Discount and consider instead?

OUT, out, brief candle! As life nears its end, thoughts can acquire urgent clarity. This truth is more perceptible among some artists than others; novelists, for example, find endless ways of disguising it. But it is so evident among playwrights, composers, and visual artists that “late style” has become an accepted critical concept. Consider the late plays of Henrik Ibsen, furiously rattling the bars of the bourgeois cage. Discount for a moment a brain-researcher’s recent suggestion that the abstraction of Willem de Kooning’s late paintings reflects the onset of dementia, and consider instead the late works of Vincent van Gogh and Francisco Goya.

http://www.economist.com/news/books-and-arts/21717018-when-time-precious-composers-and-playwrights-outdo-themselves-why-so-many-artists-do

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I don't understand the last sentence in this paragraph. First, “discount” here seems like an imperative verb(which I am not sure and it might denote the meaning of "Regard (a possibility, fact, or person) as being unworthy"). Second, given "consider instead" is the same as a hurdle to understand this sentence, I am confused whether Vincent van Gogh and Francisco Goyas' late works were born from their dementia.

Oh, by the way, and the third is how the novelists disguise that truth about clarity in life's end; I don't get it.

Thanks!