In the summer of 1975, on a small farm in the Perigord region of France, the author read Robert Ornstein's The Psychology of Consciousness, a popular account of the findings on the two hemispheres of the human brain. In reading Ornstein's book, he came to realize that he had really been celebrating intuition in his own research, uncovering it in all kinds of odd and clandestine places. This was at odds with the mainline management literature—applied no less than academic—that emphasized, almost to the point of obsession, the role of analysis in organizations, especially under so-called professional management. The author provides answers to three questions around the theme of the specialization of the hemispheres of the human brain. Scientists have known for a long time that the brain has two distinct hemispheres. They have known, further, that the left hemisphere controls movements on the body's right side while the right hemisphere controls movements on the left.

Endogenous ultradian rhythms with a periodicity of 2–3 hours operate separately in the right and left hemispheres of the human brain and modulate physiological functions, perception and cognition. Since sensory pathways from either hand terminate in the contralateral hemisphere, ultradian rhythms of the right and left brain can be monitored by variations in the tactile discrimination of the left and right hand, respectively. Thirteen right-handed German males were tested every 15 minutes for 8 hours. Time series of the tactile error rate determined for the right and left hands oscillate with significantly different ultradian periodicities. Whereas cycles in tactile discrimination of the right hand (left hemisphere) have a periodicity of about 2 hours, tactile discrimination of the left hand (right hemisphere) is modulated by longer periods of about 3 hours. This is interpreted in terms of the overall functional asymmetry of the human brain. Since the left brain is the specialized locus for verbal processing and the right brain for visual–spatial processing, lateralized ultradian rhythms operating in the hemispheres may provide a distinct frame for long-term timing of neuronal processes underlying semantic and spatial mapping of the environment. This is particularly important for interpreting biosocial behavioural rhythms seen in humans living under natural conditions.

Significance This study alters our fundamental understanding of the functional interactions between the cerebral hemispheres of the human brain by establishing that the left and right hemispheres have qualitatively different biases in how they dynamically interact with one another. Left-hemisphere regions are biased to interact more strongly within the same hemisphere, whereas right-hemisphere regions interact more strongly with both hemispheres. These two different patterns of interaction are associated with left-lateralized functions, such as language and motor abilities, and right-lateralized functions, such as visuospatial attention. Importantly, the magnitude of lateralization measured for individual participants in these regions predicted the level of cognitive ability for the respective function, demonstrating that lateralization of function is associated with improved cognitive ability.

Abstract Many studies have analyzed what organizational features distinguish the left and right hemispheres of the human brain, with most differences typically being found in language areas. In this analysis, we test whether supervised learning can categorize an unseen hemisphere as right or left based on functional connectivity. Using data from the Human Connectome Project, we find success to be extremely high (accuracies > .90) in right-handed participants (Edinburgh Handedness Inventory [EHI] > 0). Accuracies are still high, but slightly lower when trained on left-handed participants (EHI ≤ 0). In a third analysis, we test whether the same can be done to identify handedness along with hemisphere chirality. This does not succeed, however, we show that individuals’ hemispheres are less distinct the more left-handed they are. Our findings can inform developmental and post-injury work on hemispheric organization.

The realm of design, both in terms of appreciating extant artefacts (design-as-a-noun) and the practice of inventing artefacts (design-as-a-verb) is a distinctly human behavior. The physiology of the brain exhibits a clear and definite bifurcation referred to as the left and right hemispheres. After millennia of evolution the two hemispheres have developed distinct, but complementary modes of intellectual behavior. Their distinctness of orientation and conceptualization plays an important role in the processing of our sensory experience (in-the-world) and our conceptualization that impacts recognition, interpretation, and decision making (of-the-world).

To study what might be called the ‘emotional vision’ of the right and left hemispheres of the human brain, a specially designed contact lens was used to show cine films to the right or left hemisphere only. Films were chosen to provoke different kinds of emotional response. We wished to find whether the two hemispheres would take and utilise the stimulus of the film to generate a different emotional response despite the common input. In recent years clinical and experimental data have supported the hypothesis that different emotional reactions follow damage to the right or the left hemisphere1–5. We report here the first part of an investigation in which films were perceived by different hemispheres in normal subjects and the subjects were then asked to judge and rate the films. There is of course no intention of suggesting that information implanted at one hemisphere cannot be transferred to the other6,7; nevertheless, the basis of this research is that the two hemispheres can differ in their vision of the world and that each in some respects formulates its own separate and distinct emotional vision of what it sees. We seek to answer the question of what visual experience is like when that which the subject sees enters his nervous system on only one half of his brain, but this is part of the much wider question of how the two hemispheres of the brain see the world and of the relationship between the two visual halves of the brain.

Forty-two epileptic patients with distinct localization of the focus in the left (22 patients) and the right (20 subjects) hemispheres of the brain were subjected to a combined electrophysiological examination including electroencephalography at rest and under intellectual exertion and also polygraphic recording of the night dream pattern. On the basis of the data obtained the authors analyze the function of the cerebral nonspecific activating and deactivating systems in relation to the localization of the focus. The differences detected are suggestive of the functional insufficiency of the activating mechanisms in the left lateral localization of the focus as compared with the right lateral one. The feasibility of utilizing the findings obtained in the differential management of epilepsy (with the lateralization of the epileptic focus taken into account) is discussed.

Brain asymmetry is a fundamental feature of neural organization. However, the molecular basis of hippocampal lateralization in response to environmental stimuli remains poorly understood. Here, we examined the transcriptomic profiles of the left and right hippocampal CA1 regions in rats reared under isolated or enriched housing conditions to elucidate hemisphere-specific responses and shared molecular adaptations. RNA-sequencing analysis revealed lateralized differences in the number and identity of differentially expressed genes, accompanied by distinct biological themes, as indicated by overrepresentation and gene set enrichment analysis. The left CA1 region was prominently engaged in pathways related to synaptic organization and mitochondrial function, whereas the right CA1 region exhibited enrichment in transcriptional regulation and RNA metabolic processes. Despite these asymmetries, co-expression and protein-protein interaction network analyses revealed shared molecular architectures. Immediate early genes formed consistent central hubs across both hemispheres, and a common Mecp2-Grin2b-Cdkl5-Tet3 protein interaction cluster was identified as a potential integrative regulatory module. Additional enrichment analysis of differentially expressed genes shared between hemispheres further highlighted conserved responses, particularly in synaptic plasticity and cell-cell communication. Together, these findings demonstrate that the left and right CA1 regions employ distinct yet

Abstract Background Protein expression asymmetry between brain hemispheres is hypothesized to influence functional connectivity, yet its role in language‐related networks remains poorly understood. Additionally, how such molecular differences relate to brain reorganization in glioma requires further exploration. Methods We performed label‐free tandem mass spectrometry on 13 left‐hemispheric language‐related Brodmann areas (BAs) and their right‐hemispheric counterparts from 10 donor brains, identifying protein signatures across 6 language‐related functional modules. We then compared these proteomic profiles with resting‐state structural and functional connectivity data from 26 BAs across 90 subjects from the Human Connectome Project (HCP). Finally, we examined functional compensation in 13 glioma patients with tumors in Wernicke's area, correlating gray matter volume in contralateral homologs with linguistic performance. Results Protein expression heterogeneity was greater within hemispheres than between homologous contralateral BAs. Hierarchical clustering revealed interactions between core language areas (Broca's, Wernicke's, Geschwind's) and auditory/motor regions. Functional connectivity strength correlated with protein expression similarity, particularly in symmetric BA4 (primary motor cortex). Excitatory/inhibitory (E/I) neuronal markers (GRIA1/GRIA4) showed a left‐positive, right‐negative correlation with connectivity, suggesting hemispheric differences in synaptic regu

Background and purpose: Brain radiotherapy (RT) can cause white matter damage and downstream neurocognitive decline. We developed a computational neuroimaging tool to regionally partition individual white matter tracts, then analyze regional changes in diffusion metrics of white matter damage following brain RT. Materials and methods: RT dose, diffusion metrics and white matter tract structures were extracted and mapped to a reference brain for 49 patients who received brain RT, and underwent diffusion tensor imaging pre- and 9–12 months post-RT. Based on their elongation, 23 of 48 white matter tracts were selected. The Tract-Crawler software was developed in MATLAB to create cross-sectional slice planes normal to a tract’s computed medial axis. We then performed slice- and voxel-wise analysis of radiosensitivity, defined as percent change in mean diffusivity (MD) and fractional anisotropy (FA) as a function of dose relative to baseline. Results: Distinct patterns of FA/MD radiosensitivity were seen for specific tracts, including the corticospinal tract, medial lemniscus, and inferior cerebellar peduncle, in particular at terminal ends. These patterns persisted for corresponding tracts in left and right hemispheres. Local sensitivities were as high as 40%/Gy (e.g., voxel-wise: −39 ± 31%/Gy in right corticospinal tract FA, −45 ± 25%/Gy in right inferior cerebellar peduncle FA), p < 0.05. Conclusions: Tract-Crawler, a novel tool to visualize and analyze cuts of white matter str

Abnormal prefrontal functioning plays a central role in the working memory (WM) deficits of schizophrenic patients, but the nature of the relationship between WM and prefrontal activation remains undetermined. Using two functional neuroimaging methods, we investigated the neural correlates of remembering and forgetting in schizophrenic and healthy participants. We focused on the brain activation during WM maintenance phase with event-related functional magnetic resonance imaging (fMRI). We also examined oxygenated hemoglobin changes in relation to memory performance with the near-infrared spectroscopy (NIRS) using the same spatial WM task. Distinct types of correct and error trials were segregated for analysis. fMRI data indicated that prefrontal activation was increased during WM maintenance on correct trials in both schizophrenic and healthy subjects. However, a significant difference was observed in the functional asymmetry of frontal activation pattern. Healthy subjects showed increased activation in the right frontal, temporal and cingulate regions. Schizophrenic patients showed greater activation compared with control subjects in left frontal, temporal and parietal regions as well as in right frontal regions. We also observed increased 'false memory' errors in schizophrenic patients, associated with increased prefrontal activation and resembling the activation pattern observed on the correct trials. NIRS data replicated the fMRI results. Thus, increased frontal activity

Present knowledge of attention and awareness centres on deficits in patients with right brain damage who show severe forms of inattention to the left, called spatial neglect. Yet the functions that are lost in neglect are poorly understood. In healthy people, they might produce "pseudoneglect"-subtle biases to the left found in various tests that could complement the leftward deficits in neglect. But pseudoneglect measures are poorly correlated. Thus, it is unclear whether they reflect anything but distinct surface features of the tests. To probe for a common mechanism, here we asked whether visual noise, known to increase leftward biases in the grating-scales task, has comparable effects on other measures of pseudoneglect. We measured biases using three perceptual tasks that require judgments about size (landmark task), luminance (greyscales task) and spatial frequency (grating-scales task), as well as two visual search tasks that permitted serial and parallel search or parallel search alone. In each task, we randomly selected pixels of the stimuli and set them to random luminance values, much like a poor TV signal. We found that participants biased their perceptual judgments more to the left with increasing levels of noise, regardless of task. Also, noise amplified the difference between long and short lines in the landmark task. In contrast, biases during visual searches were not influenced by noise. Our data provide crucial evidence that different measures of perceptual p

The human visual system can effortlessly group small components into entities to form an object, but the role of the hemispheres in this processing is still unknown. Understanding the hemispherical processing of perceptual grouping is crucial for unraveling the complexities of visual perception. We have attempted to examine the processing of perceptual grouping in both hemispheres of the human brain. The neural data was collected for 15 healthy subjects while they viewed displays featuring either ‘structure’ (line segments composed of dots) or ‘non-structure’ (random dots). ERPs were recorded and assessed in both frontal and occipital regions of the left and right hemispheres for structure and non-structure stimuli. Our results revealed higher activation for structure compared to non-structure in both brain hemispheres, with notably amplified activity observed in the right hemisphere. Moreover, a decrease in task-related alpha power and an increase in PLI functional connectivity were observed during the perceptual grouping of structures. A novel finding that the Granger causality exhibits a higher value for perceptual grouping when information flows from the right to the left hemisphere, in contrast to communication from left to right, is obtained. Thus, the right hemisphere demonstrated distinct dominance in activation amplitude, task-related alpha power, functional connectivity, and directional functional connectivity related to perceptual grouping. Furthermore, our finding

Determining the cellular composition of specific brain regions is crucial to our understanding of the function of neurobiological systems. It is therefore useful to identify the extent to which different methods agree when estimating the same properties of brain circuitry. In this study, we estimated the number of neuronal and non-neuronal cells in the primary visual cortex (area 17 or V1) of both hemispheres from a single chimpanzee. Specifically, we processed samples distributed across V1 of the right hemisphere after cortex was flattened into a sheet using two variations of the isotropic fractionator cell and neuron counting method. We processed the left hemisphere as serial brain slices for stereological investigation. The goal of this study was to evaluate the agreement between these methods in the most direct manner possible by comparing estimates of cell density across one brain region of interest in a single individual. In our hands, these methods produced similar estimates of the total cellular population (approximately 1 billion) as well as the number of neurons (approximately 675 million) in chimpanzee V1, providing evidence that both techniques estimate the same parameters of interest. In addition, our results indicate the strengths of each distinct tissue preparation procedure, highlighting the importance of attention to anatomical detail. In summary, we found that the isotropic fractionator and the stereological optical fractionator produced concordant estimates