scholarly journals An oligarchy of NO-producing interneurons controls basal and evoked blood flow in the cortex

2019 ◽  
Author(s):  
Christina T. Echagarruga ◽  
Kyle Gheres ◽  
Patrick J. Drew
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Neural Activity ◽  
Neural Population ◽  
Neuron Activity ◽  
Arterial Diameter ◽  
Cellular Mechanisms ◽  
Population Activity ◽  
Basal Diameter ◽  
Arterial Dilation

AbstractChanges in cortical neural activity are coupled to changes in local arterial diameter and blood flow. However, the neuronal types and the signaling mechanisms that control the basal diameter of cerebral arteries or their evoked dilations are not well understood. Using chronic two-photon microscopy, electrophysiology, chemogenetics, and pharmacology in awake, head-fixed mice, we dissected the cellular mechanisms controlling the basal diameter and evoked dilation in cortical arteries. We found that modulation of overall neural activity up or down caused corresponding increases or decreases in basal arterial diameter. Surprisingly, modulation of pyramidal neuron activity had minimal effects on basal or evoked arterial dilation. Instead, the neurally-mediated component of arterial dilation was largely regulated through nitric oxide released by neuronal nitric oxide synthase (nNOS)-expressing neurons, whose activity was not reflected in electrophysiological measures of population activity. Our results show that cortical hemodynamic signals are not controlled by the average activity of the neural population, but rather the activity of a small ‘oligarchy’ of neurons.

scholarly journals nNOS-expressing interneurons control basal and behaviorally evoked arterial dilation in somatosensory cortex of mice

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Christina T Echagarruga ◽  
Kyle W Gheres ◽  
Jordan N Norwood ◽  
Patrick J Drew
Keyword(s):  
Neural Activity ◽  
Cerebral Arteries ◽  
Field Potential ◽  
Neuron Activity ◽  
Arterial Diameter ◽  
Cellular Mechanisms ◽  
Basal Diameter ◽  
Arterial Dilation ◽  
Oxide Synthase ◽  
Local Field Potential Lfp

Cortical neural activity is coupled to local arterial diameter and blood flow. However, which neurons control the dynamics of cerebral arteries is not well understood. We dissected the cellular mechanisms controlling the basal diameter and evoked dilation in cortical arteries in awake, head-fixed mice. Locomotion drove robust arterial dilation, increases in gamma band power in the local field potential (LFP), and increases calcium signals in pyramidal and neuronal nitric oxide synthase (nNOS)-expressing neurons. Chemogenetic or pharmocological modulation of overall neural activity up or down caused corresponding increases or decreases in basal arterial diameter. Modulation of pyramidal neuron activity alone had little effect on basal or evoked arterial dilation, despite pronounced changes in the LFP. Modulation of the activity of nNOS-expressing neurons drove changes in the basal and evoked arterial diameter without corresponding changes in population neural activity.

scholarly journals A Biologically Plausible Mechanism to Learn Clusters of Neural Activity

2018 ◽  
Author(s):  
Adrianna R. Loback ◽  
Michael J. Berry
Keyword(s):  
Ganglion Cell ◽  
Real Time ◽  
Neural Activity ◽  
Activity Pattern ◽  
Neural Population ◽  
Retinal Ganglion ◽  
Population Activity ◽  
Visual Areas ◽  
Cortical Hierarchy ◽  
Plausible Mechanism

When correlations within a neural population are strong enough, neural activity in early visual areas is organized into a discrete set of clusters. Here, we show that a simple, biologically plausible circuit can learn and then readout in real-time the identity of experimentally measured clusters of retinal ganglion cell population activity. After learning, individual readout neurons develop cluster tuning, meaning that they respond strongly to any neural activity pattern in one cluster and weakly to all other inputs. Different readout neurons specialize for different clusters, and all input clusters can be learned, as long as the number of readout units is mildly larger than the number of input clusters. We argue that this operation can be repeated as signals flow up the cortical hierarchy.

scholarly journals New neural activity patterns emerge with long-term learning

2019 ◽  
Vol 116 (30) ◽  
pp. 15210-15215 ◽  
Author(s):  
Emily R. Oby ◽  
Matthew D. Golub ◽  
Jay A. Hennig ◽  
Alan D. Degenhart ◽  
Elizabeth C. Tyler-Kabara ◽  
...  
Keyword(s):  
Neural Activity ◽  
Activity Patterns ◽  
Causal Link ◽  
Neural Population ◽  
Population Activity ◽  
The Brain ◽  
Neural Population Activity

Learning has been associated with changes in the brain at every level of organization. However, it remains difficult to establish a causal link between specific changes in the brain and new behavioral abilities. We establish that new neural activity patterns emerge with learning. We demonstrate that these new neural activity patterns cause the new behavior. Thus, the formation of new patterns of neural population activity can underlie the learning of new skills.

scholarly journals Correlations enhance the behavioral readout of neural population activity in association cortex

2020 ◽  
Author(s):  
Martina Valente ◽  
Giuseppe Pica ◽  
Caroline A. Runyan ◽  
Ari S. Morcos ◽  
Christopher D. Harvey ◽  
...  
Keyword(s):  
Neural Activity ◽  
Posterior Parietal Cortex ◽  
Sensory Information ◽  
Neural Population ◽  
Association Cortex ◽  
Perceptual Discrimination ◽  
Imaging Data ◽  
Stimulus Information ◽  
Population Activity ◽  
Behavioral Choice

The spatiotemporal structure of activity in populations of neurons is critical for accurate perception and behavior. Experimental and theoretical studies have focused on “noise” correlations – trial-to-trial covariations in neural activity for a given stimulus – as a key feature of population activity structure. Much work has shown that these correlations limit the stimulus information encoded by a population of neurons, leading to the widely-held prediction that correlations are detrimental for perceptual discrimination behaviors. However, this prediction relies on an untested assumption: that the neural mechanisms that read out sensory information to inform behavior depend only on a population’s total stimulus information independently of how correlations constrain this information across neurons or time. Here we make the critical advance of simultaneously studying how correlations affect both the encoding and the readout of sensory information. We analyzed calcium imaging data from mouse posterior parietal cortex during two perceptual discrimination tasks. Correlations limited the ability to encode stimulus information, but (seemingly paradoxically) correlations were higher when mice made correct choices than when they made errors. On a single-trial basis, a mouse’s behavioral choice depended not only on the stimulus information in the activity of the population as a whole, but unexpectedly also on the consistency of information across neurons and time. Because correlations increased information consistency, sensory information was more efficiently converted into a behavioral choice in the presence of correlations. Given this enhanced-by-consistency readout, we estimated that correlations produced a behavioral benefit that compensated or overcame their detrimental information-limiting effects. These results call for a re-evaluation of the role of correlated neural activity, and suggest that correlations in association cortex can benefit task performance even if they decrease sensory information.

Flow-mediated dilation analysis coupled with nitric oxide transport to enhance the assessment of endothelial function

2021 ◽  
Author(s):  
Tianxiang Ma ◽  
Xiao Liu ◽  
Quan Ren ◽  
Zhexi Zhang ◽  
Xiaoning Sun ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Blood Flow ◽  
Endothelial Function ◽  
Characteristic Parameter ◽  
Flow Mediated Dilation ◽  
Fractional Flow ◽  
Arterial Diameter ◽  
Brachial Artery Diameter ◽  
Significant Difference

Flow-mediated dilation (FMD), mainly mediated by nitric oxide (NO), aims to assess the shear-induced endothelial function, which is widely quantified by the relative change in arterial diameter after dilation (FMD%). However, FMD% is affected by individual differences in blood pressure, blood flow and arterial diameter. To reduce these differences and enhance the assessment of FMD to endothelial function, we continuously measured not only the brachial artery diameter and blood flow with ultrasound but also blood pressure with non-invasive monitor during standard FMD test. We further constructed an analytical model of FMD coupled with NO transport, blood flow, and arterial deformation. Combining the time-averaged and peak values of arterial diameter, blood flow and pressure, and the modeling, we assumed the artery was completely healthy and calculated an ideally expected FMD% (eFMD%). Then, we expressed the fractional flow-mediated dilation (FFMD%) for the ratio of measured FMD% (mFMD%) to eFMD%. Furthermore, using the continuous waveforms of arterial diameter, blood flow and pressure, the endothelial characteristic parameter (ϵ) was calculated, which describes the function of the endothelium to produce NO and ranges from 1 to 0 representing the endothelial function from healthiness to complete loss. We found that the mFMD% and eFMD% between the young age (n=5, 21.2±1.8yr) and middle age group (n=5, 34.0±2.1yr) have no significant difference (P=0.222, P=0.385). In contrast, the FFMD% (P=0.008) and ϵ (P=0.007) both show significant differences. Therefore, the fractional flow-mediated dilation (FFMD%) and the endothelial characteristic parameter (ϵ) may have the potential for specifically diagnosing the endothelial function.

Effect of nitrite on neural activity in the healthy brain

2019 ◽  
Author(s):  
Edit Franko ◽  
Martyn Ezra ◽  
Douglas C Crockett ◽  
Olivier Joly ◽  
Kyle Pattinson
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Power Spectrum ◽  
Sodium Nitrite ◽  
Neural Activity ◽  
Power Spectrum Density ◽  
Double Blind ◽  
Ischaemic Brain ◽  
Spectrum Density ◽  
The Brain

AbstractBackgroundNitrite is a major intravascular store for nitric oxide. The conversion of nitrite to the active nitric oxide occurs mainly under hypoxic conditions to increase blood flow where it is needed the most. The use of nitrite is, therefore, being evaluated widely to reduce the brain injury in conditions resulting in cerebral hypoxia, such as cardiac arrest, ischaemic stroke or subarachnoid haemorrhage. However, as it is still unknown how exogenous nitrite affects the brain activity of healthy individuals, it is difficult to clearly understand how it affects the ischaemic brain.ObjectiveHere we performed a double-blind placebo-controlled crossover study to investigate the effects of nitrite on neural activity in the healthy brain.MethodsTwenty-one healthy volunteers were recruited into the study. All participants received a continuous infusion of sodium nitrite (0.6mg/kg/h) on one occasion and placebo (sodium chloride) on another occasion. Electroencephalogram was recorded before the start and during the infusion. We computed the power spectrum density within the conventional frequency bands (delta, theta, alpha, beta), and the ratio of the power within the alpha and delta bands. We also measured peripheral cardiorespiratory physiology and cerebral blood flow.ResultsWe found no significant effect of nitrite on the power spectrum density in any frequency band. Similarly, the alpha-delta power ratio did not differ between the two conditions. However, nitrite infusion decreased the mean blood pressure and increased the methaemoglobin concentration in the blood.ConclusionOur study shows that exogenous sodium nitrite does not alter the electrical activity in the healthy brain. This might be because the sodium nitrite is converted to vasoactive nitric oxide in areas of hypoxia, and in the healthy brain there is no significant amount of conversion due to lack of hypoxia. However, this lack of change in the power spectrum density in healthy people emphasises the specificity of the brain’s response to nitrite in disease.

scholarly journals Limitations to Estimating Mutual Information in Large Neural Populations

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 490
Author(s):  
Jan Mölter ◽  
Geoffrey J. Goodhill
Keyword(s):  
Information Theory ◽  
Mutual Information ◽  
Neural Activity ◽  
Neural Population ◽  
Population Activity ◽  
Direct Estimate ◽  
Sensory Stimuli ◽  
Information Theoretic ◽  
Finite Samples ◽  
Neural Populations

Information theory provides a powerful framework to analyse the representation of sensory stimuli in neural population activity. However, estimating the quantities involved such as entropy and mutual information from finite samples is notoriously hard and any direct estimate is known to be heavily biased. This is especially true when considering large neural populations. We study a simple model of sensory processing and show through a combinatorial argument that, with high probability, for large neural populations any finite number of samples of neural activity in response to a set of stimuli is mutually distinct. As a consequence, the mutual information when estimated directly from empirical histograms will be equal to the stimulus entropy. Importantly, this is the case irrespective of the precise relation between stimulus and neural activity and corresponds to a maximal bias. This argument is general and applies to any application of information theory, where the state space is large and one relies on empirical histograms. Overall, this work highlights the need for alternative approaches for an information theoretic analysis when dealing with large neural populations.

scholarly journals Constraints on neural redundancy

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Jay A Hennig ◽  
Matthew D Golub ◽  
Peter J Lund ◽  
Patrick T Sadtler ◽  
Emily R Oby ◽  
...  
Keyword(s):  
Neural Activity ◽  
Rhesus Monkeys ◽  
Primary Motor Cortex ◽  
Activity Patterns ◽  
Computer Interface ◽  
Neural Population ◽  
Population Activity ◽  
The Brain ◽  
Selection Of ◽  
And Task

Millions of neurons drive the activity of hundreds of muscles, meaning many different neural population activity patterns could generate the same movement. Studies have suggested that these redundant (i.e. behaviorally equivalent) activity patterns may be beneficial for neural computation. However, it is unknown what constraints may limit the selection of different redundant activity patterns. We leveraged a brain-computer interface, allowing us to define precisely which neural activity patterns were redundant. Rhesus monkeys made cursor movements by modulating neural activity in primary motor cortex. We attempted to predict the observed distribution of redundant neural activity. Principles inspired by work on muscular redundancy did not accurately predict these distributions. Surprisingly, the distributions of redundant neural activity and task-relevant activity were coupled, which enabled accurate predictions of the distributions of redundant activity. This suggests limits on the extent to which redundancy may be exploited by the brain for computation.

Nitric oxide does not act as a mediator coupling cerebral blood flow to neural activity following somatosensory stimuli in rats

1993 ◽  
Vol 15 (1) ◽  
pp. 33-36 ◽  
Author(s):  
Qiong Wang ◽  
Troels Kjaer ◽  
Martin B. Jørgensen ◽  
Olaf B. Paulson ◽  
Niels A. Lassen ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Neural Activity ◽  
Somatosensory Stimuli
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