Functional organization of the right nondominant cortex: Evidence from electrical stimulation.

Studied discrete functional localization for visuo-perceptual, spatial, and nonverbal memory tasks in conjunction with focal electrical stimulation of the exposed right-dominant cortex during awake craniotomies in 22 patients. Results provide evidence for discrete functional localization in the right, nondominant hemisphere. Performance on each task was significantly impaired in association with stimulation of some, but not all, sites in comparison with performance on nonstimulation control trials. There was, generally, a strong dissociation of sites involved in separate functions across individual Ss. Contrary to the notion of diffuse functional organization in the nondominant hemisphere, visuospatial functions in the right hemisphere appear to be as discretely localized as verbal functions in the left hemisphere. Language and language-related functions of naming, reading, short-term verbal memory, nonverbal oral-facial movement, and phonemic identification were assessed in a subgroup of 10 Ss in conjunction with right nondominant cortical stimulation. In right-handed Ss, no disruptions of these tasks were seen with stimulation of sites outside the right face motor cortex itself. In 2 case studies, there was evidence for right cortical involvement in the mediation of 2 nonphonetic symbol-based language systems: Japanese Kanji and Fortran. (French abstract) (72 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Choosing sides: The left and right of the normal brain.

One view of brain organization holds that the left cerebral hemisphere controls language processes, while the right hemisphere deals with various nonverbal activities such as visuospatial tasks. It is argued that a substantial proportion of the population deviates from this modal model, and that the investigation of individual differences in brain organization through careful studies of neurologically intact Ss is critical to the understanding of cerebral function. Deviations from the modal model are seen as normal and genetically determined, rather than pathological in origin. It is suggested that different functions, such as handedness, language, and visuospatial ability, are lateralized by relatively independent mechanisms, and therefore can be dissociated. Evidence for a positive relation between brain lateralization and cognitive ability is presented. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The /O/ in OVER is different from the /O/ in OTTER: Phonological effects in children with and without dyslexia.

First-letter naming was used to investigate the role of phonology in printed word perception in children with and without dyslexia. In 2 experiments, all children showed faster first-letter-naming times in a congruent condition than in an incongruent condition, which suggests that phonology is a fundamental constraint in the printed word perception of readers of all levels and all skills. An explanation in terms of a recurrent network put forward by G. C. Van Orden and S. D. Goldinger (1996) is discussed to account for the apparent paradox in the reading behavior of readers with dyslexia, that is, that in first-letter naming, dyslexic readers appear to show phonological congruity effects, whereas in pseudoword reading, their phonological knowledge appears to be deficient or absent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for two types of spatial representations: Hemispheric specialization for categorical and coordinate relations.

Analyses of human object recognition abilities led to the hypothesis that 2 kinds of spatial relation representations are used in human vision. Evidence for the distinction between abstract categorical spatial relation representations and specific coordinate spatial relation representations was provided in 4 experiments. These results indicate that Ss make categorical judgments—on/off, left/right, and above/below—faster when stimuli are initially presented to the left cerebral hemisphere, whereas they make evaluations of distance—in relation to 2 mm, 3 mm, or 1 in. (2.54 cm)—faster when stimuli are initially presented to the right cerebral hemisphere. In addition, there was evidence that categorical representations developed with practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric changes in information processing during development.

Hemispheric processing of visually presented words and pictures was examined in 3 groups of Ss with mean ages of 8 yrs 8 mo, 12 yrs 3 mo, and 27 yrs 9 mo (154 Ss). Pictorial or symbolic stimuli were presented singly to either the right or left visual hemifield. Ss had to decide whether the 1st stimulus in a pair matched the 2nd stimulus. The major results were that (a) age groups differed in the strength of lateral differences, and (b) for all age groups, the right hemisphere was significantly faster in processing unmatched stimuli. Results suggest that lateral specialization of the left hemisphere is not complete until adolescence and that over the age range tested, the left hemisphere becomes progressively more specialized for the processing of matched data. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric differences for identification of words and nonwords in urdu-English bilinguals.

Hemispheric asymmetry was examined for Urdu-English bilinguals identifying printed Urdu words and nonwords, separated Urdu letter strings, digits, and English nonwords. In all cases, fewer errors occurred when stimuli were presented to the right visual field/left hemisphere (RVF/LH) than to the left visual field/right hemisphere (LVF/RH). Qualitative error patterns suggested that separated Urdu letter strings were processed more serially than Urdu letter strings joined to form words or pronounceable nonwords and more serially on RVF/LH than on LVF/RH trials. This qualitative laterality effect is similar to that found for Hebrew and Arabic but opposite that found for English and suggests that the qualitative manner of processing printed verbal material is influenced by language-specific factors such as scanning direction, orthographic-to-phonological mapping rules, and morphology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in hemispheric specialization for tactile spatial ability.

64 1st-, 3rd, and 5th-grade children and adults (16 in each group) performed a tactile shape-discrimination task. On each of 40 trials, after exploring a randomly generated nonsense form using only finger motion, Ss judged a tactually presented comparison form as either the same as or different from the 1st stimulus. In Condition 1, a single stimulus form and the comparison form were successively presented to the same hand. In Condition 2, stimulus forms were simultaneously presented to both hands; however, a comparison form was presented to only one hand. Results indicate that the left hand (right hemisphere) was more accurate than the right hand (left hemisphere) for 5th-grade Ss and adults, but no significant differences between hands were found for 1st- and 3rd-grade Ss. Overall, Condition 2 was more difficult than Condition 1, but similar laterality effects were found in both groups. Sex differences were found only in the adult group in which males made somewhat fewer errors than females. These results suggest that the right hemisphere becomes progressively more specialized for tactile spatial ability with increasing age. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure to improve readability with a vertical typography.

3 experiments found conventional horizontal typography to be superior to vertical. 1 experiment presented the stimulus tachistoscopically in a procedure quite similar to the procedure used in an earlier experiment that found vertical typography to be superior to conventional even with unpracticed Ss. 2 of the experiments used Ss who had been given practice reading 8000 words printed in vertical typography. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric asymmetry in Down's Syndrome children.

Examined auditory processing of linguistic stimulation presented dichotically to groups of 30 Down's Syndrome (DS) children, 20 non-DS retarded children who were MA and CA matched, and 20 MA matched nonretarded children, all of whom were right-handed. Ss completed a knowledge-of-numbers test and the Slosson Intelligence Test. They then listened to 20 trials of a dichotic message at approximately 70–75 db and repeated digits they heard. DS Ss showed a significant left ear advantage in processing the auditory linguistic material, while the other Ss showed the normal right ear advantage. Findings corroborate that having DS has a specific effect on the functional organization of the CNS auditory system. The right hemisphere may not be as efficient as the left hemisphere at language processing. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorization of disoriented faces in the cerebral hemispheres of normal and commissurotomized subjects.

We examined the capacity of the cerebral hemispheres to process faces that deviate from canonical perspective. In Experiment 1, normal Ss performed a gender categorization of faces presented at varying angular orientations in the left visual field (LVF) or right visual field (RVF). Orientation affected processing speed, more so in the RVF than in the LVF. The function relating reaction times to disorientation of the faces was approximately monotonic and reflected the increased difficulty in extracting relevant configurational information as the faces were rotated from canonical perspective. In Experiment 2, 3 commissurotomized Ss performed the same task. They responded above chance in the 2 visual fields, and the pattern of their results was similar to that obtained with the normal Ss, but the effect of disorientation was considerably more pronounced. It is suggested that the right hemisphere contribution becomes more critical the further the visual pattern departs from conventional view. Issues regarding the specification of processes correcting for disorientation and comparison of normal and commissurotomized Ss are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scanning and the familiarity effect in tachistoscopic recognition.

Tachistoscopically presented to 16 undergraduates pseudowords of 1st- or 4th-approximation to English. The pseudowords were printed in normal or in reversed orientation, and Ss were required to report the material from left to right or from right to left. Recall was lower when reporting right-left than when reporting left-right. However, the familiarity effect was controlled by the orientation of the letter sequences, not the direction of report. Results are discussed in terms of a scanning model for the familiarity effect. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

French immersion and hemispheric language processing: A dual-task study.

32 right-handed high school boys in early or late French immersion programs and 16 nonimmersion, unilingual high school boys performed verbal tasks (reading aloud and identifying pictures) in English and French while finger-tapping with the index finger of their left or right hand. Disruption scores were calculated and used to infer contralateral hemispheric involvement. All Ss showed significantly greater disruption with right-hand tapping, indicating high levels of left hemisphere involvement. Results confirm that early and late bilinguals do not differ from each other or from unilinguals in the hemispheric processing of language. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in the representation of visuospatial functions in the human brain.

Investigated sex differences in the representation of visuospatial functions in the human brain in 20 Ss with right hemisphere stroke and 40 stroke-free control Ss with the Complex Figure Test, Wechsler Adult Intelligence Scale—Revised (WAIS—R) Block Design, and Judgment of Line Orientation. Also, 3 models of sex differences in the representation of visuospatial functions in the human brain were evaluated. The stroke and control groups were composed of equal proportions of men and women. Results suggest that women may be disproportionately impaired in visuospatial functioning relative to men following right hemisphere stroke. It is proposed that visuospatial functions were bilaterally represented in the brains of men, allowing them to rely upon left hemisphere visuospatial systems following right hemisphere stroke, and that these functions were represented in the right hemisphere of women, resulting in their disproportionate impairment despite comparable lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Choice reaction-time study assessing the verbal behavior of the minor hemisphere in normal adult humans.

Conducted 2 choice RT experiments in which a total of 12 right-handed college students scanned a memory set of 1 or 6 letters for the presence of a test letter. The memory set was presented binaurally and the test letter visually to either the right or left visual field. S indicated with his left hand whether or not the test letter was contained in the memory set. Results show the RT was shorter for the left visual field test letter when the set contained only 1 letter and for the right visual field test letter when the set contained 6 letters. The possibility that Ss matched the set and test letters visually when the set contained only 1 letter and verbally when the set contained 6 letters is discussed. Results suggest that the minor hemisphere displays little, if any, verbal abilities. (31 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual laterality and iconic recognition of visual materials by Korsakoff patients and normal adults.

Compared 9 male patients with Korsakoff's syndrome to 19 normal and 11 alcoholic control Ss on their threshold for recognition of words or patterns presented monocularly to the lateral visual fields. Ss were then tested on backward visual masking of the same (target) stimuli to determine the interstimulus interval (ISI) needed to escape the masking effect (critical ISI) in each lateral field. Threshold for recognition and critical ISI were elevated in Korsakoff Ss. For all Ss, the right visual field was superior to the left for word recognition but not for pattern recognition. The critical ISIs were shorter in the right visual field for both types of material, suggesting that the dominant hemisphere is more efficient in the early (iconic) stages of information processing. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anxiety and perceptual structure: Individual differences in neuropsychological function.

Studied the cognitive performance of 24 high and 36 low trait anxious undergraduates under conditions of high and low situational stress, using tasks requiring greater contribution of the right or left hemisphere. In addition, a perceptual task was adapted from visual information processing research to assess Ss' global or analytic approaches to perception; if anxiety increased the left hemisphere's contribution to perception, anxious Ss might be expected to be more analytic and detail oriented. Results show no significant differences on left hemisphere tasks but a significant interaction of trait by state anxiety for right hemisphere tasks: Low trait Ss performed better and high trait Ss performed more poorly under situational stress. Trait anxiety showed a significant main effect on visual information processing strategy, low Ss tending to be more global and high Ss tending to process the stimulus analytically. Results support the utility of a neuropsychological model in describing the effects of emotion on perception. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dividing attention between the hands and the head: Performance trade-offs between rapid finger tapping and verbal memory.

Tested a multiple resources approach to time-sharing performance which assumes that each cerebral hemisphere controls its own set of processing resources that it cannot share with the other hemisphere. Right-handed men performed a verbal memory task while concurrently tapping the index finger of either hand as rapidly as possible. Task priority was manipulated with a payoff scheme. Ss remembered more on the verbal task when concurrently tapping with their left hands than when tapping with their right hands, and their memory performance was much better when the memory task was emphasized than when the tapping task was emphasized, regardless of hand. For the tapping task, decrements from baseline tapping rates and trade-offs between tasks were equal for both hands when Ss were reading the to-be-remembered words aloud. In contrast, during the retention interval, decrements were larger for the right hand than the left, and there were no task trade-offs. On right-hand trials, both tasks required exclusively left-hemisphere resources, whereas on left-hand trials, right-hemisphere resources were required to execute the tapping movements per se, but left-hemisphere resources were necessary to coordinate those movements with the movements required for overt speech. The data underscore the importance of manipulating task priority to obtain an accurate picture of a task's resource requirements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phonetic recoding of phonologically ambiguous printed words.

Speech detection and matching simultaneously presented printed and spoken words were used to examine phonologic and phonetic processing of Hebrew heterophonic homographs. Ss detected a correspondence between an ambiguous letter string and the amplitude envelopes of both dominant and subordinate phonological alternatives. Similar effects were obtained when the homographs were phonologically disambiguated by adding vowel marks. The matching of the unpointed printed forms of heterophonic homographs to the dominant and subordinate spoken alternatives presented auditorily was as fast as matching the pointed unambiguous forms to the respective spoken words. This outcome was not obtained when print and speech were not presented simultaneously. These results suggest that printed heterophonic homographs activate the 2 spoken alternatives they represent and provide further confirmation for fast phonetic recoding in reading. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abstract visual-form representations in the left cerebral hemisphere.

Visual-form systems in the cerebral hemispheres were examined in 3 experiments. After learning new types of visual forms, participants rapidly classified previously unseen prototypes of the newly learned types more efficiently when the forms were presented directly to the left hemisphere (in the right visual field) than when the forms were presented directly to the right hemisphere (in the left visual field). Neither previously seen nor previously unseen distortions of the prototypes were classified more efficiently when presented directly to the left hemisphere than when presented directly to the right hemisphere. Results indicate that an abstract visual-form system operates effectively in the left hemisphere and stores information that remains relatively invariant across the specific instances of a type of form to distinguish different types. Furthermore, this system functions relatively independently of another system that operates effectively in the right hemisphere and that stores details to distinguish specific instances of a type of form. (PsycINFO Database Record (c) 2010 APA, all rights reserved)