L5TT Cells: Tourists, Apparently. (Motor output, location anchoring, and perceptual detection.)

L5tt cells walk around, stopping to point things out.

These papers imply location anchoring and perceptual detection are essentially the same thing, “hey there’s this thing over there”.

They show that L5tt cells burst to cause perceptual detection and code location. They only code location upon touch, where while moving through air, they code self-movement. Upon touch, they dramatically change how they code things and code location quite precisely. So it seems like they anchor locations based on sensory info, rather than coding it constantly.

That suggests location anchoring and perceptual detection are handled together. When you notice something, that’s when locations should anchor to whatever you noticed.

L5tt cells are the motor output, but it actually makes sense for them to cause location anchoring. They probably already have synapses to change locations gradually during movement, so they could use those to set the location. L5tt cells have strong sensory responses which must do something.

If pausing motor output is a problem (for 1/20th of a second in a few cortical columns in a region), it can just use a purely motor subpopulation of L5tt cells.

This was originally a reply to Burst as a local learning rule in apical but not basal dendrites, but I don’t want to derail that discussion.

Sources and other interesting looking papers in order of relevance:
Independent representations of self-motion and object location in barrel cortex output
Nonlinear dendritic integration of sensory and motor input during an active sensing task
Active cortical dendrites modulate perception
Activity in motor-sensory projections reveals distributed coding in somatosensation
High-frequency burst spiking in layer 5 thick-tufted pyramids of rat primary somatosensory cortex encodes exploratory touch