Attention Sets in ADHD: a consideration of executive and frontal function, and the locus of control
Oades, R. D., Schepker, R., Schulte, A., & Slusarek, M.
13th Eunethydis Meeting, 4th - 6th October 2002, Cagliari, Sardinia, Italy.

The appearance of some impairment of executive function in ADHD (reviews: Pennington & Ozonoff, 1996; Sergeant et al. 2002) would be expected from the asymmetric development of activation patterns these children show in the frontal lobes (Oades et al., 1996; Rubia, 1999).
But not all executive functions are impaired and there is controversy over which are poorly expressed (e.g. Working memory impaired and helped by methylphenidate, Barnett ea 2001 vs. not impaired if IQ considered, Kuntsi et al., 2001), and if this is significant for ADHD (Denckla, 1996).
Shallice and colleagues (2002) have suggested that evidence, martialled in support of poor inhibitory control in ADHD (Barkley, 1997; Quay, 1997), more powerfully argues for a role of the frontal lobes, and may have more explanatory power in the context of an attentional system disorder (Swanson et al., 1998).

It is evident that some dissection is necessary (as some of the reports above suggest) - a consideration of a) components contributing to inhibition, b) sub-systems of executive control, c) quantity and quality of comorbid problems in the children studied.

We take attentional set as a starting point, as this is a fundamental pre-requisite for organising adaptive behaviour under changing conditions. This is also reasonable given the sensitivity of ADHD to methylphenidate and that attention-related mechanisms of switching and tuning of information are under catecholaminergic control (Oades, 1985).
From the standpoint of clinical neuropsychology Stroop tests include a key demand on selective attention (Stuss and Levine 2002) - exogenous control, through instruction and stimulus perception, of the dominant response (colour naming over word reading). While the colour-Stroop emphasises the activation of central (semantic) tendencies through instruction, the number-Stroop shifts the emphasis to the perceptual control of the activation of central tendencies.
The introduction of priming to these tasks is informative about whether the control is more exogenous (perceptual) or endogenous (monitoring). We present initial data on the negative priming impairment in children with ADHD compared to those without this diagnosis.
A/ Negative priming is absent in ADHD,
B/ The Stroop interference effect is relatively normal (but not colour naming),
C/ Medication tends to normalise differences to a very small degree,
D/ But medication does increases the ability to switch set on the trails B-A test.

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