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1.
Although most of the visual cognitive activities performed by the left hemisphere take place close to the body (peripersonal space), most visual cognitive activities mediated by the right hemisphere take place in extrapersonal space. The left hemisphere, therefore, may have a propensity to direct attention toward the body and the right hemisphere away from the body. Because attentional bias influences judgments of spatial magnitude, the authors tested this hypothesis. Normal participants were asked to compare the size of horizontal lines presented in the sagittal plane in either right or left hemispace. When participants looked leftward, lines appeared shorter than when participants looked rightward. These results are consistent with the hypothesis that the right hemisphere directs attention toward visual extrapersonal space and the left hemisphere directs attention toward visual peripersonal space. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

2.
A 75-year-old right-handed woman, after a probable cerebral infarct, developed an irregular constriction of the visual fields, a left-sided agraphia, and an anomia for objects in the left hand. Subsequent testing demonstrated an inability to name, though ability to recognize, letters and objects flashed in the homonymous left visual field. An inter-hemispheric disconnexion syndrome was inferred from these findings. The present publication concerns mainly the visual aspects of this disconnexion syndrome. Tasks were devised to test the abilities of the major and minor hemisphere: (a) the left hemisphere demonstrated a complete dominance for language expression and an incomplete dominance for written language comprehension; (b) the right hemisphere appeared to be dominant for some visuo-spatial tasks including number comprehension; (c) when the hemispheres were given contradictory visual informations on a non-verbal task (chimeric stimuli) there was a predominance of the right hemisphere. The right hemisphere appeared able to process complex information. Specialization of functional activities in each hemisphere is briefly discussed.  相似文献   

3.
The objective of this study was to analyze dynamic aspects of right hemisphere implementation in processing visual images. Two tachistoscopic, divided visual field experiments were carried out on a partial split-brain patient with no damage to the right hemisphere. In the first experiment, image generation performance for letters presented in the right visual field (/left hemisphere) was undeniably optimal. In the left visual field (/right hemisphere), performance was no better than chance level at first, but then improved dramatically across stimulation blocks, in each of five successive sessions. This was interpreted as revealing the progressive spontaneous activation of the right hemisphere's competence not shown initially. The aim of the second experiment was to determine some conditions under which this pattern was obtained. The experimental design contrasted stimuli (words and pictures) and representational activity (phonologic and visuo-imaged processing). The right visual field (/left hemisphere: LH) elicited higher performance than the left visual field (/right hemisphere, RH) in the three situations where verbal activity was required. No superiority could be found when visual images were to be generated from pictures: parallel and weak improvement of both hemispheres was observed across sessions. Two other patterns were obtained: improvement in RH performance (although LH performance remained superior) and an unexpectedly large decrease in RH performance. These data are discussed in terms of RH cognitive competence and hemisphere implementation.  相似文献   

4.
The ability voluntarily to stabilize the head in space during lateral rhythmic oscillations (0.59+/-0.09 Hz) of the trunk has been investigated during microgravity (microG) and normal gravity (nG) conditions (parabolic flights). Five healthy young subjects, who gave informed consent, were examined. The movements were performed with eyes open or eyes closed, during phases of either microG or nG. The main result was that head orientation with respect to vertical may be stabilized about the roll axis under microG with, as well as without vision, despite the reduction in vestibular afferent and muscle proprioceptive inputs. Moreover, the absence of head stabilization about the yaw axis confirms that the degrees of freedom of the neck can be independently controlled, as was previously reported. These results seem to indicate that voluntary head stabilization does not depend crucially upon static vestibular afferents. Head stabilization in space may in fact be organized on the basis of either dynamic vestibular afferents or a short-term memorized postural body schema.  相似文献   

5.
Right-handed Ss identified consonant-vowel-consonant (CVC) nonsense syllables presented tachistoscopically. The CVC on each trial was presented to the left visual field-right hemisphere (LVF-RH), to the right visual field-left hemisphere (RVF-LH), or the same CVC was presented to both visual fields ( bilateral presentation). When recognition was incorrect, the pattern of errors was qualitatively different on LVF-RH and RVF-LH trials, suggesting that each cerebral hemisphere has its own preferred mode of processing the CVC stimuli. The qualitative pattern of errors on bilateral trials was identical to that obtained on LVF-RH trials. The bilateral results are described well by a model that assumes the mode of processing characteristic of the RH dominates on bilateral trials but is applied to both the LVF-RH and RVF-LH stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

6.
Rapid environmental changes lead to formation of adaptive dominance which makes the body search for biologically appropriate reactions under the new conditions. This changes in fundamental properties of the brain, like memory, emotions, hemispheric functional asymmetry by ensuring optimization of the processing of a drastically increased flow of signals. The order of information processing is determined by its significance for the body. Selection of new and emotiogenic signals first activates by changes in cortical-subcortical relationships, the left hemisphere and the right hemisphere isolate new and emotiogenic information, respectively. Subsequent inversion of hemispheric dominance, i.e. the prevalence of right hemispheric functions provides construction of a new programme of the body's interaction with the altered environment. This may be possible as it is the right hemisphere that predominantly regulates emotional, humoral, and endocrine regulation. At this stage of adaptation, there is an increase in interhemispheric integration which eventually restores the initial interhemispheric relationships. The newly recovered dominance of the left hemisphere ensures not only an effective reproduction of the formed programme, but organizes a leading reflection of reality.  相似文献   

7.
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)  相似文献   

8.
Knowing the special function of each half of the brain is important to the clinician. If he doesn't understand what damage to the nondominant hemisphere can do, he may mistake the resulting syndrome for a psychiatric illness or generalized dementia, and the patient won't get proper treatment and counseling. The tendency is to think of dominance in terms of language, but other functions are asymmetrically located even though their input and output are bilateral. Generally, lesions in the left hemisphere cause problems with language and those in the right disrupt visual and spatial skills, attention, and emotional behavior. By far the most common syndrome in right hemisphere lesions is neglect of the left side. A patient may show lack of concern about his illness or he may deny that he is sick or even that the left side of his body belongs to him. Patients with left hemisphere lesions may neglect the right side but rarely to this extreme.  相似文献   

9.
Results from 2 divided visual field (DVF) experiments indicate that in some conditions both explicit and implicit memory are greater when same-letter-case stimuli are presented directly to the right cerebral hemisphere (in the left visual field) than when they are presented directly to the left (in the right visual field). Explicit memory was measured with word-stem cued recall, and implicit memory was measured with word-stem completion priming. Words were presented centrally during encoding, and word stems were presented directly to the right hemisphere or to the left hemisphere during testing. Results for explicit memory contrast with findings from a previous DVF study that used a different procedure, those for implicit memory replicate previous DVF findings, and both results corroborate positron emission tomography findings. It is suggested that a form-specific system in the right hemisphere may contribute to both explicit and implicit memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

10.
Tests of visual, vestibular, sensori-motor and balance function were administered to 550 women, aged between 20 and 99 years at a Balance and Gait Laboratory. All of the sensory, motor and balance system measures showed significant age-associated differences. Multiple regression analyses revealed that the measures of lower limb sensation were the consistent sensori-motor factors contributing to balance under normal conditions (standing on a firm surface with eyes open or closed). Under more challenging conditions (standing on foam with eyes open) vision, strength and reaction time played significant roles, whilst when standing on foam with eyes closed, vestibular function also made a significant contribution. Analysis of percentage increases in sway under conditions where visual and peripheral sensation systems were removed or diminished, compared with sway under optimal conditions, indicated that up until age 65 there was an increased reliance on vision for balance control. Beyond this age, the contribution made by vision declined, so that in the oldest age-groups reduced vision was less able to supplement peripheral input, resulting in increased sway areas. Peripheral sensation however was the most important sensory system in the maintenance of static postural stability at all ages.  相似文献   

11.
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)  相似文献   

12.
Two experiments were conducted to explore the interaction of the two cerebral hemispheres in motor control, by examining hand, space and attentional asymmetries in goal-directed aiming. In Experiment 1, right-handed subjects moved to targets more quickly with their right hand than their left hand. In addition, each hand was faster when moving in its own hemispace. Although in a control condition, movements were initiated more quickly with the left hand, visual distractors disrupted left hand performance more than right hand performance. For contralateral aiming, ipsilateral distractors caused the greatest interference. In Experiment 2, when targets and distractors were all presented at the midline, a right hand advantage was found for movement time along with a left hand advantage for reaction time, independent of target and distractor location. Our findings are discussed in terms of a right hemisphere role in movement preparation and the allocation of attention in space, and greater left hemisphere involvement in movement execution.  相似文献   

13.
Birds which are tested monocularly in visual discrimination tasks generally show higher performance levels with the right eye seeing. Due to the virtual complete decussation of the optic nerves, a right eye superiority is probably related to a left hemisphere dominance. If visual processes between the hemispheres differ, each half-brain might be differently prone to be deceived by visual illusions. Indeed pigeons tested with the herringbone illusions are deceived to a stronger extent with the right eye. These functional asymmetries are accompanied by anatomical left-right differences in the ascending thalamo- and tectofugal visual pathways in chicks and pigeons, respectively. The neuroanatomical and behavioral assymmetries result from an asymmetrical posture before hatching in which the embryo keeps his head turned to the right, such that the right eye is stimulated by light shining through the shell. The lateralization of adult animals are induced by this prehatching asymmetric photic stimulation since dark incubation abolishes behavioral and anatomical asymmetries. It is conceivable that the asymmetrical embryonal light stimulation increases the release of neurotrophins in the developing avian visual system in an activity dependent matter. Neurotrophins play an important role in neuronal survival and morphology and thus might represent a molecular switch bridging the gap from embryonal light stimulation to asymmetries of visual cognition in adults.  相似文献   

14.
Reverse micellar extraction of antibiotics from aqueous solutions   总被引:1,自引:0,他引:1  
PURPOSE: We reviewed 1,360 EEG reports for all patients studied in two different neurophysiology laboratories during 1 calendar year to determine whether epileptiform discharges have a hemispheric dominance. METHODS: Both inpatients and outpatients, with or without epilepsy, were included. RESULTS: Ninety-four records (6.9%) demonstrated generalized epileptiform activity. Of 95 EEG reports indicating spikes solely from one hemisphere, spikes arose from the left in 61 and from the right in 34. Among 50 other records with bilateral independent spikes with lateralization, 40 were left hemisphere dominant and 10 were right hemisphere dominant. CONCLUSIONS: These findings raise the possibility that the left cerebral hemisphere may generate focal epilepsy more frequently than the right.  相似文献   

15.
For all of us, one side of the brain, right or left, is the dominant hemisphere used to process information. In 9 out of 10 persons, the left temporal lobe becomes the dominant hemisphere. In the remaining one tenth of the population both sides develop at the same rate, forming "dual dominance," or, more rarely, the right side alone becomes highly developed. The left hemisphere of the brain serves as the analytical, sequential, cause and effect processor, whereas the right hemisphere of the brain is the mind's eye, assimilating information simultaneously and processing visual and nonverbal information and sound. Neither hemisphere works independently, and both are used to effectively learn new information. The creative teacher understands this arrangement and can successfully determine when a complex diagram or video is needed to teach a patient, or when only a clear voice is necessary.  相似文献   

16.
We describe the characteristics of displacement of the head and hip in normal young subjects standing on a moving platform undergoing continuous sinusoidal horizontal translation in the antero-posterior direction, at frequencies ranging from 0.1-1 Hz. The head, hip and malleolus were marked by light-emitting diodes (LEDs), and the displacement of each LED was quantified by (1) the measure of the shift during each cycle of translation, (2) the standard deviation (SD) of the path travelled during the whole trial, (3) the power spectrum (PS) of the signal and (4) the cross-correlation (CC) between pairs of LED signals. At each frequency of translation, with eyes open (EO), the displacement of head was smaller than that of hip, and the displacement of hip was smaller than that of malleolus. With eyes closed (EC), this order was reversed. The peak value of the CC functions of the pairs malleolus/head, malleolus/hip and hip/head decreased by passing from low to high frequency of translation, under both visual conditions, and decreased more for the pair malleolus/head than malleolus/hip. The lags between body segment displacements ranged between 30 ms and 150 ms, on average, the former segment of each pair preceding the latter. The fast Fourier transformation of hip and head displacement showed a power spectrum peak at the frequency imposed by the platform translation. The peak was larger with EC than EO. With EC, another peak appeared at 0.2 Hz, possibly corresponding to the respiratory frequency. We conclude that, when vision was allowed, subjects behaved as a non-rigid, noninverted pendulum, and stabilised head in space. When vision was denied, head oscillated more than the platform, especially at low translation frequencies. Therefore, the strategy of balance control shifted from a pendulum to an inverted-pendulum behaviour, passing from active head-and-trunk control to maximal body compliance to the perturbation.  相似文献   

17.
Right-handed subjects participated in a visual half-field experiment using "clock" stimuli. For the Categorical task, subjects indicated whether the long and short hands of a clock were above or below the horizontal midline of the dial. For the Coordinate task, they indicated whether the long and short hands of a clock formed an angle that is more or less than 60 degrees. For both tasks, clock stimuli were either analog clocks (Visual version) or digital clocks from which subjects generated images of analog clocks (Imagery version). The results indicated that for both the Visual and Imagery versions, there was a nonsignificant trend toward a left hemisphere advantage in the Categorical task, whereas there was a significant right hemisphere advantage in the Coordinate task. Implications of the results were discussed from the viewpoints of task factors in hemispheric processing of visual imagery, Kosslyn's (1987, 1994) computational model of vision and visual imagery, and vision/imagery isomorphism.  相似文献   

18.
We examined the relation between language dominance and regional cerebral blood flow (rCBF) during the intracarotid amobarbital procedure (IAP). A previous report limited to three patients suggested that dominant rather than nondominant hemisphere IAP may have a differential effect on rCBF. Behavioral assessment during the IAP also suggests that dominant hemisphere injection results in a differential effect on memory and affective symptoms rather than nondominant injection. Thirteen patients were assessed using single-photon emission CT (SPECT) brain imaging during both left and right IAP. The SPECTs were coregistered with the individual's MRI. Changes in rCBF during each IAP were compared with the patient's baseline SPECT. Nine patients had left hemisphere dominance, two were right dominant, and two had bilateral speech representation. In the left dominant subjects, left-hemisphere injection had a consistently greater effect on rCBF than right-hemisphere injection in the anterior (p < 0.005) and posterior (p < 0.01) temporal neocortex. There was also a trend for greater hypoperfusion in the frontal lobe of the left hemisphere. rCBF in the ipsilateral hippocampus was not significantly different after each injection (p > 0.05). In the two patients with right hemisphere speech, the reverse pattern was seen, with greater hypoperfusion after right (dominant) hemisphere injection. There was no consistent asymmetry in the two patients with bilateral speech. Dominant hemisphere IAP results in significantly greater hypoperfusion than does nondominant injection. These data provide a physiologic basis for behavioral differences noted after dominant versus nondominant IAP.  相似文献   

19.
In judging whether horizontal lines flashed for 100 ms extended farther to the left or right of a central fixation mark, a man (L.B.) with complete forebrain commissurotomy showed a marked bias to judge the right side longer, which is consistent with left hemineglect. Normal controls were considerably more accurate and were slightly biased toward the left, which is consistent with right pseudoneglect. L.B. showed no rightward bias when viewing the lines freely or when asked in free vision to locate the center of a horizontal line, although his performance varied more than that of controls. Therefore, commissurotomy may induce strong but transient left hemineglect that is rapidly overcome in free vision. One explanation is that control is initially left-hemispheric and subcortical transfer results in the left hemisphere receiving a spatially compressed representation of information in the left visual field. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

20.
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)  相似文献   

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