Procesamiento de relaciones conceptuales en pacientes con lesiones neurológicas focales

Conceptual relations are links that interconnect concepts together. Two such relations — thematic and taxonomic — play a fundamental role. Taxonomic relations are those that link concepts of the same semantic category, while thematic relations are defined as complementary relations between objects, people or events that interact or co-occur in time and space (Lin & Murphy, 2001). Several studies on conceptual relations have been published, but most of them provide observations on patients without neurological damage. Currently, few studies on focal brain damage exist. Some of the studies reviewed in this population provide information on the association of a type of aphasia with the impairment of some type of conceptual relation. We did not find studies that addressed the relation between the impairment and the cerebral lobe and hemisphere affected, or articles that consider the comparison between patients with and without aphasia. We did locate a single article that establishes the link between the processing of conceptual relations with the hemisphere affected by the injury and the presence of aphasia. We have not found research that reports performance differences according to the age group of assessed patients. Further, although there have been studies on the performance of people without cognitive impairment on neurological forced choice tasks (where response options are given) and free choice tasks (where both taxonomic and thematic responses are possible and there are no response options), this has not been studied in patients with focal brain lesions. To fill these gaps, we propose to compare how conceptual relations are established, both taxonomic and thematic, in patients who suffered a stroke, considering the focus of injury, the affected hemisphere, the presence and type of aphasia, and taking into account different factors such as age. It should be clarified that our interest is not to establish a neuroanatomical correspondence between a conceptual relation impairment and damage to a particular brain area, but to analyze the level of association between a particular focus of lesion and its effect on a unique type of conceptual relation impairment, so as to establish whether partially independent processes exist. Accordingly, we will take into account tasks that involve different forms of presentation and include both tasks with a single type of answer (taxonomic or thematic) and free-response tasks. The main aim of this Doctoral Thesis is to describe and analyze issues involved in the processing of taxonomic and thematic conceptual relations in different forms of presentation in patients with focal brain damage following a stroke. We administered a series of verbal and pictorial tasks to assess the processing of thematic and taxonomic conceptual relations to a group of 60 patients who suffered a stroke, segmenting the sample by type of aphasia (fluent and not fluent) and the location of brain injury (by hemisphere and lobe affected and cortical, subcortical or cortico-subcortical extent), as well as 30 control participants without neurological or cognitive impairment. Participants were divided into two age groups, young (under 60 years) and older (over 65 years). The results indicate that younger and older stroke patients have different performance profiles. The former have difficulties mainly in taxonomic relations and the latter in both types of relations. Moreover, we note that the taxonomic relations are more easily processed when presented pictorially. Additionally, with respect to the type of aphasia, although both groups of patients with aphasia have difficulties in establishing both types of conceptual relations when it came to linguistic presentation, differences were observed when it came to pictorial presentation. Patients with fluent aphasia have more difficulty in establishing taxonomic relations by way of painting, while patients with non-fluent aphasia have difficulties in the establishment of thematic relations. Moreover, with respect to the neuroanatomical correlate, the results obtained indicate that the left parietal brain area seems to contribute especially to the establishment of thematic relations in verbal format, while the temporal lobe of the left and right seems to be more involved in establishing taxonomic relations. Further, the left temporal lobe seems to be more specialized in processing taxonomic relations in pictorial format and the right in tasks that require the establishment of more complex taxonomic relations. Finally, the results suggest that thematic relations are processed independently through the language system and the conceptual system, while the taxonomic relationships are processed primarily by the conceptual system.

Conceptual relations are links that interconnect concepts together. Two such relations — thematic and taxonomic — play a fundamental role. Taxonomic relations are those that link concepts of the same semantic category, while thematic relations are defined as complementary relations between objects, people or events that interact or co-occur in time and space (Lin & Murphy, 2001).