Laminar Specific fMRI Reveals Directed Interactions in Distributed Networks During Language Processing

Sharoh, Daniel; Mourik, Tim van; Bains, Lauren J.; Weber, Kirsten; Hagoort, Peter; Norris, David G.

doi:10.1101/585844

Cited by 15 publications

(30 citation statements)

References 66 publications

(1 reference statement)

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“…If the same approach is applied to other regions then the p2t value will need to be adjusted to accommodate different cortical thicknesses using Equation 3. Various studies in laminar fMRI literature (Kok et al, 2016;Lawrence et al, 2019;Lawrence et al, 2018;Sharoh et al, 2019) divide the cortex in three layers, it that case, the equivalent peak to tail ratio to the one observed here would be 2.24.…”

Section: Validation Of the Estimated Psf And Its Approximation As A Psupporting

confidence: 47%

Estimation of Laminar BOLD Activation Profiles using Deconvolution with a Physiological Point Spread Function

Markuerkiaga¹,

Marques²,

Norris³

2020

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BackgroundThe specificity of gradient echo (GE)-BOLD laminar fMRI activation profiles is degraded by intracortical veins that drain blood from lower to upper cortical layers, propagating activation signal in the same direction. This work describes an approach to obtain layer specific profiles by deconvolving the measured profiles with a physiological Point Spread Function (PSF).New MethodIt is shown that the PSF can be characterised by a TE-dependent peak to tail (p2t) value that is independent of cortical depth and can be estimated by simulation. An experimental estimation of individual p2t values and the sensitivity of the deconvolved profiles to variations in p2t is obtained using laminar data measured with a multi-echo 3D-FLASH sequence. These profiles are echo time dependent, but the underlying neuronal response is the same, allowing a data-based estimation of the PSF.ResultsThe deconvolved profiles are highly similar to the gold-standard obtained from extremely high resolution 3D-EPI data, for a range of p2t values of 5-9, which covers both the empirically determined value (7.1) and the value obtained by simulation (6.3).Comparison with Existing Method(s)Corrected profiles show a flatter shape across the cortex and a high level of similarity with the gold-standard, defined as a subset of profiles that are unaffected by intracortical veins.ConclusionsWe conclude that deconvolution is a robust approach for removing the effect of signal propagation through intracortical veins. This makes it possible to obtain profiles with high laminar specificity while benefitting from the higher sensitivity and efficiency of GE-BOLD sequences.

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Section: Validation Of the Estimated Psf And Its Approximation As A Psupporting

confidence: 47%

Estimation of Laminar BOLD Activation Profiles using Deconvolution with a Physiological Point Spread Function

Markuerkiaga¹,

Marques²,

Norris³

2020

Preprint

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“…45 Our approach, and that of others, has generally been to identify activated regions on the basis of their aggregate response to the task, either by means of an independent activation study, or by smoothing the high resolution data and using this for a non-laminar analysis. Given that we are interested in the characteristics of the ROI as a whole, 5,18,46 an integration approach, or similar, represents the most logical strategy. Small variations caused by vasculature, or indeed gradients in functionality, will then not be accessible, and would require a different approach.…”

Section: Scope Of This Workmentioning

confidence: 99%

An in-vivo study of BOLD laminar responses as a function of echo time and static magnetic field strength

Markuerkiaga

Marques

Bains

et al. 2020

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Layer specific functional MRI requires high spatial resolution data. An approach often used for compensating for the poor signal to noise ratio (SNR) associated with small voxel sizes consists of integrating the signal from voxels at a given cortical depth over a patch of cortex. After this integration, physiological noise is expected to be the dominant noise source in the signal. In this context, the sensitivity gain in moving to higher static field strengths is expected to be lower than when thermal noise dominates. In this work, activation profiles in response to the same visual stimulus are compared at 1.5 T, 3 T and 7 T using a multi-echo, gradient echo (GE) FLASH sequence, with a 0.75 mm isotropic voxel size and the cortical integration approach. The results show that after integrating over a patch of cortex between 40 and 100 mm3(at 7 T and 1.5 T, respectively), the signal is in the physiological noise dominated regime, and that the obtained activation profiles are similar at the three different field strengths for equivalent echo times. The evolution of the resting-state signal over echo time indicates that BOLD-like noise is the dominant source of physiological noise. Consequently, the functional contrast to noise ratio is not strongly echo-time or field-strength dependent. The results show that compared to 7T, the gold standard, laminar GE-BOLD fMRI at lower field strengths is feasible at the cost of poorer spatial resolution (larger cortical integration extensions) and lower efficiency.

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“…Investigating directional laminar connectivity during task conditions has so far remained primarily the domain of invasive electrophysiological investigations in animals (1). In recent years, the development of high-resolution fMRI has made it possible to measure laminar level activity in humans noninvasively (2)(3)(4)(5)(6)(7)(8)(9). Laminar specific anatomical connections directly relate to feedforward and feedback projections between regions at different levels in the cortical hierarchy (10,11).…”

Section: Introductionmentioning

confidence: 99%

“…These projections have been related to frequency-specific directional connectivity derived from electrophysiological measures. Recently, Sharoh et al (9) demonstrated that laminar specific feedforward and feedback connections of the visual word form area with other regions can be studied with cortical depth resolved fMRI. Since frequency-specific electrophysiological synchronization has been directly related to laminar specific feedforward and feedback projections, this raises the question of how frequencyspecific neural synchronization relates to laminar level fMRI connectivity (12).…”

Section: Introductionmentioning

confidence: 99%

“…Feedback related alpha and beta band activity is thought to be conveyed from deep layers in higher order regions (layers V/VI) (1, 15,19) to layers outside layer IV in lower order regions, although for nearby regions feedback connections between superficial layers (layers II/III) have also been identified (20). Laminar fMRI allows us to study connectivity between various cortical depths non-invasively (5,9,21,22) and when combined with electrophysiological measures like EEG this allows us to relate these effects to frequency specific neural synchronization. Here we implemented this combination by first computing individual task effects in cortical depth dependent correlation based connectivity.…”

Section: Introductionmentioning

confidence: 99%

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Relating neural oscillations to laminar fMRI connectivity

Scheeringa

Bonnefond

Mourik

et al. 2020

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Laminar fMRI can non-invasively study brain activation and potentially connectivity at the laminar level in humans. In a previous simultaneous laminar fMRI/EEG experiment, we observed that attention effects in alpha, beta and gamma band EEG power relate to attention effects in fMRI activation in V1/V2/V3 at distinct cortical depths: alpha and gamma band EEG attention effects related to fMRI effects in superficial layers, whereas beta attention effects related to deep layers. Here we reanalyzed these data to investigate how EEG-attention effects relate to changes in connectivity between regions. We computed the fMRI-based attention effect on laminar connectivity between regions within a hemisphere and connectivity between layers within brain regions. We observed that the beta band strongly relates to laminar specific changes in connectivity. Our results indicate that the attention-related decrease in beta power relates to an increase in deep-to-deep layer connectivity between regions and deep/middle to superficial layer connectivity within brain regions. The attention related alpha power increase predominantly relates to increases in connectivity between deep and superficial layers within brain regions. We observed no strong relation between laminar connectivity and gamma band oscillations. These results indicate that especially beta band oscillations, and to a lesser extent alpha band oscillations relate to laminar specific changes in connectivity as measured by laminar fMRI. Together, the effects for the alpha and beta bands suggest a complex picture of possibly co-occurring neural processes that can differentially affect laminar connectivity.

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Laminar Specific fMRI Reveals Directed Interactions in Distributed Networks During Language Processing

Cited by 15 publications

References 66 publications

Estimation of Laminar BOLD Activation Profiles using Deconvolution with a Physiological Point Spread Function

Estimation of Laminar BOLD Activation Profiles using Deconvolution with a Physiological Point Spread Function

An in-vivo study of BOLD laminar responses as a function of echo time and static magnetic field strength

Relating neural oscillations to laminar fMRI connectivity

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