Article

Relatively recently, neurocognitive and neuroimaging studies have indicated that
individuals with attention-deficit/hyperactivity disorder (ADHD) may have
deficits in a range of timing functions and their underlying neural networks.
Despite this evidence, timing deficits in ADHD are still somewhat neglected in
the literature and mostly omitted from reviews on ADHD. There is therefore a lack
of integrative reviews on the up-to-date evidence on neurocognitive and
neurofunctional deficits of timing in ADHD and their significance with respect to
other behavioural and cognitive deficits. The present review provides a synthetic
overview of the evidence for neurocognitive and neurofunctional deficits in ADHD
in timing functions, and integrates this evidence with the cognitive neuroscience
literature of the neural substrates of timing. The review demonstrates that ADHD
patients are consistently impaired in three major timing domains, in motor
timing, perceptual timing and temporal foresight, comprising several timeframes
spanning milliseconds, seconds, minutes and longer intervals up to years. The
most consistent impairments in ADHD are found in sensorimotor synchronisation,
duration discrimination, reproduction and delay discounting. These neurocognitive
findings of timing deficits in ADHD are furthermore supported by functional
neuroimaging studies that show dysfunctions in the key inferior
fronto-striato-cerebellar and fronto-parietal networks that mediate the timing
functions. Although there is evidence that these timing functions are
inter-correlated with other executive functions that are well established to be
impaired in the disorder, in particular working memory, attention, and to a
lesser degree inhibitory control, the key timing deficits appear to survive when
these functions are controlled for, suggesting independent cognitive deficits in
the temporal domain. There is furthermore strong evidence for an association
between timing deficits and behavioural measures of impulsiveness and
inattention, suggesting that timing problems are key to the clinical behavioural
profile of ADHD. Emerging evidence shows that the most common treatment of ADHD
with the dopamine agonist and psychostimulant Methylphenidate attenuates most
timing deficits in ADHD and normalises the abnormally blunted recruitment of the
underlying fronto-striato-cerebellar networks. Timing function deficits in ADHD,
therefore, next to executive function deficits, form an independent impairment
domain, and should receive more attention in neuropsychological, neuroimaging,
and pharmacological basic research as well as in translational research aimed to
develop pharmacological or non-pharmacological treatment of abnormal timing
behaviour and cognition in ADHD.
CI - Copyright (c) 2012 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS