Ventromedial temporal lobe pathology in dementia, brain trauma, and schizophrenia

The ventromedial temporal area contains numerous anatomical structures collectively or selectively involved in a wide range of neurological and psychiatric disorders. Collective involvement is exemplified best by Alzheimer's disease where a host of anatomical structures and a host of cognitive and behavioral changes are manifested. Selective disease of the amygdala can yield deficits in the ability to judge and evaluate emotional expressions. While memory functions are nearly synonymous with the concept of ventromedial temporal area, they overshadow other functions associated with the diverse anatomical structures in this part of the brain. For example, it could be argued that in addition to output directed toward the hippocampal formation, the output of the ventromedial temporal area is equally strong to the ventral striatopallidal system of the basal forebrain. Denervation of these structures could be associated with the behavioral changes that occur in tandem with the memory-related changes of ventromedial temporal lobe pathology. Here we explore the anatomical and pathological correlate associated with ventromedial temporal area pathology and consider how these may impact on ventral striatopallidal conceptualizations. We conclude that ventromedial temporal area pathology deprives the basal forebrain of multimodal association information from the endstages of corticocortical sensory processing. This endstage information carries with it an analysis of real-time sensory awareness, historical-time or past sensory experiences, and decisions from hippocampal output structures regarding relevancy and novelty. In this sense, basal forebrain structures are in a unique position to regulate behavioral responses to a wide range of stimuli and to organize appropriate emotional, motor, autonomic, and endocrine responses to them.