Firstly: Natural science does not encompass the concept of a highlighted instant "now" on the time axis.
Secondly: Considerations on brain size, brain location, and propagation speed of neural signals are not relevant for your question.
You will not be satisfied by these points. Therefore I describe a rat in pure terms of natural science: Suppose it approaches a tube from which emerge attractive odours. Suddenly it receives an electrical shock. A memory trace is formed in its brain so that on the next day it refrains from going there. At the instant of the retrieval of that memory this is a present neuronal process which comes together with further present processes of seeing/smelling the tube so that the behaviour of the rat is different from that of the preceding day. Most importantly, there are no "significances" in natural science. Just as cellular processes running in the kidney, neuronal processes signify nothing (not to be confused with "correlate"). Thus, for a rat, as seen by natural science, there is no past (in a sense that it can be recalled as having happened yesterday), although the neuronal processes depend on time. The rat behaves differently on the two days, but it does not "know" this. Retrieving today even a perfect copy of a neuronal process stored yesterday is no more than running a special present neuronal process. It does not imply that you "know" what it signifies (e.g. an event having happened yesterday, or "time" in general).
The same is true for the human brain. Therefore your question cannot be answered in exclusively natural-science terms. However, being a human, I have consciousness which is subjective and which I experience internally. There is a phenomenal level of consciousness on which I find various phenomenal contents such as time, or an apple, or my entire scientific knowledge, while in my brain there are only well-organised neuronal processes. Most scholars falsely assume that phenomenal contents and neuronal processes progress (quasi-)synchronously on the time axis (which is phenomenal as well). In fact, even simple capacity considerations show that neuronal processes (including memory retrievals) cannot continuously, synchronously and constantly signal my visual perceptions (which are phenomenal contents) of my office, with a wealth of details, all perceived as absolutely constant during many hours. Rather, (scientifically not understood) the phenomenal level operates with prototypes which remain constant by definition. (This is not a physiological memory.) It bears certain similarities to Zip data compression: A collection of prototypes and a "list" of temporal occurrences for each item. Briefly, and somewhat vaguely, this list is our time concept.
There is no scientifically valid statement about the relationship between the neuronal and the phenomenal levels. Therefore one must not say that my phenomenal contents are caused by, nor that they are properties of my neuronal processes. Yet, in a purely descriptive way, I am allowed to consider the phenomenal contents of consciousness as "significances" of my neuronal processes, and an "observation" is an increment of phenomenal contents, somehow brought about via sensory processes. Visually guided lifting of the foot over a kerbstone (not involving consciousness but scientifically understandable) is not an observation. A relationship between the locus of a nervous system and a "locus of an observation" cannot be expressed in scientific terms.
I cannot answer your question. But do you believe that now you can reformulate your question?