Hemispheric Differences in a Novelty Task (original) (raw)
Related papers
Neuropsychologia, 2000
Two cognitive tasks (a letter memory task and a spatial memory task) designed to selectively activate the left or right hemisphere were combined with attentional probe tasks to measure how hemispheric activation aects attention to left and right hemi®elds. The probe task in Experiment 1 required the identi®cation of digits in the left and right hemi®eld. During the letter task, male subjects identi®ed more probes from the left hemi®eld than from the right. Their accuracy varied little across the two hemi®elds during the dots task. Experiment 2 tested whether this pattern is due to either spatial attention or interference in character processing. Instead of identifying digits, the probe task required subjects to respond to a black square that appeared in the periphery of the screen. For male subjects, the pattern was opposite of that from Experiment 1. During the letter task they responded faster to the probe in the right hemi®eld than in the left. Their response times were equivalent across the two hemi®elds during the dots task. These results indicate two separate eects of laterality in male subjects. The activation of one hemisphere produced more attention to the contralateral hemi®eld in Experiment 2, and the letter memory task interfered with the processing of other characters in the right visual ®eld more than those in the left visual ®eld in Experiment 1. Neither of these eects appeared in female subjects, corroborating earlier claims that female brains are less lateralized than male brains.
The cerebral basis of lateral asymmetries in attention
Acta Psychologica, 1970
Asymmetries in the processing of input to either side sf the midline are related to hemispheric specialization in man. These asymmetries arise when preponderant activation of one hemisphere biases attention to the contralatpral side. This l*nbalanced cerebral activation is a function of the nature of the subject's task or expectancy. A model of hemispheric integration is proposed.
Left and right hemisphere contributions to physiognomic and verbal discrimination
Neuropsychology, 2001
The relative contributions of the right-and left-temporal lobes in rapid recognition of faces and letters were studied in patients with anterior right-or left-temporal lobe excisions and a matched control group. On the basis of findings in patients with unilateral and bilateral brain damage, it was hypothesized that left hemisphere damage would not change the reaction time of letters analyzed by the right hemisphere and that right hemisphere damage would not change the reaction time of faces analyzed by the left hemisphere. The hypothesis was supported for letters but not for faces. Patients in the right-temporal group, particularly those with large hippocampal removals, were slow to recognize faces in both visual fields. Two possible explanations for the findings with faces are explored: One holds that right hemisphere mechanisms are involved even when a face is presented to the left hemisphere for rapid recognition; the other holds that specialized encoding is carried out by the right hemisphere during learning, with the encoded template then being used by each hemisphere independently.
Hemispheric asymmetries for global and local visual perception: Effects of stimulus and task factors
Journal of Experimental Psychology: Human Perception and Performance, 2001
Although neurological and physiological studies indicate a right hemisphere superiority in global processing and a left hemisphere superiority in local processing of Navon-type hierarchical letters (D. Navon, 1977), most investigations of lateralized perception in healthy participants report neither asymmetry. In 6 experiments the authors examined the influence of attentional demands, stimulus properties, and mode of response on perceptual asymmetries for global and local perception. Consistent with their theoretical predictions, asymmetries were more robust on divided-than focused-attention tasks and in response to stimuli in which local and global levels were equally salient compared with those with greater global than local saliency. Contrary to their prediction, perceptual asymmetries were not influenced by the complexity of the motor response.
Hemispheric differences in object identification
Although the right hemisphere is thought to be preferentially involved in visuospatial processing, the specialization of the two hemispheres with respect to object identification is unclear. The present study investigated the effects of hemifield presentation on object and word identification by presenting objects (Experiment 1) and words (Experiment 2) in a rapid visual stream of distracters. In Experiment 1, object images presented in the left visual field (i.e., to the right hemisphere) were identified with shorter display times. In addition, the left visual field advantage was greater for inverted objects. In Experiment 2, words presented in the right visual field (i.e., to the left hemisphere) under similar conditions were identified with shorter display times. These results support the idea that the right hemisphere is specialized with regard to object identification.
Hemispheric Differences in Global versus Local Processing: Still Unclear
Brain and Cognition, 1996
Laterality studies examining the recognition of hierarchical letter forms in normal subjects have had a checkered history. Early ones reported evidence of right hemisphere global and left hemisphere local processing, but later ones found little evidence of lateralized effects. Here three reaction time experiments examine suggestions made in the literature that the asymmetries appear only with small stimulus eccentricities, few experimental trials, or short stimulus exposures. No evidence is found to support a right-hemisphere-global and left-hemisphere-local distinction. However, Experiment 3 reports a shift toward right hemisphere processing of local letters as stimulus duration is curtailed, suggesting right hemisphere involvement when visual conditions are impoverished. These outcomes pose a challenge for clinical reports that differently lateralized cortical lesions have different effects on global and local processing.
Gender differences in hemispheric asymmetry for face processing
Background: Current cognitive neuroscience models predict a right-hemispheric dominance for face processing in humans. However, neuroimaging and electromagnetic data in the literature provide conflicting evidence of a right-sided brain asymmetry for decoding the structural properties of faces. The purpose of this study was to investigate whether this inconsistency might be due to gender differences in hemispheric asymmetry.