Hippocampal damage linked to memory loss and apathy

People with autoimmune limbic encephalitis experience memory loss associated with damage to their hippocampus. To advance understanding of the link between hippocampus damage and behavioral changes that occur from this condition, Bahaaeddin Attaallah, from Imperial College London, and Maria Raquel Maio, from the University of Oxford, led a study comparing an autoimmune limbic encephalitis patient population to healthy controls. This work is published in JNeurosci. 

Patients were unable to pair objects with specific locations in a memory task as well as healthy controls. Interestingly, in patients alone, making errors in the task was linked to apathy that was independent of depression symptoms or general cognitive ability. Examining the brain mechanism of this link between memory impairment and apathy revealed that patients who made more errors had smaller hippocampi. These individuals also had weaker connections between the hippocampus and prefrontal cortex. This behavioral and mechanistic link was only observed in the patient population. 

This work points to a brain mechanism in autoimmune limbic encephalitis patients that may explain their impaired memory and dampened motivation. Moreover, these findings may have implications for other conditions that affect the hippocampus, such as Alzheimer's disease, in which memory loss and apathy can also occur together. Speaking on future experimental plans, says Attaallah, "We are investigating the link between apathy and cognition in different cohorts with Parkinson's disease and dementia using different methods, including large data analytics and experimental tasks. This will allow us to have a deeper understanding of how human memory and motivation overlap in these diseases."