Allocentric Versus Egocentric Neglect in Stroke Patients: A Pilot Study Investigating the Assessment of Neglect Subtypes and Their Impacts on Functional Outcome Using Eye Tracking.

Objective: Few studies have investigated the assessment and functional impact of egocentric and allocentric neglect among stroke patients. This pilot study aimed to determine (1) whether allocentric and egocentric neglect could be dissociated among a sample of stroke patients using eye tracking; (2) the specific patterns of attention associated with each subtype; and (3) the nature of the relationship between neglect subtype and functional outcome.

Method: Twenty acute stroke patients were administered neuropsychological assessment batteries, a pencil-and-paper Apples Test to measure neglect subtype, and an adaptation of the Apples Test with an eye tracking measure.

Enhancing the ecological validity of tests of lateralization and hemispheric interaction: Evidence from fixated displays of letters or symbols of varying complexity.

Two experiments expand upon behavioural evidence of interactions among lateralization, hemispheric interaction, and task complexity with findings from an ecologically valid procedure. Target displays of letters or symbols were presented at fixation in go/no-go matching tasks of physical or categorical identity. Simultaneously with the target, a distractor appeared in the left visual field or right visual field to weight processing of the target to the hemisphere ipsilateral to the distractor, or the distractor did not appear at all.

List constituency and orthographic and phonological processing: a shift to high familiarity words from low familiarity words.

Two lexical decision experiments build on established patterns of laterality and hemispheric interaction to test whether the presence of low familiarity words dynamically affects the use of an orthographic or phonological strategy for high familiarity words; and, if so, whether the hemispheres are similarly flexible in adapting to the constituency change. Experiment 1 restricted word strings to the highly familiar. Experiment 2 presented the same high familiarity words, along with an equal number of low familiarity words.

Hemispheric interaction, task complexity, and emotional valence: evidence from naturalistic images.

Two experiments extend the ecological validity of tests of hemispheric interaction in three novel ways. First, we present a broad class of naturalistic stimuli that have not yet been used in tests of hemispheric interaction. Second, we test whether probable differences in complexity within the class of stimuli are supported by outcomes from measures of hemispheric interaction.

The brain's hemispheres and controlled search of the lexicon: evidence from fixated words and pseudowords.

Difference between the brain's hemispheres in efficiency of intentional search of the mental lexicon with phonological, orthographic, and semantic strategies was investigated. Letter strings for lexical decision were presented at fixation, with a lateralized distractor to the LVF or RVF. Word results revealed that both hemispheres were capable of using each of the three strategies, but the right hemisphere had better baseline processing of orthography and was better at processing semantics.

Reading disability and hemispheric interaction on a lexical decision task.

The assumptions tested were that the relative contribution of each hemisphere to reading alters with experience and that experience increases suppression of the simultaneous use of identical strategies by the non-dominant hemisphere. Males that were reading disabled and phonologically impaired, reading disabled and phonologically normal, or with no reading disability were presented familiar words, orthographically correct pseudowords, and orthographically incorrect non-words for lexical decision. Accuracy and response times in all groups showed a shift from no asymmetry in processing non-words to a stable left hemisphere advantage and clear suppression of the right hemisphere in processing words.

Conflicting strategies and hemispheric suppression in a lexical decision task.

The research tests the prediction of the inhibitory-interaction hypothesis that experience with a task accentuates the functional imbalance between the hemispheres. Right-handed males who were experienced readers were presented a letter string to the centre visual field for lexical decision. The string was or was not accompanied by a blinking light to the left or right visual field.

Laterality and pattern persistence in bistable motion perception.

Bistable motion perception refers to two competing perceptions that can result when frames consisting of three elements are displaced laterally by one element. At short inter-frame intervals, the dominant percept is that the end elements in the display are moving; at long inter-frame intervals, perception is of all the elements moving coherently to the right or left. This research shows that coherent motion is more likely to be perceived when presentations are parafoveal than foveal and when they are to the right visual field than the left visual field.