TY - JOUR
T1 - The impact of semantic impairment on verbal short-term memory in stroke aphasia and semantic dementia
T2 - a comparative study
AU - Jefferies, Elizabeth
AU - Hoffman, Paul
AU - Jones, Roy
AU - Ralph, Matthew A. Lambon
PY - 2008/1
Y1 - 2008/1
N2 - This study presents the first direct comparison of immediate serial recall in semantic dementia (SD) and transcortical sensory aphasia (TSA). Previous studies of the effect of semantic impairment on verbal short-term memory (STM) have led to important theoretical advances. However, different conclusions have been drawn from these two groups. This research aimed to explain these inconsistencies. We observed (a) qualitative differences between SD and TSA in the nature of the verbal STM impairment and (b) considerable variation within the TSA group. The SD and TSA patients all had poor semantic processing and good phonology. Reflecting this, both groups remained sensitive to phonological similarity and showed a reduced effect of lexicality in immediate serial recall. The SD patients showed normal serial position effects; in contrast, the TSA patients had poor recall of the initial list items and exhibited large recency effects on longer lists. The error patterns of the two groups differed: the SID patients made numerous phoneme migration errors whereas the TSA group were more likely to produce entire words in the wrong order, often initiating recall with terminal list items. The SID cases also showed somewhat larger effects of word frequency and imageability. We propose that these contrasting performance patterns are explicable in terms of the nature of the underlying semantic impairment. SD is associated with anterior lobe atrophy and produces degradation of semantic knowledge-this is more striking for less frequent/imageable items, accentuating the effects of these lexical/semantic variables in STM. SID patients frequently recombine the phonemes of different list items due to the reduced semantic constraint upon phonology (semantic binding: Patterson, K., Graham, N., & Hodges, J. R. (1994). The impact of semantic memory loss on phonological representations. Journal of Cognitive Neuroscience, 6, 57-69). In contrast, the semantic impairment in TSA follows frontal or temporoparietal lesions and is associated with poor executive control of semantic processing (deregulated semantic cognition: Jefferies, E., & Lambon Ralph, M. A. (2006). Semantic impairment in stroke aphasia vs. semantic dementia: a case-series comparison. Brain, 129, 2132-2147), explaining why these patients are liable to recall entire words out of serial order. (C) 2007 Elsevier Inc. All rights reserved.
AB - This study presents the first direct comparison of immediate serial recall in semantic dementia (SD) and transcortical sensory aphasia (TSA). Previous studies of the effect of semantic impairment on verbal short-term memory (STM) have led to important theoretical advances. However, different conclusions have been drawn from these two groups. This research aimed to explain these inconsistencies. We observed (a) qualitative differences between SD and TSA in the nature of the verbal STM impairment and (b) considerable variation within the TSA group. The SD and TSA patients all had poor semantic processing and good phonology. Reflecting this, both groups remained sensitive to phonological similarity and showed a reduced effect of lexicality in immediate serial recall. The SD patients showed normal serial position effects; in contrast, the TSA patients had poor recall of the initial list items and exhibited large recency effects on longer lists. The error patterns of the two groups differed: the SID patients made numerous phoneme migration errors whereas the TSA group were more likely to produce entire words in the wrong order, often initiating recall with terminal list items. The SID cases also showed somewhat larger effects of word frequency and imageability. We propose that these contrasting performance patterns are explicable in terms of the nature of the underlying semantic impairment. SD is associated with anterior lobe atrophy and produces degradation of semantic knowledge-this is more striking for less frequent/imageable items, accentuating the effects of these lexical/semantic variables in STM. SID patients frequently recombine the phonemes of different list items due to the reduced semantic constraint upon phonology (semantic binding: Patterson, K., Graham, N., & Hodges, J. R. (1994). The impact of semantic memory loss on phonological representations. Journal of Cognitive Neuroscience, 6, 57-69). In contrast, the semantic impairment in TSA follows frontal or temporoparietal lesions and is associated with poor executive control of semantic processing (deregulated semantic cognition: Jefferies, E., & Lambon Ralph, M. A. (2006). Semantic impairment in stroke aphasia vs. semantic dementia: a case-series comparison. Brain, 129, 2132-2147), explaining why these patients are liable to recall entire words out of serial order. (C) 2007 Elsevier Inc. All rights reserved.
UR - http://www.scopus.com/inward/record.url?scp=36549010879&partnerID=8YFLogxK
U2 - 10.1016/j.jml.2007.06.004
DO - 10.1016/j.jml.2007.06.004
M3 - Article
SN - 0749-596X
VL - 58
SP - 66
EP - 87
JO - Journal of Memory and Language
JF - Journal of Memory and Language
IS - 1
ER -