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PubMedDate not supplied

[Interhemispheric brain asymmetry in speech perception by persons of different age groups and the "effect of directional attention"].

Using dichotic tests, studies have been made on the degree of functional asymmetry of the brain with respect to perception of verbal information in 3-50 years old subjects. Significant age variations were found in the volume of the percepted speech information. Interhemispheral differences in speech perception, which reveal themselves in higher perception of the right ear as compared to the left one, are more evident in children under 10 years. Significant influence of the "effect of voluntary and involuntary attention" of the subjects was noted on the degree of asymmetry of dichotic speech perception, this influence alleviating the intrinsic functional asymmetry of the brain.

Adolescent↗

PubMed1982

[Mechanisms regulating perception: regulation of sensation].

The slow electrical activity of the thalamic region of the cortex, as well as the psychophysical characteristics of perception were registered in experiments on discerning light flashes in brightness in healthy probands, excitable psychopathic subjects and schizophrenic patients (simple form with apatho-abulic manifestations). It is shown that correct perception of the light flashes depends on stabilization of the thalamic region potentials in the time intervals of 100 to 200 msec following immediately the stimuli. In cases of erroneous perception no stabilization of such kind was noted. A certain relationship between the perception characteristics and the time course of the slow electrical activity on the one hand, and the proband's intention to select pairs of flashes of different or equal intensity as the signal was registered. As a result, in cases of correct perception of the signal pair of the flashes the stabilization of the slow potential was more marked than in cases of perceiving non-signal pairs. This fact points to an active character of the physiological regulation of the visual analyzer sensitivity.

Antisocial Personality Disorder↗

PubMed1995

Speech perception in children using the advanced Speak speech-processing strategy.

The Speak speech-processing strategy, developed by the University of Melbourne and commercialized by Cochlear Pty Limited for use in the new Spectra 22 speech processor, has been shown to provide improved speech perception for adults in both quiet and noisy situations. The present study evaluated the ability of children experienced in the use of the Multipeak (Mpeak) speech-processing strategy (implemented in the Nucleus Minisystem-22 cochlear implant) to adapt to and benefit from the advanced Speak speech-processing strategy (implemented in the Nucleus Spectra 22 speech processor). Twelve children were assessed using Mpeak and Speak over a period of 8 months. All of the children had over 1 year's previous experience with Mpeak, and all were able to score significantly on open-set word and sentence tests using the cochlear implant alone. Children were assessed with both live-voice and recorded speech materials, including Consonant-Nucleus-Consonant monosyllabic words and Speech Intelligibility Test sentences. Assessments were made in both quiet and in noise. Assessments were made at 3-week intervals to investigate the ability of the children to adapt to the new speech-processing strategy. For most of the children, a significant advantage was evident when using the Speak strategy as compared with Mpeak. For 4 of the children, there was no decrement in speech perception scores immediately following fitting with Speak. Eight of the children showed a small (10% to 20%) decrement in speech perception scores for between 3 and 6 weeks following the changeover to Speak. After 24 weeks' experience with Speak, 11 of the children had shown a steady increase in speech perception scores, with final Speak scores higher than for Mpeak. Only 1 child showed a significant decrement in speech perception with Speak, which did not recover to original Mpeak levels.

Adolescent↗

PubMed1994

Maternal perception of illness severity in premature infants.

This study examines relationships between the actual severity of the premature infant's medical condition, maternal perception of the severity of the infant's illness, the infant's birth weight, and maternal anxiety levels. Subjects for this study were 44 mothers who were part of a larger study of parental stress in neonatal intensive care units (NICUs). The premature infants of these mothers were hospitalized in the NICU of a large southeastern university medical center at the time of data collection. Mothers completed a severity perception scale and the State-Trait Anxiety Inventory. Data about actual severity of each infant's illness and about the infant's characteristics were collected from the medical chart. The findings indicate that maternal perceptions regarding the severity of their premature infants' illness are complex and are influenced by different factors at different points in time. A significant relationship was not found between the mother's recollection of infant severity at NICU admission and maternal perceptions at the time of the interview, two to five days after admission. Although maternal recall of the severity of the infant's illness on admission is not related to anxiety, perceptions of severity at the time of the interview (two to five days after admission) are related to anxiety scores.

Adolescent↗

PubMed1977

The development in very young children of tacit knowledge concerning visual perception.

The purpose of this study of early social-cognitive development was to assess the very young child's behaviorally expressed knowledge of people's visual-attentional acts and abilities. Boys and girls (N = 60) 1, 1 1/2, 2, 2 1/2, and 3 years of age were tested in their homes with their mother's help. Three sorts of tasks were used: 1. Percept production. The child's task was to produce a visual percept in the other. Examples include pointing to objects ("productive pointing") and a wide variety of object-showing problems. 2. Percept deprivation. The opposite, exemplified by a variety of object-hiding problems. 3. Percept diagnosis. The child's task was to determine what the other was already visually attending to, either by looking where his or her finger was pointed ("receptive pointing") or where his eyes were directed. It was found that the majority of 1-year-olds produced and comprehended pointing, and would sometimes hold out a toy to show it, but did little else. The 3-year-olds were at ceiling on virtually all tasks. At 1 1/2 years, children usually showed a picture by holding it flat so that both they and the other could see it. Jrom 2 on, they usually turned it toward the other in the adult fashion. Very few children of any age showed egocentrically--i.e., orienting the picture so only they could see it. By age 2, the children solved what were presumably novel showing problems for them: e.g., successfully showing to another a picture pasted on the inside bottom of a hollow cube. Hiding ability emerged later than showing ability but seemed well established by age 3. The role of the other's eyes in seeing appeared to be quite well understood at least by age 2-2 1/2. As examples, children of this age took the other's hands away from her or his eyes before trying to show her something, and could usually tell where she was looking from her eye orientation alone. These age trends presumably reflect important developments in the area of social interaction and communication, as well as with respect to cognition about percepts.

Age Factors↗

PubMed1996

Models of speech perception and phonological processing in reading.

Multiple measures of speech perception, phonological awareness, naming speed, verbal short-term memory, and word reading were concurrently administered to 136 third- and fourth-grade children. Structural equation modeling was used to contrast 5 models of the relations of speech perception and phonological processing skills to reading with IQ controlled. The best-fitting model, the Indirect Model, was one in which the effect of speech perception on reading was mediated by its relations with phonological processing abilities. Naming speed was particularly highly associated with speech perception, possible evidence for the Motor Theory. Phonological awareness was also substantially correlated with speech perception.

Child↗

PubMedDate not supplied

[Evaluation of perceptive activity in persons with low pressure hydrocephalus treated surgically. Preliminary report].

Preliminary assessment of perceptive activity was carried out in patients with low-pressure hydrocephalus diagnosed clinically. The purpose of the study was establishing of the valuable tests for the neuropsychological diagnosis making possible finding of perceptive processes most frequently disturbed in low-pressure hydrocephalus. The studied group comprised 53 patients operated on for this hydrocephalus. In only 9 cases the condition of the patient made possible a detailed study of the perceptive processes. In this group the tests were carried out three times: before, immediately and after a longer time after insertion of ventriculoperitoneal shunt. The results showed differences in the level of general perceptive functioning in the whole group. In the subgroup studied in detail no general perception deterioration was found, and the usual disturbances were noted in the memorization of new information and in visuospatial orientation. Late after the operation the greatest improvement was observed in the most disturbed functions.

Adult↗

PubMedDate not supplied

[Use of subjective perception of exertion in the evaluation of the tolerance to repetitive lifting: a pilot study].

This preliminary study was conducted to validate subjective perception of effort as indicator of the tolerable workload for prolonged lifting tasks. Three healthy male subjects underwent endurance and incremental lifting tests. Cardiorespiratory parameters (HR, VO2) were monitored with a portable telemetric oxygen uptake analyzer, mechanical parameters were calculated from a lift dynamometer. Rating of perceived exertion was given on Borg's CR-10 scale. Individual fitness profiles for lifting tasks were obtained from the individual relationships between oxygen consumption and heart rate at different lifting frequencies. Physiological responses to repetitive lifting were matched with subjective perceptions. The relationship between perception of exertion and time was described by power functions, Y = a.Xn, in which 0 < n < 1. A single-variable statistical regression for power functions was performed to obtain the individual "iso-perception" curves. The iso-perception curve corresponding to a "moderate effort" (CR3) identified the individual tolerable threshold for prolonged lifting tasks. The individually tolerable power output over time for lifting tasks was calculated.

Adult↗

PubMed1998

Effects of cue context on the perception of depth from combined disparity and perspective cues.

PURPOSE: In normal vision, stereoscopic cues are combined with perspective cues to provide veridical depth perception. The relative strengths of these depth cues, however, may be dependent upon context effects. We investigated the role of stimulus context on the interactions of binocular disparity, contrast, and size. METHODS: The subjects, four observers with normal stereoacuity and one stereo-amblyope, discriminated far vs. near perceived depth of Gabor patches; feedback was based on the sign of binocular disparity. Depth discrimination functions were measured under conditions in which depth cues were consonant or in conflict. Three stimulus contexts were used: (1) variable disparity with fixed spatial frequency and contrast; (2) variable contrast with fixed spatial frequency and disparity; and (3) variable spatial frequency with fixed contrast and disparity. The effects of stimulus context were derived from comparisons of discrimination rates for identical stimuli across the three sets of conditions. RESULTS: In subjects with normal stereopsis, for disparities less than 2 arcmin, depth perception was dominated by contrast in contrast-varying sessions, or by size in spatial frequency-varying sessions. With larger disparities, depth perception became dependent on disparity, regardless of the contrast or spatial frequency of the test stimulus. The results for the stereo-amblyope showed much greater dependence on perspective cues and, in most cases, the transition from perspective- to disparity-based depth perception did not occur. CONCLUSIONS: These investigations demonstrate strong stimulus context effects and have important implications for the combination rules of stereoscopic and perspective cues in depth perception of normal and stereo-deficient subjects.

Contrast Sensitivity↗

PubMedDate not supplied

[Perception of risk for infection with the human immunodeficiency virus].

Prevention of AIDS is very complex and requires, apart from basic knowledge about modes of transmission and protection, individual awareness of personal risk of infection and modification of one's risky behavior. Perception of risk has been suggested as an important element of sexual behavior change among people who engage in behaviors that place them at risk of HIV infection. This study investigates perceived risk of an HIV infection among inhabitants of municipality of Palilula. The purpose of this study was to determine the relative accuracy of risk assessment, especially for those with high-risk sexual behavior and to assess the factors related to self perception of developing AIDS. The survey was conducted as a household survey in Belgrade municipality "Palilula". The design of the survey was based on a two-stage stratified random sample. The population of Palilula municipality was divided in two stratums and 840 households were selected from each stratum. All members of selected households aged 15-49 years were interviewed. Total of 2659 persons was interviewed. Self administered questionnaire, developed by WHO and described in the Evaluation of National AIDS Programme: A Methods Package 1. Prevention of HIV infection, Geneva, 1994, was translated and adapted for local application. For analysis of findings methods of descriptive statistics, chi square test and logistic regression were used. Statistical analysis was performed using SPSS/PC. The results showed that most of the respondents (1662, 62.5%) do not perceive themselves to be at risk of HIV infection. Interestingly, almost one quarter of the sample couldn't estimate personal chances of being HIV infected. Significantly larger proportion of respondents living in urban area than those living in rural area perceived themselves at risk (17.1% of urban vs. 7.7% from rural area, chi square = 54.06, Ir0.00). Significant differences between age groups were found for perception of personal risk. Respondents up to 19 and those older than 25 in more than 60 percent and only a half of those between 20 and 24 believed that there was no chance they could become HIV infected. Almost 16% of respondents between 20 and 24 believed that they had some chances of contracting HIV, also approximately one third of them couldn't estimate personal risk of contracting HIV infection (chi square = 2.10, p = 0.00)(Graphe 1). Those who engaged in sex with irregular partners were found to perceive themselves in higher risk then those who were engaged in sex only with regular partners in previous 12 months. One fifth of those with irregular partners estimated their chances as good versus only 10% of those with only regular partners. A logistic regression analysis found that those who believed they were personally at risk knew someone with HIV, had more irregular sexual partners in last 12 months, were younger, and lived in urban area (Table 1). People correctly perceived the risk of HIV infection as being minimal as most of them didn't engage in risk behavior. Risk perception was higher among those who had more irregular partners, younger and those from urban area. Most important predictor of risk perception was knowledge of HIV positive individual.

Adolescent↗

PubMed1994

Neurophysiological differences between perception and imagery.

The present study was designed to examine brain activity underlying mental imagery is conceptualized as behavior guided by internal representation only, the activity of the prefrontal lobes was assumed to be a measure of differentiation of imagery from perception. Twenty-one subjects were requested to observe and imagine a swinging pendulum and to touch and imagine a coshball in separate trials. The EEG was recorded from 15 standard electrode sites and analyzed with (1) traditional alpha power and (2) an estimation of dimensional complexity (a measure derived from nonlinear dynamics). Both EEG measures revealed expected object-related differences during perception as well as during imagery. The visual pendulum showed relative to the tactile coshball increased dimensional complexity and less alpha power at parietal and frontal sites. However, only the EEG dimension supported the main hypothesis: Imagery resulted in increased prefrontal dimensional complexity in comparison to perception independent of the modality of the image. In contrast, for alpha power the difference between imagery and perception was due to stimulus modality.

Adolescent↗

PubMed2005

When visual perception causes feeling: enhanced cross-modal processing in grapheme-color synesthesia.

In synesthesia, stimulation of one sensory modality (e.g., hearing) triggers a percept in another, non-stimulated sensory modality (e.g., vision). Likewise, perception of a form (e.g., a letter) may induce a color percept (i.e., grapheme-color synesthesia). To date, the neural mechanisms underlying synesthesia remain to be elucidated. We disclosed by fMRI, while controlling for surface color processing, enhanced activity in the left intraparietal cortex during the experience of grapheme-color synesthesia (n = 9). In contrast, the perception of surface color per se activated the color centers in the fusiform gyrus bilaterally. The data support theoretical accounts that grapheme-color synesthesia may originate from enhanced cross-modal binding of form and color. A mismatch of surface color and grapheme induced synesthetically felt color additionally activated the left dorsolateral prefrontal cortex (DLPFC). This suggests that cognitive control processes become active to resolve the perceptual conflict resulting from synesthesia.

Acoustic Stimulation↗

PubMed1998

Right parietal cortex is involved in the perception of sound movement in humans.

Changes in the delay (phase) and amplitude of sound at the ears are cues for the analysis of sound movement. The detection of these cues depends on the convergence of the inputs to each ear, a process that first occurs in the brainstem. The conscious perception of these cues is likely to involve higher centers. Using novel stimuli that produce different perceptions of movement in the presence of identical phase and amplitude modulation components, we have demonstrated human brain areas that are active specifically during the perception of sound movement. Both functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) demonstrated the involvement of the right parietal cortex in sound movement perception with these stimuli.

Acoustic Stimulation↗

PubMed1995

Spatial-gradient limit on perception of multiple motion.

Motion is perceived whenever a subject is presented with an appropriate spatiotemporal visual pattern. Like many other visual tasks, motion perception involves both local and global processing, and thus might be subject to the well-known paradox that arises from the fact that local features and observations form the basis for global perception, but sometimes this global percept can not be easily derived from any single local observation, as is best exemplified by the aperture problem. Globally, dual (transparent) motion can be readily perceived. Spatial limits on the local ability to perceive multiple motion are sought. By using the framework of apparent motion, it is found that dual, orthogonally oriented motion can be perceived only when the dots that constitute the two motions are separated by some spatial limit. For short-range apparent motion, the limit is found to be comparable to D(max), and the visual system cannot perceive more than a single coherent motion in a local "patch" of radius D(max). It was also found that this spatial limit on local-motion perception is not constant, but depends linearly on the spatial organisation of the stimuli, and vanishes for stimuli having reverse contrast. The lower bound on the ability to perceive multiple motion is compared with some well-known bounds in stereopsis, and a cortical columnar architecture that might account for it is proposed.

Adult↗

PubMed2000

Role of chromaticity, contrast, and local orientation cues in the perception of density.

We compared the role of the red-green, blue-yellow, and luminance post-receptoral mechanisms in the perception of density. The task requires the comparison of densities between two stimuli composed of oriented bandpass elements, pseudo-randomly scattered across an area of constant size. The perception of density differences was measured by a temporal 2AFC procedure for all pairs of mechanisms and for four possible densities. We found that stimuli of identical physical densities are not perceived equally: there is a consistent bias in favour of blue-yellow stimuli which are perceived as significantly more dense than red-green and achromatic stimuli. We considered three factors that could have differentially affected the density perception of blue-yellow stimuli: an increase in the perceived size of the individual blue-yellow elements, a perceived contrast difference, and the presence of local orientation cues. We found that the increased perceived density of the blue-yellow stimuli occurred despite the fact that there was no increase in perceived size of the individual elements, and remained despite corrections for the two other factors. We conclude that the significant increase in perceived density for the blue-yellow mechanism is a global effect, associated with a perceived colour 'melting' of the elements in the array. Our data were fitted with the occupancy model of Allik and Tuulmets (1991, Perception & Psychophysics 49 303-314) and we found that blue-yellow stimuli have a greater 'occupancy' than red-green or achromatic stimuli.

Color Perception↗

PubMed2002

The relationship between cortical activation and perception investigated with invisible stimuli.

The aim of this work was to study the relationship between cortical activity and visual perception. To do so, we developed a psychophysical technique that is able to dissociate the visual percept from the visual stimulus and thus distinguish brain activity reflecting the perceptual state from that reflecting other stages of stimulus processing. We used dichoptic color fusion to make identical monocular stimuli of opposite color contrast "disappear" at the binocular level and thus become "invisible" as far as conscious visual perception is concerned. By imaging brain activity in subjects during a discrimination task between face and house stimuli presented in this way, we found that house-specific and face-specific brain areas are always activated in a stimulus-specific way regardless of whether the stimuli are perceived. Absolute levels of cortical activation, however, were lower with invisible stimulation compared with visible stimulation. We conclude that there is no terminal "perceptual" area in the visual brain, but that the brain regions involved in processing a visual stimulus are also involved in its perception, the difference between the two being dictated by a higher level of activity in the specific brain region when the stimulus is perceived.

Color Perception↗

PubMed1992

Depth, motion, and static-flow perception at metaisoluminant color contrast.

Many experiments concerned with the role of color in depth and motion perception have applied isoluminant random-dot stereograms and cinematograms. The poor performance in the absence of luminance contrast has been associated with color-blindness of stereopsis and motion perception (Livingstone, M.S. & Hubel, D.H. (1987) J. Neurosci. 7, 3416-3468). Nevertheless, isoluminant stimuli are not fully accepted as appropriate tools in isolating central mechanisms (Logothetis, N.K., Schiller, P.H., Charles, E.R. & Hurlbert, A.C. (1990) Science 247, 214-217). In our experiments we use a broad luminance range to test whether color can contribute to a given mechanism when luminance contrast is present but has a strong "veto" effect from opposite luminance contrast, a condition we named "metaisoluminance." There is no fusion in stereopsis under polarity reversal, when only luminance information is given, and reversed-phi phenomenon is experienced for motion. As a third "matching" task, we included polarity-reversed random-dot Glass-patterns, which exhibit "static flow" and also show pattern reversal. We found that color can counteract the effects of polarity reversal by restoring stereoscopic fusion and reversed phi motion and does it with increased efficiency as the hue contrast increases. We found no such effect of color in Glass-patterns. Thus, we showed that the visual system for binocular depth and motion perception is not color-blind, although correlated hue information under metaisoluminance does not appear to yield shape perception.

Color Perception↗

PubMed1999

The effects of learning and intention on the neural network involved in the perception of meaningless actions.

PET was used to explore the neural network involved in the perception of meaningless action. In two conditions, subjects observed learned and unknown meaningless actions without any purpose. In two other conditions, subjects observed the same type of stimuli for later imitation. The control condition, which consisted of the presention of stationary hands, served as a baseline. Unsurprisingly, a common network that forms part of the dorsal pathway was engaged in all conditions when compared with stationary hands, and this was interpreted as being devoted to the analysis of hand movements. One of the most striking results of the present study was that some brain areas were strongly modulated by the learning level, independent of the subject's intention. Two different effects were observed: a reduced activity in posterior regions within the common network, which correlated with specific increases in the frontopolar area 10 and in the angular gyrus during the perception of learned meaningless actions compared with the perception of unknown actions. Finally, the major effect of the subject's intention to imitate was a strong increase in the dorsal pathway extending to the lateral premotor cortex and to the dorsolateral prefrontal cortex, which reflects the information processing needed for prospective action. Overall, our results provide evidence for both an effect of the visuomotor learning level and of the subject's intention on the neural network involved during the perception of human meaningless actions.

Adult↗