RESUMEN
Three groups of subjects, children, young adults, and elderly persons with presbyacusis, were tested in a directed attention, quasidichotic paradigm in which continuous speech was monitored for syntactically and/or semantically anomalous words. The task evoked an event-related potential (ERP) characterized by a positive peak in the latency region of 600 to 1,000 msec. ERPs were separately averaged for target-word-right and target-word-left conditions. Amplitude and latency measures at the peak of the global field power waveform were calculated. Amplitude was significantly larger in children than in either adult group. In children and young adults, both amplitude and latency measures were equivalent for target-right and target-left conditions, but in elderly persons, latency was significantly greater in the target-left than in the target-right condition. Topographic maps of amplitude at the peak of the ERP waveform showed maximal positivity symmetrically distributed around the midline centroparietal area in both right-attended and left-attended conditions. In elderly persons, however, maximal positivity in the left-attended condition was significantly delayed relative to maximal positivity in the right-attended condition. Results are consistent with previous findings of interaural asymmetry in a dichotic listening task in elderly persons.
Asunto(s)
Pruebas de Audición Dicótica , Presbiacusia/diagnóstico , Adolescente , Adulto , Factores de Edad , Anciano , Niño , Electrooculografía , Potenciales Evocados/fisiología , Femenino , Humanos , Masculino , Índice de Severidad de la EnfermedadRESUMEN
In an attempt to develop a more ecologically valid measure of speech understanding in a background of competing speech, we constructed a quasidichotic procedure based on the monitoring of continuous speech from loudspeakers placed directly to the listener's right and left sides. The listener responded to the presence of incongruous or anomalous words imbedded within the context of two children's fairy tales. Attention was directed either to the right or to the left side in blocks of 25 utterances. Within each block, there were target (anomalous) and nontarget (nonanomalous) words. Responses to target words were analyzed separately for attend-right and attend-left conditions. Our purpose was twofold: (1) to evaluate the feasibility of such an approach for obtaining electrophysiologic performance measures in the sound field and (2) to gather normative interaural symmetry data for the new technique in young adults with normal hearing. Event-related potentials to target and nontarget words at 30 electrode sites were obtained in 20 right-handed young adults with normal hearing. Waveforms and associated topographic maps were characterized by a slight negativity in the region of 400 msec (N400) and robust positivity in the region of 900 msec (P900). Norms for interaural symmetry of the P900 event-related potential in young adults were derived.
Asunto(s)
Ambiente , Ruido/efectos adversos , Percepción del Habla/fisiología , Adulto , Envejecimiento/fisiología , Electroencefalografía , Electrooculografía , Potenciales Evocados/fisiología , Humanos , Fonética , Reproducibilidad de los ResultadosRESUMEN
Virtually all children with autism are deficient in joint attentional skills. The impact of this deficit may be understood in the context of pragmatically based explanations of language acquisition. In this view, each step in the ontongeny of joint attention is consequential for language development. Thus, it is important that speech-language pathologists understand the developmental course of joint attention so that intervention may start at the earliest step possible. In this article, we review the literature on joint attention and its relationship with other rule systems of language. We discuss the ontogeny of joint attention in typical children. Finally, we describe the developmental course of joint attention as a framework for language intervention through the study of one case.