Biomedical subjects

Ann D Gathers

Publications and source records attributed to Ann D Gathers.

3 recordsLinked to original sources

PubMed2003

Shared and dissociated cortical regions for object and letter processing.

The present study determined the extent to which object and letter recognition recruit similar or dissociated neural resources. Participants passively viewed and silently named line drawings of objects, single letters, and visual noise patterns and centrally fixated an asterisk. We used whole-brain functional MRI and a very conservative approach to hypothesis testing that distinguished among brain regions that were selectively activated by different experimental conditions and those that were conjointly activated. The left fusiform gyrus (BA 19 & 37) and left inferior frontal cortex BA(44/6) showed a greater degree of conjoined activation for objects and letters than selective activation for either category, whereas left inferior parietal cortex (BA 40) and the left insula showed a strong letter-selective response. Equal recruitment of left fusiform and inferior frontal regions by objects and letters reflects similar demands on cognitive processing by these two categories and argues against category-specific modules in these regions. However, cortical systems for object and letter processing are not completely shared given the exclusive activation of left inferior parietal cortex by letters.

Adult↗

PubMed2003

Effects of structural similarity on neural substrates for object recognition.

Human occipitotemporal cortex (OTC) is critically involved in object recognition, but the functional organization of this brain region is controversial. In the present study, functional magnetic resonance imaging (fMRI) signal changes were recorded in humans during an animal-matching task that parametrically varied degree of structural (i.e., shape) similarity among the items. fMRI signal in the mid- to anterior-fusiform gyrus increased as animals overlapped more in terms of structure and as reaction time increased. In contrast, relatively more posterior aspects of the fusiform gyrus and inferior occipital cortex showed greater fMRI signal when the animals overlapped less in terms of structure. A similar organization emerged when three-dimensional geometric shapes were matched, indicating that OTC is differentially tuned to varying degrees of overlap in object structure, regardless of taxonomic category. We discuss how the present findings fit in with current functional neuroanatomical approaches to object recognition.

Adult↗

PubMed2002

Natural and manufactured objects activate the fusiform face area.

Recent fMRI studies indicate that the anterior fusiform gyrus (the fusiform face area, FFA) is specialized for face recognition. However, the analyses used to determine face selectivity have not ruled out the possibility that other object categories produce significant activation in the FFA, relative to baseline. In the current fMRI study, we use a conservative hypothesis testing approach to show that FFA activation is not selective for faces. Rather, the FFA response is almost completely explained by a graded response in which faces produce more activation than either manufactured or natural objects, but those categories produce a statistically greater response than the baseline task. These findings question whether the FFA can be interpreted as a specialized module for face recognition.

Adult↗