Control Deficit Subjects are Superior for Man-Made Objects on a Verbal Semantic Task
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1
Lady Davis Institute, Jewish General Hospital, McGill University Network, Canada
When semantic deficits occur following brain damage, the subjects generally show anomia as well as deficits on semantic matching tasks such as the Camels and Cactus test. Such individuals can be further characterized as demonstrating either a semantic control deficit or a storage deficit (Jeffries & Lambon Ralph, 2006). Semantic control subjects show improved performance when responses are constrained, but storage subjects do not. In the present study, we categorized 17 subjects with neurodegenerative diseases – Alzheimer’s disease and Primary Progressive Aphasia - as Semantic Storage or Semantic Control patterns of deficit, based on their performance on three semantic tasks—Naming, Cued Naming, and Word-to-Picture Matching. This was done independent of both the subject’s localization of brain damage and clinical diagnosis. Subjects who demonstrated impaired performance on the Naming task, but showed normal performance on Cued Naming and Word-to-Picture Matching, were classified as showing a control deficit (N = 8), while subjects who were impaired on all three semantic tasks were classified as anomic subjects with a storage deficit (N = 9). Despite only using these three semantic tasks, the identified sub-groups demonstrated different patterns of semantic knowledge consistent with either a control deficit or a storage deficit. The identified sub-groups, for example, were comparable for letter fluency, but subjects with a storage deficit were significantly worse for animal fluency. Accessing subjects’ semantic knowledge with the word and picture versions of the Camels and Cactus test, we also found that storage deficit subjects’ performance was equally poor on both versions compared to normal elderly participants, whereas control deficit subjects were relatively impaired only in the word version. Finally, comparing FDG PET scans for these subjects, we noted storage deficit subjects typically had bilateral temporal damage—all but one participant—whereas control deficit subjects’ temporal lobe damage was more severe in the left hemisphere and typically unilateral. Therefore, these results suggest our three tasks were sufficient for differentiating anomic subjects with either a control deficit or a storage deficit. Also, considering the worse performance by control deficit subjects for the verbal version of the Camels and Cactus test, the results are consistent with previous arguments that the left temporal lobe is more specialized for verbal knowledge whereas the right temporal lobe is more specialized for visual knowledge (Gainotti, 2014). We also found, however, that this difference on the word version was isolated to living objects only. For manmade objects, control deficit subjects’ answers were similar to normal elderly controls. Therefore, the results suggest that animacy effects may be less related to a loss of visual semantic knowledge, as predicted by the sensory-functional hypothesis, because control deficit subjects performed well on the visual Camels and Cactus Test. Instead, animacy effects may be more related to the location of atrophy within the left temporal lobe.
Acknowledgements
We thank Dr. Karalyn Patterson for her assistance with the selection of the semantic tasks, and Stephan Probst's assistance with the collection of the FDG PET scans.
References
Gainotti, G. (2014). Why are the right and left hemisphere conceptual representations different? Behavioural Neurology, 2014, 10 pages, doi:10.1155/2014/603134.
Jefferies, E., Lambon Ralph, M.A. (2006). Semantic impairment in stroke aphasia versus
semantic dementia: a case-series comparison. Brain, 129, 2132–2147.
Keywords:
Anomia,
Semantic Dementia,
Alzheimer Disease,
Aphasia, Primary Progressive,
Temporal Lobe,
semantics,
living vs artifact categories
Conference:
Academy of Aphasia -- 52nd Annual Meeting, Miami, FL, United States, 5 Oct - 7 Oct, 2014.
Presentation Type:
Poster presentation ONLY
Topic:
Not student
Citation:
Roncero
C and
Chertkow
H
(2014). Control Deficit Subjects are Superior for Man-Made Objects on a Verbal Semantic Task.
Front. Psychol.
Conference Abstract:
Academy of Aphasia -- 52nd Annual Meeting.
doi: 10.3389/conf.fpsyg.2014.64.00038
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Received:
25 Apr 2014;
Published Online:
04 Aug 2014.
*
Correspondence:
Dr. Carlos Roncero, Lady Davis Institute, Jewish General Hospital, McGill University Network, Montreal, Canada, tcroncero@gmail.com