I will attempt to answer some of these questions. In no particular order.
-The term "allocentric location" means a location in a reference frame relative to something else. It contrasts to "egocentric location" which means a location relative to your body. I am looking at a chair in my living room right now. The char has a location relative to the room, that is an allocentric location. The chair also has a location relative to me, that is an egocentric location. If I move, the egocentric location will change but the allocentric location will remain the same.
When the brain builds a model of all the things in the world, those models must be expressed/stored in allocentric coordinates. A coffee cup is defined by a set of features relative to each other (allocentric). If I want to grab the coffee cup then I need to know where the cup is relative to me (egocentric). Our big insight is allocentric locations are being used in all sensory regions.
Grid cells encode where an animal is relative to some space, typically a cage or room in a maze. Grid cells allow an animal to know where it is in that space and therefore they play an essential role in navigating. Because grid cells give the same location regardless of what direction you are facing they could be considered allocentric. (There are separate cells that encode your direction.) Grid cells are similar to what we need for sensorimotor inference. For example, when recognizing an object via touch, the brain needs to know where your finger is relative to a touched object. Or the brain needs to know where on an object part of your retina is sensing. We are currently studying the literature on grid cells to get clues as to the exact neural mechanisms the brain might use to create allocentric locatoins for sensorimotor inference.
-"Temporal pooling". refers to an operation performed by a layer of neurons. "Pooling" means the cells in this layer will fire the same pattern for a set of input patterns. Each input pattern represents part of the same thing, so, as the input patterns change the pooling layer stays constant. For example, when moving my fingers over a coffee cup, the input patterns from my fingers will change. However, temporal pooling layer will maintain a constant activation pattern which corresponds to the cup.
The "temporal" part of temporal pooling refers to how the temporal pooling layer learns.The TP layer assumes that patterns that follow each other in time are likely part of the same thing, so the TP layer learns by forming synapses to subsequent input patterns over time.
Temporal pooling can be applied to both sensorimotor sequences and high-order sequences..Sensorimotor sequences will typically not be in any strict or repeatable order. High-order seequences,like a melody, by definition follow a defined order.
Now onto Paul Lamb's questions.
As far as we know, L5 projects through the thalamus and terminates in L6a, lower L5, L4 and lower L3. L2/3 projects directly to other regions and terminates in L4 and lower L3. These probably also connect to L6a and lower L5 , but I don't know if it is known.
I wouldn't say so. L2/3 represents objects. The location information is no longer available. Say L4 represents features at different locations on a coffee cup. L2/3 pools over L4 patterns and represents "coffee cup" There is no longer any location information in L2/3.