Biomedical subjects

Stephan Bandelow

Publications and source records attributed to Stephan Bandelow.

3 recordsLinked to original sources

PubMed2006

Perirhinal cortex activity during visual object discrimination: an event-related fMRI study.

Previous fMRI studies have demonstrated preferential involvement of the perirhinal cortex and hippocampus in tasks of object and spatial memory, respectively. Here we investigated whether similar activity would also be present when object and spatial discrimination was assessed in the absence of explicit declarative memory demands. On each trial in the scanner, participants were presented simultaneously with two arrays of objects and were asked to indicate whether both arrays were identical, differed with respect to the identity of one object or differed with respect to the spatial arrangement of the objects. It was found that the detection of an object identity change was associated with significant right perirhinal cortex activity. We suggest that this perirhinal activity indicates a role of this structure in processes beyond declarative memory, for example, short-term visual working memory or higher order perception. Significantly greater hippocampal activity was not, however, observed during the spatial arrangement condition, perhaps due to the relatively low spatial processing demands of this task.

Adolescent↗

PubMed2006

Stochastic approaches to understanding dissociations in inflectional morphology.

Computer modelling research has undermined the view that double dissociations in behaviour are sufficient to infer separability in the cognitive mechanisms underlying those behaviours. However, all these models employ multi-modal representational schemes, where functional specialisation of processing emerges from the training process. Targeted lesioning of different regions of functional specialisation leads to varied but predictable deficits in model performance. We argue that multi-modal representational schemes are not a necessary condition for the observation of double dissociations in an information processing system that shares resources across multiple tasks. Using a uni-modal representational system, we demonstrate that double dissociations may also result from stochastic processes. Lesioning experiments on a single-route, uni-modal connectionist model of regular and irregular noun and verb morphology confirm and extend earlier work demonstrating that selective impairment across tasks can result from damage to a distributed information processing system. A systematic investigation of the degree to which performance deteriorates across different inflectional classes reveals that simple and double dissociations can occur in this single-route, uni-modal model. An important prediction of the model is that double dissociations between regular and irregular inflection, resulting from stochastic processes should be extremely rare. However, they are particularly likely to occur when the researcher uses test batteries consisting of a small number of items. Given that cognitive neuropsychologists rarely provide details about the distribution of performance in a disordered population, it is concluded that a stochastic interpretation of double dissociations may have wider applicability than is normally supposed.

Alzheimer Disease↗

PubMed2004

Telephone word-list recall tested in the rural aging and memory study: two parallel versions for the TICS-M.

BACKGROUND: Parallel versions of memory tasks are useful in clinical and research settings to reduce practice effects engendered by multiple administrations. We aimed to investigate the usefulness of three parallel versions of ten-item word list recall tasks administered by telephone. METHODS: A population based telephone survey of middle-aged and elderly residents of Bradley County, Arkansas was carried out as part of the Rural Aging and Memory Study (RAMS). Participants in the study were 1845 persons aged 40 to 95 years. Word lists included that used in the telephone interview of cognitive status (TICS) as a criterion standard and two newly developed lists. RESULTS: The mean age of participants was 61.05 (SD 12.44) years; 39.5% were over age 65. 78% of the participants had completed high school, 66% were women and 21% were African-American. There was no difference in demographic characteristics between groups receiving different word list versions, and performances on the three versions were equivalent for both immediate (mean 4.22, SD 1.53) and delayed (mean 2.35 SD 1.75) recall trials. The total memory score (immediate+delayed recall) was negatively associated with older age (beta = -0.41, 95%CI=-0.11 to -0.04), lower education (beta = 0.24, 95%CI = 0.36 to 0.51), male gender (beta = -0.18, 95%CI = -1.39 to -0.90) and African-American race (beta = -0.15, 95%CI = -1.41 to -0.82). CONCLUSIONS: The two RAMS word recall lists and the TICS word recall list can be used interchangeably in telephone assessment of memory of middle-aged and elderly persons. This finding is important for future studies where parallel versions of a word-list memory task are needed. (250 words).

Aged↗