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Biomedical subjects

A L Shelton

Publications and source records attributed to A L Shelton.

5 recordsLinked to original sources

Systems of spatial reference in human memory.

Seven experiments examined the spatial reference systems used in memory to represent the locations of objects in the environment. Participants learned the locations of common objects in a room and then made judgments of relative direction using their memories of the layout (e.g., "Imagine you are standing at the shoe, facing the lamp; point to the clock"). The experiments manipulated the number of views that observers were allowed to experience, the presence or absence of local and global reference systems (e.g., a rectangular mat on which objects were placed and the walls of the room, respectively), and the congruence of local and global reference systems. Judgments of relative direction were more accurate for imagined headings parallel to study views than for imagined headings parallel to novel views, even with up to three study views. However, study views misaligned with salient reference systems in the environment were not strongly represented if they were experienced in the context of aligned views. Novel views aligned with a local reference system were, under certain conditions, easier to imagine than were novel views misaligned with the local reference system. We propose that learning and remembering the spatial structure of the surrounding environment involves interpreting the layout in terms of a spatial reference system. This reference system is imposed on the environment but defined by egocentric experience.

Adult↗

Visual memories from nonvisual experiences.

Many common activities rely on spatial knowledge acquired from nonvisual modalities. We investigated the nature of this knowledge by having people look at a collection of objects on a desktop and manually reconstruct their arrangement, without vision, as though the display had been rotated by 0 degrees 45 degrees 90 degrees 135 degrees or 180 degrees relative to the view they could see. Performance on several measures of visual-spatial memory showed that participants had better visual memory for the view they had manually reconstructed than for the view they had studied visually for several minutes. These findings provide compelling new evidence that visual-spatial knowledge of very high fidelity can be acquired from nonvisual modalities, and reveal how, visual and nonvisual spatial information may even be confused in the brain.

Discrimination Learning↗

Mental representations of large and small spatial layouts are orientation dependent.

Previous research on spatial memory indicated that memories of small layouts were orientation dependent (orientation specific) but that memories of large layouts were orientation independent (orientation free). Two experiments investigated the relation between layout size and orientation dependency. Participants learned a small or a large 4-point path (Experiment 1) or a large display of objects (Experiment 2) and then made judgments of relative direction from imagined headings that were either the same as or different from the single studied orientation. Judgments were faster and more accurate when the imagined heading was the same as the studied orientation (i.e., aligned) than when the imagined heading differed from the studied orientation (i.e., misaligned). This alignment effect was present for both small and large layouts. These results indicate that location is encoded in an orientation-dependent manner regardless of layout size.

Female↗

Human hypersensitivity to a sham vaccine prepared from mosquito-cell culture fluids.

A sham vaccine, prepared with the C6/36 cell line derived from larval Aedes albopictus mosquitoes, was skin tested on 12 volunteers. Although no reactions were observed after prick tests, three immediate reactions did occur after intradermal tests. Subcutaneous administration of the C6/36 sham vaccine was initially performed on the nine subjects who did not demonstrate immediate reactions. Five of these subjects developed delayed reactions at the site of the intradermal test within 12 hr after inoculation. A Prausnitz-Küstner test was performed on the back of one unsensitized subject by use of both unheated and heated sera from three subjects who had immediate skin reactions, three who demonstrated a delayed reaction, and one who had a negative skin response. In the Prausnitz-Küstner test, immediate skin reactions were observed with all seven unheated sera but with none of the heated serum aliquots. The determination that skin reactivity was associated with a heat-labile serum factor suggested the mechanism was IgE-mediated. Under close surveillance, the C6/36 sham vaccine was administered subcutaneously to one volunteer who had previously demonstrated an immediate response. This subject developed an anaphylactic reaction characterized by hives at the site and more distantly from the site of the subcutaneous inoculation. Hypersensitivity to A. albopictus larval antigens is common and precludes the use of C6/36 cell culture as a substrate for viral vaccines.

Cells, Cultured↗