April 2020
Intermediate to advanced
816 pages
18h 32m
Chinese
Content preview from 精通機器學習
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434
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第十四章：使用摺積神經網路來製作深度電腦視覺
視覺皮層的結構
David H. Hubel
和
Torsten Wiesel
在
1958
年
（https://homl.info/71）
1
和
1959
年
（https://
homl.info/72
）
2
對貓進行了一系列的實驗
（
並且在幾年後對猴子進行實驗
（
https://homl.
info/73
）
3
），
提出了關於視覺皮層結構的重大見解
（
這些研究讓作者獲得
1981
年諾貝爾
生理學和醫學獎
）。
他們指出
，
視覺皮層的許多神經元都有一個小型的
局部感受區
，
這意
味著它們只會對視野內的有限區域的視覺刺激做出反應
（
見圖
14-1，
圖中以虛線的圓來代
表局部感受區
）。
不同神經元的感受區可能重疊
，
它們一起創造了整個視野
。
此外
，
作者也發現有些神經元只對水平線的圖像有反應
，
有些只對不同方向的線條有反
應
（
兩個神經元可能有相同的感受區
，
但是對不同的方向有反應
）。
他們也發現
，
有些神
經元的感受區較大
，
會對較複雜的圖樣
（
低階圖樣的組合
）
做出反應
。
這些觀察導致了這
種觀點
：
高層的神經元會使用相鄰的低層神經元的輸出
（
在圖
14-1
中
，
各個神經元都只
和上一層的一些神經元連接
）。
這種強大的結構可以從視野的任何區域偵測各種複雜的圖
樣
。
圖
14-1
在視覺皮層中
，
對視野的小區域中的特定圖樣做出反應的生物神經元稱為感受區
，
當視覺訊
號通過連續的大腦模組時
，
神經元會回應更大型的感受區裡面更複雜的圖樣
。
1 David H. Hubel, “Single Unit Activity in Striate ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.