The group selected for this evaluation consisted of 109 normal people with an average age of 25, coming from two different sociocultural levels (high and low) of Mexico City. All were completely evaluated by Luria's battery for neuropsychological assessment, adapted by Ardila, Ostrosky, and Canseco, 1981. This group of tests measures nine different areas: Motor Functions, Somatosensory Knowledge, Auditory Knowledge, Visuospatial Knowledge, Cognitive Processes, Language, Reading, Writing and Basic Calculations. For all of these, the higher performance standards were achieved by the subjects from the high sociocultural level. A significant interaction between sociocultural level and sex was observed. The differences between sexes appear only in subjects from the low sociocultural level. Factor analysis of the battery revealed that the most sensitive items to sociocultural level were those related on one hand, to the handling of complex structural and conceptual aspects of language and on the other hand, to the organization of motor sequences and in general motor programming. Research related to the differences found is reviewed and implications for clinical assessment are discussed.
The use of event-related potentials (ERPS) as a technique in the study of word decoding and semantic processing in the cerebral cortex was investigated. Ten right-handed boys, aged between nine and eleven, with adequate school performance were studied. Visual ERPS were obtained using four derivations: occipital (O1-O2) and parietal (P3-P4). Four stimuli were presented: a frequently used noun written in capitals; the same noun in handwriting; the pictorial representation of this noun (drawing); and a pattern consisting of a checkerboard (25 squares). The data were analyzed using multivariate procedures. A Principal Component Analysis with varimax rotation of the solution was applied. Concepts about reading contributed by cognitive psychology, neuropsychology and neurophysiological research are reviewed, and a hypothetical model of the neuronal bases underlying the act of reading is presented. This model emphasizes the complex, dynamic interplay of the neural structures involved and points to the differences which probably exist between beginning and fluent readers. The results are discussed in accordance with the proposed model.
The purpose of this study was to distinguish the characteristics and components of event related potentials (ERPs) correlated with word decoding and semantic processing in a subgroup of children with specific reading disabilities related to visual processing deficiencies. The results were compared with those obtained from a group of normal readers previously studied (Ostrosky et al. in press). Visual ERPs were recorded to four stimuli: three physically different but with the same semantic content: a frequently used noun written in capitals (COCHE), the same noun in handwriting, the pictorial representation of the noun (drawing), and a neutral stimulus consisting of a checkerboard. Four derivations were used: occipital (O1-O2) and parietal (P3-P4) with reference to linked mastoids. Data were analyzed using multivariate procedures. A Principal Component Analysis with Varimax rotation of the solution was applied. In the normal readers, we found some components in the occipital derivations which identified the words presented in different styles of handwriting and others which seemed to identify these words with the pictorial representation (and not with the neutral stimuli). The first "verbal" components were situated around the 156-256 ms latency range and the second "semantic" components were observed at over 380 ms. In the disabled readers, there was no "verbal" or "semantic" recognition grouping of these physically different stimuli. As opposed to the normal readers, interhemispheric responses were symmetrical. At the left parietal leads in the normal readers, the morphology of the verbal stimuli (capitals and handwriting) were very similar throughout the sweep and both were very different from the nonverbal stimuli. At 376 ms the four stimuli elicited a prominent negative peak in which the verbal stimuli elicited significantly higher amplitude than the nonverbal stimuli. In the disabled group, the morphologies of the four stimuli were very similar and no significant differences were observed. The results are discussed in accordance with a hypothetical model of the neural bases underlying reading. The model takes into account the complexity of the reading process and the various cognitive skills required for its adequate performance, and emphasizes a complex, dynamic interplay between occipital, parietal and temporal areas.
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