98901
Speech errors associated with certain kinds of aphasia have been used to map certain components of speech onto the brain and see the relation between different aspects of production : for example , the difficulty of expressive aphasia patients in producing regular past-tense verbs , but not irregulars like ' sing-sang ' has been used to demonstrate that regular inflected forms of a word are not individually stored in the lexicon , but produced from affixation of the base form .
 expressive aphasia
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 expressive aphasia