title: Auditory responses in a rodent model of Attention Deficit Hyperactivity Disorder.
abstract: A central component of Attention Deficit Hyperactivity Disorder (ADHD) is increased distractibility in response to visual and auditory stimuli, which is linked to the superior colliculus (SC). Furthermore, there is now mounting evidence of altered collicular functioning in ADHD and it is proposed that a hyper-responsive SC could mediate symptoms of ADHD, including distractibility. In the present study we conducted a systematic characterisation of the intermediate and deep layers of the SC in the most commonly used and well-validated model of ADHD, the spontaneously hypertensive rat (SHR), building on prior work showing increased distractible behaviour in this strain using visual distractors. We examined collicular-dependent orienting behaviour, local field potential (LFP) and multiunit activity (MUA) in response to auditory stimuli in the anaesthetised rat, and morphological measures, in the SHR in comparison to the Wistar Kyoto (WKY) and Wistar (WIS). We found no evidence of increased distractibility in the behavioural data but suggest that this may arise due to cochlear hearing loss in the SHR. Furthermore, the electrophysiology data indicate that the SC in the SHR may still be hyper-responsive, normalising the amplitude of auditory responses that would otherwise be reduced due to the hearing impairment. The morphological measures of collicular volume, cell density and ratios did not indicate this potential hyper-responsiveness had a basis at the structural level examined. These findings have implications for future use of the SHR in auditory processing studies and may represent a limitation to the validity of this animal model.
authors.affiliation: Department of Life, Health and Chemical Sciences, The Open University, Milton Keynes MK7 6AA, UK.
authors.forename: Louise 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: Igor
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: Claire 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: Michael G
authors.initials: MG
authors.lastname: Stewart
authors.affiliation: Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Overton
authors.affiliation: Department of Life, Health and Chemical Sciences, The Open University, Milton Keynes MK7 6AA, UK; Department of Psychology, Institute of Psychiatry, Psychology and Neuroscience, King׳s College London, London SE1 3QD, UK. Electronic address: Eleanor.dommett@kcl.ac.uk.
authors.forename: Eleanor J
authors.initials: EJ
authors.lastname: Dommett
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology*; D001307:Auditory Perception / Q000502:physiology*; D004195:Disease Models, Animal; D008297:Male; D009043:Motor Activity / Q000502:physiology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013477:Superior Colliculi / Q000503:physiopathology*
keywords: Distractibility; Hearing loss; Orienting; Spontaneously hypertensive rat; Superior colliculus; Validity