RESUMEN
Adaptive behavior in a nonstationary world requires humans to learn and track the statistics of the environment. We examined the mechanisms of adaptation in a nonstationary environment in the context of visual-saccadic inhibition of return (IOR). IOR is adapted to the likelihood that return locations will be refixated in the near future. We examined 2 potential learning mechanisms underlying adaptation: (a) a local tracking or priming mechanism that facilitates behavior that is consistent with recent experience and (b) a mechanism that supports retrieval of knowledge of the environmental statistics based on the contextual features of the environment. Participants generated sequences of 2 saccadic eye movements in conditions where the probability that the 2nd saccade was directed back to the previously fixated location varied from low (.17) to high (.50). In some conditions, the contingency was signaled by a contextual cue (the shape of the movement cue). Adaptation occurred in the absence of contextual signals but was more pronounced in the presence of contextual cues. Adaptation even occurred when different contingencies were randomly intermixed, showing the parallel formation of multiple associations between context and statistics. These findings are accounted for by an evidence accumulation framework in which the resting baseline of decision alternatives is adjusted on a trial-by-trial basis. This baseline tracks the subjective prior beliefs about the behavioral relevance of the different alternatives and is updated on the basis of the history of recent events and the contextual features of the current environment.
Asunto(s)
Adaptación Fisiológica/fisiología , Toma de Decisiones/fisiología , Aprendizaje por Probabilidad , Movimientos Sacádicos/fisiología , Percepción Visual/fisiología , Adolescente , Adulto , Señales (Psicología) , Femenino , Humanos , Inhibición Psicológica , Masculino , Persona de Mediana Edad , Modelos Teóricos , Tiempo de Reacción/fisiologíaRESUMEN
Initiating an eye movement is slowed if the saccade is directed to a location that has been fixated in the recent past. We show that this inhibitory effect is modulated by the temporal statistics of the environment: If a return location is likely to become behaviorally relevant, inhibition of return is absent. By fitting an accumulator model of saccadic decision-making, we show that the inhibitory effect and the sensitivity to local statistics can be dissociated in their effects on the rate of accumulation of evidence, and the threshold controlling the amount of evidence needed to generate a saccade.
Asunto(s)
Movimientos Sacádicos/fisiología , Visión de Colores , Señales (Psicología) , Toma de Decisiones , Ambiente , Medio Ambiente Extraterrestre , Fijación Ocular , Lateralidad Funcional , Humanos , Modelos Biológicos , Estimulación Luminosa , Probabilidad , Tiempo de ReacciónRESUMEN
Human observers take longer to re-direct gaze to a previously fixated location. Although there has been some exploration of the characteristics of inhibition of saccadic return (ISR), the exact mechanisms by which ISR operates are currently unknown. In the framework of accumulation models of response times, in which evidence is integrated over time to a response threshold, ISR could reflect a reduction in the rate of accumulation for saccades to return locations or an increase in the effective criterion for response. In two experiments, participants generated sequences of three saccades, in response to a peripheral or a central cue. ISR occurred across these manipulations: saccade latency was consistently increased for movements to the immediately previously fixated location. Latency distributions from individual observers were fit with a Linear Ballistic Accumulator model. ISR was best accounted for as a change in the accumulation rate. We suggest this parameter represents the overall desirability of a particular course of action, the evidence for which may be derived from a variety of sensory and non-sensory sources.
Asunto(s)
Inhibición Neural/fisiología , Movimientos Sacádicos/fisiología , Adulto , Análisis de Varianza , Atención/fisiología , Señales (Psicología) , Femenino , Fijación Ocular/fisiología , Humanos , Modelos Neurológicos , Orientación/fisiología , Estimulación Luminosa , Desempeño Psicomotor/fisiología , Tiempo de Reacción/fisiología , Vías Visuales/fisiología , Percepción Visual/fisiologíaRESUMEN
Cystic fibrosis is rare in the Asian population, and is often associated with consanguinity and rare genotypes. We report on a 23-year-old Asian man from a consanguineous pedigree referred to the regional cystic fibrosis unit after a diagnosis of congenital bilateral absence of the vas deferens during investigations for infertility. A detailed history revealed several previous episodes of acute pancreatitis. Full diagnostic appraisal showed homozygosity for a novel cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation, but normal sweat test and nasal potential difference studies. An endoscopic retrograde cholangiopancreatogram (ERCP) showed chronic pancreatitis with bulky side branches. The vas deferens and the pancreas appeared exquisitely sensitive to mild CFTR dysfunction. Patients with cystic fibrosis and unexplained upper abdominal pain should be screened for pancreatitis, and consideration should be given to screening patients with idiopathic pancreatitis for mutations in the CFTR gene.