The authors claim this correlation is likely caused by the mouse paying attention to its dreams, while skeptics say no such conclusion can be made. One skeptic (Blumberg) is pursuing a hypothesis in which, in REM sleep, the brain is test-driving the body.
The article was quite vague about what signals the head direction neurons normally respond to, but this paper [1] seems to suggest that they respond to head-rotation information from the horizontal semicircular canals - in transgenic mice which lack functional horizontal canals, "the neural network for the head direction signal remains intact in these mice, but that the absence of normal horizontal canals results in an inability to control the network properly and brings about an unstable head direction signal."
As we know that the head-direction signals in sleeping mice are not caused by head movement, one of the first questions I would have is whether we can figure out what, if anything, they are responding to - or whether they are like the unstable signals of the transgenic mice. Unfortunately, one cannot ask a mouse to imagine that it is rotating its head and see whether that triggers the head direction cells, but in a setup where the mouse's body and its visual field can be rotated independently, it might be possible to figure out the causal chains (For all I know, this is already well-understood.) If the head direction signals are the unstable output of a network disconnected from its when-awake inputs, and the eye movements are in response to that, they may have nothing to do with dreams.
If Blumberg is right, could dreams be the result of conscious minds trying to make sense of the sort of test signals he proposes?
mannykannot|3 years ago
The article was quite vague about what signals the head direction neurons normally respond to, but this paper [1] seems to suggest that they respond to head-rotation information from the horizontal semicircular canals - in transgenic mice which lack functional horizontal canals, "the neural network for the head direction signal remains intact in these mice, but that the absence of normal horizontal canals results in an inability to control the network properly and brings about an unstable head direction signal."
As we know that the head-direction signals in sleeping mice are not caused by head movement, one of the first questions I would have is whether we can figure out what, if anything, they are responding to - or whether they are like the unstable signals of the transgenic mice. Unfortunately, one cannot ask a mouse to imagine that it is rotating its head and see whether that triggers the head direction cells, but in a setup where the mouse's body and its visual field can be rotated independently, it might be possible to figure out the causal chains (For all I know, this is already well-understood.) If the head direction signals are the unstable output of a network disconnected from its when-awake inputs, and the eye movements are in response to that, they may have nothing to do with dreams.
If Blumberg is right, could dreams be the result of conscious minds trying to make sense of the sort of test signals he proposes?
[1] https://pubmed.ncbi.nlm.nih.gov/26791205/