On Dec 7th 2022, we will host the 5th virtual layer-fMRI dinner.
The board of the layer-fMRI dinner group has invited the following speakers to initiate discussions on the theme: Layer-fMRI signal origin: From neurons to vessels to BOLD.
- Serge Dumoulin (NINS; Utrecht University): How population receptive field properties change across cortical laminae: from vision to cognition.
- Anna Devor (Boston University): Layer-resolved imaging of resting CMRO2 in awake mice with phosphorescent O2 probes.
- Lars Muckli (University of Glasgow): From man to non-human primates and mouse: Two top-down streams in different layers of retinotopic visual cortex (the ground truth).
Moderated by Luca Vizioli and Tyler Morgan
The entire event will last for about 90 min (including discussion).
The meeting will be recorded and published on Youtube and embedded on this website by Dec 8, 2022.
Everyone is welcome. No registration required. Zoom link:
https://layerfmri.page.link/Zoom
| Los Angeles | Chicago | New York | UK | Europe | Beijing | Sydney |
| 6:00 | 8:00 | 9:00 | 14:00 | 15:00 | 22:00 | 23:00 |
Introduction
Serge Dumoulin
How population receptive field properties change across cortical laminae: from vision to cognition.
A key advantage brought by ultra-high field MRI at 7 Tesla and more is the possibility to increase the spatial resolution at which data is acquired, with little reduction in image quality. This opens a new set of opportunities for cognitive neuroscience, for example to probe how signals vary across cortical thickness and laminae. Here, I present recent work on computational modelling of population receptive field properties. I will discuss how they vary across cortical laminae, how these properties are influenced by attention and extend these protocols from primary visual cortex towards numerical cognition in association
cortex. I will also discuss some of the limitations and the potential of laminar imaging in human cortex.
Anna Devor
Layer-resolved imaging of resting CMRO2 in awake mice with phosphorescent O2 probes.
The cerebral cortex is organized in cortical layers that differ in their cellular density, composition, and wiring. Cortical laminar architecture is also readily revealed by staining for cytochrome oxidase – the last enzyme in the respiratory electron transport chain located in the inner mitochondrial membrane. It has been hypothesized that a high-density band of cytochrome oxidase in cortical layer IV reflects higher oxygen consumption under baseline (unstimulated) conditions. We tested the above hypothesis using direct measurements of the partial pressure of O2 (pO2) in cortical tissue by means of 2-photon phosphorescence lifetime microscopy (2PLM). We revisited our previously developed method for extraction of the cerebral metabolic rate of O2 (CMRO2) based on 2-photon pO2 measurements around diving arterioles and applied this method to estimate baseline CMRO2 in awake mice across cortical layers. Our results revealed a decrease in baseline CMRO2 from layer I to layer IV. This decrease of CMRO2 with cortical depth was paralleled by an increase in tissue oxygenation. Higher baseline oxygenation and cytochrome density in layer IV may serve as an O2 reserve during surges of neuronal activity or certain metabolically active brain
states rather than baseline energy needs.
Lars Muckli
From man to non-human primates and mouse: Two top-down streams in different layers of retinotopic visual cortex (the ground truth).
Using laminar fMRI, we identified two top-down processing streams. (1) One stream is for contextualizing visual input based on fast recurrent processing of contextual information and (2) a second top-down projection is used for visual imagery. Both top-down streams are based on non-direct geniculate input to visual cortex. To investigate the ‘ground-truth’ of this top-down processing, collaborators in the Human Brain Project (HBP) conducted parallel experiments in monkeys and mice using microelectrode recording and two-photon calcium imaging. The contextual feedback effects in complex visual fields are fast, dependent on learning and are likely communicated by disinhibition in superficial layers of cortex.
Complex cognitive tasks are difficult to instruct in non-human primates and in rodents, but in humans we can see that top-down feedback processing is used for visual imagery, and also object comparison and navigation.
Discussion
layer fMRI blog 