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Paper   IPM / Cognitive / 7473
School of Cognitive Sciences
  Title:   Implicit Use of Semantic Auditory Information in Auditory Associative Agnosia
1.  R. Nilipour
2.  G. Tarighat Saber
3.  B. Noudoost
  Status:   In Proceedings
  Proceeding: 12th World Congress of Psychophysiology, The Olympics of the Brain
  Year:  2004
  Supported by:  IPM
Implicit usage of visual information (Blind sight) and auditory information (Deaf hearing) has been discussed as an evidence for segregation of systems for extraction of implicit vs. explicit knowledge. More recent data also shows implicit usage of auditory spatial cues in a case of auditory spatial deafness. In this paper we report a case of auditory associative agnosia with preserved implicit usage of auditory semantic information. H.A. is a 60 years old male patient with a left temporoparietal lesion; he shows an associative type auditory agnosia in classic sound recognition task (sound-picture matching task). Two patients with right, two with left temporoparietal lesion and six normal subjects were compared with him in this task. In comparison with normal subjects, H.A. showed a lower performance (P.value = 0.04) and higher reaction time (P.value =0.01) in recognition task. Also his performance was significantly lower in comparison with other patients (P. value= 0.02). In addition, analysis of error types shows a prominent deficit in semantic information processing which is, by definition, representative of an associative auditory agnosia. At the second step, subjects performed a sound-matching task. The subjects were asked to decide whether the two consecutive acoustically different sounds belonged to the same sound object or not. Performance of all patients was lower than normal population but there wasn?t any significant difference between H.A. and other patients. Interestingly H.A.?s reaction time was in the range of normal subjects (P.value=0.67) and was significantly better than patients group (P.value=0.005). His good performance in sound-matching task suggests that he can use auditory information to determine if two acoustically different sounds belong to the same source or not. But when he asked to report his auditory perception in a sound-picture matching task, he showed a profound deficit with predominant semantic errors. Our data is suggestive for preservation of systems for implicit decision about the origin of sound samples, in spite of deficit in reporting its source explicitly by choosing its visual equivalent. In addition, normal range reaction time in sound-matching task and longer reaction time in sound-picture matching task is suggestive for contribution of two different processing systems in these two tasks.

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