[A theoretical review of category-specific impairment, its entity and the methodological problems associated with its study]. / Revisión teórica del deterioro categorial, su entidad y los problemas metodológicos asociados a su estudio.

INTRODUCTION: Studies on category-specific claim to provide insights on structure and organization of semantic information. This type of phenomenon consists of the selective impairment of the information on a domain, for instance, living things (animals) but the sparing of nonliving things (tools), or vice versa. Despite the large number of studies purportedly documenting double dissociations between both domains, the lack of theoretical debate on how to empirically define such dissociations is unclear, e.g. how they should be evaluated and reported. DEVELOPMENT: In this work, a review of literature on category-specific and the explanatory models is showed. A critical methodological is done, on the basis of three findings: 1) lack of normal control groups in the majority of case studies; 2) the questionable utilization of double dissociations; and 3) the presence of problems due to a 'ceiling effect' in most group studies of Alzheimer disease patients. CONCLUSIONS: It is claimed that while domain specificity may be a legitimate phenomenon, the critical review of literature do not provide a strong empirical foundation for the domain fractionations claimed in this literature.

Revisión teórica del deterioro categorial, su entidad y los problemas metodológicos asociados a su estudio / A theoretical review of category-specific impairment, its entity and methodological problems associated with its study

Introducción. Los estudios sobre el deterioro de categorías específicas pretenden ofrecer luz sobre la estructura y la organización de la información semántica. Este tipo de fenómenos consiste en la pérdida selectiva de la información sobre un dominio de conocimiento, por ejemplo el de los seres vivos (animales) frente al de los seres no vivos (herramientas) o viceversa. Pese al gran número de estudios que se han centrado en las dobles disociaciones entre ambos dominios, destaca la ausencia de debates teóricos sobre cómo definir empíricamente este tipo de déficit, es decir, cómo deberían evaluarse y/o documentarse. Desarrollo. En este trabajo se ofrece una revisión de la literatura sobre el deterioro categorial y de los modelos propuestos para explicar este fenómeno. Se realiza una crítica metodológica fundamentada en tres hallazgos: 1) la ausencia de grupos de control en la mayoría de los estudios de caso; 2) el uso cuestionable de las llamadas ‘dobles disociaciones’; y 3) la existencia de problemas asociados al hallazgo de un ‘efecto techo’ en la mayoría de los estudios grupales en la enfermedad de Alzheimer. Conclusiones. Aunque el deterioro categorial parece ser un fenómeno genuino, la revisión de la bibliografía no muestra la suficiente evidencia empírica como para legitimar el fraccionamiento de dominios propuesto en esta área de conocimiento

Introduction. Studies on category-specific claim to provide insights on structure and organization of semantic information. This type of phenomenon consists of the selective impairment of the information on a domain, for instance, living things (animals) but the sparing of nonliving things (tools), or vice versa. Despite the large number of studies purportedly documenting double dissociations between both domains, the lack of theoretical debate on how to empirically define such dissociations is unclear, e.g. how they should be evaluated and reported. Development. In this work, a review of literature on category-specific and the explanatory models is showed. A critical methodological is done, on the basis of three findings: 1) lack of normal control groups in the majority of case studies; 2) the questionable utilization of double dissociations; and 3) the presence of problems due to a ‘ceiling effect’ in most group studies of Alzheimer disease patients. Conclusions. It is claimed that while domain specificity may be a legitimate phenomenon, the critical review of literature do not provide a strong empirical foundation for the domain fractionations claimed in this literature

[Alzheimer's disease, category-specific impairment and relevant variables in object naming]. / Enfermedad de Alzheimer, deterioro categorial y variables relevantes en la denominación de objetos.

INTRODUCTION: The study of the dissociations or category-specific effects between the domains of living beings and non-living beings in Alzheimer's disease (AD) is a controversial issue in the cognitive neurosciences. The lack of agreement among the different studies may be due to deficient control of certain cognitive and psycholinguistic variables that affect processing of the items. AIM: To determine whether the presence of category-specific effects in AD can be caused by inadequate control of variables, such as the typicality or familiarity of the items. Furthermore, since the groups may contain different types of patients with opposing impairments (which would mask this kind of effect in the group analysis), both group and individual analyses were conducted. SUBJECTS AND METHODS: A retrospective study was carried out to evaluate 66 participants (32 patients with AD) using a colour photo naming task with items controlled for seven disruptive variables. RESULTS: No evidence of living/non-living dissociation was found in the analyses by groups, although the individual-based analysis did show some cases of category-specific effects. CONCLUSIONS: Our data show that category-specific effects are not as widespread as they were believed to be and that the lack of control over the so-called disturbing variables may play an important role in studies on category-specific impairment. Our study also highlights the importance of conducting individual analyses in order to avoid overlooking certain effects that are masked in the group studies.

Enfermedad de Alzheimer, deterioro categorial y variables relevantes en la denominación de objetos / Alzheiher´s disease, category-specific impairment and relevant variables in object naming

Introducción. El estudio de las disociaciones o efectos categoriales entre los dominios de seres vivos y seres novivos en la enfermedad de Alzheimer (EA) es un tema polémico para las neurociencias cognitivas. La falta de acuerdo entrelos estudios puede deberse a un deficiente control sobre determinadas variables cognitivas y psicolingüísticas que influyen enel procesamiento de los ítems. Objetivo. Verificar si en la EA la presencia de efectos categoriales puede deberse a un controlinadecuado de variables como la tipicidad o la familiaridad de los ítems. Además, dado que en los grupos puede haber tiposde pacientes con deterioros opuestos –que enmascararían esta clase de efectos en los análisis de grupo– se realizaron análisisde grupo e individuales. Sujetos y métodos. Se evaluó a 66 participantes (32 pacientes con EA) de forma retrospectiva conuna tarea de denominación de fotografías en color con ítems controlados en siete variables perturbadoras. Resultados. No sehalló evidencia de disociación vivo/no vivo al realizar análisis de grupo, aunque el análisis individualizado mostró algunoscasos de efectos categoriales. Conclusiones. Nuestros datos muestran que los efectos categoriales no son tan generales comose pensaba y que la falta de control de las llamadas variables perturbadoras puede desempeñar una función importante en losestudios sobre deterioro categorial. Además, se verifica la importancia de realizar análisis individuales que impidan pasarpor alto algunos efectos enmascarados por los estudios de grupo

Introduction. The study of the dissociations or category-specific effects between the domains of living beings andnon-living beings in Alzheimer’s disease (AD) is a controversial issue in the cognitive neurosciences. The lack of agreementamong the different studies may be due to deficient control of certain cognitive and psycholinguistic variables that affectprocessing of the items. Aim. To determine whether the presence of category-specific effects in AD can be caused by inadequatecontrol of variables, such as the typicality or familiarity of the items. Furthermore, since the groups may containdifferent types of patients with opposing impairments (which would mask this kind of effect in the group analysis), both groupand individual analyses were conducted. Subjects and methods. A retrospective study was carried out to evaluate 66 participants(32 patients with AD) using a colour photo naming task with items controlled for seven disruptive variables. Results. Noevidence of living/non-living dissociation was found in the analyses by groups, although the individual-based analysis didshow some cases of category-specific effects. Conclusions. Our data show that category-specific effects are not as widespreadas they were believed to be and that the lack of control over the so-called disturbing variables may play an important role instudies on category-specific impairment. Our study also highlights the importance of conducting individual analyses in orderto avoid overlooking certain effects that are masked in the group studies