Subcortical transfer of cognitive information in subjects with complete forebrain commissurotomy

Three complete commissurotomy subjects were tested for the ability to integrate cognitive information presented for a prolonged duration to opposite visual hemi-fields. A sample stimulus was projected to one hemi-field and a three-choice array to the other, with one choice related to the sample on an abstract or concrete basis. All subjects performed the non-verbal matching task at well above chance level, with scores comparable to those attained when the task was performed completely within one or the other hemisphere. Transfer was equally successful in the two directions, though the pathway originating in the right and terminating in the left hemisphere may be more sensitive to affective components of the stimulus. The information relayed subcortically is neither verbal nor imagic in nature, but appears to correspond to contextual or connotative associates of the stimulus. The results are discussed in terms of a cognitive system common to the two hemispheres and involving associational networks but not lateralized functions such as language and complex visuospatial processes.