I think of the sensorium as being something like an extremely resonant bell.  Sensory inputs or rather the processed remnants of sensory inputs, that is to say the effects of sensory inputs, prime various patterns in the sensorium and alter the way that subsequent sensory inputs are processed.  This process manifests itself as what we call short-term memory, intermediate term memory, long-term memory, as well as some form of learning.  Because we think of memory as the acquisition of factual information and not the development in the sensorium of patterns or the recognition of patterns, we’re not accustomed to thinking of short-term memory as learning.

Assuming that there is some sort of automatic recirculating mechanism, I wonder if the fact that in short-term (and long-term) memory experiments there is a clear effect favoring recall of the first item of a list is simply an artifact that results because generally the first item of a list is preceded by silence or by some irrelevant stimulus.  I wonder if short-term memory is some kind of more or less fixed time constant.  One might think of an initial stage of processing in which inputs are recirculated after some time.  This raises the question of whether observed limits on the number of memory chunks that can be stored in short-term memory is a result of the amount of time it takes for each chunk to be entered.  No, it’s probably much more complicated than that.  There is already an interaction between sensory inputs and pre-existing patterns from the get go.  That’s why zillions of short-term memory experiments use nonsense syllables.

Rather than thinking of attention as adding processing power to particular sensory inputs it may make more sense to think of attention as a way of suppressing, or at least reducing, the strength of competing sensory inputs.  That of course makes more sense than thinking that the brain has excess processing capacity just lying around waiting to be called into action for the purpose of attention.

How long is “now”?  I don’t think the question really has an answer.  I think the hetero phenomenological experience of “now” depends on the contents of the recirculating short-term memory buffer.  When I talk about the recirculating short-term memory buffer I mean that at a certain point in the processing of incoming sensory inputs, the processed inputs are fed back to an earlier point in the processing and somehow combined with the current incoming sensory inputs.  At the same time, the processed inputs continue to be further processed.

As I think more about “now” I realized that there are a number of different now’s depending on the sensory modality.  Well even that’s not right.  We know from various tachistoscopic experiments that there is a short-term visual buffer with a very short time constant, which suggests that there is a very short visual “now”.  I can’t think of any good evolutionary reason why each modality’s “now” should have the same time constant.

I see that I’ve written “the” recirculating short-term memory buffer.  I certainly don’t know that there’s only one, and I don’t know that any of my conclusions depend on there being only one.  Indeed I think that patterns recirculate with differing time constants depending in some way on the nature (whatever that means) of each pattern.

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