1/56. A progressive category-specific semantic deficit for non-living things.We report a longitudinal study of a patient, ES, with a progressive degenerative disorder resulting from generalised cerebral atrophy. Across a range of tasks, ES showed a greater difficulty in recognising and naming artifacts than living things. This deficit for artifacts emerged over time, as she became more severely impaired. In one task, picture naming, there was a crossover from an initial deficit for living things to the later artifact deficit. All materials were carefully controlled to rule out potential confounding factors such as concept familiarity or age of acquisition. There was no evidence that ES's deficit for artifacts was associated with a greater loss of functional than visual information. The pattern of results are consistent with a recently proposed distributed connectionist model, in which a deficit for artifact concepts can emerge as the result of severe, general damage to semantic memory.- - - - - - - - - - ranking = 1keywords = memory (Clic here for more details about this article) |
2/56. The role of speech production in auditory-verbal short-term memory: evidence from progressive fluent aphasia.We report investigations of auditory-verbal short-term memory (AVSTM) in a patient with progressive fluent anomic aphasia. Despite having apparently normal AVSTM as measured by digital span, FM was significantly impaired in immediate serial recall of short sequences of familiar words, and even in reproducing a single word after a filled delay of just a few seconds. In both tasks, unlike normal subjects, she produced numerous phonological errors, often consisting of phonological segments from the intended target word concatenated with segments from other words in the stimulus sequence. Her success in these tasks was modulated (i) consistently by word frequency (high > low), (ii) inconsistently by word imageability (high > low), and (iii) most dramatically by 'nameability': that is, FM was much more likely to reproduce a word correctly in AVSTM if it was a word that she could also produce successfully in picture-naming tasks. On the basis of these and additional experiments designed to exclude other interpretations, we conclude that AVSTM may be crucially supported by activation of the lexical phonological representations responsible for production of content words in speech.- - - - - - - - - - ranking = 5keywords = memory (Clic here for more details about this article) |
3/56. The impact of semantic memory impairment on spelling: evidence from semantic dementia.We assessed spelling and reading abilities in 14 patients with semantic dementia (with varying degrees of semantic impairment) and 24 matched controls, using spelling-to-dictation and single-word reading tests which manipulated regularity of the correspondences between spelling and sound, and word frequency. All of the patients exhibited spelling and reading deficits, except at the very earliest stages of disease. Longitudinal study of seven of the patients revealed further deterioration in spelling, reading, and semantic memory. The performance of both subject groups on both spelling and reading was affected by regularity and word frequency, but these effects were substantially larger for the patients. Spelling of words with exceptional (or more precisely, unpredictable) sound-to-spelling correspondences was most impaired, and the majority of errors were phonologically plausible renderings of the target words. reading of low frequency words with exceptional spelling-to-sound correspondences was also significantly impaired. The spelling and reading deficits were correlated with, and in our interpretation are attributed to, the semantic impairment.- - - - - - - - - - ranking = 5keywords = memory (Clic here for more details about this article) |
4/56. Hemispheric dominance for emotions, empathy and social behaviour: evidence from right and left handers with frontotemporal dementia.Although evidence from primates suggests an important role for the anterior temporal cortex in social behaviour, human research has to date concentrated almost solely on the orbitofrontal cortex and amygdala. By describing four cases of the temporal variant of frontotemporal dementia we show how this degenerative condition provides an excellent model for investigating the role of the anterior temporal lobe, especially the right, in emotions, empathy and social behaviour. Assessments of semantic memory, processing of emotional facial expression and emotional prosody were made, empathy was measured, and facial expressions of emotion were coded. Of the two right handers described, one subject with predominantly left temporal lobe atrophy had severe semantic impairment but normal performance on all emotional tasks. In contrast, the subject with right temporal lobe atrophy showed severely impaired recognition of emotion from faces and voices that was not due to semantic or perceptual difficulties. empathy was lost, interpersonal skills were severely affected and facial expression of emotion was characterized by a fixed expression that was unresponsive to situations. Additionally, two left handers with right temporal lobe atrophy are described. One demonstrated the same pattern of hemispheric lateralization as the right handers and had emotional impairment. The other left hander showed the opposite pattern of deficits, suggesting a novel presentation of anomalous dominance with reversed hemispheric specialization of semantic memory and emotional processing.- - - - - - - - - - ranking = 2keywords = memory (Clic here for more details about this article) |
5/56. Postencephalitic pure anomic aphasia: 2-year follow-up.We report a patient with pure anomic aphasia following encephalitis. brain magnetic resonance imaging (MRI) revealed bilateral temporal lesions, and subsequent focal atrophy in the left anterior inferior temporal lobe. Over the course of a 2-year follow-up, the patient's naming difficulty persisted without other dysfunction of language or memory. These observations indicate a contribution of the left anterior inferior temporal region to object naming.- - - - - - - - - - ranking = 1keywords = memory (Clic here for more details about this article) |
6/56. names and words without meaning: incidental postmorbid semantic learning in a person with extensive bilateral medial temporal damage.The authors describe a densely amnesic man who has acquired explicit semantic knowledge of famous names and vocabulary words that entered popular culture after the onset of his amnesia. This new semantic knowledge was temporally graded and existed over and above the implicit memory he demonstrated in reading speed and accuracy, familiarity ratings, and his ability to make correct guesses on unfamiliar items. However, his postmorbid knowledge was limited to verbal labels denoting famous people and words; he possessed virtually no explicit knowledge of the meaning of these words or the identities of these individuals, although there was some evidence that some of this information had been acquired at an implicit level. Findings are discussed in the context of a neural network model (J. L. McClelland, B. L. McNaughton, & R. C. O'Reilly, 1995) of semantic acquisition.- - - - - - - - - - ranking = 1keywords = memory (Clic here for more details about this article) |
7/56. Deep dysphasic performance in non-fluent progressive aphasia: a case study.We present a patient (PW) with non-fluent progressive aphasia, characterized by severe word finding difficulties and frequent phonemic paraphasias in spontaneous speech. It has been suggested that such patients have insufficient access to phonological information for output and cannot construct the appropriate sequence of selected phonemes for articulation. Consistent with such a proposal, we found that PW was impaired on a variety of verbal tasks that demand access to phonological representations (reading, repetition, confrontational naming and rhyme judgement); she also demonstrated poor performance on syntactic and grammatical processing tasks. However, examination of PW's repetition performance also revealed that she made semantic paraphasias and that her performance was influenced by imageability and lexical status. Her auditory-verbal short-term memory was also severely compromised. These features are consistent with 'deep dysphasia', a disorder reported in patients suffering from stroke or cerebrovascular accident, and rarely reported in the context of non-fluent progressive aphasia. PW's pattern of performance is evaluated in terms of current models of both non-fluent progressive aphasia and deep dysphasia.- - - - - - - - - - ranking = 1keywords = memory (Clic here for more details about this article) |
8/56. Relearning of verbal labels in semantic dementia.Semantic dementia is a degenerative disorder of temporal neocortex characterised by loss of word and object concepts. There is limited evidence that temporary relearning of lost vocabulary may be possible, attributed to sparing of hippocampal structures. However, learning is variable across patients and factors underlying learning success are poorly understood. The study investigated relearning of object names in two severely anomic semantic dementia patients. Following memory models that assume that hippocampal memories require some neocortical representation to underpin them it was predicted that relearning would be influenced by patients' residual semantic information about stimuli. Experiment 1 confirmed that residual knowledge influenced learning success. On the assumption that neocortical knowledge encompasses concepts of space and time, as well as words and objects, it was predicted that learning would be affected by the availability of contextual (temporo-spatial) information. Experiment 2 demonstrated effective learning of object names, attributed to the patient's use of temporal order and spatial position knowledge. Retention of object names over months was linked to the patient's capacity for autobiographical experiential (temporo-spatial contextual) association. The findings indicate that relearning of lost vocabulary is possible in semantic dementia, indicating a role of the medial temporal lobes in the acquisition of semantic information. Effective learning does not imply reinstatement of lost concepts, but, it is argued, does involve some reacquisition of meaning. The findings challenge the traditional semantic-episodic memory dichotomy and are consistent with a "levels of meaning" account of semantic memory.- - - - - - - - - - ranking = 3keywords = memory (Clic here for more details about this article) |
9/56. anomia for common names and geographical names with preserved retrieval of names of people: a semantic memory disorder.This paper describes the case of an anomic patient (FH) who is impaired at naming pictures of objects but has no difficulties in recalling the names of familiar people. Even though his performance on McKenna's (1997) Category Specific Naming Test was at the first percentile, he consistently recalled the names of familiar people as successfully as controls. It is argued that the pattern of performance displayed by FH represents a much clearer double dissociation with proper name anomia than any case previously reported (Cipolotti et al., 1993; Semenza and Sgaramella, 1993). FH is unable to provide detailed semantic information about many of the objects that he cannot name, even though he can recall semantic information about familiar people. Consequently his case appears to represent the mirror image of the proper name anomic patient (APA) described by Miceli et al. (2000) who was unable to recall detailed semantic information about many of the people she was unable to name. Further investigation of FH's anomia revealed impairments in retrieving both common nouns and verbs, and difficulties in retrieving and comprehending geographical names. It is argued that FH's preserved ability to name and recall biographical information about people supports the view that knowledge about familiar people may be subserved by its own dedicated neural subsystem (Kay and Hanley, 1999; Miceli et al., 2000; Gentileschi et al., 2001).- - - - - - - - - - ranking = 4keywords = memory (Clic here for more details about this article) |
10/56. Development of selective verbal memory impairment secondary to a left thalamic infarct: a longitudinal case study.A 68 year old man suffered an acute dysphasic episode with persistent memory disturbance while taking part as a control in a longitudinal magnetic resonance imaging (MRI) study. A small new left thalamic infarct involving the mamillo-thalamic tract could be demonstrated on volumetric MRI, coinciding with the development of a selective verbal memory impairment. This suggests that lateralisation of cognitive processing of visual and verbal material exists at the thalamic as well as the cortical level. High resolution volumetric MRI may be helpful in demonstrating small subcortical infarcts that may not be seen using computed tomography or conventional MRI.- - - - - - - - - - ranking = 6keywords = memory (Clic here for more details about this article) |
| | Next -> |