The relationship between sensory modality and information processing was examined. Available hypotheses concerning modality influence were not supported, but an interaction between modality and information complexity could be discerned. With simpler information (reaction signals and unidimensional discriminations) modalities are equivalent; contextual and parametric factors determine intermodal relations. With complex information (spatial or temporal patterns) specific modalities are adept with certain kinds of information, and what is received in nonadept modalities is recoded in the most adept. Generalizations about modality-information interactions depend on control of response factors. Implications of data and generalizations for theories .of memory, for measuring deficit in pathology, and for resolving the nativismempiricism controversy are discussed.

These results suggest that there may be specific patterns to the effect of prenatal alcohol exposure on cognitive performance that can be identified during adolescence. In this study of sustained attention, processing in the visual modality was more affected than that in the auditory modality. Deficits in visual processing seemed to result from insensitivity to target stimuli.

No abstract

Phenylketonuria provides a human model for the study of the effect of phenylalanine on brain function. Although irreversible mental retardation is preventable through newborn diagnosis and dietary phenylalanine restriction, controversy exists regarding the effects of increased concentrations of phenylalanine in older patients. We have studied ten older, treated, phenylketonuric patients using a triple-blind, multiple trials, crossover design. Each patient was tested at the end of each of three 1-wk periods of high or low phenylalanine intakes. Tests included a repeatable battery of neuropsychological tests, analysis of plasma amino acids, and measurement of urine amino acids, phenyl organic acids, dopamine, and serotonin. In all 10 patients, plasma phenylalanine rose (9004,000 AM). In 9 of 10 patients there was an inverse relationship between plasma phenylalanine and urine dopamine excretion. When blood phenylalanine was elevated, these patients had prolonged performance times on neuropsychological tests of higher but not lower integrative function. Urinary serotonin fell during phenylalanine loading in six patients. The concentration of phenylacids in the urine was not proportional to the plasma phenylalanine at concentrations below 1.5 mM. In one patient, neither performance time nor dopamine excretion varied as blood phenylalanine rose or fell. We interpret these data as follows: blood phenylalanine above 13 mM impairs performance on neuropsychological tests of higher integrative function, this effect is reversible, and one mechanism may involve impaired biogenic amine synthesis.

These results suggest that there may be specific patterns to the effect of prenatal alcohol exposure on cognitive performance that can be identified during adolescence. In this study of sustained attention, processing in the visual modality was more affected than that in the auditory modality. Deficits in visual processing seemed to result from insensitivity to target stimuli.