The ability to localize sound sources rapidly allows human beings to efficiently understand the surrounding environment. Previous studies have suggested that there is an auditory "where" pathway in the cortex for processing sound locations. The neural activation in regions along this pathway encodes sound locations by opponent hemifield coding, in which each unilateral region is activated by sounds coming from the contralateral hemifield. However, it is still unclear how these regions interact with each other to form a unified representation of the auditory space. In the present study, we investigated whether functional connectivity in the auditory "where" pathway encoded sound locations during passive listening. Participants underwent functional magnetic resonance imaging while passively listening to sounds from five distinct horizontal locations (-90°, -45°, 0°, 45°, 90°). We were able to decode sound locations from the functional connectivity patterns of the "where" pathway. Furthermore, we found that such neural representation of sound locations was primarily based on the coding of sound lateralization angles to the frontal midline. In addition, whole-brain analysis indicated that functional connectivity between occipital regions and the primary auditory cortex also encoded sound locations by lateralization angles. Overall, our results reveal a lateralization-angle-based representation of sound locations encoded by functional connectivity patterns, which could add on the activation-based opponent hemifield coding to provide a more precise representation of the auditory space.
Humans ; Sound Localization/physiology* ; Male ; Female ; Magnetic Resonance Imaging ; Young Adult ; Functional Laterality/physiology* ; Adult ; Brain Mapping ; Auditory Cortex/physiology* ; Acoustic Stimulation ; Auditory Pathways/physiology* ; Brain/physiology*

The visual cortex is an essential part of the brain for processing visual information. It exhibits structural and functional plasticity, which is crucial for adapting to complex visual environments. The quintessential manifestation of visual cortical plasticity is ocular dominance plasticity during the critical period, which involves numerous cellular and molecular events. While previous studies have emphasized the role of visual cortical neurons and their associated functional molecules in visual plasticity, recent findings have revealed that structural factors such as the extracellular matrix and glia are also involved. Investigating how these molecules interact to form a complex network that facilitates plasticity in the visual cortex is crucial to our understanding of the development of the visual system and the advancement of therapeutic strategies for visual disorders like amblyopia.
Neuronal Plasticity/physiology* ; Dominance, Ocular/physiology* ; Visual Cortex/physiology* ; Humans ; Animals ; Neurons/physiology*

Musical training can counteract age-related decline in speech perception in noisy environments. However, it remains unclear whether older non-musicians and musicians rely on functional compensation or functional preservation to counteract the adverse effects of aging. This study utilized resting-state functional connectivity (FC) to investigate functional lateralization, a fundamental organization feature, in older musicians (OM), older non-musicians (ONM), and young non-musicians (YNM). Results showed that OM outperformed ONM and achieved comparable performance to YNM in speech-in-noise and speech-in-speech tasks. ONM exhibited reduced lateralization than YNM in lateralization index (LI) of intrahemispheric FC (LI_intra) in the cingulo-opercular network (CON) and LI of interhemispheric heterotopic FC (LI_he) in the language network (LAN). Conversely, OM showed higher neural alignment to YNM (i.e., a more similar lateralization pattern) compared to ONM in CON, LAN, frontoparietal network (FPN), dorsal attention network (DAN), and default mode network (DMN), indicating preservation of youth-like lateralization patterns due to musical experience. Furthermore, in ONM, stronger left-lateralized and lower alignment-to-young of LI_intra in the somatomotor network (SMN) and DAN and LI_he in DMN correlated with better speech performance, indicating a functional compensation mechanism. In contrast, stronger right-lateralized LI_intra in FPN and DAN and higher alignment-to-young of LI_he in LAN correlated with better performance in OM, suggesting a functional preservation mechanism. These findings highlight the differential roles of functional preservation and compensation of lateralization in speech perception in noise among elderly individuals with and without musical expertise, offering insights into successful aging theories from the lens of functional lateralization and speech perception.
Humans ; Speech Perception/physiology* ; Music ; Male ; Functional Laterality/physiology* ; Female ; Aged ; Adult ; Young Adult ; Aging/physiology* ; Middle Aged ; Magnetic Resonance Imaging ; Brain/physiology*

Humans ; Functional Laterality ; Forensic Medicine ; Autopsy ; Asphyxia/etiology*

Animals ; Brain Mapping ; Dominance, Cerebral ; Magnetic Resonance Imaging ; Parietal Lobe ; Primates

Objective: To determine the relationship of the surgeon handedness and operative site laterality on operative duration and hearing improvement in otologic surgery, and to further explore whether this relationship may be related to surgeon experience. Methods: Design: Retrospective Cohort Setting: Tertiary Private Teaching Hospital Participants: Seventy-three (73) patients aged 18 to 65 years old who underwent primary ear surgery under general anesthesia between January 2016 and December 2019 were retrospectively divided into two groups: 39 contralateral and 34 ipsilateral. The operative durations and hearing improvements were compared using independent t-tests, with consideration of surgeon experience in years further stratifying patients. Results: There was no significant difference in operative duration, t(71) = 1.14, p = .26, between the contralateral (M = 281.95 minutes, SD = 71.82) and ipsilateral (M = 261.15, SD = 79.26) groups. This same pattern was more pronounced among surgeons with 10+ years of experience although there was also no significant difference in operative time, t(33) = 1.31, p = .19 for both ipsilateral and contralateral surgeries There was no statistically significant difference, t(36) = -0.72, p = .47, in overall mean hearing gain among patients in the contralateral (M = +2.22 dB, SD = 10.54) and ipsilateral (M = +5.12 dB, SD = 14.26) groups. Although the difference was also not statistically significant, t(16) = -1.94, p = .07 for contralateral (M = 0.00, SD = 5.43) and ipsilateral (M = +7.95 dB, SD = 11.52) procedures performed by surgeons with experience of 10 years or more, a mean hearing gain of +7 dB in the ipsilateral group compared to 0 dB in the contralateral group was notable. Conclusion: This study did not prove that regardless of surgeon experience, right-handed surgeons operating on the right ear and left-handed surgeons operating on the left ear have better ear surgery outcomes of operative duration and hearing improvement compared to right- handed surgeons operating on the left ear and left-handed surgeons operating on the right ear. Future studies on larger samples with more complete data may yet demonstrate this effect.
Functional Laterality ; otologic surgical procedures ; hearing ; operative time

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.
Adult ; Aphasia ; Apraxias ; Dominance, Cerebral ; Education ; Extremities ; Humans ; Incidence ; Prospective Studies ; Psychometrics ; Reproducibility of Results ; Stroke

PURPOSE: To investigate the relationship between dominant eye and refractive error in patients with myopic anisometropia. METHODS: This study population consisted of myopes less than 15 years old who were followed up for anisometropia defined as interocular difference of spherical equivalent (SE) ≥1.0 diopter (D). All patients underwent the hole-in-the-card test at far and near to determine ocular dominance. The data were analyzed for statistical significance using Fisher's exact test. RESULTS: A total of 102 eyes in 51 patients were analyzed. The mean age of the patients was 10.4 ± 1.4 years and 54.9% were male. The mean SE was −2.97 ± 1.95 D in the right eye and −3.02 ± 1.92 D in the left eye. The right eye was the dominant eye in 43.1% and 37.3% at distance and near, respectively. The agreement of dominancy between distant and near was 82.4%. The near dominant eyes showed statistically significant accordance with more myopic eyes (p = 0.009). On the other hand, there was no statistically significant relationship between more myopic eyes and distant dominant eyes (p = 0.09). CONCLUSIONS: The near dominant eye was more myopic eye in patients with myopic anisometropia. This was considered to be related with the lag of accommodation in dominant eye with near distance.
Anisometropia ; Dominance, Ocular ; Hand ; Humans ; Male ; Myopia ; Refractive Errors

Anatomic Variation ; Catheterization ; Female ; Functional Laterality ; Hand ; Health Personnel ; Humans ; Jordan ; Lighting ; Male ; Upper Extremity ; Veins

PURPOSE: The purpose of this study was to evaluate whether eye dominance changes after conventional pseudophakic monovision, and to identify factors that affect changes in eye dominance. METHODS: This retrospective study included 70 patients who underwent bilateral conventional monovision cataract surgery. Patients were divided into two groups based on whether they experienced a change in the dominant eye. We compared patients' uncorrected distance visual acuity (UCDVA), uncorrected near visual acuity (UCNVA), best-corrected visual acuity (BCVA), spherical equivalent, stereopsis, and time interval between cataract surgeries. RESULTS: The mean age was 71.26 ± 10.84 (range, 25–90) years, mean interval between surgery in each eye was 118.46 ± 183.50 (range, 17–1,018) days, and mean postoperative diopter difference was 1.16 ± 0.53 (range, 0.00–2.75) diopters. After bilateral cataract surgery, 22 patients (31.43%) experienced a change in eye dominance, whereas 48 patients (68.57%) experienced no change. There were no differences in the time interval between cataract surgeries, preoperative UCDVA and UCNVA, pre- and postoperative BCVA, or stereopsis in either group. Patients who experienced a change in eye dominance showed smaller differences between preoperative and postoperative spherical equivalent, compared with patients who experienced no change in eye dominance (t-test, p < 0.05). CONCLUSIONS: Twenty-two (31.43%) patients whose nondominant eyes were targeted for near vision showed altered eye dominance after conventional monovision cataract surgery. Eye dominance shows greater plasticity in patients with smaller differences between preoperative and postoperative spherical equivalent.
Cataract ; Clinical Study ; Depth Perception ; Dominance, Ocular ; Humans ; Plastics ; Presbyopia ; Retrospective Studies ; Visual Acuity