Quality of representation: PhD Proposal

Here is an idea that I am toying with for my PhD research.

In aging, the idea is that neural representations change in several ways. Right now, we know there are changes, but we don't know what they are exactly, or why they happen the way they do. One obvious objective change we are pretty certain of is that, with age, processing speed slows down.

Now, is this a result of nerve conduction changes? Or is this more to do with changes in the processes themselves. That is, neuronal connectivity is changing, so the process computation changes as well, and changes in a way that results in slowing of the process. In addition, connectivity may also be changing in terms of a reduction in neural plasticity, the ability of neurons to form (or prune) connections based on experience.

One test I propose is related to ascertaining if the observations about neural changes with age relate to changes in processes vis a vis changes in connectivity. If neural representations are poorer with age, then it also means that they are less able to dissociate between similar representations. That is, aging reduces distinctiveness between neural representations. We should be able to measure this using the adaptation paradigm. In theory, if two representations are similar, the adaptation should be greater. To the extent that two representations are distinct, there will be less adaptation. Thus, with younger adults, there should be less adaptation to similar but different stimuli, or, there should be adaptation only when stimuli are very similar. In older adults, adaptation should happen at a lower threshold of similarity, for stimuli that are in fact quite distinct compared to that for the young.

In addition, since the neural representational quality in the lower perceptual areas feeds the cognitive processes that operate on them downstream (e.g. perceptual matching, target identification, memory, attention, decision-making etc) then it stands that if the neural representation is poorer, the cortex involved in working on these representations will either work harder to produce the same result, or be incapable of producing the same result if the representations were clearer. So, this could be measured as a correlation of frontal cortex activity with the degree of adaptation in the posterior, more perceptual areas.