Cerebral White Matter — Historical Evolution of Facts and Notions Concerning the Organization of the Fiber Pathways of the Brain

Gross and microscopic studies by early investigators led the cerebral white matter from being regarded as an amorphous mass to an intricately organized system of fasciculi that facilitate the highest expression of cerebral activity. Here we pay homage to the anatomists whose observations resulted in the evolution of ideas about the cerebral white matter. We also draw attention to limitations of the earlier methodologies and to some of the conflicts and controversies that have characterized this field and that persist in the current literature. We conclude with brief reference to the principles of organization of the fiber pathways derived from our studies in the monkey using the autoradiographic tract tracing technique, another step in the ongoing investigations of the cerebral white matter. This historical review has contemporary relevance because the fiber pathways of the brain are crucial components of the distributed neural circuits that subserve nervous system function; the clinical manifestations of white matter damage are recognized with greater frequency and clarity; and magnetic resonance imaging tractography has made it possible to view these fiber bundles within the living human brain.     

Cerebral white matter--historical evolution of facts and notions concerning the organization of the fiber pathways of the brain

Gross and microscopic studies by early investigators led the cerebral white matter from being regarded as an amorphous mass to an intricately organized system of fasciculi that facilitate the highest expression of cerebral activity. Here we pay homage to the anatomists whose observations resulted in the evolution of ideas about the cerebral white matter. We also draw attention to limitations of the earlier methodologies and to some of the conflicts and controversies that have characterized this field and that persist in the current literature. We conclude with brief reference to the principles of organization of the fiber pathways derived from our studies in the monkey using the autoradiographic tract tracing technique, another step in the ongoing investigations of the cerebral white matter. This historical review has contemporary relevance because the fiber pathways of the brain are crucial components of the distributed neural circuits that subserve nervous system function; the clinical manifestations of white matter damage are recognized with greater frequency and clarity; and magnetic resonance imaging tractography has made it possible to view these fiber bundles within the living human brain.     

Learning through Upheaval: Strategies for Analyzing and Construing Emerging Sociopolitical Transformations in the Middle East

The irreducible complexity and singular unpredictability of the upheavals that have roiled the Middle East since December 2010 challenge analysts—from university students to policymakers—to grapple with irresolvable questions; this, rather than analysts' superimposing their own visions of what might constitute the upheavals' driving forces, and what will, or should be the outcomes of the regional turmoil. Drawing on strategies gleaned from teaching about the Arab uprisings, this article asserts that the uprisings may be collectively read as comprising a text that contains signs of indeterminacy pointing to many possible meanings and sources of meanings. Focus is placed on those signs that embody the differing discourses through which the Middle East upheavals are, have been, or can be represented and assessed; and the fluid, multidimensional forms of political identity that have contributed to the upheavals, and are being further reshaped, in their wake. By reading these signs with intellectual openness and humility, interpreters can achieve greater insight into the profoundly contingent and unforeseeable dynamics at work across the region.