Effects of bilateral stimulation and stimulus redundancy on interhemispheric interaction.

Abstract

Recent visual laterality studies have included trials in which critical stimulus information is presented simultaneously in both visual half-fields and, thereby, simultaneously to both cerebral hemispheres. To investigate interhemispheric interaction, researchers compare performance on bilateral redundant trials with performance on unilateral trials in which a single copy of the target is presented to one hemisphere or the other. The authors used the identification of nonword letter trigrams to examine the relationship between unilateral and bilateral performance when the 2 types of trials were equated for the number of locations stimulated (Experiment 1) and the number of redundant copies of the target (Experiment 2). Results suggest that when the number of stimulated locations is held constant, each of 2 copies of a target stimulus can be processed with the same efficiency and the same strategy as it would have been had it been the only copy.

How the brain encodes the order of letters in a printed word: The SERIOL model and selective literature review

“…When stimuli are presented bilaterally, the error pattern that emerges is more similar to the LVF/RH pattern than to the RVF/LH pattern (Marks & Hellige, 1999). Thus, even though the LH is more effective than the RH at performing the task, the RH's mode of processing (i.e., error pattern) seems to dominate when the stimuli are presented to both hemispheres simultaneously.…”

“…Despite the unorthodox vertical format, we assume that encoding processes similar to those used for horizontal presentation were invoked. Hellige and colleagues (Hellige et al, 1995;Hellige & Scott, 1997;Marks & Hellige, 1999), in their analyses, also assume that the data from these experiments are relevant to normal string processing. More specifically, we assume that the elements of the string are mentally rotated to the canonical horizontal position, and, then, the rotated image is processed as usual.…”

“…Patterns of positional errors have also been taken as evidence for different hemispheric modes of processing (Hellige, Cowin, & Eng, 1995;Hellige & Scott, 1997;Marks & Hellige, 1999). Subjects were to identify quickly displayed CVC trigrams presented in a vertical column, with each letter in the upright position.…”

Effects of type of cognitive demand on bilateral advantage in interhemispheric processing

“…Recently, some studies (Banich & Belger, 1990;Banich & Karol, 1992;Marks & Hellige, 1999;Reuter-Lorenz, Stanczak, & Miller, 1999) have demonstrated BLA in relation to socalled redundancy gain, where BLA accrues when both hemispheres receive information compared with when only one hemisphere does.…”

Functional asymmetry and interhemispheric cooperation in the perception of emotions from facial expressions

“…For instance, the RTE has been shown using simple flashes (Corballis 2002;Savazzi and Marzi 2002), checkerboards (Miniussi et al 1998), shapes and colours (Mordkoff and Yantis 1993), letters (Grice and Reed 1992;Mordkoff and Miller 1993), and letterstrings (Marks and Hellige 1999), on healthy subjects as well as on neurological patients (with hemianopia and blindsight: de Gelder et al 2001;Marzi et al 1986;hemispherectomy: Tomaiuolo et al 1997;split-brain: Corballis 1995;Forster and Corballis 2000;Iacoboni et al 2000;Mohr et al 1994;Reuter-Lorenz et al 1994;Corballis 2002, 2003;and visual extinction: Marzi et al 1996). In normal viewers the RTE has also been demonstrated with meaningful stimuli such as words (Hasbrooke and Chiarello 1998;Mohr et al 1996), numbers (Ratinckx and Brysbaert 2002), drawings of animals or objects (Koivisto 2000), and familiar neutral faces (Mohr et al 2002).…”