A small region of the brain called the anterior thalamus could hold the key for restoring memory function after a traumatic brain injury. Researchers in New Zealand and the University of Oxford in the UK have shown that targeted electrical stimulation of the anterior thalamus could help with memory restoration in patients with brain injury.
Given how complex the brain is, scientists do not fully understand the extent to which memory impairments following TBI or stroke are caused by irreversible tissue loss and are therefore not treatable or by treatable dysfunctions in the wider brain networks. The hypothesis tested in this study is that lost memory function may be in part due to network dysfunction that can be improved with targeted stimulation. The results of this study support this thesis and could ultimately revolutionize therapies for memory defects.
Past research has suggested that memory recovery is dependent on structures such as the hippocampus and prefrontal cortex. These researchers found that memory loss can be caused by damage to one or more key points in the distributed memory system, in particular to the mammillothalamic tract (MTT), an important connection in this hub. In the study, rats were subjected to lesions in the MTT, which affected their ability to find food in a maze – indicating poor working memory and the development of an amnesia-like syndrome. Using optogenetics, a light-based technique that allows activation of specific neurons, they stimulated anterior thalamus neurons in the rats with the MTT lesions and then tested their performance in the maze again. Regular stimulation not only improved the spatial working memory of the rats, it also increased the expression of a protein indicating neural activity across the memory system. Interestingly, stimulation based on activity in the hippocampus, which has long been considered the seat of spatial memory, yielded no memory-enhancing effects in the rats with MTT lesions. This study provides the first clear piece of evidence on the role of increased neuronal activity within the anterior thalamus in supporting memory.
Scientists have often referred to the human brain as “the most complex organ in the known universe.” Studies like this one incrementally increase our understanding of how this complex organ operates and open up new avenues for future treatment.