Biomedical subjects

I Gauthier

Publications and source records attributed to I Gauthier.

22 records · Page 2Linked to original sources

PubMed1997

Levels of categorization in visual recognition studied using functional magnetic resonance imaging.

BACKGROUND: Recent functional neuroimaging results implicate part of the ventral temporal lobe of the brain in face recognition, and have, together with neurophysiological findings, been used as evidence for a face-specific neural module in the brain. Experimental designs, however, have often failed to distinguish between the class of the object used as the stimulus (face or non-face) and the level of categorization at which the stimulus is recognized (the 'basic' level, such as 'bird', at which familiar objects are first recognized, or more subordinate levels - 'sparrow', for example - which require additional perceptual processing). We have used echo-planar functional magnetic resonance imaging to compare brain activation for the matching of non-face objects with subordinate-level and basic-level descriptors. RESULTS: The additional visual processing required to verify the subordinate level of a picture over its basic level was associated with activation of the fusiform and inferior temporal gyri (FIT) as well as the temporal poles. These areas correspond closely to those previously implicated in the processing of facial images. CONCLUSIONS: Our results indicate that areas of the ventral visual pathway that have been associated with face recognition are sensitive to manipulations of the categorization level of non-face objects. This idea offers an alternative to the dominant view that FIT may be organized according to conceptual categories, and our results establish the importance of manipulating task requirements when evaluating a 'neural module' hypothesis.

Brain Mapping↗

PubMed1997

Comparison of programs for preventing drug-nutrient interactions in hospitalized patients.

Three programs with different levels of pharmacist intervention designed to prevent drug-nutrient interactions (DNIs) were studied. Six drugs were selected for the study on the basis of their potential for involvement in significant DNIs and the hospital's drug-use profile. During a two-week control phase, the existing pharmacy system, in which no patient-specific information on DNIs is provided, was assessed. During the next four weeks, patients were randomly assigned to intervention 1, placement of a brightly colored label in the medication drawer and on the cover of the nursing medication card flip-chart, or to intervention 2, placement of the labels plus a five-minute structured patient-counseling session. Occurrence of DNIs and nurses' and patients' knowledge of DNIs were assessed. A DNI was defined as potentially altered drug absorption due to inappropriate timing or administration of a drug in relation to food. The occurrence of DNIs decreased significantly under the label system (from 24% to 19%) and under the combined label-counseling system (to 16%). However, the frequency of DNIs did not differ significantly between the two intervention groups. Patients' and nurses' knowledge of DNIs improved as a result of the interventions. The frequency of DNIs decreased when labels were used to alert nurses to proper medication timing.

Adult↗

PubMed1997

Becoming a "Greeble" expert: exploring mechanisms for face recognition.

Sensitivity to configural changes in face processing has been cited as evidence for face-exclusive mechanisms. Alternatively, general mechanisms could be fine-tuned by experience with homogeneous stimuli. We tested sensitivity to configural transformations for novices and experts with nonface stimuli ("Greebles"). Parts of transformed Greebles were identified via forced-choice recognition. Regardless of expertise level, the recognition of parts in the Studied configuration was better than in isolation, suggesting an object advantage. For experts, recognizing Greeble parts in a Transformed configuration was slower than in the Studied configuration, but only at upright. Thus, expertise with visually similar objects, not faces per se, may produce configural sensitivity.

Discrimination, Psychological↗

PubMed1997

Orientation priming of novel shapes in the context of viewpoint-dependent recognition.

Can visual similarity between shapes facilitate orientation priming? Five experiments are reported in which this possibility was explored by using novel two-dimensional shapes that formed homogeneous stimulus classes. After training on individual shapes in a canonical view, the recognition of these shapes was tested in several picture-plane orientations. In experiments 1 and 2 an identification task was used to replicate the classic finding obtained with the mirror-judgment task-that prior orientation cueing does not reduce the magnitude of orientation dependence in processing rotated shapes. The results of experiment 3, however, indicate that blocking trials by orientation is one condition in which orientation priming may be obtained. Experiment 4 builds on this result, and it is suggested that awareness of the blocking manipulation is not required to obtain orientation priming. In experiment 5 the mechanisms underlying this finding are explored, and evidence is offered that orientation priming is a consequence of representations that encode both shape and orientation. Such results may be considered as an extension to the 'image-based' approach to object recognition, demonstrating that generalization across exemplars may occur within recognition mechanisms that are viewpoint dependent.

Humans↗