Seen by a Glance, But Not by a Stare-A Case Study of a Patient With Simultanagnosia

Simultanagnosia is a rare neuropsychological symptom characterized by difficulty recognizing global structures while preserving perception of local detail. The condition is classified into ventral and dorsal types. Clinical presentation of ventral simultanagnosia includes a reduced ability to recognize multiple visual stimuli rapidly, that is, part-by-part recognition. Here, we report a case of ventral simultanagnosia with a unique presentation; when short-duration visual stimuli were presented, the patient could perform global recognition by improving his part-by-part approach. To investigate the relationship between local and global perception bias and the duration of the present stimulus, we conducted a visual perception test using hierarchically organized Navon figures.

The patient was a 62-year-old right-handed man who suffered from cerebral infarction in the right occipitotemporal lobe. He had no language dysfunction but exhibited left unilateral neglect, prosopagnosia, and ventral-type simultanagnosia. We conducted a visual perception test using the Navon figures and control figures as a visual stimulus. We randomly presented the figures for intervals of 0.2 or 20 s and let the patient report all the letters (global and/or local element) that he recognized. Global elements of the Navon letter were recognized a rate of 0% and 78.3% at intervals of 20 and 0.2 s, respectively, indicating that shorter presentation made the part-by-part approach less likely to manifest.

We assumed that the simultanagnosia in this case was caused by failure to maintain the initially perceived global information for a long period of time during visual presentation, due to right occipitotemporal damage.