1. We have studied how neurons of primary somatic sensory (SI) cortex encode the direction and speed of moving tactile stimuli delivered to the glabrous skin of the contralateral hand. 2. From a total of 178 neurons recorded in SI cortex of 3 awake Macaca mulatta monkeys, 103 were selected for quantitative analysis. Forty-six neurons had slowly adapting (SA) responses, 43 quickly adapting (QA), and 14 mixed SA-QA properties. All possessed cutaneous receptive fields on the distal segments of digits 2, 3, or 4. Receptive fields were scanned with a metal probe (2 mm diam, hemispheric tip) in four different directions (0, 90, 180, and 270 degrees), over a fixed traverse distance of 6 mm, at a variety of speeds (4-100 mm/s), and with a static normal force of 20 g by means of a computer-controlled tactile stimulator. 3. Most neurons gave statistically significant differences in mean impulse rate during the moving stimuli (Wilcoxon, P < 0.01), in at least one of the four directions, compared with the control (nonstimulus) period. The Kruskal-Wallis test (P < 0.01) and the direction index (DI > 35%) determined that about one-half of SI cortical neurons showed significant differences in mean impulse rates associated with the direction of the stimuli at the speeds of 23, 50, and 100 mm/s, and about one-third at 4 mm/s. 4. We determined how the temporal covariance of the neural activity was associated with the parameters of the moving stimuli by calculating the coefficients of the Karhunen-Loève (KL) transform for each set of stimulus responses. Decomposition of the neural activity into principal components indicated that approximately 85% of the impulse train variance during the stimulus responses was contained in the 1st 10 coefficients of the KL transform for the speeds of 23, 50, and 100 mm/s, and approximately 75% at the speed of 4 mm/s. The line spectra calculated from the coefficients of the KL transform showed that the variance contained in the impulse trains in about one-half of the neurons is related to the stimuli. 5. We investigated how the temporal covariance of the neuronal activity was correlated with the direction of the stimulus, by fitting the first coefficient of the KL transform to a weighting function model. This analysis showed that the first coefficient of the KL transform varied as an orderly function of the direction of the moving stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

1. We have studied the neuronal activity in the supplementary motor area (SMA) of two monkeys who categorized the speed of moving tactile stimuli delivered to the glabrous skin of the hand ipsilateral to the site of cortical recording and contralateral to the responding arm. 2. A large number of SMA neurons responded to the stimuli of all speeds (176 of 522) but only when those stimuli controlled behavior. 3. A second class of SMA neurons responded differentially in the categorization task (35 during the stimuli and 51 during the reaction time period) and predicted its outcome. 4. To dissociate the interrupt target switches presses from the tactile categorization responses, sixteen neurons, which responded to the stimuli in all speeds, and 11 neurons, which discharged differentially, were tested in a visual control task. None of these two classes of neurons responded in this situation. 5. It is concluded that the SMA ipsilateral to sensory input and contralateral to the responding arm is involved in the sensory decision process in this somesthetic categorization task.

Este trabajo ha tenido como objetivo analizar la prevalencia de las dificultades específicas de aprendizaje (DEA) en adolescentes españoles. El primer estudio analiza la prevalencia del alumnado identificado dentro de esta categoría de diagnóstico en la Comunidad Autónoma de Canarias. Un segundo estudio, se centra en el área curricular de lengua, con objeto de averiguar si en la detección de las DEA es suficiente el criterio curricular o, es necesario establecer además criterios diagnósticos específicos asociados al área curricular. Los resultados demuestran que en la categoría de diagnóstico DEA se registran las cifras de prevalencia más altas en el ámbito de la Educación Especial. Este hecho es consecuencia de la ausencia de criterios específicos para la identificación de DEA. Asimismo, se demuestra que delimitar de forma operativa la dificultad específica de aprendizaje, combinando el criterio curricular con el criterio psicométrico, reduce la tasa de prevalencia de alumnado identificado con DEA.

No abstract

The main objective of this research was to analyze the impact of transcription skills of Spanish writers when writing an independently composed sentence within a writing-level design. The free-writing sentence task from the Early Grade Writing Assessment (Jiménez, in press) was used to examine the production, accuracy, speed, syntactic complexity, quality, and fluency of children with poor transcription skills (PTS). The results showed that there were significant differences between children with PTS and peers who had good transcription skills. The PTS group members were less accurate, slower, and less fluent or even dysfluent. Furthermore, their sentences were less complex and contained lower quality content. These results suggest that transcription skills play a crucial role in early written expression in Spanish, and poor transcription abilities hamper the acquisition and normal development of sentence composition.