the altered BOLD responsivity of the corticolimbic circuitry in GAD.

scholarly journals Statistical Power or More Precise Insights into Neuro-Temporal Dynamics? Assessing the Benefits of Rapid Temporal Sampling in fMRI

2021 ◽  
Author(s):  
Logan T Dowdle ◽  
Geoffrey Ghose ◽  
Kamil Ugurbil ◽  
Essa Yacoub ◽  
Luca Vizioli
Keyword(s):  
Statistical Power ◽  
Temporal Dynamics ◽  
Blood Oxygen Level Dependent ◽  
Neuronal Firing ◽  
Blood Oxygen Level ◽  
Non Invasive ◽  
Temporal Sampling ◽  
Simple Question ◽  
Technological Developments ◽  
Human Neuroimaging

Functional magnetic resonance imaging (fMRI), a non-invasive and widely used human neuroimaging method, is most known for its spatial precision. However, there is a growing interest in its temporal sensitivity. This is despite the temporal blurring of neuronal events by the blood oxygen level dependent (BOLD) signal, the peak of which lags neuronal firing by 4 to 6 seconds. Given this, the goal of this review is to answer a seemingly simple question - "What are the benefits of increased temporal sampling for fMRI?". To answer this, we have combined fMRI data collected at multiple temporal scales, from 323 to 1000 milliseconds, with a review of both historical and contemporary temporal literature. After a brief discussion of technological developments that have rekindled interest in temporal research, we next consider the potential statistical and methodological benefits. Most importantly, we explore how fast fMRI can uncover previously unobserved neuro-temporal dynamics - effects that are entirely missed when sampling at conventional 1 to 2 second rates. With the intrinsic link between space and time in fMRI, this temporal renaissance also delivers improvements in spatial precision. Far from producing only statistical gains, the array of benefits suggest that the continued temporal work is worth the effort.

scholarly journals Precapillary sphincters control cerebral blood flow

2019 ◽  
Author(s):  
Søren Grubb ◽  
Changsi Cai ◽  
Bjørn O. Hald ◽  
Lila Khennouf ◽  
Jonas Fordsmann ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Functional Neuroimaging ◽  
Smooth Muscle Actin ◽  
Cell Activity ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen Level ◽  
Brain Capillary ◽  
Blood Flow Control ◽  
Precapillary Sphincter

AbstractActive nerve cells produce and release vasodilators that increase their energy supply by dilating local blood vessels, a mechanism termed neurovascular coupling, which is the basis of the BOLD (blood-oxygen-level-dependent) functional neuroimaging signals. We here reveal a unique mechanism for cerebral blood flow control, a precapillary sphincter at the transition between the penetrating arteriole and the first capillary that links blood flow in capillaries to the arteriolar inflow. Large NG2-positive cells, containing smooth muscle actin, encircle the sphincters and rises in nerve cell activity cause astrocyte and neuronal Ca2+ rises that correlate to dilation and shortening of the sphincter concomitant with substantial increases in the RBC flux. Global ischemia and cortical spreading depolarization constrict sphincters and cause vascular trapping of blood cells. These results reveal precapillary sphincters as bottlenecks for brain capillary blood flow.

Endothelial Dysfunction and Inflammatory Markers of Vascular Disease

2020 ◽  
Vol 19 (3) ◽  
pp. 243-249 ◽  
Author(s):  
Sevket Balta
Keyword(s):  
Endothelial Dysfunction ◽  
Vascular Disease ◽  
Inflammatory Markers ◽  
Vascular Diseases ◽  
Intima Media Thickness ◽  
Carotid Intima Media Thickness ◽  
Non Invasive ◽  
Von Willebrand ◽  
The Relationship ◽  
Willebrand Factor

: Vascular diseases are the main reason for morbidity and mortality worldwide. As we know, the earlier phase of vascular diseases is endothelial dysfunction in humans, the endothelial tissues play an important role in inflammation, coagulation, and angiogenesis, via organizing ligand-receptor associations and the various mediators’ secretion. We can use many inflammatory non-invasive tests (flowmediated dilatation, epicedial fat thickness, carotid-intima media thickness, arterial stiffness and anklebrachial index) for assessing the endothelial function. In addition, many biomarkers (ischemia modified albumin, pentraxin-3, E-selectin, angiopoietin, endothelial cell specific molecule 1, asymmetrical dimethylarginine, von Willebrand factor, endothelial microparticles and endothelial progenitor cells) can be used to evaluate endothelial dysfunction. We have focused on the relationship between endothelial dysfunction and inflammatory markers of vascular disease in this review.

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