add the negative connections

[etuleu]

I am not sure about these so please review carefully @rcoreilly

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: -0.04% :warning:

Comparison is base (80cbe43) 30.01% compared to head (4dfc1fb) 29.97%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #295 +/- ## ========================================== - Coverage 30.01% 29.97% -0.04% ========================================== Files 85 85 Lines 15385 15421 +36 ========================================== + Hits 4618 4623 +5 - Misses 10503 10534 +31 Partials 264 264 ``` | [Files Changed](https://app.codecov.io/gh/emer/axon/pull/295?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=emer) | Coverage Δ | | |---|---|---| | [axon/pvlv\_net.go](https://app.codecov.io/gh/emer/axon/pull/295?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=emer#diff-YXhvbi9wdmx2X25ldC5nbw==) | `0.00% <0.00%> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/emer/axon/pull/295/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=emer)

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[etuleu]

Logically, there is no connection between positive and negative USs. VsMatrix and OFCus are all organized around positive USs. Therefore, it only makes sense to have full projections from Neg to these layers. Can you give that a try?

Also, don't forget to run boa TestStdCPUnData1 with SaveStandard = true to update test results after updating something like this, to pass the tests.

Made the changes. Take a look again please.