The anatomy of fronto-occipital connections from early blunt dissections to contemporary tractography
Cortex. 2014-07-01; 56: 73-84
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1. Cortex. 2014 Jul;56:73-84. doi: 10.1016/j.cortex.2012.09.005. Epub 2012 Sep 20.
The anatomy of fronto-occipital connections from early blunt dissections to
Forkel SJ(1), Thiebaut de Schotten M(2), Kawadler JM(3), Dell’Acqua F(4), Danek
A(5), Catani M(3).
(1)NATBRAINLAB, Department of Forensics and Neurodevelopmental Sciences, King’s
College London, Institute of Psychiatry, UK; Department of Neuroimaging Sciences,
King’s College London, Institute of Psychiatry, UK. Electronic address:
(2)NATBRAINLAB, Department of Forensics and Neurodevelopmental Sciences, King’s
College London, Institute of Psychiatry, UK; Inserm – UPMC UMRS 975, Brain and
Spine Institute, Groupe Hospitalier Pitié-Salpêtrière, Paris, France.
(3)NATBRAINLAB, Department of Forensics and Neurodevelopmental Sciences, King’s
College London, Institute of Psychiatry, UK.
(4)Department of Neuroimaging Sciences, King’s College London, Institute of
Psychiatry, UK; NIHR Biomedical Research Centre for Mental Health at South London
and Maudsley NHS Foundation Trust and Institute of Psychiatry, King’s College
(5)Neurology Department, Ludwig-Maximilians-Universität Munich, Germany.
The occipital and frontal lobes are anatomically distant yet functionally highly
integrated to generate some of the most complex behaviour. A series of long
associative fibres, such as the fronto-occipital networks, mediate this
integration via rapid feed-forward propagation of visual input to anterior
frontal regions and direct top-down modulation of early visual processing.
Despite the vast number of anatomical investigations a general consensus on the
anatomy of fronto-occipital connections is not forthcoming. For example, in the
monkey the existence of a human equivalent of the ‘inferior fronto-occipital
fasciculus’ (iFOF) has not been demonstrated. Conversely, a ‘superior
fronto-occipital fasciculus’ (sFOF), also referred to as ‘subcallosal bundle’ by
some authors, is reported in monkey axonal tracing studies but not in human
dissections. In this study our aim is twofold. First, we use diffusion
tractography to delineate the in vivo anatomy of the sFOF and the iFOF in 30
healthy subjects and three acallosal brains. Second, we provide a comprehensive
review of the post-mortem and neuroimaging studies of the fronto-occipital
connections published over the last two centuries, together with the first
integral translation of Onufrowicz’s original description of a human
fronto-occipital fasciculus (1887) and Muratoff’s report of the ‘subcallosal
bundle’ in animals (1893). Our tractography dissections suggest that in the human
brain (i) the iFOF is a bilateral association pathway connecting ventro-medial
occipital cortex to orbital and polar frontal cortex, (ii) the sFOF overlaps with
branches of the superior longitudinal fasciculus (SLF) and probably represents an
‘occipital extension’ of the SLF, (iii) the subcallosal bundle of Muratoff is
probably a complex tract encompassing ascending thalamo-frontal and descending
fronto-caudate connections and is therefore a projection rather than an
associative tract. In conclusion, our experimental findings and review of the
literature suggest that a ventral pathway in humans, namely the iFOF, mediates a
direct communication between occipital and frontal lobes. Whether the iFOF
represents a unique human pathway awaits further ad hoc investigations in
Copyright © 2012 Elsevier Ltd. All rights reserved.
PMID: 23137651 [Indexed for MEDLINE]