Dissociable laminar profiles of concurrent bottom-up and top-down modulation in the human visual cortex.
Samuel Jd LawrenceDavid G NorrisFloris P de LangePublished in: eLife (2019)
Recent developments in human neuroimaging make it possible to non-invasively measure neural activity from different cortical layers. This can potentially reveal not only which brain areas are engaged by a task, but also how. Specifically, bottom-up and top-down responses are associated with distinct laminar profiles. Here, we measured lamina-resolved fMRI responses during a visual task designed to induce concurrent bottom-up and top-down modulations via orthogonal manipulations of stimulus contrast and feature-based attention. BOLD responses were modulated by both stimulus contrast (bottom-up) and by engaging feature-based attention (top-down). Crucially, these effects operated at different cortical depths: Bottom-up modulations were strongest in the middle cortical layer and weaker in deep and superficial layers, while top-down modulations were strongest in the superficial layers. As such, we demonstrate that laminar activity profiles can discriminate between concurrent top-down and bottom-up processing, and are diagnostic of how a brain region is activated.
Keyphrases
- resting state
- functional connectivity
- endothelial cells
- locally advanced
- machine learning
- magnetic resonance
- working memory
- induced pluripotent stem cells
- deep learning
- pluripotent stem cells
- white matter
- solar cells
- squamous cell carcinoma
- radiation therapy
- gene expression
- genome wide
- magnetic resonance imaging
- computed tomography
- single cell
- contrast enhanced
- cerebral ischemia
- brain injury