# Index for natural scenes starts from -1 in Neuropixels data

**URL:** <https://community.brain-map.org/t/index-for-natural-scenes-starts-from-1-in-neuropixels-data/1017>\
**Category:** Technical\
**Tags:** brain-observatory-visual-coding\
**Created:** [April 1, 2021, 4:07pm UTC](https://community.brain-map.org/t/index-for-natural-scenes-starts-from-1-in-neuropixels-data/1017 "2021-04-01T16:07:29Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Bichidian](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@Bichidian](https://community.brain-map.org/u/Bichidian)\
**Post date:** [April 1, 2021, 4:07pm UTC](https://community.brain-map.org/t/index-for-natural-scenes-starts-from-1-in-neuropixels-data/1017/1 "2021-04-01T16:07:29Z")

</div>

I went through the tutorial `ecephys_quickstart.ipynb` , and found that the indices for natural scenes in the downloaded data ( `scene_presentations["frame"]` in the notebook) range from -1 to 117, but I think the indices should actually range from 0 to 117, since there are only 118 natural scenes and the argument for `cache.get_natural_scene_template` ranges from 0 to 117. (All ranges above are inclusive.) What does -1 mean?

OS & version: Manjaro 21.0  
Python version: 3.7.10  
AllenSDK version: 2.8.0

---

<div class="post-metadata">

**Author:** ![saskiad](https://yyz1.discourse-cdn.com/flex027/user_avatar/community.brain-map.org/saskiad/32/1695_2.png) [@saskiad](https://community.brain-map.org/u/saskiad)\
**Post date:** [April 1, 2021, 4:13pm UTC](https://community.brain-map.org/t/index-for-natural-scenes-starts-from-1-in-neuropixels-data/1017/2 "2021-04-01T16:13:37Z")

</div>

Hi Bichidian,

Scene\_presentations[“frame”] = -1 is the blank sweep. Values 0-117 correspond to the 118 natural scenes in the template.

Saskia