A case of thalamic aphasia with postmortem verification

This study discusses a case of aphasia after dominant thalamic lesion, a hemorrhagic infarction. Unlike other such cases, both repeated standardized assessment and postmortem verification were available. The patient was assessed at 3 weeks and again at 9 weeks postonset. The aphasia demonstrated the syndrome common to dominant thalamic hemorrhage: fluent but paraphasic output sometimes deteriorating to jargon, comprehension less impaired than this type of output usually indicates, and the least impairment in repetition. As sometimes reported in previous cases, semantic paraphasias were more common than phonemic paraphasias. The lesion was located in the dorsal aspect of the lateral nucleus, but it extended into the pulvinar, including the anterior superior lateral aspect which has been implicated in language by previous studies. Thus, data from this case are consistent with an involvement of the dominant pulvinar in language and suggest that this role involves the semantic aspects of language.     

Spatial variables and the feature-positive effect

Pigeons were trained in discriminations where S+ and S? shared common visual elements but were distinguished by the presence or absence of a visual feature. When S+ contained the distinctive feature (the feature-positive condition), the pigeons rapidly learned to withold responses to S?: The learning rate was not markedly affected by changes in the relative size of the feature and the common element. When S? contained the distinctive feature (the feature-negative condition), the pigeons learned to withhold responses to S? more rapidly when the feature was large relative to the common element than when the feature was small relative to the common element. This effect was observed when the stimuli were present at the locus of response and when the stimuli were remote from the locus of response. To explain these results, and the results of generalization tests, it was proposed that the effectiveness of the feature in suppressing responding to the common element during feature-negative training depended on the relative size of the feature and the common element.