Intelligence, learning disabilities, and event‐related potentials

Is neuropsychology a psychosocial science?

Many early investigators of brain-behavior relationships focused their investigative efforts on the psychiatric implications of brain damage and dysfunction. Descriptions of emotional dyscontrol and other psychosocial difficulties appeared frequently in their writings. Although dimensions of perception, memory, and cognition dominate the current neuropsychological literature, the psychosocial implications of patterns of neuropsychological assets and deficits retain their importance (e.g., in the study of the dementing diseases of adulthood). Our investigations of brain-behavior relationships and their impact on psychosocial functioning have attempted to expand upon and chart a somewhat different (subtypal) course for this area of study. One clearly evident conclusion of these efforts is that neuropsychology is a psychosocial science. Some implications of our findings for research and clinical practice are outlined.

Efficiency of visual information processing in children at-risk for dyslexia: habituation of single-trial ERPs

To investigate underlying learning mechanisms in relation to the development of dyslexia, event-related potentials to visual standards were recorded in five-year-old pre-reading children at-risk for familial dyslexia (n=24) and their controls (n=14). At the end of second grade the children aged 8 years were regrouped into three groups according to literacy level and risk factor. Single-trial analyses revealed N1 habituation in the normal-reading controls, but not in the normal-reading at-risks, and a N1 amplitude increase in the group of poor-reading at-risks and poor-reading controls. No P3 habituation was found in either group. The normal-reading at-risk group exhibited the longest N1 and P3 latencies, possibly compensating for their reduced neuronal activity during initial information extraction. In contrast, the poor-reading group only showed prolonged P3, and their increase in (initial small) N1 amplitude together with normal N1 latencies, suggests inefficient processing in an early time window, which might explain automatisation difficulties in dyslexic readers.

Learning disability subtypes and the role of attention during the naming of pictures and words: an event-related potential analysis

The role of attention in the processing of pictures and words was investigated for a group of normally achieving children and for groups of learning disability sub-types that were defined by deficient performance on tests of reading and spelling (Group RS) and of arithmetic (Group A). An event-related potential (ERP) recording paradigm was employed in which the children were required to attend to and name either pictures or words that were presented individually or in superimposed picture-word arrays that varied in degree of semantic relation. For Group RS, the ERP waves to words, both presented individually or attended in the superimposed array, exhibited reduced N450 amplitude relative to controls, whereas their ERP waves to pictures were normal. This suggests that the word-naming deficiency for Group RS is not a selective attention deficit but rather a specific linguistic deficit that develops at a later stage of processing. In contrast to Group RS and controls, Group A did not exhibit reliable early frontal negative waves (N280) to the super-imposed pictures and words, an effect that may reflect a selective attention deficit for these children that develops at an early stage of visuo-spatial processing. These early processing differences were also evident in smaller amplitude N450 waves for Group A when naming either pictures or words in the superimposed arrays.

Developmentally advanced EEG alpha power in gifted male and female adolescents

An electroencephalographic (EEG) study of gifted and average ability male and female adolescents, as well as college students of both sexes, was conducted to investigate further the relative contributions the left and right cerebral hemispheres during an eyes open (baseline) task in all groups. A total of 90 subjects had baseline EEG recorded in three groups with equal numbers of males and females: 30 gifted adolescents, 30 average ability adolescents, and 30 college-age subjects. Overall alpha power (8-12 Hz resting potential) was significantly greater in average ability subjects compared to both college-age subjects. Moreover, there were no significant differences in overall alpha power between college-age and gifted adolescent subjects. However, college-age and gifted adolescent subjects had different RH/LH patterns of activation such that at temporal and parietal locations college-age and gifted adolescent subjects had greater LH alpha power levels whereas gifted adolescents had greater RH alpha power. These findings suggest that gifted adolescents may have a developmentally enhanced state of brain activity, one that more closely resembles that of college-age adults to whom they also resemble in terms of cognitive development.