title: Lack of contextual-word predictability during reading in patients with mild Alzheimer disease.
abstract: In the present work we analyzed the effect of contextual word predictability on the eye movement behavior of patients with mild Alzheimer disease (AD) compared to age-matched controls, by using the eyetracking technique and lineal mixed models. Twenty AD patients and 40 age-matched controls participated in the study. We first evaluated gaze duration during reading low and highly predictable sentences. AD patients showed an increase in gaze duration, compared to controls, both in sentences of low or high predictability. In controls, highly predictable sentences led to shorter gaze durations; by contrary, AD patients showed similar gaze durations in both types of sentences. Similarly, gaze duration in controls was affected by the cloze predictability of word N and N+1, whereas it was the same in AD patients. In contrast, the effects of word frequency and word length were similar in controls and AD patients. Our results imply that contextual-word predictability, whose processing is proposed to require memory retrieval, facilitated reading behavior in healthy subjects, but this facilitation was lost in early AD patients. This loss might reveal impairments in brain areas such as those corresponding to working memory, memory retrieval, and semantic memory functions that are already present at early stages of AD. In contrast, word frequency and length processing might require less complex mechanisms, which were still retained by AD patients. To the best of our knowledge, this is the first study measuring how patients with early AD process well-defined words embedded in sentences of high and low predictability. Evaluation of the resulting changes in eye movement behavior might provide a useful tool for a more precise early diagnosis of AD.
authors: Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina, Instituto de Investigaciones en Ingeniería Eléctrica (IIIE) (UNS-CONICET), Bahía Blanca, Buenos Aires, Argentina. Electronic address: gerardo.fernandez@uns.edu.ar.
authors: Gerardo
authors: G
authors: Fernández
authors: Institute of Cognitive Neurology (INECO), Buenos Aires, Argentina.
authors: Facundo
authors: F
authors: Manes
authors: Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB) (UNS-CONICET), Bahía Blanca, Buenos Aires, Argentina.
authors: Nora P
authors: NP
authors: Rotstein
authors: Hospital Municipal de Agudos, Bahía Blanca, Buenos Aires, Argentina.
authors: Oscar
authors: O
authors: Colombo
authors: Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina, Instituto de Investigaciones en Ingeniería Eléctrica (IIIE) (UNS-CONICET), Bahía Blanca, Buenos Aires, Argentina.
authors: Pablo
authors: P
authors: Mandolesi
authors: Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB) (UNS-CONICET), Bahía Blanca, Buenos Aires, Argentina.
authors: Luis E
authors: LE
authors: Politi
authors: Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina, Instituto de Investigaciones en Ingeniería Eléctrica (IIIE) (UNS-CONICET), Bahía Blanca, Buenos Aires, Argentina.
authors: Osvaldo
authors: O
authors: Agamennoni
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000150:complications*; D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000209:etiology*; D016022:Case-Control Studies; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011237:Predictive Value of Tests; D011569:Psychiatric Status Rating Scales; D011932:Reading; D012660:Semantics; D014825:Vocabulary
keywords: Contextual predictability effect; Eye movements; Mild Alzheimer disease; Reading