Left-handed Subjects Research Articles

Lateralization of the Fine Motor Skills in Right - and Left-handed Men and Women

Introduction: Motor performance is an important feature that can be measured to observe the development of the central and peripheral nervous system. Fine motor skill assessed by Morische-Leistungs-Serie (MLS) was studied in normal male and female right-handers and left-handers considering familial sinistrality and writing hand. Evaluations were conducted by measuring fine motor performance through the use of a modern computerized model. Materials and Methods: Hand preference was assessed by the Edinburgh Handedness Inventory Geschwind score (GS). Fine motor skills were measured by the MLS in the computerized Vienna Test System. Results: Left-handed volunteers had a significantly higher fine motor skills in both dominant and nondominant hands compared to right-handed volunteers. Conclusions: These results suggest that the contributions of the right and left cerebral hemispheres to the motor output of the brain depend on sex and more importantly, hand preference. It was determined that left handed subjects were more skillfull than right-handed subjects when dominant hands or weak hands were compared.

EVALUATION OF THE EFFECT OF HAND DOMINANCE ON MEDIAN NERVE CROSS-SECTIONAL AREA AMONG HEALTHY ADULT SUBJECTS: A CROSS-SECTIONAL STUDY

Background:This study was designed considering the existing controversies on the normal range of median nerve cross-sectional area (MNCSA) and its association with hand dominance. Methods:In this cross-sectional descriptive study, the upper limbs of 100 healthy subjects (46 men and 54 women) were assessed bilaterally by sonography. MNCSA was measured at the level of the carpal tunnel inlet. Results:Calculated MNCSA values were 9.29 mm2 and 9.54 mm2 for the right and left sides, respectively. No significant difference was observed between the right and left hands. No significant correlation was observed between hand dominance and MNCSA in right-handed or left-handed subjects. Conclusion:Hand dominance does not significantly affect MNCSA at the wrist level, and thus does not affect the diagnosis of carpal tunnel syndrome.

Classification of primitive manufacturing tasks from filtered event data

Collaborative robots are increasingly present in industry to support human activities. However, to make the human–robot collaborative process more effective, there are several challenges to be addressed. Collaborative robotic systems need to be aware of the human activities to (1) anticipate collaborative/assistive actions, (2) learn by demonstration, and (3) activate safety procedures in shared workspace. This study proposes an action classification system to recognize primitive assembly tasks from human motion events data captured by a Dynamic and Active-pixel Vision Sensor (DAVIS). Several filters are compared and combined to remove event data noise. Task patterns are classified from a continuous stream of event data using advanced deep learning and recurrent networks to classify spatial and temporal features. Experiments were conducted on a novel dataset, the dataset of manufacturing tasks (DMT22), featuring 5 classes of representative manufacturing primitives (PickUp, Place, Screw, Hold, Idle) from 5 participants. Results show that the proposed filters remove about 65% of all events (noise) per recording, conducting to a classification accuracy up to 99,37% for subjects that trained the system and 97.08% for new subjects. Data from a left-handed subject were successfully classified using only right-handed training data. These results are object independent.

Overview of workers hand skin hydration levels on tofu maker at the tofu factory in Matraman district, East Jakarta

The parameters of human skin health can be assessed from the level of skin hydration. Skin hydration level is the water content in the stratum corneum which is strongly influenced by natural moisturizing factor (NMF) and intercellular lipids. These components can be disrupted when exposed to irritants, such as detergents, too acidic substances, and so on. This condition can cause a decrease in skin hydration levels and becomes inactive, thereby it increases the skin's sensitivity to exogenous factors and infections. Traditional tofu factory workers are workers who have a risk of experiencing a decrease in skin hydration levels due to frequent exposure to tofu-making ingredients with an acidic pH. In Matraman Sub-district, East Jakarta, there are several tofu factories with the manufacturing process that is still processed traditionally. This descriptive observational study with a cross-sectional design aims to determine the overview of hand skin hydration levels in tofu-making workers located in the traditional tofu factory at Matraman District, East Jakarta. So that the workers and factory owners are expected to improve the quality of their workers. Data were obtained by measuring skin hydration levels in 100 study subjects using SK-IV corneometer and filling out questionnaires. Results: an overview of the skin hydration levels of right-handed and left-handed subjects with an average of 20,42% (very dry skin). The average level of skin hydration was lowest in the 60-70 year age group (19,35%), and in the 20-30 year age group (21,65%) and the male group had higher levels (20,59%). Level measurement at the hand location was obtained very dry skin category on the back of the right hand (100%). The more frequent of the frequency exposure to chemicals, the lower the hydration level of the skin (20,08%).

Electroencephalographic and Autonomic Correlates of Imaginary and Real Movements of Legs in Right-Handers and Left-Handers

—Changes in the spectral power (SP) of electroencephalogram (EEG) in the α-band and the heart rate variability (HRV) were studied in subjects with right and left motor dominance profiles during imaginary and real flexion of right and left feet. During the implementation of motor tasks, a pronounced desynchronization of α-rhythm in frontal and central leads and its less significant changes in parietal and occipital zones of both hemispheres were revealed. The peculiarity of right-handers during mental and real leg movements was the variable and asymmetric character of changes in the SP of α-rhythm in the bilateral leads from various cortical areas. In left-handed subjects, when imagining and performing movements, the desynchronization of α-rhythm in different leads had the same severity and there were practically no hemispheric asymmetry in SP. Right-handers had are latively stable vegetative status during the performance of motor tasks, and HRV changes occurred mainly with real leg movements. In left-handers HRV parameters changed more strongly and mainly during mental actions with their feet. Correlations were found between the α-rhythm SP and HRV parameters, depending on the type of movement and the motor dominance profile of subjects. The obtained data reflect the peculiarities of regulation mechanisms of voluntary leg movements and the differences in the vegetative support of motor activity in right-handed and left-handed people.

Impact of handedness on interlimb transfer depending on the task complexity combined with motor and cognitive skills

PurposeTask complexity could affect acquisition efficiency of motor skills and interlimb transfer; however, how task complexity affects interlimb transfer remains unclear. We hypothesized that left- and right-handed participants may have different interlimb transfer efficiency depending on the task complexity. MethodsLeft-hand (n = 28) and right-hand (n = 28) dominant participants (age = 24.70 ± 4.02 years, male:female = 28:28) performed a finger sequence test with two levels of complexity (simple: one-digit with four fingers vs. complex: two-digit with five fingers) before and after ten trials of 2-min practice each on the same apparatus. The speed and task errors were measured and analyzed. ResultsRight-handed participants failed to improve performance on their right hand (non-trained hand) after contralateral left-hand practice in the simple finger sequence task. In contrast, the left-handed participants improved performance on non-trained hands both right and left after contralateral practices. In the complex task, however, both the left- and right-handed participants improved performance on non-trained hands by contralateral practices. ConclusionOur results showed that task complexity of skilled practice gave different effects on interlimb transfer between right- and left-handed subjects. It appears that a certain level of appropriate complexity is necessary to detect inter-limb transfers in motor learning in right-handed subjects.

Two neuroanatomical subtypes of males with autism spectrum disorder revealed using semi-supervised machine learning

BackgroundClinical and etiological varieties remain major obstacles to decompose heterogeneity in autism spectrum disorders (ASD). Recently, neuroimaging raised new hope to identify neurosubtypes of ASD for further understanding the biological mechanisms behind the disorder.MethodsIn this study, brain structural MRI data and clinical measures of 221 male subjects with ASD and 257 healthy controls were selected from 7 independent sites from the Autism Brain Image Data Exchange database (ABIDE). Heterogeneity through discriminative analysis (HYDRA), a recently-proposed semi-supervised clustering method was utilized to divide individuals with ASD into several neurosubtypes by regional volumetric measures of gray matter, white matter, and cerebrospinal fluid. Voxel-wise volume, clinical measures, dynamic resting-state functional magnetic resonance imaging (R-fMRI) measures among different neurosubtypes of ASD were explored. In addition, support vector machine (SVM) model was applied to test whether the neurosubtyping of ASD could improve diagnostic accuracy of ASD.ResultsTwo neurosubtypes of ASD with different voxel-wise volumetric patterns were revealed. The full-scale intelligence quotient (IQ), verbal IQ, Autism Diagnostic Observation Schedule (ADOS) total scores and ADOS severity scores were significantly different between the two neurosubtypes, the total intracranial volume was correlated with performance IQ in Subtype 1 and was correlated with ADOS communication score and ADOS social score in Subtype 2. Compared with Subtype 2, Subtype 1 showed lower dynamic R-fMRI measures, lower dynamic functional architecture stability, higher mean and lower standard deviation (SD) of concordance among dynamic R-fMRI measures in cerebellum. In addition, classification accuracies between ASD neurosubtypes and healthy controls were significantly improved compared with classification accuracy between entire ASD group and healthy controls.LimitationsThe present study excluded female subjects and left-handed subjects, which limited the ability to investigate the associations between these factors and the heterogeneity of ASD.ConclusionsThe two distinct neuroanatomical subtypes of ASD validated by other data modalities not only adds reliability of the result, but also bridges from brain phenomenology to clinical behavior. The current neurosubtypes of ASD could facilitate understanding the neuropathology of this disorder and could be potentially used to improve clinical decision-making process and optimize treatment.

Decoding self-automated and motivated finger movements using novel single-frequency filtering method – An EEG study

Electroencephalography (EEG) provides the temporal resolution required to map the neural activations for studying motor movements and control. This study aims to compare the power amplitude of electrodes covering the central and frontal regions of a 32-channel scalp EEG. The activations from a standard index finger-tapping and a game paradigm are analyzed. Twenty-five right-handed and five left-handed healthy subjects (range = 18–30 years; mean = 24.25 years; SD = 3.96 years) participated in this study. A novel single-frequency filter (SFF) bank was applied to identify the peak amplitude from the power spectral density plots. The results show that the gaming paradigm yields lower or comparable power amplitudes than the standard finger tapping. We observed that the right-hand finger tapping by the left-handed subjects shows lower between-subject dispersion in amplitude. Nonparametric Spearman correlation showed no association between game scores and power amplitude for the right-handed participants. However, for left-handers, both positive and negative associations were observed. This study demonstrates the efficacy of SFF for extracting power amplitudes with a better signal-to-noise ratio, which has implications in BCI and motor rehabilitation applications. The findings support the role of game paradigms for motor movement research and in understanding bilateral hemispheric activations in cognitive tasks.

Tractography of the arcuate fasciculus in healthy right-handed and left-handed multilingual subjects and its relation to language lateralization on functional MRI

Functional MRI (fMRI) enables evaluation of language cortical organization and plays a central role in surgical planning. Diffusion Tensor Imaging (DTI) or Tractography, allows evaluation of the white matter fibers involved in language. Unlike fMRI, DTI does not rely on the patient’s cooperation. In monolinguals, there is a significant correlation between the lateralization of language on fMRI and on DTI. Our objective is to delineate the arcuate fasciculus (AF) in right- and left-handed trilinguals and determine if the AF laterality on DTI is correlated to language lateralization on fMRI. 15 right and 15 left-handed trilingual volunteers underwent fMRI and DTI. Laterality Index was determined on fMRI (fMRI-LI). Mean Diffusivity, Fractional Anisotropy (FA), Number of Fibers, Fiber Length, Fiber Volume and Laterality Index (DTI-LI) of the AF were calculated on DTI. 28 of the 30 subjects presented a bilateral AF. Most subjects (52%) were found to have a bilateral language lateralization of the AF on DTI. Only 4 subjects had bilateral lateralization of language on fMRI. The right AF demonstrated lower diffusivity than the left AF in the total participants, the right-handed, and the left-handed subjects. FA, Volume and Length of the AF were not significantly different between the two hemispheres. No correlation was found between the DTI-LI of the AF and the fMRI-LI. A prominent role of the right AF and a bilateral structural organization of the AF was present in our multilingual population regardless of their handedness. While in prior studies DTI was able to determine language lateralization in monolingual subjects, this was not possible in trilingual highly educated subjects.

Classifying handedness with MRI

When aggregating neuroimaging data across many subjects, an important consideration is establishing some group-level uniformity prior to further statistical analysis. Spatial normalization and motion correction are two important preprocessing steps that help achieve this goal. Researchers have also often excluded left-handed subjects due to presumptions about variable asymmetries relating to both brain structure and function, which may interfere with achieving a desired level of group homogeneity. It is well-known, however, that hand-preference is not a binary attribute and is not a perfect representation of structural asymmetry or hemispheric specialization. In an effort to demonstrate a more objective, data-driven approach for quantifying asymmetries across handedness, we tested the reliability of single-subject classification of handedness using data obtained from structural MRI in extant samples. We utilized data from deformation fields created during the spatial normalization process within a priori regions of interest (ROIs), including the motor and somatosensory cortex, and Broca's and Wernicke's areas. Using these deformation fields as features in machine learning classifiers, we achieved classification accuracies greater than 75% across two independent datasets (i.e., a sample of incarcerated adult offenders and a sample of community adults from the Netherlands). These results demonstrate reliability of morphological features attributable to handedness as represented in neuroimaging data and further suggest that application of data-driven techniques may be a principled approach for addressing asymmetries in group analysis.

Effect of Tactile Sensory Substitution on the Proprioceptive Error Map of the Arm.

Proprioceptive error of estimated fingertip position in two-dimensional space is reduced with the addition of tactile stimulation to the fingertip. This tactile input does not disrupt the subjects’ estimation strategy, as the individual error vector maps maintain their overall geometric structure. This relationship suggests an integration of proprioception and tactile sensory information to enhance proprioceptive estimation. To better understand this multisensory integration, we explored the effect of electrotactile and vibrotactile stimulation to the fingertips in place of actual contact, thus limiting interaction forces. This allowed us to discern any proprioceptive estimation improvement that arose from purely tactile stimulation. Ten right-handed and ten left-handed subjects performed a simple right-handed proprioceptive estimation task under four tactile feedback conditions: hover, touch, electrotactile, and vibrotactile. Target sets were generated for each subject, persisted across all feedback modalities, and targets were presented in randomized orders. Error maps across the workspace were generated using polynomial models of the subjects’ responses. Error maps did not change shape between conditions for any right-handed subjects and changed for a single condition for two left-handed subjects. Non-parametric statistical analysis of the error magnitude shows that both modes of sensory substitution significantly reduce error for right-handed subjects, but not to the level of actual touch. Left-handed subjects demonstrated increased error for all feedback conditions compared to hover. Compared to right-handed subjects, left-handed subjects demonstrated more error in each condition except the hover condition. This is consistent with the hypothesis that the non-dominant hand is specialized for position control, while the dominant is specialized for velocity. Notably, our results suggest that non-dominant hand estimation strategies are hindered by stimuli to the fingertip. We conclude that electrotactile and vibrotactile sensory substitution only succeed in multisensory integration when applied to the dominant hand. These feedback modalities do not disrupt established dominate hand proprioceptive error maps, and existing strategies adapt to the novel input and minimize error. Since actual touch provides the best error reduction, sensory substitution lacks some unidentified beneficial information, such as familiarity or natural sensation. This missing component could also be what confounds subjects using their non-dominant hand for positional tasks.

Comparison of Interests and Special Abilities of Left- and Right-handers

Cerebral lateralization is associated with differences in brain organization and handedness is seen as its main marker. In order to verify the hypothesis that differences in brain organization tend to be associated with different patterns of interests and abilities, 379 normal left-handed subjects (221 women, aged 18 – 72 years) and 366 normal right-handed subjects (256 women, aged 18 – 72 years) were interviewed about their interests and special abilities. The following interests and special abilities were studied: singing, playing an instrument, dancing, painting, acting, foreign language skills, sports skills, and writing poetry.The results in the left-handers group showed that there is a significantly higher percentage of subjects with a pronounced interest in playing an instrument. In the group of right-handers, the study demonstrated a significantly higher percentage of subjects specifically interested in learning foreign languages. With respect to the abilities, a significantly higher incidence of participants with vocal, instrumental, sports, and foreign language skills was found in the left-handers’ group. Differences in functional cerebral organization between left- and right-handers were suggested as possible explanation for the relationship of handedness with special abilities.

Anatomical bases of fast parietal grasp control in humans: A diffusion-MRI tractography study

The dorso-posterior parietal cortex (DPPC) is a major node of the grasp/manipulation control network. It is assumed to act as an optimal forward estimator that continuously integrates efferent outflows and afferent inflows to modulate the ongoing motor command. In agreement with this view, a recent per-operative study, in humans, identified functional sites within DPPC that: (i) instantly disrupt hand movements when electrically stimulated; (ii) receive short-latency somatosensory afferences from intrinsic hand muscles. Based on these results, it was speculated that DPPC is part of a rapid grasp control loop that receives direct inputs from the hand-territory of the primary somatosensory cortex (S1) and sends direct projections to the hand-territory of the primary motor cortex (M1). However, evidence supporting this hypothesis is weak and partial. To date, projections from DPPC to M1 grasp zone have been identified in monkeys and have been postulated to exist in humans based on clinical and transcranial magnetic studies. This work uses diffusion-MRI tractography in two samples of right- (n = 50) and left-handed (n = 25) subjects randomly selected from the Human Connectome Project. It aims to determine whether direct connections exist between DPPC and the hand control sectors of the primary sensorimotor regions. The parietal region of interest, related to hand control (hereafter designated DPPChand), was defined permissively as the 95% confidence area of the parietal sites that were found to disrupt hand movements in the previously evoked per-operative study. In both hemispheres, irrespective of handedness, we found dense ipsilateral connections between a restricted part of DPPChand and focal sectors within the pre and postcentral gyrus. These sectors, corresponding to the hand territories of M1 and S1, targeted the same parietal zone (spatial overlap > 92%). As a sensitivity control, we searched for potential connections between the angular gyrus (AG) and the pre and postcentral regions. No robust pathways were found. Streamline densities identified using AG as the starting seed represented less than 5 % of the streamline densities identified from DPPChand. Together, these results support the existence of a direct sensory-parietal-motor loop suited for fast manual control and more generally, for any task requiring rapid integration of distal sensorimotor signals.

Migraine and handedness.

Migraine is a typically unilateral disorder in adulthood; however, the reasons for painful lateralization have been little investigated. The possible influence of manual dominance was suggested. We aimed to investigate the localization of pain in migraine attacks in right-handed and left-handed subjects. The retrospective study collected 546 patients with migraine aged between 16 and 65 years, reporting the manual dominance to the Edinburgh test. We included 466 right-handed and 80 left-handed subjects with migraine. We registered 4215 unilateral painful attacks. The right-handers had 3412 unilateral episodes; 62.8% of the attacks were characterized by pain on the right side and 37.2% by pain on the left. The left-handed subjects reported 803 unilateral pain with 63.5% of unilateral pain episodes on the left side and 36.5% of attacks with lateralized pain on the right (p < 0.001). Our data suggest that manual dominance may influence the side of pain lateralization in migraine.

A study on inter-finger variation and hand dominance in peripheral capillary oxygen saturation values recorded from the different fingers of the hands by pulse oximetry

Background: To measure percentage of oxygen saturation of hemoglobin in the capillary blood (SpO2), pulse oximeter is used as an imperative noninvasive device. There is lack of reported study evaluating the hand dominance and inter-finger variation of SpO2 readings. Aim and Objectives: Our study aims at providing comparison of peripheral capillary blood oxygen saturation of hemoglobin (SpO2 values) among every finger of the two hands in healthy subjects with different hand dominance. Materials and Methods: In this study, 100 healthy subjects of age group between 18 and 30 years were enrolled, in which 76 subjects were right handed, 24 subjects were left handed. No subject was identified as ambidextrous. After 5 min of rest, they were monitored. After collecting different relevant demographic parameters such as age, sex, height, weight, noninvasive blood pressure, heart rate, body temperature and fasting period, SpO2 values were recorded from every finger of two hands with the same pulse oximeter. All the SpO2 values were measured providing at least 1 min of interval after each recording. Total 1000 SpO2 recordings were obtained from 100 subjects. Results: Our result shows that highest average SpO2 values were obtained from middle finger in both the left and right handed subjects. There was no statistically significant difference in the SpO2 values between the middle finger of dominant and non-dominant hand in both the right handed and left handed subjects. Again, thumb showed the second highest average SpO2 value. There was no statistically significant difference in the SpO2 values between the thumbs in right handed and left handed subjects. Lowest SpO2 values were obtained in little fingers of both the hands without showing significant difference of hand dominance. Conclusion: While recording the SpO2 by pulse oximeter, the middle fingers show the highest values followed by the thumbs. Lowest values are recorded from the little fingers. Again, result depicts that there is no statistically significant difference in SpO2 values between corresponding fingers of dominant and non-dominant hand.

Handedness affecting sensory nerve conduction study of median and ulnar nerve

Background: Sensory nerve conduction studies (SNCSs) are specific measurement for functional integrity of peripheral sensory nervous system as well as invaluable testing in clinical electrophysiology testing and these studies confirm for underlying abnormality to differentiate at pre-ganglionic level or post-ganglionic level in large myelinated axons. Right handedness is a striking asymmetrical cerebral function in >90% of population which is under the control of the left cerebral hemisphere. Aim and Objective: To study SNCS of upper limb in the right and sensory nerve conduction velocity [SNCV]) of median and ulnar nerve antidromically on between the right-handed and left-handed subjects. Materials and Methods: This present study was conducted on 91 healthy subjects using instrument RMS Aleron EMG/NCV EP-II Mark-401 instrument 4 channels after obtaining permission from Human Ethics Committee, Government Medical College, Bhavnagar. Results: Our study shows longer latencies, duration, and amplitude but slow SNCV in right-handed subjects which statistically not significant between the right- and left-handed subjects. Conclusion: In this study, it indicates that SNCV was longer in the left-handed subjects. It may be due to limb and cerebral dominance is developed from childhood by different types of perceptions along with learning process involvement

Impact of handedness on mental and neuropsychological performance in young adults

Background: Handedness is predominance of one hand over the other. Factors such as prenatal environment, genetic factors, cultural influences, and person’s environment contribute to handedness. Each cerebral hemisphere is responsible for different tasks that are not usually carried out by opposite hemisphere. Hence, handedness may have notable impact on neuropsychological capacities. Aims and Objectives: The main purpose of this study is to find out there any differences in mental and neuropsychological performance in left-handed and right-handed individuals using standard tests of cognitive function. Materials and Methods: This cross-sectional study was conducted on thirty right-handed and thirty left-handed males under the age range of 18–25 years. Subjects were chosen by simple sampling, by applying criteria for inclusion and exclusion. Standardized tests have been used to assess the various aspects of mental and neuropsychological performance. We compared the findings using student’s Unpaired “t-test.” Results: The left-handed subjects took less time than the right-handed to finish the trail making test. No difference was found in the Digit Span test score between the groups. In Folstein mini-mental status examination, no significant differences were found in memory score but the memory score duration was less in left-handed subjects. Most of the right-handed have auditory as style of learning while majority of the left-handed have visual as style of learning. Conclusion: Our study showed that left-handed individuals showed high mental and neuropsychological performance than right-handed individuals.

Functional MRI study of language organization in left-handed and right-handed trilingual subjects

Functional MRI (fMRI) is gaining importance in the preoperative assessment of language. Selecting the appropriate language to test by fMRI in trilingual patients is intricate. Our objective is to compare fMRI maps for all three languages in left- and right-handed trilingual subjects. 15 right- and 15 left-handed trilingual volunteers were included in the study. We performed fMRI for each volunteer with a visual responsive naming paradigm that was repeated three times, once in each language. The activated areas and the laterality indices were calculated and correlation with the age of acquisition and proficiency of each language was determined. Strong statistical correlation was found between the Laterality Index (LI) of the three languages, in both the right and left-handed groups. Discordant lateralization of language was only observed in four left-handed subjects who demonstrated bilateral and left-lateralization. In right-handed subjects, the activation maps for the first and the second acquired language were similar. The largest activation was seen with the last acquired language. Irrespective of language proficiency and age of acquisition, the language lateralization might change for left-handed subjects. In right-handed subjects, there is no change and the last acquired language results in the largest activation. fMRI performed for a single language can accurately determine language lateralization in right-handed subjects, whereas in left-handed subjects, it is mandatory to test all languages.

Handedness related differences in the intracranial fluid spaces in healthy adults

Purpose: Our study aimed to determine the possible differences in linear measurements and linear indices values of intracranial fluid spaces (IFS) between right- and left-handed adults.Methods: This work has been carried out on 148 subjects (72 men and 76 women). In the study, 88 right-handers and 60 left-handers were included. Forty of the right-handers were male, 48 were female, and 32 of the left-handers were male, and 28 were female. The ages were between 20 and 50 years. Linear measurements were obtained based on magnetic resonance imaging (MRI) studies. A 1.5-T MRI scanner was used to obtain axial images. The ten parameters were estimated from MRI scans.Results: There was no correlation between parameters and age. In our study, interestingly, as can be seen from the tables, most of the parameters with statistically significant differences were higher in favour of left-handed subjects. In most of the linear measurement results, IFS values of the right hemisphere in right-handers, and the left hemisphere in left-handers were higher. Similar results were found in favour of the left-handed in most of the linear ventricular indices.Conclusion: Linear measurements and linear indices values of IFS were mostly higher in left-handers than in right-handed individuals.

Empirical assessment of changing sample-characteristics in task-fMRI over two decades: An example from gustatory and food studies.

Over the past two decades, functional neuroimaging has not only grown into a large field of research, but also substantially evolved. Here we provide a quantitative assessment of these presumed in sample composition and data analysis, using fMRI studies on food/taste research published between 1998 and 2019 as an exemplary case in which the scientific objectives themselves have remained largely stable. A systematic search for papers written in English was done using multiple databases and identified 426 original articles that were subsequently analyzed. The median sample size significantly increased from 11.5 to 35.5 while the ratio of male to female subjects remained stable. There were, however, more papers involving female subjects only, rather than male subjects only, since 2003. There was a decline in uncorrected results and statistical correction by false‐discovery rate. Reflecting a trend toward more conservative thresholding, the number of foci reported per paper did not change significantly and sample size (power) did not correlate with the number of reported foci. The median journal impact factor and the normalized number of citations (citations per year) of the papers, in turn, showed a significantly decreasing trend. Number of citations negatively correlated to sample size, publication year but positively correlated to journal impact factor, and was also influenced by statistical correction method. There was a decreasing trend in studies recruiting both left‐handed and right‐handed subjects. In summary, the present paper quantifies several large‐scale trends that have often been anecdotally discussed and reveals the changing nature of neuroimaging studies that may be considered when pursuing meta‐analytic approaches.