The vertical occipital fasciculus: A century of controversy resolved by in vivo measurements

Abstract

The vertical occipital fasciculus (VOF) is the only major fiber bundle connecting dorsolateral and ventrolateral visual cortex. Only a handful of studies have examined the anatomy of the VOF or its role in cognition in the living human brain. Here, we trace the contentious history of the VOF, beginning with its original discovery in monkey by Wernicke (1881) and in human by Obersteiner (1888), to its disappearance from the literature, and recent reemergence a century later. We introduce an algorithm to identify the VOF in vivo using diffusion-weighted imaging and tractography, and show that the VOF can be found in every hemisphere (n = 74). Quantitative T1 measurements demonstrate that tissue properties, such as myelination, in the VOF differ from neighboring white-matter tracts. The terminations of the VOF are in consistent positions relative to cortical folding patterns in the dorsal and ventral visual streams. Recent findings demonstrate that these same anatomical locations also mark cytoarchitectonic and functional transitions in dorsal and ventral visual cortex. We conclude that the VOF is likely to serve a unique role in the communication of signals between regions on the ventral surface that are important for the perception of visual categories (e.g., words, faces, bodies, etc.) and regions on the dorsal surface involved in the control of eye movements, attention, and motion perception. T he vertical occipital fasciculus (VOF) is the only major fiber bundle connecting dorsal and ventral regions of occipital, parietal, and temporal cortex. The signals carried by the VOF are likely to play an essential role in an array of visual and cognitive functions. Characterizing the VOF connections and tissue structure in the living human brain is important for the study of human vision and cognitive neuroscience alike.Carl Wernicke discovered the VOF (1). For the next 30 y, the VOF was included in many major neuroanatomy atlases and journal articles (1-14). However, Wernicke's study contradicted a widely accepted principle of white-matter organization proposed by Meynert, Wernicke's mentor. Over the subsequent decades, there emerged a camp of neuroanatomists who acknowledged Wernicke's discovery and another group that, like Meynert, disregarded the discovery. Due to its controversial beginnings, haphazard naming convention, and the difficulty of standardizing postmortem procedures, the VOF largely disappeared from the literature for most of the next century. A century later, Yeatman et al. (15) rediscovered the VOF using diffusion magnetic resonance imaging (dMRI); they were the first to characterize the VOF cortical projections in the living, behaving, human brain.Why would such an important pathway disappear from the literature for so long? The disappearance can be traced to controversies and confusions among some of the most prominent neuroanatomists of the 19th century (1-13, 16-18). Modern, in vivo, MRI measurements and algorithms allow for precise, reproducible, scalable computations that can resolve these cen...

Cross-linguistic transfer in bilinguals reading in two alphabetic orthographies: The grain size accommodation hypothesis

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The Structural Properties of Major White Matter Tracts in Strabismic Amblyopia

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“…42 The first step is to generate a whole-brain connectome by probabilistic tractography. Probabilistic tractography assumes a distribution of principal direction of orientations instead of a single orientation, thus it performs better at locations where complicated fiber crossings are present.…”

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(A)Historical Science

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