Asymmetries of selective listening and attention switching in children.

Administered a selective listening task to 155 normal right-handed 3–12 yr old children. The stimuli consisted of dichotic digits, ranging from single pairs to strings of 4 pairs/trial. Each S attempted to focus attention on 1 ear for 8 practice trials and 28 test trials before switching attention to the opposite ear. Separate analyses of correct responses and intrusion errors yielded almost identical results: There was a significant right-ear advantage (REA) and a developmental increase in overall performance, but there was no developmental change in degree of asymmetry. The REA increased with increasing list length, but independent analyses for each list length failed to reveal any developmental changes in REA. Listening asymmetry was influenced markedly by the order in which the ears were monitored; Ss of all ages had difficulty in switching attention from right ear to left. Results support the developmental invariance hypothesis of cerebral lateralization and demonstrate that auditory asymmetry is not merely a direct reflection of some fixed structural asymmetry in the brain. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Endogenous and exogenous control of attention in dichotic listening.

Dichotic listening to verbal stimuli results in a right ear advantage (REA), indicating a left hemisphere processing superiority. The magnitude of the REA can be modulated by instructions to direct attention to the left or right ear stimulus. A previous study from our laboratory showed that presenting a prime syllable before the presentation of the dichotic syllables increases reports of the nonprimed syllable, apparently a negative priming effect that inhibits attention to the distracting prime representation. The present study combined attention instruction and priming, making up a 3 × 3 factorial design. The prime stimulus was a single consonant-vowel syllable presented binaurally just before onset of the dichotic consonant-vowel syllables. Results showed that both instructions and priming manipulations had an effect on which dichotic stimulus was selected. There was also a significant interaction between attention instruction and priming manipulation, indicating that the mechanism for instructed attention and the mechanism for negative priming work on the same level of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of directed attention on cerebral asymmetries in normal and learning-disabled children.

Using a dichotic listening task employing both undirected and directed attention conditions, cerebral asymmetries were examined in matched populations of 32 normal and 32 learning-disabled (LD) children (ages 7 yrs 6 mo–13 yrs 2 mo). The analysis of recall performance indicated that development was not a significant factor in either group; both the normal and LD Ss showed a right-ear effect, although the LD Ss performed at a degraded level and were unable to demonstrate a right-ear advantage (REA) when attention was directed to the left ear, unlike normal Ss, who produced the REA despite the directed attention conditions. Results suggest that LD children probably do not suffer from developmental delays but rather from a defect in callosal functioning that interferes with their ability to process verbal information simultaneously. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perspectives on the use of the baboon in embryology and teratology research

This paper summarizes the developmental stages of the baboon during the period of organ formation and provides comparative information for other primates, including the human. Special attention is directed to the early development of the nervous system, eye, ear and nose/palate. The similarity in development of these structures with humans indicates that the baboon is a suitable model for studies of normal and abnormal neurological development. Spontaneous prenatal loss rates in the baboon (2.4-11.2%) are slightly lower than those reported in rhesus and cynomologus monkeys. The baboon, in addition to the cynomologus monkey and macaque, has been used as a model in teratology research to assess the potential risk of thalidomide, sex steroids, Bendectin and rubella virus, as well as to study the pathogenesis of malformations associated with the corticosteroid triamcinolone acetonide. The rate of spontaneous malformations (<1%) in baboons, similar to that reported for other commonly used primates, supports their continued use as a teratological model. In this regard, a sample protocol is provided for the safety evaluation of biotechnology products using nonhuman primates, which are the most appropriate model for those compounds which are bioactive in species closely related to humans.     

Contralateral auditory stimulation alters acoustic distortion products in humans

It is now generally accepted that otoacoustic emissions (OAE) represent the only objective and non-intrusive means of functional exploration of the active micromechanical characteristics of the outer hair cells of the organ of Corti. Previous studies showed a decrease of the transiently evoked otoacoustic emissions and spontaneous otoacoustic emissions in humans, during acoustic stimulation of the contralateral ear, and attributed this effect to the medial efferent system. Such an effect has been shown on acoustic distortion product otoacoustic distortion emissions (DPOAE) in guinea pigs, but has not been investigated for DPOAEs recorded in humans, although DPOAEs represent the easiest means of exploring active micromechanical cochlear properties both in humans and in laboratory animals. The present study sought to investigate the existence and characteristics of a contralateral auditory stimulation effect on DPOAEs recorded in humans. This study shows that contralateral broad-band noise (BBN) has a suppressive effect on DPOAEs recorded from 0.5 kHz to 5 kHz. This effect is not due to air conduction, as no change in the noise floor occurred under increasing contralateral stimulation, and as no reduction in DPOAE amplitude was obtained in subjects whose contralateral ear was sealed with a plastic ear plug. Moreover, cross-over attenuation by bone transmission has been ruled out, as no change in DPOAE amplitude was recorded in the healthy ear of total unilaterally deaf patients during acoustic stimulation of the deaf ear. The effect seen was not entirely due to the acoustic reflex, as it was found and could indeed be even greater in subjects with no acoustic reflex. Results presented here show that the contralateral BBN effect is greater at low levels of ipsilateral stimulation, which leads us to discuss the involvement of both passive and active mechanisms in DPOAE generation at high stimulation levels. The contralateral BBN effect seems to be greater in mid frequency cochlear regions. There is strong evidence that the medial efferent system is involved and that afferent and efferent inputs are, at least partly, integrated at a brainstem level in order to ensure cochlear interaction. DPOAEs provide an interesting model for functional exploration of the efferent system, since they seem to be the only type of otoacoustic emission that can be recorded in both humans and in the majority of animals, and since results are obtained in the same way from both animals and humans, which allows experimental animal models very close to the human model.     

Theoretical and applied external ear acoustics

The external ear (pinna and earcanal) plays a major role in transforming acoustic signals from free field to the tympanic membrane in humans. It acts as a filter to reduce low frequencies, a resonator to enhance mid frequencies (2.0 to 7.0 kHz), and a direction-dependent filter at high frequencies to augment spatial perception. The external ear transfer function is altered by variations in the physical dimension of the external ear either due to individual differences or due to mechanical obstructions such as blockages, hearing aid placement, perforation of the tympanic membrane, and use of insert earphone. It is significant that any change in the characteristics of the acoustic signal can produce considerable disparity in within- and between-individual responses. The present paper examines published studies on sound pressure transfer function provided by the external ear in humans.     

Allocation of attention in dichotic listening: Differential effects on the detection and localization of signals.

In 2 dichotic listening experiments, 96 normal right-handed adults attended selectively to the left and right ear and divided their attention equally between both ears. Participants listened for specified targets and reported the ear of entry. The material consisted of pairs of consonant–vowel syllables in Experiment 1 and pairs of rhyming consonant–vowel–consonant words in Experiment 2. Both experiments yielded a right-ear advantage for detection and for localization. Attention instructions had no effect on detection. However, focusing attention on 1 ear increased the number of targets attributed to that ear while decreasing the number of targets attributed to the opposite ear. The dissociation between detection and localization indicates that volitional shifts of attention influence late (response selection) processes rather than early (stimulus identification) processes. Selective-listening effects can be accounted for by a 2-stage model in which a fixed input asymmetry is modulated by a biased selection of responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Controlling for stimulus dominance in dichotic listening tests: A modification of !l.

Dichotic listening procedures have been used to assess cerebral lateralization in normal Ss. One particularly useful technique is the use of stimuli that fuse into a single percept. Although this procedure has many advantages over other dichotic listening methods, it is particularly susceptible to stimulus dominance, which acts as noise in a S's response data, thus reducing the power of any statistical test of the ear advantage. It is proposed that the solution to this problem is a log-linear analysis of the response data to yield a λ-type index (λ*) that is a measure of ear dominance independent of stimulus dominance. Details of the analysis are provided, as well as a sample analysis of data collected from 104 right-handed and 30 left-handed Ss. Comparisons are drawn between the log-linear analysis and other methods that have been proposed to control for stimulus dominance in this single-response dichotic fusion procedure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular analysis of multiple isolates of the major serotypes of group B streptococci

Serotyping of clinical isolates is a widely used technique for epidemiologic study of group B streptococcal infections. However, serotyping cannot definitively determine epidemiologically related or unrelated isolates. We investigated the use of restriction endonuclease analysis (REA) with both conventional agarose gel electrophoresis (AGE) and pulsed-field gel electrophoresis (PFGE) in 50 isolates of the major serotypes of group B streptococci. Single digestion with HindIII and HaeIII and double digestion with HindIII and then EcoRI were used for conventional AGE, and digestion with SmaI was used for PFGE. The molecular profile of one strain was compared with those of the strains within the same serotype as well as with the profiles from strains of different serotypes. Among 10 type Ia, Ia/alpha, Ia/alpha+beta, and Ia/R1 isolates and depending on the restriction enzyme used, we found between five and six REA patterns by conventional AGE and seven by PFGE; among 4 type Ib/alpha+beta isolates we found 2 to 4 REA patterns by conventional AGE and 4 by PFGE; among 21 type II, II/alpha, II/beta, II/alpha+beta, and II/R4 isolates, we found 11 REA patterns by both AGE and PFGE; and among 14 type III, III/R1, and III/R4 isolates, we found from 7 to 12 different REA patterns by AGE and 10 by PFGE. In total, among 13 serotypes and one nontypeable strain, we found 29 to 31 REA patterns by conventional AGE and 33 by PFGE. A particular REA pattern within a serotype was different from the patterns found in the other serotypes, suggesting that REA analysis by using conventional AGE or PFGE is a sensitive method for analyzing genetic relatedness and diversity in group B streptococci and has potential value in molecular epidemiologic studies.     

Attention allocation modulates the processing of hierarchical visual patterns: A comparative analysis of capuchin monkeys (Cebus apella) and humans.

Humans show a global advantage when processing hierarchical visual patterns, and they detect the global level of stimulus structure more accurately and faster than the local level in several stimulus contexts. By contrast, capuchins (Cebus apella) and other monkey species show a strong local advantage. A key factor which, if manipulated, could cause an inversion of this effect in monkeys is still to be found. In this study, we examined whether it was possible to induce attention allocation to global and local levels of perceptual analysis in capuchin monkeys and if by doing so, their local dominance could be reversed. We manipulated attentional bias using a matching-to-sample (MTS) task where the proportion of trials requiring global and local processing varied between conditions. The monkeys were compared with humans tested with the same paradigm. Monkeys showed a local advantage in the local bias condition but a global advantage in the global bias condition. The role of attention in processing was confined to the local trials in a first phase of testing but extended to both local and global trials in the course of task practice. Humans exhibited an overall global dominance and an effect of attentional bias on the speed of processing of the global and local level of the stimuli. These results indicate a role for attention in the processing of hierarchical stimuli in monkeys and are discussed in relation to the extent to which they can explain the differences between capuchin monkeys and humans observed in this and other studies. (PsycINFO Database Record (c) 2011 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)     

Dichotic listening performance in relation to callosal area on the MRI scan.

The structural model of dichotic listening performance predicts reduced left ear scores in people with left hemisphere language dominance and impairment of the corpus callosum. The prediction was tested in patients with multiple sclerosis and evidence on the basis of magnetic resonance imaging (MRI) of callosal thinning. The results are partly in accordance with the structural model but indicate an effect of attentional set that correlated with quantitative measures of preserved callosal connections. The pattern of ear advantage was reversed in a small group of non-right-handed people. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does early care affect joint attention in great apes (Pan troglodytes, Pan paniscus, Pongo abelii, Pongo pygmaeus, Gorilla gorilla)?

The ability to share attention with another is the foundation on which other theory of mind skills are formed. The quality of care received during infancy has been correlated with increased joint attention in humans. The purpose of this study was to assess the effects of care style (responsive or basic) and caregiver type (ape or human) during the first 6 months on joint attention in 4 great ape species (Pan troglodytes, Gorilla gorilla, Pongo spp., and Pan pansicus). Great apes engaged in joint attention with conspecifics and humans regardless of the style of early care they experienced from either a great ape mother or human caregiver. This finding suggests that joint attention is a robust ability in great apes that is resilient against at least some differences in early care. Future studies using additional measures of early care quality are recommended. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats and humans paying attention: Cross-species task development for translational research.

Substantial gains have been made on the neurobiology of attention from systems neuroscience work in animal models and human cognitive neuroscience. However, the integration of rodent-based research on the specific neurotransmitter systems that subserve attention with the results from human behavioral and neuroimaging studies has been hampered by the lack of tasks that validly assess attention in both species. To address this issue, an operant sustained attention task that has been extensively used in research on the neurobiology of attention in rats was redesigned and validated for use in humans. Although humans showed better performance overall, the two species showed similar effects of several attention-related variables, including the introduction of distractor-related challenge. This task provides a useful tool for integrative, cross-species research and may help to determine how specific neurotransmitter systems contribute to the hemodynamic changes observed in human functional neuroimaging experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deconfounding the effects of dominance and social acceptance on self-esteem.

Three studies examined the independent effects of social acceptance and dominance on self-esteem. In Studies 1 and 2, participants received false feedback regarding their relative acceptance and dominance in a laboratory group, and state self-esteem was assessed. Results indicated that acceptance and dominance feedback had independent effects on self-esteem. Study 2 showed that these effects were not moderated by individual differences in participants' self-reported responsivity to being accepted versus dominant. In Study 3, participants completed multiple measures of perceived dominance, perceived acceptance, and trait self-esteem. Results showed that both perceived dominance and perceived acceptance accounted for unique variance in trait self-esteem, but that perceived acceptance consistently accounted for substantially more variance than perceived dominance. Also, trait self-esteem was related to the degree to which participants felt accepted by specific people in their lives, but not to the degree to which participants thought those individuals perceived them as dominant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Opposing effects of DHEA replacement in elderly subjects on declarative memory and attention after exposure to a laboratory stressor

Aging is accompanied by a continuous decline of the adrenal steroid hormone DHEA and its ester DHEAS. Results from studies in rodents have demonstrated that DHEA(S) administration can enhance memory in several test paradigms. However studies from this laboratory did not find positive effects of DHEA treatment on cognitive performance in young and elderly humans. With respect to a possible mechanism of DHEA activity, effects on several neurotransmitter receptors as well as a possible antiglucocorticoid action are discussed. For high levels of glucocorticoids, a disruptive effect on hippocampal mediated memory is documented in rodents and humans. Therefore it was speculated that, if an antiglucocorticoid action of DHEA would underlie the observed beneficial effects of DHEA on memory, these effects might only be detectable if subjects are stressed (and therefore have high cortisol levels). To test this hypothesis 75 elderly women and men participated in a placebo controlled experiment. Subjects took DHEA (50 mg/day) or placebo for 2 weeks (double blind). Thereafter they participated in a standardized psychosocial laboratory stressor (Trier Social Stress Test; TSST). Before and after stress exposure subjects completed two declarative memory tests (visual-verbal and spatial) as well as one attention test. In addition recall of visual material learned before stress was assessed after stress. Baseline DHEAS levels were significantly lower compared with young adults. DHEA replacement increased DHEAS levels into ranges found in young subjects. DHEA-substituted subjects showed a trend towards a larger cortisol stress response. In the visual memory test subjects under DHEA recalled less items after stress which they had learned before stress. In the attention test however subjects under DHEA performed better than subjects from the placebo group after stress. No interaction between stress and DHEA was found for the spatial memory task. The effects of DHEA substitution on memory and attention after stress exposure seem to be heterogenous. While recall of previously learned material seems to be impaired, attention is enhanced. These results do not support the idea of a direct antiglucocorticoid or anti-stress effect of DHEA on hippocampal mediated memory functions.     

Multifrequency tympanometry in chinchillas

Multifrequency tympanometry (MFT), using probe frequencies ranging from 226-2,000 Hz, was performed on normal chinchillas to obtain normative data against which to compare results from animals with middle ear pathology. A series of validating experiments was conducted to determine the effects of anatomical alterations of the middle ear on MFT. These included artificially extending the ear canal, opening the bulla, injecting saline into the middle ear, and disrupting the ossicular chain. The results indicate that MFT characteristics of chinchilla ears are qualitatively similar to those observed in normal humans and patients with middle ear disease, and MFT provides information that is not available from the 226-Hz tympanogram.     

Reliability and magnitude of perceptual asymmetries in a dichotic word recognition task.

The hypothesis that control of idiosyncratic attention deployment and retrieval strategies would improve the reliability and magnitude of laterality effects obtained in an auditory word recognition task was investigated. Sixty participants completed a dichotic word recognition task under 1 of 3 conditions. In free recall, they reported the 2 words presented on each trial (1 to each ear). In focused attention, they reported only the word presented to a prespecified ear. In target detection, they indicated whether a target word was presented to either ear on each trial. Results showed that the target-detection condition produced the largest and most reliable laterality effects compared with the other 2 conditions. The mechanisms likely to be responsible for these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is the afferent auditory message modulated by the cortex?

An eventual modulation of the afferent auditory message by the cortex is the subject of this study. To test this hypothesis, clicks (10 Hz, 100 microseconds) of white noise of 40 and 70 dB Hl were sent alternatively into the ears of normally hearing volunteers, while the brainstem evoked potentials were recorded. The subjects were asked to focus or relax their attention on one or other ear. Thirty subjects aged less than 25 years (15 men and 15 women) with normal hearing level, were split into two groups. The first group was asked to focus first on the more strongly stimulated ear (70 dB), the second group on the more weakly stimulated one (40 dB). Each subject received (1) without any instruction about attention: 40 dB on the left ear (L), 70 dB on the right ear (R); 40 dB then 70 dB bilateral; (2) 2 runs with 40 dB on the L and 70 dB on the R focussing on the most or less strongly stimulated ear; (3) a run without instruction with 70 dB on the L and 40 dB on the R, and (4) two runs with 70 dB on the L and 40 dB on the R focussing enough on the more or less strongly stimulated ear. On the evoked potentials simultaneously recorded, amplitudes and latencies of the pikes were measured and compared. From these experiments, the following elements were obtained. (1) The measured potentials were always caused by ipsilateral stimuli. (2) Focussing on left or right ear was not equivalent. (3) A gender difference appeared in the brainstem auditory responses. (4) Preferential attention paid to the left ear was more efficient than to the right one. (5) Attention can alter the whole nervous pathway with considerable lengthening of O-I, O-III, O-V, III-V, I-V but not I-III latencies. The III wave amplitude generally decreased on the side where attention was focussed while V waves seemed not to vary. These first results indicate that a cortico-efferent pathway stimulated by the attention plays a role in the auditory responses modifying the afferent message. These effects were not the same among the side focussing attention and among sex.