For the millions living with Alzheimer’s disease, finding their way home can become an overwhelming challenge, even in their own familiar neighborhoods.
This spatial disorientation, often called wandering, reflects a breakdown in the brain’s internal navigation system: a complex computational network that most of us rely on without realizing.
Omar Ahmed, associate professor of psychology at the University of Michigan, is working to understand how that system functions and why it fails in those with Alzheimer’s and many living with Parkinson’s. His lab combines experimental neuroscience with computational modeling to identify the brain regions, neurons and calculations that allow humans and many other animals to orient themselves and navigate through the world.
Many species, including humans, navigate using a process called dead reckoning, an internal sense of direction that continuously updates as we move, without reliance on external cues. A person standing on their street intuitively knows which direction their house is because the brain is constantly making that calculation.
Central to this process is the retrosplenial cortex, a region of the brain that appears fundamental for computing the angles that connect location A to location B. Damage to this region, whether from hemorrhages or glioblastoma, produces the same disorientation seen in patients with Alzheimer’s and Parkinson’s.
To understand the computations underlying navigation, Ahmed’s team first had to do extensive experimental work recording and characterizing every type of neuron in the retrosplenial cortex.
What they found was unexpected. The region contains a unique class of neuron found nowhere else in the brain.
These uniquely small neurons fire constantly, making the retrosplenial cortex one of the most metabolically demanding regions in the human brain. This constant firing is likely due to the continuous calculations being run, which are critical to survival.
Read the complete article at MResearch
