PubMed · 8609523
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B Anderson. 1996. Semantic neglect?. https://doi.org/10.1136/jnnp.60.3.349-a
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Two right-handed patients who exhibited language disability after left frontal infarction are described. The patients spoke fluently and exhibited excellent repetition ability from the onset of infarction without exhibiting any oral apraxia, but had deficits in auditory comprehension, naming, reading and writing. In both patients, brain magnetic resonance imaging (MRI) revealed infarction in the left inferior frontal gyrus, the middle frontal gyrus and the anterior part of the lower precentral gyrus. Single photon emission computed tomography (SPECT) revealed decreased blood flow in the same regions as those shown to be infarcted by MRI. The MRI and SPECT findings and the symptoms of these patients suggest that left frontal lesions that encompass Broca's area produce fluent aphasia if the posterior part of the left precentral gyrus or motor cortex remains intact and that lesions anterior to Broca's area and the middle frontal gyrus produce a deficit in auditory comprehension of single words as well as sentences.
On tests of autobiographical memory, patients with semantic dementia demonstrate significantly better retrieval of episodic events from the recent past compared with the distant past. This reversal of the Ribot effect has been attributed to the relative sparing of the hippocampal complex in the disorder. Current computational models of long-term memory predict a similar time-dependent pattern of impairment on tests of remote semantic memory. Five patients with semantic dementia were tested on recognition (familiarity) and identification (knowledge) of famous names selected from four different time-periods: 1950's, 1980's, 1990-1993 (early 1990's) and 19941996 (current). As expected, it was found that one patient DM (who had focal left temporal lobe atrophy) showed no significant impairment on recognition of famous names, but was significantly better at producing information about people who were currently famous compared to people famous in the other three time-periods. The other four patients (who had bilateral temporal lobe damage) showed better recognition of famous names from the current time-period (and to a lesser extent the 1950's), yet were profoundly impaired on the identification component, producing very little information across all four time-periods. The results are discussed with respect to current views of the neural organisation of person-specific and general semantic memory.
Auditory evoked magnetic fields (AEF) were recorded in 2 cases with pure word deafness. AEF examination were performed with a novel 129-channel vector neuromagnetic imaging system (SBI 100). The latency and the location of equivalent current dipole (ECD) of N100 m after 1,000 Hz tone burst stimulation, one of the most prominent peak of AEF, were evaluated. One patient, 59-year-old man, suffered from left putaminal hemorrhage and the other, 59-year-old man, had a history of bilateral putaminal hemorrhage. There was no N100 m detected in the left temporal lobe with the right ear stimulation in both patients. However normal N100 m was obtained in the right hemisphere with the left ear stimulation in both cases. And the position of ECD of N100 m in the right hemisphere were correctly superimposed on the Heschl gyrus in brain MRI. The pathophysiology of pure word deafness has been postulated that a disconnection between Wernicke area and bilateral auditory inputs played one of important roles in progression of pure word deafness. Because there was no pathological lesion in temporal lobe verified by MRI study in both patients, N100 m in the left could not be evoked due to interception of the auditory pathway to the Heschl gyrus, but not due to destruction of Heschl gyrus. AEF test is one of the most useful tools in order to estimate central auditory function in patients with pure word deafness.