Affiliations: Department of Psychology, Royal Holloway, University of
London, London, UK | Division of Neuroscience and Mental Health, Imperial
College London, London, UK | Centre for Functional MRI of the Brain, University of
Oxford, Oxford, UK | Ashford and St Peter's Hospital, UK
Note: [] Corresponding author: Narender Ramnani, PhD, Cognitive
Neuroscience Laboratory, Department of Psychology, Royal Holloway University of
London, Egham, Surrey TW20 0EX, UK. Tel.: +44 01784 443519; Fax: +44 01784
434347; E-mail: n.ramnani@rhul.ac.uk
Abstract: Recent research has characterized the anatomical connectivity of the
cortico-cerebellar system – a large and important fibre system in the
primate brain. Within this system, there are reciprocal projections between the
prefrontal cortex and Crus II of the cerebellar cortex, which both play
important roles in the acquisition and execution of cognitive skills. Here, we
propose that this system also plays a particular role in sustaining skilled
cognitive performance in patients with Relapsing-Remitting Multiple Sclerosis
(RRMS), in whom advancing neuropathology causes increasingly inefficient
information processing. We scanned RRMS patients and closely matched healthy
subjects while they performed the Paced Auditory Serial Addition Test (PASAT),
a demanding test of information processing speed, and a control task. This
enabled us to localize differences between conditions that change as a function
of group (group-by-condition interactions). Hemodynamic activity in some
patient populations with CNS pathology are not well understood and may be
atypical, so we avoided analysis strategies that rely exclusively on models of
hemodynamic activity derived from the healthy brain, using instead an approach
that combined a `model-free' analysis technique (Tensor Independent Component
Analysis, TICA) that was relatively free of such assumptions, with a post-hoc
'model-based' approach (General Linear Model, GLM). Our results showed
group-by-condition interactions in cerebellar cortical Crus II. We suggest that
this area may have in role maintaining performance in working memory tasks by
compensating for inefficient data transfer associated with white matter lesions
in MS.
