Cerebral dominance representation of directed connectivity within and between left-right hemispheres and frontal-posterior lobes in mild cognitive impairment.

Electroencephalography can assess connectivity between brain hemispheres, potentially influencing cognitive functions. Much of the existing electroencephalography research primarily focuses on undirected connectivity, leaving uncertainties about directed connectivity alterations between left-right brain hemispheres or frontal-posterior lobes in mild cognitive impairment. We analyzed resting-state electroencephalography data from 34 mild cognitive impairment individuals and 23 normal controls using directed transfer function and graph theory for directed network analysis. Concerning the dominance within left-right hemispheres or frontal-posterior lobes, the mild cognitive impairment group exhibited decreased connectivity within the frontal compared with posterior brain regions in the delta and theta bands. Regarding the dominance between the brain hemispheres or lobes, the mild cognitive impairment group showed reduced connectivity from the posterior to the frontal regions versus the reverse direction in the same bands. Among all participants, the intra-lobe frontal-posterior dominance correlated positively with executive function in the delta and alpha bands. Inter-lobe dominance between frontal and posterior regions also positively correlated with executive function, attention, and language in the delta band. Additionally, interhemispheric dominance between the left and right hemispheres positively correlated with attention in delta and theta bands. These findings suggest altered cerebral dominance in mild cognitive impairment, potentially serving as electrophysiological markers for neurocognitive disorders.

A Case of Swallowing Apraxia Due to Acute Infarct in the Right Precentral Gyrus.

Swallowing apraxia is an intriguing type of apraxia where the patient cannot swallow despite normal neurological examinations including motor, sensory and cerebellar function. In this case report, we present a 60-year-old hypertensive male with swallowing apraxia. There was no attempt to swallow when food materials were given inside his mouth. Although he had normal examination findings including intact lip, tongue, palatal movement, and gag reflex. His cognition was also intact, as he could follow simple commands accurately. Except for a small infarct in the right precentral gyrus in the MRI (Magnetic Resonance Imaging) of the brain, his investigation findings were normal. We treated him with nasogastric feeding, and he gradually recovered over a month. Clinicians should consider swallowing apraxia as one of the clinical features of stroke when patients present with acute onset of swallowing problems. This case report is believed to increase awareness regarding this condition and add valuable information to relevant further studies.

Cerebral asymmetry in bipolar disorders: A scoping review.

Current brain stimulation protocols for patients with bipolar disorders propose brain stimulation according to a model of opposing cerebral dominance in mania and bipolar depression by stimulating the right or left dorsolateral prefrontal cortex during manic or depressive episodes, respectively. However, there is very little observational, rather than interventional, research on such opposing cerebral dominance. In fact, this is the first scoping review that summarizes resting-state and task- related functional cerebral asymmetries measured with brain imaging techniques in manic and depressive symptoms or episodes in patients with formal bipolar disorder diagnoses. In a three-step search process MEDLINE, Scopus, APA PsycInfo, Web of Science Core Collection, and BIOSIS Previews databases as well as reference lists of eligible studies were searched. Data from these studies were extracted with a charting table. Ten resting-state EEG and task-related fMRI studies met inclusion criteria. In line with brain stimulation protocols, mania relates to cerebral dominance in regions of the left frontal lobe, such as the left dorsolateral prefrontal cortex and dorsal anterior cingulate cortex. Bipolar depression relates to cerebral dominance in regions of the right frontal and temporal lobe, such as the right dorsolateral prefrontal cortex, orbitofrontal cortex and temporal pole. More observational research on cerebral asymmetries in mania and bipolar depression can advance brain stimulation protocols and potentially inform standard treatment protocols.

Development, and validation of non-speech dichotic listening test.

Background: Classic dichotic listening tests using speech stimuli result in right ear advantage, due to the dominant crossed pathway for speech and language. It is presumed that similar crossed dominance could exist for non-speech stimuli too. Hence, this is an attempt to develop and validate the dichotic non-speech test using environmental stimuli and explore the effect of focused attention on this test. Materials and method: Three lists of dichotic stimuli were created using these sounds with fifteen tokens in each list. Four professionals and non-professionals validated these materials. Normative estimation was obtained by administering the newly developed test on 70 adults and 70 children using a free-recall and forced-recall condition. Result: The results showed a significant difference between the left ear and right scores where the left ear score was better than the right, depicting left ear advantage (LEA) for free recall condition in both groups. In the forced recall condition, LEA was not seen; rather the mean score was significantly higher in the attended ear, irrespective of the stimuli presented to the right or left ear. The test-retest reliability in free recall was good in both the ears and moderate for forced right ear conditions. Conclusion: The novel test consistently showed LEA with good reliability and can be used to assess the hemispheric asymmetry in normal subjects and also in test batteries for the clinical population.

Reconsidering the Relationship Between Hand Preference and Cerebral Vascular Dominance: A Computed Tomography (CT) Angiography Study.

Background: To date, it has been suggested that there may be many genetic, environmental, and vascular factors that affect hand preference. In previous studies evaluating the relationship between cerebral dominance and hand preference, carotid and vertebral artery (VA) Doppler ultrasonography (USG) was generally preferred; and these studies only measured VA diameters. Unlike other studies, we aimed to reevaluate the relationship between hand preference and cerebral vascular dominance by measuring VA and internal carotid artery (ICA) diameters. In addition, we used carotid and VA computed tomography (CT) angiography instead of Doppler USG. Methods and Material: A total of 345 participants were included in the study. The results of carotid and VA CT angiography taken during hospitalization were retrospectively evaluated by two radiologists, and the Edinburgh Hand Preference Questionnaire was applied to these patients. Results: In right-handed patients, the diameter of the left VA was significantly larger than the diameter of the right VA (p = 0.005). In left-handed patients, the diameter of the left ICA was larger than the diameter of the right ICA, but the difference was not statistically significant (p = 0.055). There was no significant difference between the diameter of the right and left ICA in right-handed patients (p = 0.771). Conclusions: In our study, we found a correlation between the dominant hemisphere VA diameter and hand preference. Using CT angiography, we were able to eliminate many challenges of ultrasonography that make radiological evaluation difficult, such as differences of opinion between radiologists, and technical and anatomical reasons.

Warm-Up Improves Balance Control Differently in the Dominant and Non-Dominant Leg in Young Sportsmen According to Their Experience in Asymmetric or Symmetric Sports.

The aim of this study was to investigate the acute effects of a warm-up on balance control and inter-limb balance asymmetries by analyzing the influence of the nature of the sport practiced by participants. Twelve sportspeople were recruited. They had to stand on a force plate for 30 s in a one-leg stance on their dominant (used to perform skilled movements) and non-dominant leg (used to support the body) before and 2, 5, 10, 15 and 20 min after a 10 min warm-up exercise performed at moderate intensity on a cycle ergometer. The center of foot pressure displacements was recorded. Statistical analysis was performed by considering one group of all participants and with two subgroups according to the symmetrical or asymmetrical nature of the sport they practiced. The warm-up exercise improved acute balance control only on the dominant leg after a 20 min rest without significantly reducing inter-limb balance asymmetries. This effect was more characteristic of participants with experience in asymmetric sports. These results confirm previous findings of the greater sensitivity of the dominant leg to the physiological state and reveal that between-leg differences in balance control appear mainly in subjects with experience in asymmetric sports in a specific physiological condition (post-warm-up state).

Unification of frequentist inference and machine learning for pterygomaxillary morphometrics.

BACKGROUND: The base of the skull, particularly the pterygomaxillary region, has a sophisticated topography, the morphometry of which interests pathologists, maxillofacial and plastic surgeons. The aim of the study was to conduct pterygomaxillary morphometrics and test relevant hypotheses on sexual and laterality-based dimorphism, and causality relationships. MATERIALS AND METHODS: We handled 60 dry skulls of adult Asian males (36.7%) and females (63.3%). We calculated the prime distance D [prime] for the imaginary line from the maxillary tuberosity to the midpoint of the pterygoid process between the upper and the lower part of the pterygomaxillary fissure, as well as the parasagittal D [x-y inclin.] and coronal inclination of D [x-z inclin.] of the same line. We also took other morphometrics concerning the reference point, the maxillary tuberosity. RESULTS: Significant sexual as well as laterality-based dimorphism and bivariate correlations existed. The univariate models could not detect any significant effect of the predictors. On the contrary, summative multivariate tests in congruence with neural networks, detected a significant effect of laterality on D [x-y inclin.] (p-value = 0.066, partial eta squared = 0.030), and the interaction of laterality and sex on D [x-z inclin.] (p-value = 0.050, partial eta squared = 0.034). K-means clustering generated three clusters highlighting the significant classifier effect of D [prime] and its three-dimensional inclination. CONCLUSIONS: Although the predictors in our analytics had weak-to-moderate effect size underlining the existence of unknown explanatory factors, it provided novel results on the spatial inclination of the pterygoid process, and reconciled machine learning with non-Bayesian models, the application of which belongs to the realm of oral-maxillofacial surgery.

Franz Joseph Gall on hemispheric symmetries.

Franz Joseph Gall believed that the two cerebral hemispheres are anatomically and functionally similar, so much so that one could substitute for the other following unilateral injuries. He presented this belief during the 1790s in his early public lectures in Vienna, when traveling through Europe between 1805 and 1807, and in the two sets of books he published after settling in France. Gall seemed to derive his ideas about laterality independently of French anatomist Marie François Xavier Bichat (1771-1802), who formulated his "law of symmetry" at about the same time. He would, however, later cite Bichat, whose ideas about mental derangement were different from his own and who also attempted to explain handedness, a subject on which Gall remained silent. The concept of cerebral symmetry would be displaced by mounting clinical evidence for the hemispheres being functionally different, but neither Gall nor Bichat would live to witness the advent of the concept of cerebral dominance.

Reliability and Validity of the Comprehensive Limb and Oral Apraxia Test: Standardization and Clinical Application in Korean Patients With Stroke.

OBJECTIVE: To develop and standardize the Limb and Oral Apraxia Test (LOAT) for Korean patients and investigate its reliability, validity, and clinical usefulness for patients with stroke. METHODS: We developed the LOAT according to a cognitive neuropsychological model of limb and oral praxis. The test included meaningless, intransitive, transitive, and oral praxis composed of 72 items (56 items on limb praxis and 16 items on oral praxis; maximum score 216). We standardized the LOAT in a nationwide sample of 324 healthy adults. Intra-rater and inter-rater reliability and concurrent validity tests were performed in patients with stroke. We prospectively applied the LOAT in 80 patients and analyzed the incidence of apraxia. We also compared the clinical characteristics between the apraxia and non-apraxia groups. RESULTS: The internal consistency was high (Cronbach's alpha=0.952). The inter-rater and intra-rater reliability and concurrent validity were also high (r=0.924-0.992, 0.961-0.999, and 0.830, respectively; p<0.001). The mean total, limb, and oral scores were not significantly different according to age and education (p>0.05). Among the 80 patients with stroke, 19 (23.8%) had limb apraxia and 21 (26.3%) had oral apraxia. Left hemispheric lesions and aphasia were significantly more frequently observed in the limb/oral apraxia group than in the non-apraxia group (p<0.001). CONCLUSION: The LOAT is a newly developed comprehensive test for limb and oral apraxia for Korean patients with stroke. It has high internal consistency, reliability, and validity and is a useful apraxia test for patients with stroke.

Is the asymmetry between the vertebral arteries related to cerebral dominance?

Background/aim: The two vertebral arteries (VAs) are usually unequal in size; the left one is generally larger than the right one. It was hypothesized that the asymmetry results from the need of the dominant cerebral hemisphere for more glucose and oxygen, i.e. more blood supply. In this study, we aimed to test this hypothesis in patients by evaluating their arterial diameter and hand preference, as it is the most common criterion to determine the dominance of the hemisphere. Materials and methods: The study was performed with 844 participants who consented to participate in the study. We identified the dominant cerebral hemisphere by asking participants about their hand preference. Then we measured both the VA diameter and VA flow volume by Doppler ultrasonography. After demonstrating the asymmetry, correlation was tested. Results: Among 844 participants included in the study, the mean diameter of the right VA was 3.14 ± 0.35 mm and that of the left VA was 3.41 ± 0.54 mm, while the mean flow volume of the right VA was 119.21 ± 44.98 mL/min and that of the left VA was 151.45 ± 57.26 mL/min. It was recorded that 771 (86.43%) participants were right-handed and 73 (8.18%) were left-handed. Conclusion: No significant relationship was found between the increased blood demand of the dominant cerebral hemisphere and the vertebral artery dominance.

The depth and breadth of multiple perceptual asymmetries in right handers and non-right handers.

Several non-verbal perceptual and attentional processes have been linked with specialization of the right cerebral hemisphere. Given that most people have a left hemispheric specialization for language, it is tempting to assume that functions of these two classes of dominance are related. Unfortunately, such models of complementarity are notoriously hard to test. Here we suggest a method which compares frequency of a particular perceptual asymmetry with known frequencies of left hemispheric language dominance in right-handed and non-right handed groups. We illustrate this idea using the greyscales and colourscales tasks, chimeric faces, emotional dichotic listening, and a consonant-vowel dichotic listening task. Results show a substantial "breadth" of leftward bias on the right hemispheric tasks and rightward bias on verbal dichotic listening. Right handers and non-right handers did not differ in terms of proportions of people who were left biased for greyscales/colourscales. Support for reduced typical biases in non-right handers was found for chimeric faces and for CV dichotic listening. Results are discussed in terms of complementary theories of cerebral asymmetries, and how this type of method could be used to create a taxonomy of lateralized functions, each categorized as related to speech and language dominance, or not.

Quantifying the Confidence in fMRI-Based Language Lateralisation Through Laterality Index Deconstruction.

In epilepsy patients, language lateralisation is an important part of the presurgical diagnostic process. Using task-based fMRI, language lateralisation can be determined by visual inspection of activity patterns or by quantifying the difference in left- and right-hemisphere activity using variations of a basic formula [(L-R)/(L+R)]. However, the values of this laterality index (LI) depend on the choice of activity thresholds and regions of interest. The diagnostic utility of the LI also depends on how its continuous values are translated into categorical decisions about a patient's language lateralisation. Here, we analysed fMRI data from 712 epilepsy patients who performed a verbal fluency task. Each fMRI data set was evaluated by a trained human rater as depicting left-sided, right-sided, or bilateral lateralisation or as being inconclusive. We used data-driven methods to define the activity thresholds and regions of interest used for LI computation and to define a classification scheme that allowed us to translate the LI values into categorical decisions. By deconstructing the LI into measures of laterality (L-R) and strength (L+R), we also modelled the relationship between activation strength and conclusiveness of a data set. In a held-out data set, predictions reached 91% correct when using only conclusive data and 82% when inconclusive data were included. Although only trained on human evaluations of fMRIs, the approach generalised to the prediction of language Wada test results, allowing for significant above-chance accuracies. Compared against different existing methods of LI-computation, our approach improved the identification and exclusion of inconclusive cases and ensured that decisions for the remaining data could be made with consistently high accuracies. We discuss how this approach can support clinicians in assessing fMRI data on a single-case level, deciding whether lateralisation can be determined with sufficient certainty or whether additional information is needed.

Reliability and Validity of the Comprehensive Limb and Oral Apraxia Test: Standardization and Clinical Application in Korean Patients With Stroke

OBJECTIVE: To develop and standardize the Limb and Oral Apraxia Test (LOAT) for Korean patients and investigate its reliability, validity, and clinical usefulness for patients with stroke. METHODS: We developed the LOAT according to a cognitive neuropsychological model of limb and oral praxis. The test included meaningless, intransitive, transitive, and oral praxis composed of 72 items (56 items on limb praxis and 16 items on oral praxis; maximum score 216). We standardized the LOAT in a nationwide sample of 324 healthy adults. Intra-rater and inter-rater reliability and concurrent validity tests were performed in patients with stroke. We prospectively applied the LOAT in 80 patients and analyzed the incidence of apraxia. We also compared the clinical characteristics between the apraxia and non-apraxia groups. RESULTS: The internal consistency was high (Cronbach’s alpha=0.952). The inter-rater and intra-rater reliability and concurrent validity were also high (r=0.924–0.992, 0.961–0.999, and 0.830, respectively; p0.05). Among the 80 patients with stroke, 19 (23.8%) had limb apraxia and 21 (26.3%) had oral apraxia. Left hemispheric lesions and aphasia were significantly more frequently observed in the limb/oral apraxia group than in the non-apraxia group (p<0.001). CONCLUSION: The LOAT is a newly developed comprehensive test for limb and oral apraxia for Korean patients with stroke. It has high internal consistency, reliability, and validity and is a useful apraxia test for patients with stroke.

Evaluación de parámetros de banda ancha en la determinación de dominancia cerebral durante la hipnosis / Evaluation of wide band parameters in the determination of cerebral dominance during hypnosis

Se realizó un estudio cuasiexperimental de 21 estudiantes que cursaban la carrera de medicina, los cuales se encontraban en estado de hipnosis, atendidos en el Hospital General Docente Dr Juan Bruno Zayas Alfonso de Santiago de Cuba, desde septiembre del 2014 hasta junio del 2015, con vistas a identificar las medidas espectrales de banda ancha sensibles en la determinación de la dominancia cerebral durante dicho estado. Entre las variables analizadas figuraron: nivel de profundidad hipnótica, medidas espectrales de banda ancha y derivación. Se utilizó el estadígrafo false discovery rate como prueba de hipótesis para validar la información estadística y el análisis de varianza multivariado Manova. Los resultados revelaron que el poder relativo theta resultó ser la medida espectral con modificaciones más significativas y mostró un predominio discreto de la energía en el hemisferio izquierdo. Se concluyó que este hallazgo tuvo lugar como consecuencia de las tareas indicadas durante la hipnosis

A quasi-experiment of 21 students that were studying the medicine career, who were in hypnosis state, assisted in Dr Juan Bruno Zayas Alfonso Teaching General Hospital in Santiago de Cuba, was carried out from September, 2014 to June, 2015, aimed at identifying the wide band spectral measures sensitive in the determination of cerebral dominance during this state. Among the analyzed variables we can mention: level of hypnotic depth and spectral measures of wide band and derivation. The false discovery rate stadigraph was used as hypothesis test to validate the statistical information and the Manova multivaried analysis of variance. The results revealed that theta relative power was the spectral measure with more significant modifications and showed a discreet prevalence of energy in the left hemisphere. It was concluded that this finding took place as a consequence of the given tasks during hypnosis

Laterality of proprioception in the orofacial muscles and temporomandibular joint.

Laterality of function in the orofacial musculature suggests there may be side-to-side asymmetry of proprioceptive acuity in lip movement compared to the temporomandibular joint (TMJ). In the present work, 14 young adults were tested for acuity of lip and TMJ closure movements onto plugs varying from 5 to 8mm without visual feedback. Testing was conducted on both left and right sides, using the same psychophysical task and stimuli. Results showed superior proprioceptive acuity at the lips, with no significant side effect. However, there was side-to-side asymmetry in the correlations between proprioceptive performance for the two anatomical structures, with performance on the right side strongly correlated but not on the left. This is consistent with the need for coordination between structures during chewing. When acuity at different points in the stimulus range was examined, the right side lips were better with small stimuli. Overall, results support enhanced use-specific proprioception.

Development and Validation of a Persian Version of Dichotic Emotional Word Test.

INTRODUCTION: Emotional words in comparison with neutral words have different hemispheric specialization. It is assumed that the right hemisphere has a role in processing every kind of emotional word. The objective of the present study was the development of a Persian version of the dichotic emotional word test and evaluate its validation among adult Persian speakers. MATERIALS AND METHODS: The present study was done on 60 adults, with the age ranging from 18-30 years for both genders, who had no history of neurological disorders with normal hearing. The developed test included eight main lists; each had several dichotic emotional/ neutral pairs of words. Participants were asked to recall as many words in each list as they could after they listened to them. A content validity index was used to analyze the validity of the test. RESULTS: The mean content validity index score was 0.94. The findings showed that in the left ear, emotional words were remembered more than neutral ones (P=0.007). While in the right ear, neutral words were remembered more (P=0.009). There were no significant differences in male and female scores. CONCLUSION: Dichotic emotional word test has a high content validity. The ability to remember emotional words better in the left ear supports the dominant role of the right hemisphere in emotional word perception.

Motor behavior reflects reduced hemispheric asymmetry in the psychosis risk period.

BACKGROUND: A body of work focusing on brain connectivity, language dominance, and motor laterality research suggests that reduced hemispheric asymmetry is a core feature in schizophrenia. However, there is little consensus about whether reduced dominance is present in those at ultrahigh risk (UHR) for psychosis. METHODS: A total of 94 demonstrated right-handed neuroleptic free participants (38 UHR and 56 matched healthy controls) were assessed with structured clinical interviews and completed an innovative handwriting task using a digital tablet computer. A laterality quotient (LQ) was calculated using kinematic variables from the participant's left and right hands. A subset of the sample (26 UHR and 29 controls) returned after 12-months to complete clinical interviews in order to examine relationships between handwriting laterality and progression of psychosis risk symptoms. RESULTS: The UHR group showed decreased dextrality compared to healthy controls. At the 12-month follow-up, decreased dextrality accounted for 8% of the variance in worsened positive symptoms within the UHR group. CONCLUSION: The current results suggest that disrupted cerebral dominance is also present in the ultrahigh risk period and that decreased dextrality may serve as a novel biomarker for the progression of psychosis risk.

Acquired dysgraphia in adults following right or left-hemisphere stroke / Disgrafias adquiridas em adultos após acidente vascular cerebral unilateral nos hemisférios direito e esquerdo

Objective: This study aimed to assess the strengths and difficulties in word and pseudoword writing in adults with left- and right-hemisphere strokes, and discuss the profiles of acquired dysgraphia in these individuals. Methods: The profiles of six adults with acquired dysgraphia in left- or right-hemisphere strokes were investigated by comparing their performance on word and pseudoword writing tasks against that of neurologically healthy adults. A case series analysis was performed on the patients whose impairments on the task were indicative of acquired dysgraphia. Results: Two patients were diagnosed with lexical dysgraphia (one with left hemisphere damage, and the other with right hemisphere damage), one with phonological dysgraphia, another patient with peripheral dysgraphia, one patient with mixed dysgraphia and the last with dysgraphia due to damage to the graphemic buffer. The latter patients all had left-hemisphere damage (LHD). The patterns of impairment observed in each patient were discussed based on the dual-route model of writing. Conclusion: The fact that most patients had LHD rather than right-hemisphere damage (RHD) highlights the importance of the former structure for word processing. However, the fact that lexical dysgraphia was also diagnosed in a patient with RHD suggests that these individuals may develop writing impairments due to damage to the lexical route, leading to heavier reliance on phonological processing. Our results are of significant importance to the planning of writing interventions in neuropsychology.

Objetivo: Investigar aspectos preservados e dificuldades na escrita de palavras e pseudopalavras em adultos que sofreram acidente vascular cerebral (AVC) à esquerda e à direita e discutir os perfis de disgrafia adquirida nesses indivíduos. Métodos: Investigaram-se perfis de disgrafia adquirida a partir da avaliação das habilidades e dificuldades na escrita de palavras e pseudopalavras de seis adultos que sofreram AVC no hemisfério direito (LHD) e no hemisfério esquerdo (LHE), comparados a adultos neurologicamente saudáveis. Realizou-se análise de séries de casos com os pacientes que apresentaram desempenho deficitário na escrita de palavras, que indicavam a presença de uma disgrafia adquirida. Resultados: Foram identificados dois casos com disgrafia lexical (sendo um com LHE e outro com LHD), um caso com disgrafia fonológica, um com disgrafia periférica, um com disgrafia mista e um com disgrafia por déficit no buffer grafêmico, todos estes com LHE. Destacou-se nesse estudo a heterogeneidade das habilidades linguísticas dos casos clínicos, discutidas de acordo com o modelo cognitivo de dupla-rota de escrita. Conclusão: O maior prejuízo encontrado nos pacientes com LHE ressalta a importância desse hemisfério cerebral para o processamento da escrita de palavras. A presença de um caso com LHD com perfil de disgrafia lexical destaca a necessidade de melhor estudar o papel do hemisfério direito no processamento de palavras. Espera-se que esse estudo contribua para o planejamento de estratégias de intervenção neuropsicológica direcionadas à escrita de palavras.