RESUMEN
The balance between goal-directed and habitual control has been proposed to determine the flexibility of instrumental behaviour, in both humans and animals. This view is supported by neuroscientific studies that have implicated dissociable neural pathways in the ability to flexibly adjust behaviour when outcome values change. A previous Diffusion Tensor Imaging study provided preliminary evidence that flexible instrumental performance depends on the strength of parallel cortico-striatal white-matter pathways previously implicated in goal-directed and habitual control. Specifically, estimated white-matter strength between caudate and ventromedial prefrontal cortex correlated positively with behavioural flexibility, and posterior putamen-premotor cortex connectivity correlated negatively, in line with the notion that these pathways compete for control. However, the sample size of the original study was limited, and so far, there have been no attempts to replicate these findings. In the present study, we aimed to conceptually replicate these findings by testing a large sample of 205 young adults to relate cortico-striatal connectivity to performance on the slips-of-action task. In short, we found only positive neural correlates of goal-directed performance, including striatal connectivity (caudate and anterior putamen) with the dorsolateral prefrontal cortex. However, we failed to provide converging evidence for the existence of a neural habit system that puts limits on the capacity for flexible, goal-directed action. We discuss the implications of our findings for dual-process theories of instrumental action.
Asunto(s)
Cuerpo Estriado , Objetivos , Vías Nerviosas , Sustancia Blanca , Humanos , Sustancia Blanca/fisiología , Sustancia Blanca/diagnóstico por imagen , Sustancia Blanca/anatomía & histología , Masculino , Femenino , Adulto , Cuerpo Estriado/fisiología , Cuerpo Estriado/diagnóstico por imagen , Cuerpo Estriado/anatomía & histología , Adulto Joven , Vías Nerviosas/fisiología , Adolescente , Corteza Cerebral/fisiología , Corteza Cerebral/diagnóstico por imagen , Imagen de Difusión Tensora/métodosRESUMEN
According to dual-system theories, instrumental learning is supported by dissociable goal-directed and habitual systems. Previous investigations of the dual-system balance in healthy aging have yielded mixed results. To further investigate this issue, we compared performance of young (17-24 years) and older (69-84 years) adults on an instrumental learning task. Following the initial learning phase, the behavioral autonomy of the motivational significance of the instrumental outcome was assessed with an outcome-devaluation test and slips-of-action test. The present study provides evidence for a disrupted dual-system balance in healthy aging, as reflected in reduced outcome-induced conflict during acquisition, as well as in impaired performance during the test stage, during which participants had to flexibly adjust their actions to changes in the current desirability of the behavioral outcome. These findings will be discussed in relation to previous aging studies into habitual and goal-directed control, as well as other cognitive impairments, challenges that older adults may face in everyday life, and to the neurobiological basis of the developmental pattern of goal-directed action across the lifespan.
Asunto(s)
Envejecimiento/fisiología , Condicionamiento Operante/fisiología , Objetivos , Discapacidades para el Aprendizaje/fisiopatología , Adolescente , Factores de Edad , Anciano , Anciano de 80 o más Años , Análisis de Varianza , Discriminación en Psicología/fisiología , Femenino , Humanos , Masculino , Memoria a Corto Plazo/fisiología , Estimulación Luminosa , Desempeño Psicomotor , Adulto JovenRESUMEN
Ninety-six couples, consulting for primary (n = 73) or secondary (n = 23) infertility, and thought to be infertile due to a varicocele in the husband associated with sperm abnormalities, were subjected to a follow-up study. Of these, 57 were surgically corrected and 39 were not, depending only on the patient's choice. All women were intensively treated where necessary. All patients who were corrected were subjected to scrotal exploration in a search for epididymal anomalies. From our data we conclude that (1) on a statistical basis, comparing observed with expected pregnancy rates, varicocelectomy is useful in primary infertility and unnecessary in secondary infertility and (2) on an individual basis, patients with primary infertility and 'pure' varicoceles have a better prognosis than patients with concomitant epididymal dysfunction.