28619
OBJECTIVES : The aim of the present research was to determine if amphetamine - abstinent ecstasy users have changes in occipital lobe functioning , as revealed by two studies : a masking study that directly measured the width of orientation tuning bandwidths and a contour integration task that measured the strength of long - range connections in the visual cortex of drug users compared to controls .
 amphetamine, ecstasy
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 amphetamine, ecstasy