How Impedance Measurements and Imaging Can Be Used to Characterize the Conductivity of Tissues During the Workflow of an Electroporation-Based Therapy.

In this article we investigate the possibility of using needles, which the interventional radiologist inserts near a deep-seated tumor during an electroporation-based therapy, to characterize the electrical conductivity of patient's tissues. Specifically, we propose to exploit voltage/current measurements and imaging that are performed prior to the application of electroporation pulses. The approach is partly based on the concepts of electrical impedance tomography; however, imaging is used to build a specific geometric model and compensate for the lack of information resulting from the small number of electrodes available. 3D canonical and clinical examples, where a few electrodes surround a tumor, demonstrate the feasibility of this method: solving the inverse problem to estimate tissues conductivity converges in a few iterations. For a given error on the measurement, it is also possible to calculate the error on the estimated conductivities. The uncertainty error with clinical data is at best 5% for one of the tissues identified, due to the limitations of the clinical device used. Various improvements to clinical devices are discussed to make the conductivity estimation more accurate but also to extract more information.

Assessment of 0.5 T static field exposure effect on yeast and HEK cells using electrorotation.

This study aims to examine the influence of a 0.5 T static magnetic field (SMF) on yeast and human embryonic kidney (HEK) 293 cell using electrorotation (ROT). Following 48 h exposition to the SMF, no difference was noted between ROT spectra of unexposed and exposed yeast cells, which extend previous reports on the absence of SMF effects on yeast. We also compared the ROT spectrum and the extracted electrical characteristics of HEK cells exposed during 72 h to a 0.5 T uniform static magnetic field with those of unexposed cells. SMF potential effects on HEK proliferation kinetics and cell morphology were also assessed by using the trypan blue exclusion method and scanning electron microscopy, respectively. At last, no significant differences were observed between control and exposed HEK cells concerning electrical properties, growth, and morphology.

Gender differences in laterality on a dichotic task: the influence of report strategies.

Four experiments were conducted to investigate the influence of report strategies on gender differences in laterality. Ten males and 10 females completed a dichotic consonant-vowels pairs task under four conditions manipulating reporting strategies. Free recall allowed participants to report syllables in any order they chose, whereas order of report control required the report of a pre-specified ear first. In focused attention, they reported only one response from a pre-specified ear. Finally, in ABX discrimination, participants were required to indicate whether a binaural probe was one of the stimuli presented dichotically on the same trial. It was hypothesized that improved control of report strategies would increase the likelihood of detecting significant gender differences in laterality. This was confirmed when results showed no significant gender differences in laterality for the free recall and order of report control conditions, whereas focused attention produced marginal gender differences and clearly significant differences were obtained in the ABX discrimination condition. These findings have implications for interpretations of gender differences in laterality based on strategy effects. Interpretations emphasize the role of attention deployment in the measurement of laterality.

Reliability and magnitude of auditory laterality effects: the influence of attention.

Three experiments investigated the effect of attention on the reliability and magnitude of laterality effects in a dichotic listening task. In Experiment 1, 40 undergraduate students were randomly assigned to either a free-recall or focused-attention condition. In Experiment 2, 40 undergraduate students completed a dichotic listening task with exogenous cueing. They were randomly assigned to either a 150-ms stimulus onset asynchrony (SOA) or a 450-ms SOA condition. In Experiment 3, 20 participants completed a task where the SOA for the exogenous cue was randomized on a trial to trial basis. Results indicated that focused attention increased the magnitude of the laterality effect. Contrary to predictions, this finding was not due to reduced variability in the focused-attention task compared to the free-recall task. In addition, a cueing tone was only effective at directing attention in Experiment 3. Specifically, a significant right ear advantage observed at the 150-ms SOA was reduced at the 450-ms SOA. It appears that, in Experiment 3, the tone was effective at controlling attention because it reduced the systematic bias that has been suggested to account for the laterality effects observed in dichotic tasks.

Reliability and magnitude of visual laterality effects: the influence of attention.

Two studies investigated the test-retest reliability of laterality effects in visual tasks. In each of the studies, 160 right-handed participants were tested. In Experiment 1, a lexical decision task was used under four testing conditions: no control of attention, fixation control, bilateral presentation with endogenous cue, and bilateral presentation with exogenous cue. In Experiment 2, the same four conditions were used in a letter-matching task in which participants had to indicate whether two letters in a different case had the same name. Results showed a significant right visual field advantage in the first testing session. However, this advantage was eliminated in the second session, suggesting that attention was not fully controlled by any of the procedures. In addition, the reliability of laterality effects was greater when control of attention was applied. The discussion focuses on the importance of controlling attention when assessing laterality by means of a visual task. Alternative explanations of the present findings are also considered.

Reliability of a dichotic consonant-vowel pairs task using an ABX procedure.

The present study examined the reliability of a dichotic consonant-vowels (CV) pairs task using an ABX procedure. Twenty-four right-handed subjects (12 females, 12 males) completed a dichotic CV pairs task twice in a test-retest approach. The conventional free-recall or directed-attention procedure was replaced by an ABX procedure, in which participants were required to determine whether a CV heard binaurally was present in a dichotic pair presented on the same trial. Results showed the expected right-ear advantage in dichotic listening for verbal material. However, reliability was not as high as has been reported with a directed-attention procedure. Methods for improving the reliability of the ABX discrimination task are discussed. In addition, the discussion emphasizes the usefulness of the ABX approach for testing clinical populations.

On the reliability and validity of noninvasive laterality measures.

The purpose of the present study was to quantify the reliability and validity of laterality effects obtained with noninvasive measures. A meta-analytic approach was used with 88 significance levels pertaining to reliability data and 11 significance levels concerning the validity of the measures. Results showed that reliability is affected by a number of procedural factors. In general, reliability was found to be at a moderate level. The validity of laterality measures was found to be significant but low. These findings suggest that more empirical work is needed to investigate and to improve the validity and reliability of the tasks used in the assessment of laterality effects.

Scoring procedure, performance factors, and magnitude of sex differences in spatial performance.

The purpose of the present study was to demonstrate the influence of procedural factors on the magnitude of sex differences in a test of spatial ability. Two hundred and seven females and 155 males were administered the Mental Rotations Test (MRT) under timed and untimed conditions. Four different scoring procedures were used: total score, ratio of correct responses to the number of items attempted, score out of 24, and score out of 48. Significant sex differences were obtained in the timed condition but not in the untimed condition. Results also revealed that the magnitude of sex differences was reduced when a ratio score was used. Analysis of the pattern of responses provided insights into the causes of sex differences on the MRT. Results are interpreted in terms of their implications for research on sex differences in spatial ability.

On the magnitude of laterality effects and sex differences in functional lateralities.

In the last 20 years, the hypothesis that men and women differ in functional lateralities has been used to account for sex-related differences in verbal and spatial skills. However, this hypothesis has not been clearly supported, with some reviewers confirming it (McGlone, 1980 for example), and others rejecting it (Fairweather, 1982 for example). The purpose of the present study was to provide a definite test of this hypothesis and to estimate the magnitude of overall laterality effects by means of a meta-analytic procedure. A total of 396 significance levels from a variety of studies on functional asymmetries utilising auditory, visual, or tactile presentation of verbal or nonverbal stimuli were sampled. Results showed that laterality effects tend to be large and significant but that they are heterogeneous in the visual modality. Homogeneity was generally achieved by a partition of the studies in terms of the specific task used. The results also showed sex differences to be significant in two modalities (visual and auditory). The data indicated the presence of sex differences in favour of men in functional asymmetries. However, it appears that the findings are not resistant to the file drawer problem. The results are discussed with regard to their implications for explanations of individual differences in cognitive abilities. The relation between functional lateralities and anatomical asymmetries is also discussed.

Effect of practice on laterality in a mental rotation task.

The purpose of the present study was to investigate the effect of practice on the lateralization of mental rotation skills. Forty-six females and 46 males completed four blocks of 64 trials in a lateralized mental rotation task. Results revealed a reduction in reaction time and error rate across blocks, thus demonstrating a practice effect. A shift from a right hemisphere advantage to a left hemisphere advantage across blocks of trials was also found. The results are discussed in terms of their implication for hypotheses linking laterality and training. Practical implications for laterality research are also discussed.

Magnitude of sex differences in spatial abilities: a meta-analysis and consideration of critical variables.

In recent years, the magnitude, consistency, and stability across time of cognitive sex differences have been questioned. The present study examined these issues in the context of spatial abilities. A meta-analysis of 286 effect sizes from a variety of spatial ability measures was conducted. Effect sizes were partitioned by the specific test used and by a number of variables related to the experimental procedure in order to achieve homogeneity. Results showed that sex differences are significant in several tests but that some intertest differences exist. Partial support was found for the notion that the magnitude of sex differences has decreased in recent years. Finally, it was found that the age of emergence of sex differences depends on the test used. Results are discussed with regard to their implications for the study of sex differences in spatial abilities.

Masking and visual field effects on a lateralized rod-and-frame test.

The rod-and-frame test (RFT) has been widely used in the study of sex differences in spatial abilities. However, laterality studies involving this test are very scarce. An experiment was conducted to investigate whether laterality effects would be affected by post-stimulus masking. Ninety-six subjects participated in the experiment. For half the subjects, stimuli were followed by a blank screen, while for the other half, stimuli were followed by a mask. An overall left visual field advantage (LVFA) was found in the task. An interaction of sex of subjects, masking conditions, and frame tilt was also found. Further analyses showed that the sex by angle of frame interaction was significant when a mask was presented after the stimuli, but not when no mask followed the stimuli. Data tended to confirm the hypothesis that the LVFA was only significant when a mask was presented after the stimuli. These findings demonstrate the usefulness of a masking procedure in visual field studies, whereas the right hemisphere advantage found on the RFT is consistent with previous findings with visuo-spatial tasks.

Cognitive abilities in androgen-insensitive subjects: comparison with control males and females from the same kindred.

To determine the effect of androgen insensitivity on cognitive abilities, subjects with the syndrome of complete androgen insensitivity (AI) were compared to control males and females from the same kindred on the Spanish version of the Wechsler Adult Intelligence Scale (WAIS). All subjects had similar sociocultural backgrounds and only right-handed subjects were used in the primary analysis. This design was chosen to diminish the effect of critical variables on test performance, thereby highlighting the effect of androgen unresponsiveness on cognition. The results indicated that control males and females were superior to androgen insensitive subjects on the Perceptual Organization factor, which included five visuospatial subtests. Separate analysis of these subtests revealed that males performed significantly better than females on Block Design, Picture Completion, and Object Assembly, and better than androgen insensitive subjects on all five subtests. Females were superior to androgen insensitive subjects on four subtests (Block Design, Picture Completion, Digit Symbol, and Picture Arrangement). Despite the small sample size, when female siblings were compared to their AI sisters, they were also superior on these four visuospatial subtests. The difference between the Verbal Comprehension and Perceptual Organization factors was greatest in androgen-insensitive subjects, while control males demonstrated the least difference. Females and AI subjects did not differ from one another on the Freedom from Distractibility factor nor on the subtests comprising it, but their performances were poorer than control males. None of the groups differed significantly on Full Scale IQ, Verbal IQ, the Verbal Comprehension factor, or any subtests included in this category.(ABSTRACT TRUNCATED AT 250 WORDS)

Gender, level of spatial ability, and lateralization of mental rotation.

The present study indicates that some of the inconsistencies in studies of the lateralization of mental rotation may be a consequence of uncontrolled individual differences in the general level of spatial ability. In order to investigate the relation between spatial ability and the lateralization of mental rotation, 48 subjects (24 males and 24 females) were divided into three groups based on their performance on a standardized test of spatial ability. They then performed a lateralized two-dimensional mental rotation task. The results showed the typical mental rotation function in that angle of rotation and reaction time were linearly related. A significant spatial ability by visual field interaction indicated that subjects with low spatial ability had a left field advantage, whereas subjects with medium spatial ability showed no field advantage and subjects with high spatial ability showed a right field advantage. Gender also interacted with visual field, with males showing a left visual superiority and females an insignificant right visual field advantage. A significant three-way interaction of gender, spatial ability, and angle of rotation reflected the fact that low spatial males were more profoundly affected by rotation than the other groups. The results suggest that at least some of the inconsistent findings in studies of lateralization of mental rotation may be accounted for by differences in the level of spatial ability.