Understanding layer-specific contributions to perception and learning in human cortex

Thomas Jefferson University, Philadelphia PA

Investigators

Abstract

Understanding how feedforward information from primary sensory cortices and feedback information from ‘higher-order’ brain areas are organized across cortical layers in regions that are involved in complex perceptual and learning processes is fundamental to understanding sophisticated cognitive functions and treating related mental disorders. Recently, a cutting-edge functional MRI (fMRI) method called vascular space occupancy (VASO) has made it possible to use fMRI to probe cortical layers in humans. However, while VASO has made it possible to study the functional organization of cortical layers in behaving adult humans, most layer-fMRI studies to date have focused on primary sensory and motor cortices, leaving higher-order cortex, and thus many sophisticated mental processes, understudied. Furthermore, layer-fMRI results thus far have not been validated by correlating changes in layer-specific activation with behavioral and cognitive measures. The main hypotheses being tested in the proposed research are that feedforward and feedback information can be reliably dissociated across layers of human cortex both within and beyond primary sensory and motor cortices, and these layer-specific responses have a meaningful and measurable relationship to cognition and behavior. The specific aims of this project are: 1) to validate layer-fMRI results by determining the behavioral relevance of layer-specific cortical changes; 2) to map feedforward and feedback signals to specific layers of domain-specific regions in ventral occipital temporal cortex (VOTC), and thus provide evidence for prominent models of laminar circuitry in ‘high-level’ visual regions outside of primary visual cortex; and 3) to examine how representations of different viewpoints of faces and their identities change across layers of the fusiform face area. Validating layer-fMRI methods and mapping the functional organization of layers in human cortex will push the field of neuroimaging into a new era of in-vivo laminar imaging, thus further bridging the gap between cellular and systems neuroscience