Brain substrates of visual scene memory: a lesion-behavior mapping study

Background: The brain network supporting visual-scene memory includes ventral (what) and dorsal (where, how) visual processing streams, and hubs within the medial temporal cortex, plus frontal, temporal, and parietal regions comprising the core-recollection memory system. However, the exact relationship between these regions and the capacity to memorize different types of visual-scene elements remains debated. Functional neuroimaging studies point to dissociable as well as common network components supporting perception and memory of different aspects of visual information. In the current neuropsychological study, we assess impact of stroke lesion topography on recall of identity, location, and action of event participants, as assessed by the WMS-III Family Pictures subtest. Methods: Ninety-three first-event stroke patients (54 and 39 right- and left-hemisphere damaged, respectively; RHD, LHD) in the sub-acute phase performed the Family Pictures task. Voxel-based lesion-symptom mapping (VLSM) analysis identified brain lesions implicated in memory deficits for the composite score and separately for each scene element: characters' identity, the action they performed, and location of occurrence. Results: Behavioral analysis revealed significant impairment in identity, location, and action memory among right hemisphere damage (RHD) patients compared to matched healthy controls. Performance was significantly lower in delayed compared to immediate testing condition, and memory domains showed a hierarchy of scores: highest for identity, intermediate for location, and lowest for action. VLSM revealed a markedly different pattern of lesion effects in the two hemispheres. In the RH, network was dominated by large voxel clusters in middle and superior temporal and inferior parietal regions. In contradistinction, the LH network was dominated by large voxel clusters in temporo-occipital and medial temporal lobe (MTL) regions. VLSM conjunction analysis disclosed further distinctions between anatomical regions subserving memory of character identity, action, and location. Discussion: Visual scene memory is supported by a bi-hemispheric network dominated in the LH by temporo-occipital/MTL structures and in the RH by temporo-parietal components of the core recollection network. The LH network regions were mostly implicated in a non-specific manner, whereas in the RH network more regions were implicated in memory for specific scene elements.