ABSTRACT
Research on central functions presents difficult problems, including heterogeneity among normals and subjects with central nervous system (CNS) defects. General conclusions are that there is an ear advantage related to cerebral dominance; testing for results of CNS damage requires stimuli of reduced redundancy; and fusion of dichotic stimuli is a brainstem function. Responses to digits presented dichotically were obtained. Data were in agreement with the usual findings that brain injury results in a reduced ability to understand dichotic speech and that injury to the dominant cerebral hemisphere results in lower speech perception via the opposite ear than by the ipsilateral ear. Significantly almost one third of the subjects performed differently than other members of their respective subgroups. A direction for additional research is to consider factors in otherwise apparently homogeneous groups that lead to nonhomogenous responses.
