title: Altered visual processing in a rodent model of Attention-Deficit Hyperactivity Disorder.
abstract: A central component of Attention-Deficit Hyperactivity Disorder (ADHD) is increased distractibility, which is linked to the superior colliculus (SC) in a range of species, including humans. Furthermore, there is now mounting evidence of altered collicular functioning in ADHD and it is proposed that a hyper-responsive SC could mediate the main symptoms of ADHD, including distractibility. In the present study we have provided a systematic characterization of the SC in the most commonly used and well-validated animal model of ADHD, the spontaneously hypertensive rat (SHR). We examined collicular-dependent orienting behavior, local field potential (LFP) and multiunit responses to visual stimuli in the anesthetized rat and morphological measures in the SHR in comparison to the Wistar Kyoto (WKY) and Wistar (WIS). We found that SHRs remain responsive to a repeated visual stimulus for more presentations than control strains and have a longer response duration. In addition, LFP and multiunit activity within the visually responsive superficial layers of the SC showed the SHR to have a hyper-responsive SC relative to control strains, which could not be explained by altered functioning of the retinocollicular pathway. Finally, examination of collicular volume, neuron and glia densities and glia:neuron ratio revealed that the SHR had a reduced ratio relative to the WKY which could explain the increased responsiveness. In conclusion, this study demonstrates strain-specific changes in the functioning and structure of the SC in the SHR, providing convergent evidence that the SC might be dysfunctional in ADHD.
authors.affiliation: Department of Life, Health and Chemical Sciences, The Open University, Milton Keynes MK7 6AA, UK.
authors.forename: L R
authors.initials: LR
authors.lastname: Brace
authors.affiliation: Department of Life, Health and Chemical Sciences, The Open University, Milton Keynes MK7 6AA, UK.
authors.forename: I
authors.initials: I
authors.lastname: Kraev
authors.affiliation: Department of Life, Health and Chemical Sciences, The Open University, Milton Keynes MK7 6AA, UK.
authors.forename: C L
authors.initials: CL
authors.lastname: Rostron
authors.affiliation: Department of Life, Health and Chemical Sciences, The Open University, Milton Keynes MK7 6AA, UK.
authors.forename: M G
authors.initials: MG
authors.lastname: Stewart
authors.affiliation: Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
authors.forename: P G
authors.initials: PG
authors.lastname: Overton
authors.affiliation: Department of Psychology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 8AF, UK. Electronic address: Eleanor.dommett@kcl.ac.uk.
authors.forename: E J
authors.initials: EJ
authors.lastname: Dommett
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications* / Q000473:pathology*; D004195:Disease Models, Animal; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009949:Orientation / Q000502:physiology; D010468:Perceptual Disorders / Q000209:etiology*; D010775:Photic Stimulation; D011601:Psychophysics; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013045:Species Specificity; D013477:Superior Colliculi / Q000473:pathology / Q000503:physiopathology*; D014795:Visual Pathways / Q000473:pathology / Q000503:physiopathology
keywords: distractibility; orienting; spontaneously hypertensive rat; superior colliculus