Haptic curvature discrimination at several regions of the hand

Static haptic discrimination of the curvature of convex, concave, or straight 20-cm-long strips was investigated for nine placements on the hand. In one condition, the strips were touched with the palmar side of the hand, and in the other condition, with the dorsal side. The influence of the lengths of the strips, and thus of contact lengths, was also investigated. For all placements, discrimination was poorer in the dorsal than in the palmar condition, owing to poorer cutaneous resolution on the dorsal side of the hand (the kinesthetic stimulation was the same in both conditions). Thus cutaneous stimulation is important. In both experiments, performance appeared to depend primarily on contact length. Moreover, the discrimination thresholds for all different placements and contact lengths followed the same trend. We conclude that in these experiments the effective stimulus for the discrimination of curved strips is the total difference of local surface attitude--that is, the slope difference over the far ends of the stimulus.     

Hemispheric differences in context sensitivity during lexical ambiguity resolution

Three experiments were conducted to investigate the influence of contextual constraint on lexical ambiguity resolution in the cerebral hemispheres. A cross-modal priming variant of the divided visual field task was utilized in which subjects heard sentences containing homonyms and made lexical decisions to targets semantically related to dominant and subordinate meanings. Experiment 1 showed priming in both hemispheres of dominant meanings for homonyms embedded in neutral sentence contexts. Experiment 2 showed priming in both hemispheres of dominant and subordinate meanings for homonyms embedded in sentence contexts that biased a central semantic feature of the subordinate meaning. Experiment 3 showed priming of dominant meanings in the left hemisphere (LH), and priming of the subordinate meaning in the right hemisphere (RH) for homonyms embedded in sentences that biased a peripheral semantic feature of the subordinate meaning. These results are consistent with a context-sensitive model of language processing that incorporates differential sensitivity to semantic relationships in the cerebral hemispheres.     

Hemispheric differences in layer III pyramidal neurons of the anterior language area

OBJECTIVE: The major objective of this study was to determine if the lateralization of motor speech functions may be associated with hemispheric differences in the size of layer III pyramidal neurons in Brodmann's area 45. DESIGN: A case series design involving postmortem human specimens was used to compare the cross-sectional area of NissI-stained layer III pyramidal neurons of Brodmann's area 45 from the left and right hemispheres. SUBJECTS: A convenience sample consisting of seven cases with no known neurological or psychiatric disorders was obtained at autopsy. MAIN OUTCOME MEASURES: The cross-sectional area of layer III pyramidal neurons in both left and right hemispheres was measured in four fields per hemisphere per brain using a computerized image analysis system. Measurements of both the largest layer III pyramids and of all layer III pyramids were done. RESULTS: The largest layer III pyramidal neurons of area 45 were significantly larger in the left than in the right hemisphere in both an unblinded and a blinded series of measurements. However, this hemispheric difference appeared to be restricted to the largest neurons, since the mean size of all layer III pyramids in this area was not significantly different in the left and right hemispheres. CONCLUSIONS: The presence of a unique population of large pyramidal neurons in left Brodmann's area 45 may be related to the involvement of this region in the circuitry that mediates motor speech functions.     

Hemispheric differences in sizes of receptive fields or attentional biases?

Ss judged whether 2 successive line segments had the same orientation. The pairs were lateralized, and the location on the screen and the distance between the segments in a pair were varied. When stimuli were relatively close to the center of the screen, Ss evaluated segments that were relatively far apart more quickly when they were presented in the left visual field and tended to judge segments that were close together more quickly when they were presented in the right visual field. In contrast, when the line segments were moved into the periphery, the previous pattern of results was reversed. In addition, results in a second block of trials depended on how attention had been set in the 1st set of trials. The observed hemispheric differences were due to attentional effects, not stable physiological properties of the brain. Previously observed hemispheric differences in spatial frequency analysis could reflect attentional biases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric differences in indexical specificity effects in spoken word recognition.

Variability in talker identity, one type of indexical variation, has demonstrable effects on the speed and accuracy of spoken word recognition. Furthermore, neuropsychological evidence suggests that indexical and linguistic information may be represented and processed differently in the 2 cerebral hemispheres, and is consistent with findings from the visual domain. For example, in visual word recognition, changes in font affect processing differently depending on which hemisphere initially processes the input. The present study examined whether hemispheric differences exist in spoken language as well. In 4 long-term repetition-priming experiments, the authors examined responses to stimuli that were primed by stimuli that matched or mismatched in talker identity. The results demonstrate that indexical variability can affect participants' perception of spoken words differently in the 2 hemispheres. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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

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

Empirical assessment of visceral self-perception: Individual and sex differences in the acquisition of heartbeat discrimination.

Employed a new methodology based on the theory of signal detection to evaluate objectively and quantitatively the performance of 9 male and 9 female undergraduates. Results confirm the validity of the methodology for assessing heartbeat detection and also confirmed earlier observations that males are able to learn to detect their own heartbeats but females are not. Findings are discussed with particular reference to implications for viscerally based theories of emotion. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in response to novelty, amphetamine-induced activity and drug discrimination in rats

Individual group, and ethnic differences in behavior have been an object of long, continuing, and contentious interest, both in the sciences and in popular culture. For well over 2,000 years, psychological traits, particularly those described as 'intelligence', have generally been considered the major factors in fitness in humans. After reviewing contemporary scientific thinking on intelligence, the psychometric methods used for the construction of psychological tests are presented and examined in the context of natural selection and metric characters. There are essential differences between the disciplines of genetics and of psychology such that the concepts of the two are more divergent than might superficially appear to be the case. The analysis leads to the conclusion that standard psychometric methodology cannot yield tests appropriate for measurement of evolutionary fitness characters.     

Hemispheric priming in a reading task

Some theories of reading and of reading disorders assume that the right hemisphere plays an important role in reading. However, despite the evidence supporting the competence of the right hemisphere in recognizing isolate words, there is little direct evidence to support the claim that the right hemisphere is involved in the continuous reading of connected text. This study used a stationary window technique to present text passages in a continuous reading task. At intervals during the reading of the text, a lexical decision was required to a target projected to the left or right side of the visual field. On some trials, the target was primed by a semantic associate which appeared in the passage immediately prior to the presentation of the target. It was found that these associative primes facilitated responses to LVF and RVF targets to an equal degree. It was also found, in agreement with previous investigations, that overall RTs to LVF targets were longer than RTs to RVF targets. It is suggested that these results indicate that the right hemisphere is actively involved in the comprehension of text in normal reading. However, the right hemisphere may not acquire text information directly, but may instead receive most of its information following initial analysis and decoding by the left.     

Hemispheric specialization in commissurotomized man.

Following surgical division of the neocortical commissures in humans, it is possible to test independently the 2 cerebral hemispheres on the same task and thus determine directly their competence for various cognitive skills. Studies examining the limits of language expression and comprehension in the minor hemisphere of these patients are reviewed. Evidence of right-hemispheric superiority for the perception of spatial and part-whole relations is discussed with respect to theories postulating a basic dissimilarity in the manner by which information is processed in the major and minor hemispheres. Data are also reviewed which suggest that competition between the 2 hemispheres for control of the motor system is resolved in favor of the hemisphere dominant for the cognitive function required in the task. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric asymmetries in category-specific word retrieval

We examined whether 53 adult non-aphasic patients with either left (22) or right temporal lobe lesions (31) demonstrate dissociable patterns of hemispheric asymmetries in category-specific word fluency tasks. The patients were asked to articulate as many appropriate words as possible within 60 or 90 s in response to six target categories. There was no effect of patient groups on the overall fluency. However, patients with a left-sided temporal lobe lesion were impaired retrieving words to 'initial letters' and to the category 'animals'. Right temporal lobe patients were impaired retrieving 'tools' and words referring to specific visual attributes. There were no fluency differences for 'food-supermarket goods' and 'flat interior'. We conclude that temporal lobe damage can result in category-specific impairments in word retrieval depending on the affected hemisphere.     

Individual differences in humans responding under a cocaine discrimination procedure: Discriminators versus nondiscriminators.

Twenty-six cocaine-abusing volunteers were trained to discriminate cocaine (80 mg/70 kg, p.o.) from placebo. On the basis of a discrimination acquisition criterion (i.e., >80% drug-appropriate responding for 4 consecutive sessions within 8–10 sessions), 18 participants were classified as discriminators (Ds) and 8 as nondiscriminators (NDs). Relative to Ds, NDs reported a greater amount of cocaine use per time. During the training phase, NDs showed significantly lower ratings than Ds on a stimulant ratings scale, regardless of the training drug condition. During the test-of-acquisition phase, cocaine-induced increases in scores on ratings of drug strength, anxious-nervous and cocaine high, as well as on a euphoria ratings scale, were significantly greater in Ds than NDs, relative to placebo. These results suggest that drug use history, general arousal level, and drug sensitivity may be important variables influencing the acquisition of cocaine versus placebo discrimination in cocaine abusers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric asymmetry in Down's Syndrome children.

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

Hemispheric lateralization of EEG in early infantile autism

Autoregressive (AR) analysis and component analysis were applied to EEGs during sleep stage 2 of normal and autistic children, since AR-coefficients of EEG characterize the autocovariance and power spectral density of EEG. In addition, as the Mahalanobis' generalized distance of the average AR coefficient vector of an EEG group at one side from that at the opposite side follows a F-distribution, the statistical inferences were carried out, whether or not there is hemispheric specialization in EEG in 21 right handed autistic children and whether there is difference between AR-spectral pattern of EEG in the autistic children and that of 28 normal children of the same age range or not. The results obtained were as follows: 1) The significant hemispheric lateralization in EEG at the significant level of 0.01 was observed in normals, whereas none of the lateralization was confirmed in autistic children. 2) The random click stimulation caused a cumulative effect on the hemispheric lateralization in the normals, but not in the autistic children. On the contrary, the effects of random flash light stimulation on hemispheric asymmetry were verified in the autistic children as well as in the normals. 3) The EEG components of autistic children were significantly different from the normal ones in frequency range of alpha-2 component wave at bilateral frontal (F1 and F2) regions and the activity of these component waves were higher in the autistic children than in the normal ones over 5 years-old. 4) These findings suggest that autistic children are not only less responsive to external stimuli, but also neurophysiologically less active in the internal regulatory mechanism.     

Hemispheric specialization and the growth of human understanding.

Connectionistic notions of hemispheric specialization and use are considered incompatible with the network organization of the human brain, and alternative concepts are suggested. The functionally specialized areas of the cerebrum are diffusely interconnected; differences in degree of connection define a "functional cerebral space" within which similar activities are represented in adjacent loci but dissimilar activities in loci that are further apart. This explains why one can easily do dissimilar things at the same time but similar things only one after another. Bilaterally represented processes relate the organism to the periphery. Lateralized processes are deployed in focal attention, the specifics being extracted by the left hemisphere and related to each other in space by the right hemisphere. These contributions to mental life are complementary modes of processing. They can be dissociated only when mentally represented. Item and relational aspects of a problem can be separately abstracted, elaborated, and communicated; there has been relatively independent growth of understanding in these 2 domains. (61 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Species differences in size discrimination in the paracellular pathway reflected by oral bioavailability of poly(ethylene glycol) and D-peptides

Animal models are frequently used to aid prediction of intestinal absorption in humans. However, there is little comparative quantitative information on species differences in paracellular permeation, which is an important route for oral absorption of small to medium-sized hydrophilic drug molecules. This study addresses this issue by comparing the molecular mass (MM) dependency in oral bioavailability between rat and dog of poly(ethylene glycol) (PEG), a polydispersed model mixture commonly used to characterize paracellular absorption, and of a series of eight D-peptides (based on D-phenylalanine). Fasted rats and dogs received PEG (400/900) and the D-peptides (MM 236-406 Da), orally and intravenously, with total 24-48 h urine collection to estimate oral bioavailability. After HPLC separation, the individual PEG oligomers and D-peptides were determined using radiometric detection, for radiolabeled material, and LC-MS, for unlabeled (PEG) material. All compounds were predominantly excreted unchanged following intravenous administration. After oral administration, the predominant peak in the radiochromatogram was unchanged material, indicating stability of the compounds in the gastrointestinal tract. A clear molecular mass dependency in oral bioavailability was seen with both series, but with absorption much greater in dog than rat. Thus, for PEG in rat, bioavailability decreased sharply from 79 to around 2% with increasing MM between 282 and 591 Da, and then tapered to around 1. 5% up to 1295 Da. Whereas in dog, bioavailability remained around 100% for oligomers up to 600 Da and then decreased quite sharply with increasing MM, tending to plateau around 13% beyond 900 Da. Likewise, for the d-peptides in rat, bioavailability decreased from 30 to 1% with increasing MM between 236 and 406 Da, whereas in dog it was 100%, declining to 16% over the same molecular range. This species difference appears to be due to a larger pore size and greater frequency of pores in the paracellular pathway of dog compared to rat. Furthermore, on the basis of comparison with literature data for PEG and selected drugs, rat would appear to be a better predictor than dog of absorption of hydrophilic compounds in human.     

Mechanism of age-related differences in frequency discrimination with backward masking: Speed of processing or stimulus persistence?

In Exp 1, frequency-discrimination thresholds were estimated in a 2-interval, forced-choice, backward masking procedure with a masker acoustically dissimilar to the targets. Young Ss were more efficient in escaping the effects of masking than were their elderly counterparts. In Exp 2, young and elderly Ss performed the same task, with a masker acoustically similar to the targets and with a target-dissimilar masker. Under target-similar masking and at short target–masker intervals, the elderly demonstrated significant improvement, reaching the level of performance of the young, whereas under the target-dissimilar masker, the age-related differences were restored. Both age-related slowing of information processing and increase in stimulus persistance can account for the results of Exp 1, but only increased stimulus persistence explains the results of Exp 2. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric interactions are different in left-handed individuals.

In a previous study, N. Cherbuin and C. Brinkman (2006) showed that in right-handed participants, interhemispheric transfer time (measured with A. T. Poffenberger's, 1912, paradigm) was a significant predictor of the efficiency of hemispheric interactions (measured with a split visual field, letter-matching task). No effect was found for degree of handedness in this study. This was surprising because handedness has been shown to be associated with differences in the morphology and the structure of the corpus callosum, and cerebral anatomical lateralization, as well as functional lateralization both in behavioral and scanning studies. Because these findings were found in a large sample, but one limited to right-handed participants, the aim of the present study was to determine whether a similar relationship was present between interhemispheric transfer time and hemispheric interaction in left-handed participants (using identical measures) and to assess whether the analysis of a larger sample that comprised both left- and right-handed participants might reveal an effect of handedness. Results demonstrate significant handedness effects, suggesting that left-handed individuals tend to have more efficient hemispheric interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)