Scientists have identified a new 'GPS' neuron, a discovery that may open up new treatment strategies for people with impaired sense of navigation such as Alzheimer's patients.
"This seems to be a new type of neuron, which we have informally dubbed the 'neighbourhood cell'. This neuron seems to enable the brain to specifically differentiate between distinct segments (neighbourhoods) of the environment," said Jeroen Bos, researcher at the University of Amsterdam (UvA) in the Netherlands.
Researchers investigated how large scale navigational knowledge is coded within the brain and whether this process indeed occurs in different structures within the temporal lobe.
They trained rats to perform a visually guided task in a figure-8 maze consisting of two loops that overlap in the middle lane.
During the experiment, researchers measured electrical activity in the brain by using a novel instrument which allowed them to simultaneously record groups of neurons from four different areas.
They recorded from the perirhinal cortex, hippocampus and two sensory areas. Recordings from the perirhinal cortex revealed sustained activity patterns.
The level of electrical activity clearly rose and fell depending on the segment the rats were in and persisted throughout that entire segment, researchers said.
They found a pronounced difference between the responses in the perirhinal cortex and responses in other areas of the brain.
Units from the perirhinal cortex had sustained responses throughout the whole loop. By contrast, responses from hippocampal place cells were scattered across the maze and their fields were much smaller than the loops of the maze, researchers said.
"We were surprised to see the perirhinal cortex's responses align so closely with the layout of the maze, primarily because the region is commonly associated with object recognition," Bos said.
The discovery is an important step towards understanding how the brain codes navigation behaviour at larger scales and could potentially open up new treatment strategies for people with impaired topographical orientation like Alzheimer's patients, researchers said.
"It is known that patients with Alzheimer's disease or with damage to the temporal lobe have great difficulty finding their way, especially to remote goal locations', said Cyriel Pennartz, professor at UvA.
The results may guide patients with Alzheimer's or other diseases in using other spatial strategies than the ones most severely affected, researchers said.
The study was published in the journal Nature Communications.