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NEUROLOGICAL FOUNDATIONS OF COGNITIVE NEUROSCIENCE - PART 8

Đơn âm mục tiêu, mà đã không được lựa chọn vì những lỗi dự đoán, sau đó đạt được một mức độ kích hoạt cao hơn so với các đơn âm trước đó đã chọn bây giờ đàn áp,, kết quả trao đổi. Khía cạnh khác của các lỗi paraphasic của aphasics thông thạo cũng có thể được cung cấp bằng cách mô hình giả định nào đó được chấp nhận | Jeffrey R. Binder 198 node for this phoneme is transiently suppressed. The target phoneme which had not been selected because of the anticipation error then achieves an activation level higher than the previously selected now suppressed phoneme resulting in an exchange. Other aspects of the paraphasic errors made by fluent aphasics can also be accommodated by the model if certain assumptions are accepted. For example as mentioned earlier contextual phoneme errors usually involve pairs of phonemes that occupy the same position in their respective syllables e.g. onset vowel or final position . This can be explained by assuming that phoneme nodes are position specific. Thus an exchange such as spy fled fly sped is possible but the exchange spy fled dye flesp is highly unlikely because the sp target node of the first word is represented in the network specifically as an onset phoneme. An analogous phenomenon at the lemma level is the observation that contextual errors nearly always occur between words of the same grammatical class. For example an exchange involving two nouns such as writing a mother to my letter is possible whereas exchange of a noun for a possessive pronoun such as writing a my to letter mother is highly unlikely. This preservation of grammatical class follows from the assumption that lemmas contain information about grammatical class which constrains the set of lemmas that are candidates for selection at any given position in an utterance. What kinds of lesions in the network lead to an increased incidence of paraphasic errors and do different kinds of lesions produce different error patterns Do such lesions have any meaning in terms of real brain lesions These questions are just beginning to be addressed but preliminary reports are interesting Dell et al. 1997 Hillis Boatman Hart Gordon 1999 Martin et al. 1994 Schwartz et al. 1994 . Martin et al. 1994 proposed the idea of modeling their patient s paraphasic errors by increasing the decay parameter .