Blog Archives

The role of ambiguity in idiom comprehension: The case of a patient with a reversed concreteness effect

The semantic structure of many idioms is constituted by concrete (literal) actions that convey abstract (figurative) mental states and events. We investigated the comprehension of idioms in an Italian patient (MC) with selective atrophy of the left temporal pole, inferior and middle temporal gyri who showed a reversed concreteness effect on nouns (Papagno, Capasso, Zerboni, & Miceli, 2009). Since idioms convey abstract figurative meanings, we assessed whether idiom comprehension was preserved. We tested the extent to which the number of meanings associated with a linguistic unit affected her ability to provide a meaning definition for ambiguous and unambiguous idioms, and for polysemous and non-polysemous words. Only the comprehension of unambiguous idioms was impaired despite the fact that both types of idiom convey abstract mental states. Polysemous word meanings were preserved. Our results suggest that: (1) the integrity of the left temporal lobe is required to process unambiguous idioms; (2) a relatively undamaged right temporal lobe allows the comprehension of ambiguous linguistic units.

from the Journal of Neurolinguistics

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Category-specific recognition and naming deficits following resection of a right anterior temporal lobe tumor in a patient with atypical language lateralization

We present a patient with right-hemispheric speech lateralization who exhibited severe recognition and naming deficits for unique objects (famous faces and landmarks) and grossly normal recognition and naming performances for nonunique objects (animals and man-made objects) following an anterior right temporal lobe (TL) resection of a ganglioglioma. While recognition deficits have been reported for famous faces following right temporal pole lesions, and for landmarks and geographic regions following right TL damage in general, this is the first reported case of both recognition and naming deficits for these objects resulting from a single lesion. These results are consistent with research suggesting that the neuroanatomic substrates for the recognition and naming of unique objects lie in the anterior TL regions. Left temporal pole lesions have been associated with naming deficits for unique objects while right temporal pole lesions have been associated with recognition deficits for unique objects. However, these findings suggest that the substrates of naming can be located in homotopic regions of the right hemisphere when language lateralization is atypical. As various object categories appear to have different neuroanatomical representations in the TLs, we discuss the possible benefits of sampling a wider array of objects during cortical stimulation mapping of language.

from Cortex

Semantic access dysphasia resulting from left temporal lobe tumours

Unlike semantic degradation disorders, the mechanisms and the anatomical underpinnings of semantic access disorders are still unclear. We report the results of a case series study on the effects of temporal lobe gliomas on semantic access abilities of a group of 20 patients. Patients were tested 1–2 days before and 4–6 days after the removal of the tumour. Their semantic access skills were assessed with two spoken word-to-picture matching tasks, which aimed to separately control for rate of presentation, consistency and serial position effects (Experiment 1) and for word frequency and semantic distance effects (Experiment 2). These variables have been held to be critical in characterizing access in contrast to degraded-store semantic deficits, with access deficits characterized by inconsistency of response, better performance with slower presentation rates and with semantically distant stimuli, in the absence of frequency effects. Degradation deficits show the opposite pattern. Our results showed that low-grade slowly growing tumours tend not to produce signs of access problems. However, high-grade tumours especially within the left hemisphere consistently produce strong semantic deficits of a clear access type: response inconsistency and strong semantic distance effects in the absence of word frequency effects were detected. However, effects of presentation rate and serial position were very weak, suggesting non-refractory behaviour in the tumour patients tested. This evidence, together with the results of lesion overlapping, suggests the presence of a type of non-refractory semantic access deficit. We suggest that this deficit could be caused by the disconnection of posterior temporal lexical input areas from semantic system.

from Brain

Semantic access dysphasia resulting from left temporal lobe tumours

Unlike semantic degradation disorders, the mechanisms and the anatomical underpinnings of semantic access disorders are still unclear. We report the results of a case series study on the effects of temporal lobe gliomas on semantic access abilities of a group of 20 patients. Patients were tested 1–2 days before and 4–6 days after the removal of the tumour. Their semantic access skills were assessed with two spoken word-to-picture matching tasks, which aimed to separately control for rate of presentation, consistency and serial position effects (Experiment 1) and for word frequency and semantic distance effects (Experiment 2). These variables have been held to be critical in characterizing access in contrast to degraded-store semantic deficits, with access deficits characterized by inconsistency of response, better performance with slower presentation rates and with semantically distant stimuli, in the absence of frequency effects. Degradation deficits show the opposite pattern. Our results showed that low-grade slowly growing tumours tend not to produce signs of access problems. However, high-grade tumours especially within the left hemisphere consistently produce strong semantic deficits of a clear access type: response inconsistency and strong semantic distance effects in the absence of word frequency effects were detected. However, effects of presentation rate and serial position were very weak, suggesting non-refractory behaviour in the tumour patients tested. This evidence, together with the results of lesion overlapping, suggests the presence of a type of non-refractory semantic access deficit. We suggest that this deficit could be caused by the disconnection of posterior temporal lexical input areas from semantic system.

from Brain

Acute auditory agnosia as the presenting hearing disorder in MELAS

Abstract MELAS is commonly associated with peripheral hearing loss. Auditory agnosia is a rare cortical auditory impairment, usually due to bilateral temporal damage. We document, for the first time, auditory agnosia as the presenting hearing disorder in MELAS. A young woman with MELAS (A3243G mtDNA mutation) suffered from acute cortical hearing damage following a single stroke-like episode, in the absence of previous hearing deficits. Audiometric testing showed marked central hearing impairment and very mild sensorineural hearing loss. MRI documented bilateral, acute lesions to superior temporal regions. Neuropsychological tests demonstrated auditory agnosia without aphasia. Our data and a review of published reports show that cortical auditory disorders are relatively frequent in MELAS, probably due to the strikingly high incidence of bilateral and symmetric damage following stroke-like episodes. Acute auditory agnosia can be the presenting hearing deficit in MELAS and, conversely, MELAS should be suspected in young adults with sudden hearing loss.

from Neurological Sciences