Direction balance depends on the weight proxy and orientation cutoff in 155 released ferret spine records

We tested whether anatomical weights give a consistent direction contrast among inputs with similar orientation preference to their parent soma. We used 155 public ferret visual cortex records that link calcium imaging and electron microscopy. At a 22.5 degree orientation cutoff, 29 inputs prefer the same direction and 33 prefer the opposite direction. Weight by postsynaptic density area changes the count balance from -0.0645 to 0.0698. The exact critical factor for independent multiplicative weight error is 1.072466. A factor 1.073 can thus remove the positive sign. Some two-row deletions also reverse it. At 45 and 90 degrees, the area-weighted balance is negative. Head volume and simulated voltage give different margins. These results do not give a stable reversal across the tested choices. We supply exact bounds, row-deletion results, source hashes, code, and a figure. Missing cell and animal labels prevent population inference. The contrast is not a stimulus response model and does not show a causal mechanism or transfer across animals.

structure and function · dendritic spines · direction preference · ferret visual cortex · sensitivity analysis · electron microscopy