Dataset Information

Layer-specific BOLD activation in human V1.

ABSTRACT: The neocortex is known to have a distinct laminar structure which has previously been probed in animals using high-resolution fMRI. Detection of layer-specific activation in humans has however to date proven elusive. In this study we demonstrate for the first time such layer-specific activation, specifically at a depth corresponding to layer IV of human primary visual cortex (V1). We used a gradient-echo (GE) sequence at 3T with an isotropic resolution of 0.75 mm, in which a stria at the depth of layer IV was visible in the averaged time series, and could be used as an anatomical landmark. Upon visual stimulation (7.5 Hz flickering checkerboard) the signal increase of 3% in layer IV was significantly higher than in the neighboring laminae. The width of this activation peak was 0.8-1 mm. Based on this result and known laminar organization of the intracortical vasculature we conclude that in the direction perpendicular to the cortical surface the intrinsic spatial resolution of the GE-BOLD fMRI signal is in the submillimetre range. Human laminar fMRI is a significant development which may improve our understanding of intracortical activation patterns and of the way in which different cortical regions interact.

SUBMITTER: Koopmans PJ

PROVIDER: S-EPMC6870878 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Layer-specific BOLD activation in human V1.

Koopmans Peter J PJ Barth Markus M Norris David G DG

Human brain mapping 20100901 9

The neocortex is known to have a distinct laminar structure which has previously been probed in animals using high-resolution fMRI. Detection of layer-specific activation in humans has however to date proven elusive. In this study we demonstrate for the first time such layer-specific activation, specifically at a depth corresponding to layer IV of human primary visual cortex (V1). We used a gradient-echo (GE) sequence at 3T with an isotropic resolution of 0.75 mm, in which a stria at the depth o ...[more]

PMID: 20082333

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Project description:The influence of cortical cell spiking activity on nearby cells has been studied extensively in vitro. Less is known, however, about the impact of single cell firing on local cortical networks in vivo. In a pioneering study, Kwan and Dan (Kwan and Dan, 2012) reported that in mouse layer 2/3 (L2/3), under anesthesia, stimulating a single pyramidal cell recruits ~2.1% of neighboring units. Here we employ two-photon calcium imaging in layer 2/3 of mouse V1, in conjunction with single-cell patch clamp stimulation in layer 2/3 or layer 4, to probe, in both the awake and lightly anesthetized states, how (i) activating single L2/3 pyramidal neurons recruits neighboring units within L2/3 and from layer 4 (L4) to L2/3, and whether (ii) activating single pyramidal neurons changes population activity in local circuit. To do this, it was essential to develop an algorithm capable of quantifying how sensitive the calcium signal is at detecting effectively recruited units ("followers"). This algorithm allowed us to estimate the chance of detecting a follower as a function of the probability that an epoch of stimulation elicits one extra action potential (AP) in the follower cell. Using this approach, we found only a small fraction (<0.75%) of L2/3 cells to be significantly activated within a radius of ~200 ?m from a stimulated neighboring L2/3 pyramidal cell. This fraction did not change significantly in the awake vs. the lightly anesthetized state, nor when stimulating L2/3 vs. underlying L4 pyramidal neurons. These numbers are in general agreement with, though lower than, the percentage of neighboring cells (2.1% pyramidal cells and interneurons combined) reported by Kwan and Dan to be activated upon stimulating single L2/3 pyramidal neurons under anesthesia (Kwan and Dan, 2012). Interestingly, despite the small number of individual units found to be reliably driven, we did observe a modest but significant elevation in aggregate population responses compared to sham stimulation. This underscores the distributed impact that single cell stimulation has on neighboring microcircuit responses, revealing only a small minority of relatively strongly connected partners.One sentence summaryPatch-clamp stimulation in conjunction with 2-photon imaging shows that activating single layer-2/3 or layer-4 pyramidal neurons produces few (<1% of local units) reliable single-cell followers in L2/3 of mouse area V1, either under light anesthesia or in quiet wakefulness: instead, single cell stimulation was found to elevate aggregate population activity in a weak but highly distributed fashion.

Dataset Information

Layer-specific BOLD activation in human V1.

Publications

Layer-specific BOLD activation in human V1.

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