Monday, April 21, 12:00 – 1:30 pm, in 489 Minor Hall

Model-based neuroanatomy: Validation and statistical inference in living connectomes

presented by

Franco Pestilli, Ph.D.,
Research Associate, Department of Psychology, Stanford University

 

Magnetic resonance diffusion imaging and computational tractography are the only technologies that enable neuroscientists to measure white matter in the living human brain. In the decade since their development, these technologies revolutionized our understanding of the importance of the human white-matter for health and disease. There are good reasons to make these measurements in human. The human brain (1400 g) is 15 times the volume of the rhesus monkey (90 g), 700 times the volume of the rat (2 g) and 2,300 times the volume of the mouse brain (0.6 g). The human brain comprises of functionally specific clusters of maps communicating via an extensive network of long-range, myelinated, axonal projects. The size of the human brain imposes significant challenges for communicating across different regions

 

Prior to these technologies, the white matter was thought of as a passive cabling system. But modern measurements show that white matter axons and glia respond to experience and that the tissue properties of the white matter are transformed during development and following training. The white matter pathways comprise a set of active wires and the responses and properties of these wires predict human cognitive and emotional abilities in health and disease. We can now predict confidently that to crack the neural code in mapping the human brain, neuroscientists will have to develop an account of the connections and tissue properties of these active wires. Whereas there are many impressive findings, it is widely agreed that there is an urgent need to keep developing and improving tractography methods. The need for a systematic approach to tractography validation and for a framework to perform statistical model testing can be seen in recent reports in Science that set out to characterize human white matter structure.

 

I will present new methods to perform both tractography validation and statistical hypotheses testing on the network of brain connections. These new methods improve current techniques in fundamental ways and can be applied to any type of diffusion data. I will show that by using the methods we were able to identify a major white-matter pathway communicating information between the dorsal and ventral visual streams, the Vertical Occipital Fasciculus (VOF). This pathway is large and its organization suggests that the human ventral and dorsal visual streams communicate substantial information through areas V3A/B and hV4/VO-1. We suggest that the VOF is crucial for transmitting signals between regions that encode object properties including form, identity and color information and regions that map spatial location to action plans.

 

Host: Michael Silver

 

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