Biomedical subjects

Cathy J Price

Publications and source records attributed to Cathy J Price.

39 records · Page 3Linked to original sources

PubMed2002

Is there an anatomical basis for category-specificity? Semantic memory studies in PET and fMRI.

Patients with semantic impairments sometimes demonstrate category-specific deficits suggesting that the anatomical substrates of semantic memory may reflect categorical organisation, however, neuroimaging studies have failed to provide consistent data in support of a category-based account. We conducted three functional neuroimaging experiments to investigate the neural correlates of semantic processing, two with positron emission tomography (PET) and a third with functional magnetic resonance imaging (fMRI). The first experiment used a lexical decision task to search for brain regions selectively activated by concepts from four different categories--animals, fruit, tools, and vehicles. The second experiment used a semantic categorisation task to increase the demands on the semantic system and to look for evidence of consistent activations for the domains of natural kinds or man-made items. The final experiment was a replication of the semantic categorisation task using fMRI to increase the spatial resolution and statistical sensitivity of the experiment. The results of these experiments reliably identified a distributed neural system common to both natural kinds and artifacts but failed to find robust evidence of functional segregation by domain or categories. Category effects were neither reliable nor consistently present across experiments although some were consistent with previous studies. We discuss the implications of these findings, arguing that they are most consistent with a semantic system undifferentiated by category at the neural level.

Adult↗

PubMed2002

Functional imaging studies of neuropsychological patients: applications and limitations.

Functional imaging studies of neuropsychologically impaired patients have not enjoyed the immediate success that was attained by functional imaging studies of normal subjects. This is largely because it has taken time to appreciate some of the deeper issues surrounding study design, analysis and interpretation. The most significant limitation is that functional imaging experiments with patients need tasks that the patients can perform. This precludes direct investigations of the physiological correlates of cognitive deficits. Nevertheless, functional imaging studies of brain-damaged patients who retain task competence can provide information that is not available from structural imaging, behavioural assessments or functional imaging with normal subjects. This is because intact task performance, following a brain lesion, does not necessarily entail normal neuronal responses in undamaged cortical areas. Abnormal neuronal responses, in the context of normal performance, can indicate alternative neuronal and cognitive mechanisms for supporting the same task. This, in turn, has important implications for understanding the mechanisms that mediate recovery and the organizational principles that underlie functional architectures in the human brain.

Brain Damage, Chronic↗

PubMed2002

Can segregation within the semantic system account for category-specific deficits?

Functional neuroimaging was used to investigate the extent to which category-specific semantic deficits in patients can be accounted for in terms of the demands placed on neural systems underlying different types of semantic knowledge. Unlike previous functional imaging studies of category specificity, we used a factorial design that crossed category (tools and fruits) with tasks requiring retrieval of either action or perceptual (real life size) knowledge. The presentation of tools relative to fruit increased activation in the same left posterior middle temporal area that was linked to the retrieval of action knowledge in general (for fruit as well as tools). However, we found no correlation between activation evoked by fruit and the size retrieval task. The left medial anterior temporal cortex was the only region to be activated for fruit relative to tools. We argue that the sensory-functional theory of category-specific effects is insufficient to account for the current neuroimaging literature. However, the data do support a more refined version of the theory: tools, relative to fruit, are more strongly linked to manipulative/motor knowledge and, for some tasks, fruit may be more reliant on integrating multiple semantic features.

Adult↗