Structure determines function. How does the functional organization of the brain produce perception, thought, and behavior? To answer this question Dr. Anna Wang Roe and her team study the organization and connectivity of the functional modules (roughly 200 µm in size) in the cerebral cortex of nonhuman primates. Such a study can reveal how these modules underly both visual (form, color/brightness, depth, and motion) and tactile (texture and shape) perception.

On May 27, 2022, Professor Anna Wang Roe and Hu Jiaming’s team from the BBMI and the Institute of Systemic Neuroscience and Cognitive Sciences, School of Medicine, Zhejiang University, published a research paper entitled functionally specific and sparse domain based micro-networks in monkey V1 and V2 in the internationally renowned online journal Current Biology. Their work revealed fundamental mesoscale connectional architecture in the primate visual cortex.

The Macaque monkey's cerebral cortex consists of roughly 10⁹ neurons organized into roughly 10⁵ clusters (columns) of 10⁴ neurons each. Previous anatomical evidence has shown that neurons within single columns (which share similar functionality e.g., preference for color, orientation, motion, and depth information) have connections with other clusters of similar functionality. Anna’s research group hypothesized that these connected clusters comprised what they call a ‘columnar micro-network’ in the brain, and that such micro-networks are common units of connectivity in the visual cortex.

To address this hypothesis, Dr. Hu Jiaming in Anna’s research group developed an in vivo method of studying mesoscale functional connections. For this, they developed a focal electrical stimulation method to activate single functional columns and used intrinsic signal optical imaging to map the evoked connections to other columns. When applied to visual area 2 (V2) in the macaque monkey visual cortex, this revealed that standard columnar microcircuits do indeed exist to integrate both local intra-areal (V2-V2) and inter-areal (V2-V1) information. They then discovered that such micro-circuits are common across networks that process color and orientation information. Furthermore, moving the electrode and successively stimulating different points in the cortex lead to the activation of micro-networks that shifted depending on the position of stimulation (Fig.1).

Such data introduced the perspective that there are basic micro-network units in the brain that are common and operate across different aspects of functionality and that the architecture of the brain is comprised of these fundamental micro-networks. These findings add significantly to our fundamental understanding of how network architecture is built into the primate brain.