“Interfacing mind and machine: Neuronal circuitry underlying visual and tactile perception”.

My lab studies the neuronal circuitry and functional organization underlying visual and tactile behavior in awake, behaving monkeys. To map these functions in the brain, we use an array of optical imaging, fMRI, electrophysiological, anatomical and optogenetics methods. Chronic implanted windows on the brain permit: 1) study of sensory and attentional processes and 2) methods to influence brain activity with electrical, laser, and optogenetic stimulation methods. This combined behavioral, functional, anatomical, and neuroengineering approach will lead to development of future mind-machine interfaces that modify and enhance function in normal and diseased states.

Brodmann divided the neocortex into 47 different cortical areas based on differences in laminar myeloarchitecture and cytoarchitecture. The ability to do so in vivo with anatomical magnetic resonance (MR) methods in awake subjects would be extremely advantageous. We used a combination of MR microscopy and new MR contrasts at 4.7 T with voxel size of 62.5 × 62.5 × 1000 μm³ to image visual cortex of awake Macaque monkeys. Both the phase and magnitude components of the T₂*-weighted image were used to generate laminar profiles reflecting differential myelin and local cell density content across cortical depth. Based on this, we were able to infer the six layered laminar structure characteristic of V1,

including the stripe of Kaes-Bechterew (in layer II/III), the stripe of Gennari (in layer IV), the internal band of Baillarger (in layer V), as well as three sub-layers within layer IV (IVa, IVb, and IVc). Based on their laminar profiles, areas V1, V2, and V4 in awake macaques could also be distinguished. Following the tradition of Brodmann, MR-based cortical laminar visualization will make it possible to discriminate cortical regions in awake subjects based on differences in myeloarchitecture and cytoarchitecture. From

Chen G, Wang F, Gore, JC, Roe AW (2011) Identification of cortical lamination in awake  monkeys by high resolution magnetic resonance imaging. Neuroimage. 2011 Nov 3.

Lu HD, Chen GC, Tanigawa H, Roe AW (2010) A motion direction map in Macaque V2, Neuron, 68(5):1002-1013.

Feature Article: Functional organization of V4

Visual area V4 in the macaque monkey contains a diverse complement of cells, including those with preference for color, orientation, disparity, as well as higher order feature preferences. However, unlike V1 and V2, it is unknown whether V4 is characterized by any distinct functional organizations. Here, using intrinsic signal optical imaging methods in awake, behaving monkeys, we demonstrate that functional organization for preferential response to color or luminance are largely separate from orientation selective regions. Color preference domains are characterized by the presence of hue maps. These results help resolve long-standing controversies regarding functional diversity and retinotopy within V4 and indicate the presence of spatially distinct distribution of featural representation in V4 in the ventral visual pathway.

Feature Book: Imaging the Brain with Optical Methods

Imaging the Brain with Optical Methods presents the history of optical imaging and its use in the study of brain function, and the rapidly developing optical technologies and their applications that have recently developed. These include intrinsic signal optical imaging, near-infrared optical imaging, fast optical imaging based on scattered light, optical imaging with voltage sensitive dyes, and 2 photon imaging of hemodynamic signals.

Roe AW (2009) Imaging the Brain with Optical Methods (Roe AW, ed). Springer, New York.