RESUMEN
Several studies have shown that behavioral and electrophysiological correlates of processing visual images containing low or high spatial frequency (LSF or HSF) information undergo development after early childhood. However, the maturation of spatial frequency sensitivity during school age has been investigated using abstract stimuli only. The aim of the current study was to assess how LSF and HSF features affect the processing of everyday photographs at the behavioral and electrophysiological levels in children aged 7-15â¯years and adults. We presented grayscale images containing either animals or vehicles and their luminance-matched modified versions filtered at low or high spatial frequencies. Modulations of classification accuracy, reaction time, and visual event-related potentials (posterior P1 and N1 components) were compared across five developmental groups and three image types. We found disproportionately worse response accuracies for LSF stimuli relative to HSF images in children aged 7 or 8â¯years, an effect that was accompanied by smaller LSF-evoked P1 amplitudes during this age period. At 7 or 8â¯years of age, P1 and N1 amplitudes were modulated by HSF and LSF stimuli (P1: HSFâ¯>â¯LSF; N1: LSFâ¯>â¯HSF), with a gradual shift toward the opposite pattern (P1: LSFâ¯>â¯HSF; N1: HSFâ¯>â¯LSF) with increasing age. Our results indicate that early cortical processing of both spatial frequency ranges undergo substantial development during school age, with a relative delay of LSF analysis, and underline the utility of our paradigm in tracking the maturation of LSF versus HSF sensitivity in this age group.
Asunto(s)
Desarrollo Infantil/fisiología , Potenciales Evocados Visuales/fisiología , Reconocimiento Visual de Modelos/fisiología , Estimulación Luminosa/métodos , Percepción Espacial/fisiología , Adolescente , Factores de Edad , Niño , Femenino , Humanos , Masculino , Complejo Nuclear Oculomotor/fisiología , Tiempo de Reacción/fisiologíaRESUMEN
The modulatory effects of low and high spatial frequencies on the posterior C1, P1 and N1 event-related potential (ERP) amplitudes have long been known from previous electrophysiological studies. There is also evidence that categorization of complex natural images relies on top-down processes, probably by facilitating contextual associations during the recognition process. However, to our knowledge, no study has investigated so far how such top-down effects are manifested in scalp ERPs, when presenting natural images with attenuated low or high spatial frequency information. Twenty-one healthy subjects participated in an animal vs. vehicle categorization task with intact grayscale stimuli and images predominantly containing high (HSF) or low spatial frequencies (LSF). ERP scalp maps and amplitudes/latencies measured above occipital, parietal and frontocentral sites were compared among the three stimulus conditions. Although early occipital components (C1 and P1) were modulated by spatial frequencies, the time range of the N1 was the earliest to show top-down effects for images with unmodified low spatial frequency spectrum (intact and LSF stimuli). This manifested in ERP amplitude changes spreading to anterior scalp sites and shorter posterior N1 latencies. Finally, the frontocentral N350 and the centroparietal LPC were differently influenced by spatial frequency filtering, with the LPC being the only component to show an amplitude and latency modulation congruent with the behavioral responses (sensitivity index and reaction times). Our results strengthen the coarse-to-fine model of object recognition and provide electrophysiological evidence for low spatial frequency-based top-down effects within the first 200 ms of visual processing.
Asunto(s)
Mapeo Encefálico , Potenciales Evocados/fisiología , Reconocimiento Visual de Modelos/fisiología , Percepción Espacial/fisiología , Adulto , Análisis de Varianza , Corteza Cerebral/fisiología , Electroencefalografía , Femenino , Humanos , Masculino , Estimulación Luminosa , Tiempo de Reacción/fisiología , Adulto JovenRESUMEN
Although it is widely accepted that colors facilitate object and scene recognition under various circumstances, several studies found no effects of color removal in tasks requiring categorization of briefly presented animals in natural scenes. In this study, three experiments were performed to test the assumption that the discrepancy between empirical data is related to variations of the available meaningful global information such as object shapes and contextual cues. Sixty-one individuals categorized chromatic and achromatic versions of intact and scrambled images containing either cars or birds. While color removal did not affect the classification of intact stimuli, the recognition of moderately scrambled achromatic images was more difficult. This effect was accompanied by amplitude modulations of occipital event-related potentials emerging from approximately 150ms post-stimulus. Our results indicate that colors facilitate stimulus classification, but this effect becomes prominent only in cases when holistic processing is not sufficient for stimulus recognition.
Asunto(s)
Percepción de Color/fisiología , Formación de Concepto/fisiología , Potenciales Evocados/fisiología , Reconocimiento Visual de Modelos/fisiología , Desempeño Psicomotor/fisiología , Adulto , Señales (Psicología) , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
Implicit skill learning is an unconscious way of learning which underlies not only motor but also cognitive and social skills. This form of learning is based on both motor and perceptual information. Although many studies have investigated the perceptual and motor components of "online" skill learning, the effect of consolidation on perceptual and motor characteristics of skill learning has not been studied to our knowledge. In our research we used a sequence learning task to determine if consolidation had the same or different effect on the perceptual and the motor components of skill acquisition. We introduced a 12-h (including or not including sleep) and a 24-h (diurnal control) delay between the learning and the testing phase with AM-PM, PM-AM, AM-AM and PM-PM groups, in order to examine whether the offline period had differential effects on perceptual and motor learning. Although both perceptual and motor learning were significant in the testing phase, results showed that motor knowledge transfers more effectively than perceptual knowledge during the offline period, irrespective of whether sleep occurred or not and whether there was a 12- or 24-h delay period between the learning and the testing phase. These results have important implications for the debate concerning perceptual/motor learning and the role of sleep in skill acquisition.