ORCID Profile
0000-0002-1512-7667
Current Organisation
The University of Edinburgh
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Publisher: Elsevier BV
Date: 11-2012
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2012.07.006
Abstract: It has been proposed that domain-specific regions in extrastriate cortex, parahippoc al cortex and the medial temporal lobe (MTL, particularly the hippoc us, HC, and perirhinal cortex, PrC) may respond differently to the degree of feature complexity present in sets of visual stimuli, with the latter two regions tuned to represent the differences among stimuli with a high degree of visual overlap or featural ambiguity (Graham, Barense, & Lee, 2010 Cowell, Bussey, & Saksida, 2010a). To test this prediction, healthy participants viewed blocks containing visually similar or visually different exemplars from four stimulus categories (scenes, faces, inanimate objects and animate objects). Independent functional regions of interest were identified in extrastriate and MTL regions that were preferentially responsive to one or more of these visual categories, and the main experimental data interrogated for any evidence of an interaction between visual category and degree of feature overlap. In PrC and posterior HC (PostHC) viewing sets of stimuli with a large number of overlapping features resulted in greater activity than blocks containing items that were more visually distinct. The opposite pattern was found in fusiform face area (FFA), parahippoc al place area (PPA) and lateral occipital complex (LOC). The increased response in the HC and PrC to high visual similarity was seen only for visual categories that effectively activate these regions (PrC-faces and objects PostHC-scenes). This study confirms that regions throughout the visual ventral stream, parahippoc al cortex and MTL are engaged differentially by visual complexity, consistent with recent lesion experiments in which MTL damage affects discrimination and learning of, as well as recognition memory for, exemplars with a high degree of visual feature overlap.
Publisher: Oxford University Press (OUP)
Date: 05-01-2005
DOI: 10.1093/BRAIN/AWH348
Abstract: Early and severe memory impairment is generally held to be an exclusion criterion for the clinical diagnosis of frontotemporal dementia (FTD). However, clinical experience suggests that some patients with otherwise typical FTD can be amnesic from presentation, or even present solely with amnesia. A review of severe amnesia at presentation in patients with pathologically proven FTD is therefore warranted. The present study examined the records of all patients in the joint Cambridge-Sydney neuropathological series of patients with dementia and a pathological diagnosis of FTD to identify those for whom memory complaints were dominant at presentation. Eight of 71 patients met these criteria. For two patients, memory loss was the only complaint for one patient, memory loss was accompanied by personality change for two patients, memory loss was accompanied by prominent dysexecutive symptoms and for three patients, memory loss was accompanied by apathy but no other behavioural changes. In seven patients local specialist teams initially diagnosed Alzheimer's disease four patients entered anticholinesterase drug trials. All eight later developed behavioural features: in four, the diagnosis was revised to FTD, while in four the diagnosis of FTD was made only on neuropathological examination after death. In conclusion, severe amnesia at presentation in FTD is commoner than previously thought and the clinical consensus criteria for the diagnosis of FTD may need to be revised. The underlying basis of the memory impairments in patients with FTD may be heterogeneous, with different explanations in different subgroups.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 28-10-2009
Publisher: Oxford University Press (OUP)
Date: 10-12-2008
DOI: 10.1093/BRAIN/AWN336
Abstract: Transient epileptic amnesia (TEA) is a recently recognised form of epilepsy of which the principle manifestation is recurrent, transient episodes of isolated memory loss. In addition to the amnesic episodes, many patients describe significant interictal memory difficulties. Performance on standard neuropsychological tests is often normal. However, two unusual forms of memory deficit have recently been demonstrated in TEA: (i) accelerated long-term forgetting (ALF): the excessively rapid loss of newly acquired memories over a period of days or weeks and (ii) remote autobiographical memory loss: a loss of memories for salient, personally experienced events of the past few decades. The neuroanatomical bases of TEA and its associated memory deficits are unknown. In this study, we first assessed the relationship between subjective and objective memory performance in 41 patients with TEA. We then analysed MRI data from these patients and 20 matched healthy controls, using manual volumetry and voxel-based morphometry (VBM) to correlate regional brain volumes with clinical and neuropsychological data. Subjective memory estimates were unrelated to performance on standard neuropsychological tests but were partially predicted by mood, ALF and remote autobiographical memory. Manual volumetry identified subtle hippoc al volume loss in the patient group. Both manual volumetry and VBM revealed correlations between medial temporal lobe atrophy and standard anterograde memory scores, but no relation between atrophy and ALF or remote autobiographical memory. These results add weight to the hypothesis that TEA is a syndrome of mesial temporal lobe epilepsy. Furthermore, they suggest that although standard anterograde memory test performance is related to the degree of mesial temporal lobe damage, this is not true for ALF and autobiographical amnesia. It is possible that these unusual memory deficits have a more diffuse physiological basis rather than being a consequence of discrete structural damage.
Publisher: Public Library of Science (PLoS)
Date: 26-06-2014
Publisher: Society for Neuroscience
Date: 19-06-2013
Publisher: Elsevier BV
Date: 2002
DOI: 10.1016/S0028-3932(01)00155-5
Abstract: Studies of autobiographical memory in semantic dementia have found relative preservation of memories for recent rather than remote events. As semantic dementia is associated with progressive atrophy to temporal neocortex, with early asymmetric sparing of the hippoc us, this neuropsychological pattern suggests that the hippoc al complex plays a role in the acquisition and retrieval of recent memories, but is not necessary for the recall of older episodic events. In an alternative view of memory consolidation, however, the hippoc us plays a role in the retrieval of all autobiographical memories, regardless of the age of the memory [Curr. Opin. Neurobiol. 7(1997)217]. This 'multiple trace theory' predicts that patients with semantic dementia should show no effects of time in their autobiographical recall. In this article, we ask whether it is possible to reconcile the data from semantic dementia with the multiple trace theory by investigating whether the time-dependent pattern of autobiographical retrieval seen in the disease is due to (i) patients showing this effect being exceptional in their presentation and/or (ii) patients with semantic dementia exhibiting impaired strategic retrieval from concomitant frontal damage. A series of experiments in patients with semantic dementia, the frontal variant of frontotemporal dementia and Alzheimer's disease clearly demonstrates that neither of these two factors can explain the documented effect of time seen in semantic dementia. Nonetheless, we discuss how damage to semantic knowledge could result in an autobiographical memory deficit and suggest that data from semantic dementia may be consistent with both views of hippoc al involvement in long-term memory.
Publisher: Society for Neuroscience
Date: 03-09-2014
DOI: 10.1523/JNEUROSCI.0026-14.2014
Abstract: Transection of the nonhuman primate fornix has been shown to impair learning of configurations of spatial features and object-in-scene memory. Although damage to the human fornix also results in memory impairment, it is not known whether there is a preferential involvement of this white-matter tract in spatial learning, as implied by animal studies. Diffusion-weighted MR images were obtained from healthy participants who had completed versions of a task in which they made rapid same/different discriminations to two categories of highly visually similar stimuli: (1) virtual reality scene pairs and (2) face pairs. Diffusion-MRI measures of white-matter microstructure [fractional anisotropy (FA) and mean diffusivity (MD)] and macrostructure (tissue volume fraction, f ) were then extracted from the fornix of each participant, which had been reconstructed using a deterministic tractography protocol. Fornix MD and f measures correlated with scene, but not face, discrimination accuracy in both discrimination tasks. A complementary voxelwise analysis using tract-based spatial statistics suggested the crus of the fornix as a focus for this relationship. These findings extend previous reports of spatial learning impairments after fornix transection in nonhuman primates, critically highlighting the fornix as a source of interin idual variation in scene discrimination in humans.
Publisher: Oxford University Press (OUP)
Date: 13-03-2012
Abstract: Episodic memory has recently been shown to be impaired in the behavioral variant of frontotemporal dementia (bvFTD) when so-called non-progressive cases are excluded. Such non-progressive cases present with the behavioral features of bvFTD, but show no evidence of cognitive decline over time. To date, evidence regarding episodic memory performance in bvFTD subgroups on more stringent tasks is lacking. We investigated temporal and spatial source memory in progressive (n = 7) versus non-progressive (n = 12) bvFTD. BvFTD cases were retrospectively classified based on general cognitive decline on the Addenbrooke's Cognitive Examination Revised, and the presence of atrophy on structural neuroimaging, over 3 years following diagnosis. Progressors showed impaired temporal and spatial source retrieval. Non-progressors displayed temporal source deficits only. These differential source memory profiles point to the variability of episodic memory performance in bvFTD, and underscore the importance of differential diagnosis of bvFTD subgroups using longitudinal and neuroimaging data.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Kim Graham.