Development of selective listening and hemispheric asymmetry.

In 2 experiments binaural and dichotic tasks of varying complexity were given to 64 7- and 9-yr-old children to investigate the interaction of laterality and selective attention. One of each digit pair was spoken by a male and the other by a female. Ss recalled 3 of the digits spoken in a specified voice. With the attended voice in one ear, performance improved relative to the binaural condition in both age groups. However, when location and voice cues were uncorrelated, the younger Ss' performance was more adversely affected. The right ear advantage (REA) increased as a function of task difficulty. With slow presentation rates, the REA remained constant with age but decreased with age in the faster conditions, which was opposite to the predicted increase in cerebral asymmetry of language function with age. The 7-yr-olds responded according to their perceptual asymmetry, recalling right-ear items whether the attended voice was in the left or right ear. The developmental changes in selective attention are explained by a capacity model. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multitask investigation of individual differences in hemispheric asymmetry.

Right-handed subjects (N?=?120) participated in four different laterality tasks designed to measure aspects of cerebral hemisphere asymmetry: identification of dichotically presented consonant-vowel syllables (CVs), examination of the effects of concurrent repetition of CVs and concurrent anagram solution on finger-tapping by the right and left hands, lateralized identification of CVs presented tachistoscopically to the left and right visual fields, and left/right biases on a free-vision face task involving judgments of emotion. Ear differences in the dichotic listening task were related to the pattern of lateralized interference in the dual-task finger-tapping paradigm. There were no other significant relations between pairs of tasks, but when the present results are considered in the light of other recent experiments, there appears to be a relation between lateral bias on the free-vision face task and visual field differences in tachistoscopic identification. The pattern of results has implications for hypothesized individual differences among right-handers in cerebral dominance for verbal processes, input pathway dominance, and asymmetric arousal of the two cerebral hemispheres. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distributions of hemispheric asymmetry in left-handers and right-handers: Data from perceptal asymmetry studies.

Although hemispheric asymmetry among individuals is often treated as a categorical variable with 3 values (i.e., left hemisphere dominance, right hemisphere dominance, and bilateral dominance), it is best viewed as a continuously distributed variable ranging from strong asymmetry in favor of the left hemisphere through nearly equal asymmetry to strong asymmetry in favor of the right hemisphere. The present study compared distributions of hemispheric asymmetry in left- and right-handers, based on behavioral indexes of hemispheric asymmetry, such as visual field asymmetry on divided visual field tasks and ear asymmetry on dichotic listening tasks. Meta-analyses of prior studies using these indexes indicate that distributions of hemispheric asymmetry in left- and right-handers differ both in the mean and in the variance. Right-handers have greater mean hemispheric asymmetry than left-, whereas left-handers have greater variance in hemispheric asymmetry than right-handers. Within left-handers, those without sinistral relatives have greater variance in hemispheric asymmetry than those with sinistral relatives, suggesting that sinistral patterns of hemispheric asymmetry determined by environmental factors may be more variable than those determined by genetic factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences and similarities in patterns of cerebral hemispheric asymmetry.

Younger (M age?=?20.4 years) and older (M age?=?70.7 years) adults participated in 3 visual half-field experiments. These were designed to examine specific aspects of hemispheric asymmetry: (a) hemispheric dominance for phonetic–linguistic processing (as measured by identification of nonword trigrams), (b) hemispheric differences in trigram processing strategy, (c) characteristic perceptual biases thought to reflect hemispheric arousal asymmetries, and (d) hemispheric dominance for processing emotions shown on faces. Patterns of left–right asymmetries were comparable for older and younger participants, and intercorrelations among the various measures of asymmetry were similar for both groups. In view of the present results, it seems unlikely that changes in hemispheric asymmetry contribute significantly to age-related changes in cognitive functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the input in visual hemispheric asymmetries.

Because the nature of the input is one of the most important variables in determining how the brain will process information, findings from tachistoscopic studies aimed at assessing hemispheric lateralization of functions are examined in terms of the characteristics of the incoming information either available or required for processing. The basic features of tachistoscopic experiments are analyzed with a special emphasis on methodology. Variables determining the quality of the input are investigated as a function of the properties of the human visual system. Exposure duration, luminance, retinal eccentricity, and stimulus size all contribute to the efficiency of the hemispheres and interact in complex ways in the emergence of visual-field superiorities. Task demands are also examined in terms of the information necessary for efficient processing. The present review suggests that in tachistoscopic experiments, the factors determining the quality of the input must be controlled if this technique is to prove a reliable source of information for assessing hemispheric asymmetries. (5 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lateral eye movements and hemispheric asymmetry: A critical review.

Eye movements to the left or right have been hypothesized to reflect activation of the cerebral hemisphere contralateral to the direction of gaze. This hypothesis was tested by comparing the direction of lateral eye movements (LEMs) following questions designed to engage the left or right hemisphere. The evidence from such studies was equivocal. Fewer than half found the predicted pattern of more right LEMs for left-hemisphere questions, and conceptual and methodological ambiguities in the questions, scoring, and experimental situation made interpretation of these studies difficult. In addition, findings showing more upward eye movements and more stares for right-hemisphere questions cannot be incorporated into the hemispheric asymmetry model of LEMs. Studies on individual differences in LEM patterns indicated a fair degree of stability and some consistency in their correlates. However, since "right" and "left movers" do not differ in verbal or spatial abilities, there is little justification for linking LEM patterns with "hemisphericity." It is concluded that further research on the relationship between directional ocular events and cognitive-affective processes is required before inferences about hemispheric function can be drawn from studies of lateral eye movements. (2? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivation, affect, and hemispheric asymmetry: Power versus affiliation.

In 4 experiments, the authors examined to what extent information related to different social needs (i.e., power vs. affiliation) is associated with hemispheric laterality. Response latencies to a lateralized dot-probe task following lateralized pictures or verbal labels that were associated with positive or negative episodes related to power, affiliation, or achievement revealed clear-cut laterality effects. These effects were a function of need content rather than of valence: Power-related stimuli were associated with right visual field (left hemisphere) superiority, whereas affiliation-related stimuli were associated with left visual field (right hemisphere) superiority. Additional results demonstrated that in contrast to power, affiliation primes were associated with better discrimination between coherent word triads (e.g., goat, pass, and green, all related to mountain) and noncoherent triads, a remote associate task known to activate areas of the right hemisphere. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Processing of preconsciously acquired information measured by hemispheric asymmetry and selection accuracy.

Two groups of 14 right-handed female undergraduates saw a series of slides for 1 msec. Subsequently, these slides were paired with similar but novel slides. One group was asked to view the pairs analytically and to select the one they thought they had seen before. The other group was asked to view the pairs holistically and indicate which of the 2 they preferred. Results support the hypothesis that analytically instructed Ss would be more likley to engage the parietal region of their left hemisphere and holistically instructed Ss would favor relative activation of the right parietal region. An inverse relation was also detected between parietal laterality and selection accuracy. It is suggested that differential hemispheric involvement may account for the observation that affective discrimination can be performed in the absence of conscious awareness. Findings are discussed in terms of a memory model of information processing. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of sensory limitations on hemispheric processing.

How the brain processes information is partly determined by the characteristics of the input. To examine whether the 2 cerebral hemispheres are equally affected by manipulations of quality of incoming information, 3 experiments using M. I. Posner and R. F. Mitchell's (1967) paradigm (matching pairs of letters of same or different case or name) were conducted under 8 viewing conditions, consisting of manipulations of exposure duration, retinal eccentricity, and stimulus size. The same procedure but different designs were used in the 3 studies: a between-S design in Exp I; a within-S design with viewing conditions blocked in Exp II; and a within-S design with viewing conditions mixed in Exp III. In all experiments, which used 88 18–30 yr old right-handed Ss, exposure duration and retinal eccentricity each interacted with visual fields, whereas the interaction of letter size and visual field was significant only in Exp II. Results are interpreted with respect to the properties of the visual system and its capacity to extract information in terms of the spatial-frequency spectral components of a stimulus. Methodological implications are discussed. (French abstract) (2? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential hemispheric processing of faces: Methodological considerations and reinterpretation.

Examines the procedures and stimuli (physiognomies) used in lateralized face recognition experiments with normal Ss, as well as in related perceptual and identification experiments. Results reveal that in general a left visual field (right hemisphere) advantage is obtained when: (a) stimulus information is degraded; (b) faces to be compared are highly discriminable; (c) set of unfamiliar faces is used; and (d) task requirements allow a lax criterion of recognition. These conditions seem to make holistic processing adequate for the task; if the conditions require analytic judgments, then a right visual field (left hemisphere) advantage may be obtained. Thus, no hemifield has an inherent or absolute advantage and these procedural conditions may critically determine what hemifield advantage is observed in any given experiment with faces (or other types of stimuli). Apparently, both hemispheres may contribute to the processing of faces but their contributions vary as a function of task demands. A right hemisphere advantage may reflect an enhanced role of the processes of configuration, completion, categorization, or set. A left hemisphere advantage need not involve the language function but it may reflect a genuine visuospatial contribution. (60 ref) (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)     

Age and the selectivity of visual information processing.

Two experiments assessed age differences in the selectivity of visual information processing. Selectivity was measured by the amount of interference caused by nontarget letters when Ss detected a target letter in a visual display. In both experiments, young and elderly groups participated in search and nonsearch conditions; in the search condition, targets appeared anywhere in the display, whereas in the nonsearch condition targets were confined to the center position of the display. In Exp I, 20 19–27 yr olds and 20 65–90 yr olds were assigned to either condition for 2 sessions of testing. In Exp II, 16 young (mean age 19.8 yrs) and 16 elderly (mean age 71.8 yrs) Ss participated in both conditions. In both experiments, nontargets produced larger interference effects for old compared to young Ss in the search condition but not in the nonsearch condition. The obtained pattern of age effects could not be explained by age-related reductions in parafoveal acuity. Findings indicate that the magnitude of divided-attention deficit increases with age, whereas focused-attention deficits are unaffected by aging. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual variation in hemispheric asymmetry: Multitask study of effects related to handedness and sex.

Functional hemispheric asymmetries were examined for right- or left-handed men and women. Tasks involved (1) auditory processing of verbal material, (2) processing of emotions shown on faces, (3) processing of visual categorical and coordinate spatial relations, and (4) visual processing of verbal material. Similar performance asymmetries were found for the right-handed and left-handed groups, but the average asymmetries tended to be smaller for the left-handed group. For the most part, measures of performance asymmetry obtained from the different tasks did not correlate with each other, suggesting that individual Ss cannot be simply characterized as strongly or weakly lateralized. However, ear differences obtained in Task 1 did correlate significantly with certain visual field differences obtained in Task 4, suggesting that both tasks are sensitive to hemispheric asymmetry in similar phonetic or language-related processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional magnetic resonance imaging of motor cortex: hemispheric asymmetry and handedness

A hemispheric asymmetry in the functional activation of the human motor cortex during contralateral (C) and ipsilateral (I) finger movements, especially in right-handed subjects, was documented with nuclear magnetic resonance imaging at high field strength (4 tesla). Whereas the right motor cortex was activated mostly during contralateral finger movements in both right-handed (C/I mean area of activation = 36.8) and left-handed (C/I = 29.9) subjects, the left motor cortex was activated substantially during ipsilateral movements in left-handed subjects (C/I = 5.4) and even more so in right-handed subjects (C/I = 1.3).     

Sound affects the speed of visual processing.

The authors examined the effects of a task-irrelevant sound on visual processing. Participants were presented with revolving clocks at or around central fixation and reported the hand position of a target clock at the time an exogenous cue (1 clock turning red) or an endogenous cue (a line pointing toward 1 of the clocks) was presented. A spatially irrelevant sound presented 100 ms before the cue speeded visual latency when compared with a sound presented 100 ms after the cue. The effect of the sound was larger the farther the target was from fixation, and it was larger for endogenous than exogenous cues. A visual temporal warning signal had different effects on perceptual latency. These results demonstrate that an asynchronous sound can shift the perceived time of occurrence of a visual cue (temporal ventriloquism) and speed the velocity of the attentional shift toward the target. Sounds thus have multiple effects on visual perception. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Parallel pattern processing and visual agnosia.

Conducted 3 visual-search experiments to examine parallel pattern processing in a man with visual agnosia, who suffered a stroke at age 61 yrs. The authors examined "search for targets" as defined by (1) the combination of features relative to homogeneous distractors, (2) the combination of features relative to heterogeneous distractors, and (3) a single feature difference relative to the distractors. The patient's performance was compared with that of 2 control groups: 10 young (aged 20–36 yrs) and 6 age-matched non-brain damaged controls (aged 63–68 yrs). The patient showed normal search functions for single-feature targets and for combined-feature targets among heterogeneous distractors. The relations between the patient's agnosia and his problem in the parallel grouping of form conjunctions are discussed. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of task and input factors on hemispheric involvement in face processing.

Two experiments with 17 undergraduate students examined the respective role of the cerebral hemispheres in face perception and the nature of their contribution depending on task demands and on the spatial-frequency composition of the stimuli. 16 faces of members of the Ss' department were presented as stimuli, with men, women, and professors, and nonprofessors, being equally represented. In Exp I, high-resolution black-and-white photographs of faces were used in 3 reaction-time (RT) tasks: verbal identification, manual membership categorization, and manual male/female categorization, in a within-S design. Identification and membership categorization were significantly better performed in right-visual-field presentations, whereas the male/female categorization yielded a nonsignificant left-visual-field superiority. In Exp II, 2 versions of the same faces were used: digitized low-pass (0–2 cycles/degree of visual angle) and digitized broad-pass (0–32 cycle/degree) faces. Broad–pass faces produced the same laterality pattern as in Exp I, while low-pass faces were better processed in left-visual-field presentations for all 3 tasks. Results suggest that the 2 hemispheres play a role in face perception and that their contribution may vary as a function of the task demands and of spatial-frequency components of the incoming information. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Size in the visual processing of faces and words.

Three experiments, with 34 right-handed university students, studied the influence of variations of stimulus size upon recognition of words and faces. Ss viewed a series of 640 slides of words of faces presented in 1 of 5 sizes and responded as to whether or not stimulus had been previously presented. Size played an important role in the recognition of faces but was irrelevant to the recognition of words. Analysis revealed that although irrelevant to recognition, size of words was nevertheless encoded, with some consequences similar to those for recognition of faces. The likelihood of recognition declined linearly with the numbers of words intervening between a word and its recurrence, while the likelihood of recognizing a face declined exponentially in the same circumstances. Results are interpreted in terms of stimulus-specific analyses, and this view is contrasted with other notions of mental representation. Variant measures are appended. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contributions of postrhinal and perirhinal cortex to contextual information processing.

The role of the postrhinal cortex (POR) and the perirhinal cortex (PER) in processing relational or contextual information was examined with Pavlovian fear conditioning. Rats with electrolytic or neurotoxic lesions of the POR or PER were tested in 2 contextual fear conditioning paradigms. In Experiment 1, electrolytic lesions of the POR or PER produced impairments in contextual fear conditioning but not in conditioning to a phasic auditory conditioned stimulus. Neurotoxic lesions of the POR or PER likewise resulted in anterograde (Experiment 2) and retrograde (Experiment 3) deficits in fear conditioning to the training context in an unsignaled shock paradigm. The results suggest that operations performed on sensory information by the POR and PER are necessary to support contextual learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)