Color perception deficits in co-existing attention-deficit/hyperactivity disorder and chronic tic disorders

Preliminary findings suggest that color perception, particularly of blue-yellow stimuli, is impaired in attention-deficit/hyperactivity disorder (ADHD) as well as in chronic tic disorders (CTD). However, these findings have been not replicated and it is unclear what these deficits mean for the comorbidity of ADHD + CTD. Four groups (ADHD, CTD, ADHD + CTD, controls) of children with similar age, IQ and gender distribution were investigated with the Farnsworth-Munsell 100 Hue Test (FMT) and the Stroop-Color-Word Task using a factorial design. Color perception deficits, as indexed by the FMT, were found for both main factors (ADHD and CTD), but there were no interaction effects. A preponderance of deficits on the blue-yellow compared to the red-green axis was detected for ADHD. In the Stroop task only the 'pure' ADHD group showed impairments in interference control and other parameters of Stroop performance. No significant correlations between any FMT parameter and color naming in the Stroop task were found. Basic color perception deficits in both ADHD and CTD could be found. Beyond that, it could be shown that these deficits are additive in the case of comorbidity (ADHD + CTD). Performance deficits on the Stroop task were present only in the 'pure' ADHD group. Hence, the latter may be compensated in the comorbid group by good prefrontal capabilities of CTD. The influence of color perception deficits on Stroop task performance might be negligible. © 2007 Springer-Verlag

Impaired metabolic capacity in the perirhinal and posterior parietal cortex lead to dissociation between attentional, motivational and spatial components of exploration in the Naples High-Excitability rat

This study aimed at investigating the neural substrates of spatial and non-spatial Behavioural components of exploration to novelty by a neurogenctic approach. Thus, functional imaging and Behavioural analysis were carried out in the Naples High-Excitability (NHE) rats, a model of hyperactivity and attention-deficit. Quantitative cytochrome oxidase (C.O.) histochemistry was used to measure the basal metabolic capacity of different forebrain structures. In parallel experiments, exploration in an 8-arm radial maze (Olton-maze) with extra-maze cues was used to measure attentional, motivational and spatial components of Behaviour after feeding rats' ad-libitum or at a reduced diet. Functional imaging analysis: brains from naive rats were stained for quantitative C.O. histochemistry along with standards. NHE rats showed lower C.O. activity in perirhinal and posterior-parietal cortex (all layers) and cortical amygdala, and greater activity in entorhinal cortex (superficial layers). The outer granular cell layer of the dentate gyrus had greater activity in NHE. Behavioural analysis: at low and high motivational level, maze exploration was reinforced during shaping throughout and then only a single arm. The Behaviour was monitored by a CCD camera and videotaped. (i) There was no line difference in working memory during non reinforced maze exploration, independent of the motivational level; (ii) during shaping with all baited arms, there was no line difference in working-memory, but NHE rats showed a very low or lower food consumption at low and high motivational level, respectively; (iii) rats showed a higher working memory in finding the single baited arm at high motivational level; (iv) NHE rats paid little attention towards reinforcement upon visiting the baited arm only at low motivational level. Thus, Behavioural and functional neuroimaging analysis suggests the neural substrates of spatial and non-spatial components of exploration to be underlined by different network operations in the neocortical and limbic cortices in the NHE rat lines. Therefore, they appear as an useful tool to the understanding of Attention-Deficit Hyperactivity Disorder (ADHD) in children. (Supported by Telethon-Italy grant E.513). (C) 2002 Elsevier Science B.V. All rights reserved