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 neurogenetic 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.
Gallo
A
A
Laboratory of Neurophysiology, Behaviour and Neural Networks, Department of Experimental Medicine, Section of Human Physiology F. Bottazzi, II University of Naples, Costantinopoli 16, Naples 80138, Italy.
Gonzalez-Lima
F
F
Sadile
A G
AG
D000818:Animals; D001288:Attention / Q000502:physiology*; D003463:Cues; D003576:Electron Transport Complex IV / Q000378:metabolism; D005106:Exploratory Behavior / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology; D009042:Motivation; D010296:Parietal Lobe / Q000201:enzymology / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D013028:Space Perception / Q000502:physiology*
D003576:Electron Transport Complex IV