RESUMEN
For complex linguistic strings such as idioms, making a decision as to the correct meaning may require complex top-down cognitive control such as the suppression of incorrect alternative meanings. In the study presented here, we used transcranial direct current stimulation to test the hypothesis that a domain general dorsolateral prefrontal cognitive control network is involved in constraining the complex processing involved. Specifically, we sought to test prominent theoretical stances on the division of labour across dorsolateral prefrontal cortex in the left- and right-hemispheres of the brain, including the role of salience and fine vs. coarse semantic coding. 32 healthy young adult participants were randomly allocated to one of two stimulation montage groups (LH anodal/RH cathodal or RH anodal/LH cathodal). Participants were tested twice, completing a semantic decision task after either receiving active or sham stimulation. The semantic decision task required participants to judge the relatedness of an idiom and a target word. The target word was figuratively related, literally related, or unrelated to the idiom. Control non-literal non-idiomatic sentences were also included that only had a literal meaning. The results showed that left-hemisphere dorsolateral prefrontal cortex is highly involved in processing figurative language, whereas both left- and right- dorsolateral prefrontal cortex contributed to literal language processing. In comparison, semantic processing for the non-idiomatic control sentences did not require domain general cognitive control as it relates to suppression of the rejected alternative meaning. The results are discussed in terms of the interplay between need for domain general cognitive control in understanding the meaning of complex sentences, hemispheric differences in semantic processing, and salience detection.
Asunto(s)
Cognición/fisiología , Lateralidad Funcional/fisiología , Corteza Prefrontal/fisiología , Semántica , Estimulación Transcraneal de Corriente Directa , Adolescente , Adulto , Análisis de Varianza , Toma de Decisiones/fisiología , Femenino , Humanos , Masculino , Pruebas Neuropsicológicas , Tiempo de Reacción/fisiología , Adulto JovenRESUMEN
Familiar stimuli are typically accompanied by decreases in neural response relative to the presentation of novel items, but these studies often include explicit instructions to discriminate old and new items; this creates difficulties in partialling out the contribution of top-down intentional orientation to the items based on recognition goals. Here, we used an incidental recognition functional MRI paradigm to compare response to repetition of novel and familiar stimuli in the absence of any ongoing memory task demand. The inferior frontal gyrus and hippocampus both displayed enhanced response to novelty and suppressed response to familiar stimuli, notably, under conditions which did not encourage intentional orientation to recognize novel or old items. Functional connectivity analyses additionally suggested that familiarity processing is associated with a network incorporating the hippocampus and prefrontal cortex. We conclude that recognition memory substrates can be fractionated even in the absence of memory goals.