Uncorrected Author Proof Journal of Alzheimer’s Disease xx (20xx) x–xx DOI 10.3233/JAD-131331 IOS Press 1 Animal Spotting in Alzheimer’s Disease: An Eye Tracking Study of Object Categorization 1 2 Muriel Boucart a,∗ , Giovanna Bubbico a , S´ ebastien Szaffarczyk a and Florence Pasquier b 3 a Laboratoire de Neurosciences et Pathologies Fonctionnelles, Universit´ e Lille-Nord de France, CNRS, France 4 b Universit´ e Lille Nord de France, EA1046, CHU, Centre m´ emoire, Lille, France 5 Handling Associate Editor: Kirk Daffner 6 Accepted 29 August 2013 Abstract. We investigated rapid object categorization and, more specifically, the ability to detect a target object within a natural scene in people with mild Alzheimer’s disease (AD) using a saccadic choice task. It has been suggested that the anatomical pathway likely used to initiate rapid oculomotor responses in the saccadic choice task could involve the Frontal Eye Field, a structure that is part of the dorsal attentional network, in which connectivity is disrupted in AD. Seventeen patients with mild AD and 23 healthy age-matched controls took part in the study. A group of 24 young healthy observers was included as it has been reported that normal aging affects eye movements. Participants were presented with pairs of colored photographs of natural scenes, one containing an animal (the target) and one containing various objects (distracter), displayed for 1 s left and right of fixation. They were asked to saccade to the scene containing an animal. Neither pathology nor age affected temporal (saccade latencies and durations) and spatial (saccade amplitude) parameters of eye movements. Patients with AD were significantly less accurate than age-matched controls, and older participants were less accurate than young observers. The results are interpreted in terms of noisier sensory information and increased uncertainty in relation to deficits in the magnocellular pathway. The results suggest that, even at a mild stage of the pathology, people exhibit difficulties in selecting relevant objects. 7 8 9 10 11 12 13 14 15 16 17 18 Keywords: Alzheimer’s disease, eye movements, saccade, scene perception 19 INTRODUCTION 20 Although memory impairments are typically the ear- 21 liest symptoms in patients with Alzheimer’s disease 22 (AD), it has become clear that deficits in visual process- 23 ing are also common. Alterations have been reported 24 at lower levels of visual processing such as contrast 25 sensitivity, acuity, and color and motion perception 26 (see [1–3] for reviews), though other studies [4] have 27 reported spared basic sensory functions. Neuropsy- 28 chological studies on object perception in patients 29 with AD have found evidence of deficits at inter- 30 mediate levels (perceptual organization, figure/ground 31 segregation) [5] as well as higher order visual func- 32 tions such as semantic representations, picture naming, 33 ∗ Correspondence to: Muriel Boucart, CHU Lille, Hˆ opital Roger Salengro, Laboratoire de Neurosciences et Pathologies Fonction- nelles, 59037 Lille, France. E-mail: muriel.boucart@chru-lille.fr. face discrimination, spatial localization, and visuo- 34 motor coordination [6]. For instance, several studies 35 have reported deficits in tasks involving recognition 36 of degraded images, either incomplete or filtered, for 37 which patients with AD need a less filtered, or a more 38 complete version, than age-matched controls to rec- 39 ognize the pictures [7–9]. Various aspects of object 40 perception have been examined mostly with neu- 41 ropsychological tests. With object decision and object 42 completion tasks, Hajilou and Done [10] observed that 43 patients with AD were impaired in tasks involving 44 access to stored structural knowledge about objects. 45 Van Rhijn and colleagues [11] reported that 50% of 46 the patients tested were impaired in face, letter-word, 47 and object perception tasks. Adlington et al. [12] and 48 Zannino et al. [13] found that, compared to controls, 49 people with AD did not benefit from additional sur- 50 face information like texture, grey levels, or color in 51 an object naming task. 52 ISSN 1387-2877/13/$27.50 © 2013 – IOS Press and the authors. All rights reserved