Oculomotor Abnormalities during Reading in the Offspring of Late-Onset Alzheimer's Disease.

INTRODUCTION: Eye movement patterns during reading are well defined and documented. Each eye movement ends up in a fixation point, which allows the brain to process the incoming information and program the following saccade. In this work, we investigated whether eye movement alterations during a reading task might be already present in middle-aged, cognitively normal offspring of late-onset Alzheimer's disease (O-LOAD). METHODS: 18 O-LOAD and 18 age-matched healthy individuals with no family history of LOAD participated in the study. Participants were seated in front of a 20-inch LCD monitor, and single sentences were presented on it. Eye movements were recorded with an eye tracker with a sampling rate of 1000 Hz. RESULTS: Analysis of eye movements during reading revealed that O-LOAD displayed more fixations, shorter saccades, and shorter fixation durations than controls. CONCLUSION: The present study shows that O-LOAD experienced alterations in their eye movements during reading. O-LOAD eye movement behavior could be considered an initial sign of oculomotor impairment. Hence, the evaluation of eye movement during reading might be a useful tool for monitoring well-defined cognitive resources.

Amyloid and anatomical correlates of executive functioning in middle-aged offspring of patients with late-onset Alzheimer's disease.

A traditional hallmark of cognitive impairment associated with late-onset Alzheimer´s disease (LOAD) is episodic memory impairment. However, early alterations have been identified in brain regions associated with executive function in asymptomatic, middle-age offspring of patients with LOAD (O-LOAD) compared to those with no family history. We hypothesized that executive function among O-LOAD would correlate with structural and amyloid brain imaging differently from those without a family history of LOAD (control subjects, CS). Executive function, cortical thickness, and in-vivo Aß deposits were quantified in 30 O-LOAD and 25 CS. Associations were observed among O-LOAD only. Cortical thickness in the left lateral orbitofrontal cortex was positively associated with Design Fluency. The Stroop Color and Word Test, correlated positively with right rostral mid-frontal cortex thickness. Trails Making Test-B was inversely related to left medial orbitofrontal thickness. Tower of London total time was positively associated with ß-amyloid deposition in the right precuneus. These results support previous evidence that early executive dysfunction might reflect subtle, early changes in persons at risk of LOAD and suggests that executive function alterations deserve further exploration in the LOAD literature.

Executive functioning in cognitively normal middle-aged offspring of late-onset Alzheimer's disease patients.

Episodic memory deficits are traditionally seen as the hallmark cognitive impairment during the prodromal continuum of late-onset Alzheimer's disease (LOAD). Previous studies identified early brain alterations in regions subserving executive functions in asymptomatic, middle-aged offspring of patients with LOAD (O-LOAD), suggesting that premature episodic memory deficits could be associated to executive dysfunction in this model. We hypothesized that O-LOAD would exhibit reduced executive performance evidenced by increased errors and decreased strategy use on an episodic memory task. We assessed 32 asymptomatic middle-aged O-LOAD and 28 age-equivalent control subjects (CS) with several tests that measure executive functions and the Rey Auditory Verbal Learning Test (RAVLT) to measure memory performance. All tests were scored using both traditional and process scores (quantification of errors and strategies underlying overall performance). T-tests were used to compare performance between both groups and Spearman correlations were implemented to measure associations between variables. O-LOAD participants exhibited decreased executive performance compared to CS as it relates to initiation time (Tower of London), mental switching (Trail Making Test B), and interference effects (Stroop Word-Color condition). Traditional RAVLT measures showed a poorer performance by O-LOAD and RAVLT process scores revealed increased interference effects on this group. Positive correlations (rs) were found between the executive measures and several RAVLT measures for O-LOAD but not for CS. In conclusion, O-LOAD participants exhibited early subtle cognitive changes in executive processing. Observed memory difficulties may be associated in part to executive deficits suggesting an interplay between memory and executive functions. Process score impairments were observed earlier than clinical decline on neuropsychological scores in this at-risk cohort and might be useful cognitive markers of preclinical LOAD.

Relationship between Cognitive and Sleep-wake Variables in Asymptomatic Offspring of Patients with Late-onset Alzheimer's Disease.

Early neuropathological changes characteristic of late-onset Alzheimer's disease (LOAD) involve brain stem and limbic structures that regulate neurovegetative functions, including sleep-wake rhythm. Indeed, sleep pattern is an emerging biomarker and a potential pathophysiological mechanism in LOAD. We hypothesized that cognitively asymptomatic, middle-aged offspring of patients with LOAD (O-LOAD) would display a series of circadian rhythm abnormalities prior to the onset of objective cognitive alterations. We tested 31 children of patients with LOAD (O-LOAD) and 19 healthy individuals without family history of Alzheimer's disease (control subjects, CS) with basic tests of cognitive function, as well as actigraphy measures of sleep-wake rhythm, cardiac autonomic function, and bodily temperature. Unexpectedly, O-LOAD displayed subtle but significant deficits in verbal episodic memory (Rey Auditory Verbal Learning Test delayed recall 10.6 ± 0.4 vs. 8.6 ± 0.6, t = 4.97, df = 49, p < 0.01) and language (Weschler's vocabulary 51.4 ± 1.3 vs. 44.3 ± 1.5, t = 2.49, df = 49, p < 0.001) compared to CS, even though all participants had results within the clinically normal range. O-LOAD showed a phase-delayed rhythm of body temperature (2.56 ± 0.47 h vs. 3.8 ± 0.26 h, t = 2.48, df = 40, p = 0.031). Cognitive performance in O-LOAD was associated with a series of cardiac autonomic sleep-wake variables; specifically indicators of greater sympathetic activity at night were related to poorer cognition. The present results suggest sleep pattern deserves further study as a potential neurobiological signature in LOAD, even in middle-aged, at risk individuals.

The Effect of Culture on Two Information-Processing Speed Tests.

The Symbol Digit Modalities Test (SDMT) has been proposed to replace the Paced Auditory Serial Addition Test-3 (PASAT-3) in the Multiple Sclerosis Functional Composite because it has the same validity but easy and shorter administration. However, among the two tests, the one that is most affected by culture is still unknown. The purpose of this study was to compare the performance of Argentinian and North American populations on the SDMT and PASAT-3. The SDMT and PASAT-3 were administered to 137 healthy volunteers from Buffalo, NY, and 137 healthy participants from Buenos Aires, Argentina. Participants were matched by gender, age (±2), and education (±1). Significant differences were found on the SDMT but not on the PASAT-3. Significant and low correlations were found between the tests and years of education. The SDMT is more affected by culture than is the PASAT-3. Possible interpretations of this result are presented.

Prevalencia del control instruccional sobre las consecuencias diferenciales de respuesta en la emergencia de conductas derivadas / Prevalence of instructional control over differencial consequences in the emergence of derived behavior

Varios estudios han abordado cómo las instrucciones compiten con contingencias de reforzamiento para controlar conductas complejas, pero no se ha estudiado cabalmente cómo el control instruccional afecta a conductas derivadas, no explícitamente entrenadas. Este estudio intentó determinar si las instrucciones ejercen mayor control que las consecuencias diferenciales de respuesta sobre conductas derivadas, en sintonía con la literatura sobre “insensibilidad a las contingencias”. Cuarenta y seis participantes realizaron una tarea de emparejamiento con la muestra, analizándose su preferencia para derivar relaciones de equivalencia entre estímulos que fueron vinculados de dos maneras contradictorias, una por instrucciones y otra por consecuencias diferenciales. Se observó una mayor eficacia del método de entrenamiento por instrucciones para aprender relaciones condicionales entre estímulos. Por otro lado, se constató una significativa prevalencia para formar relaciones de equivalencia de aquello aprendido previamente por instrucciones, aunque este aspecto podría estar vinculado a la mayor eficacia en el aprendizaje de los contenidos previos...

El razonamiento analógico desde el modelo de la teoría de los marcos relacionales / Analogical reasoning from the perspective of relational frame theory

El objetivo del presente trabajo es exponer una breve revisión del estudio del razonamiento analógico desde la Teoría de los Marcos Relacionales (TMR), considerando los modelos formulados hasta la actualidad y la exploración experimental. A sua vez, se abordará el estudio del desarrollo del razonamiento analógico en la infancia, surgido en el marco de las controversias generadas por los distintos enfoques de la psicología. Se expondrán los hallazgos obtenidos utilizando métodos de imágenes cerebrales desde las ciencias cognitivas. Finalmente se comentarán las posibles aplicaciones de este paradigma. Los estudios revisados acerca del razonamiento analógico desde la TMR proveen relevante evidencia empírica, principalmente en el ámbito de la evaluación y sugieren ventajas de este paradigma en comparación con aproximaciones cognitivistas. A su vez, se propone su implementación como instrumento de entrenamiento cognitivo. En conclusión, la TMR propone un modelo útil al estudio del razonamiento analógico desde la perspectiva del análisis del comportamiento.

The main goal of the present work is to summarize the Relational Frame Theory (RFT) account of analogical reasoning, reviewing theoretical models and experimental studies published so far. Additionally, developmental studies of analogical reasoning during childhood will be addressed, considering the alternative hypothesis and controversies between different psychological theories. Findings from cognitive studies using neuroimaging techniques will also be discussed. Finally, the potential applications of the paradigm will be considered. The studies reviewed about analogical reasoning from the RFT provide relevant empirical evidence, mainly in the field of assessment and suggest advantages of this paradigm compared to cognitivist approaches. In turn, its implementation is proposed as a tool for cognitive training. In conclusion, the RFT offers a useful model to study analogical reasoning from the behavior analysis perspective.

El fenómeno de transferencia en gramáticas artificiales: efectos de la forma de entrenamiento / Transference in artificial grammar: effects of training procedures

En este trabajo se utilizó una gramática artificial, consistente en una serie de reglas que especifican posibles órdenes de secuencias de letras, para evaluar la capacidad de transferencia de los sujetos, esto es la extracción de estas reglas y su aplicación a patrones de letras novedosas. Para ello 57 sujetos se asignaron aleatoriamente a dos formas de entrenamiento: una estándar donde debían memorizar y transcribir las secuencias correctas (gramaticales), y otra donde debían discriminar por ensayo y error entre secuencias correctas e incorrectas (no gramaticales) mediante un procedimiento de realimentación. Con esta forma de entrenamiento se obtuvieron desempeños significativamente mejores que con el procedimiento estándar. Se discuten los resultados en el contexto de la aplicación de las gramáticas artificiales como paradigma experimental para el estudio de los procesos subyacentes a la adquisición del lenguaje.

In this work an artificial grammar has been used, which consists in a set of rules that specifies possible orders of strings of letters, to evaluate subjects ability to transfer the extracted rules and implement these to patterns of novel letters. 57 subjects were randomly assigned to two learning procedures: a standard one in which they had to memorize and transcribe the correct (grammatical) sequences, and one in which they had to discriminate between correct and incorrect (ungrammatical) sequences by use of a feedback procedure. Subjects trained with the feedback procedure had a significantly better performance than subjects trained with the standard one. These results are discussed in the context of the implementation of artificial grammar as an experimental paradigm for studying processes underlying language acquisition.