Motivated by the vast amount of information that is rapidly accumulating about the human brain in digital form, we embarked upon a program in 1992 to develop a four–dimensional probabilistic atlas and reference system for the human brain. Through an International Consortium for Brain Mapping (ICBM) a dataset is being collected that includes 7000 subjects between the ages of eighteen and ninety years and including 342 mono– and dizygotic twins. Data on each subject includes detailed demographic, clinical, behavioural and imaging information. DNA has been collected for genotyping from 5800 subjects. A component of the programme uses post–mortem tissue to determine the probabilistic distribution of microscopic cyto– and chemoarchitectural regions in the human brain. This, combined with macroscopic information about structure and function derived from subjects in vivo , provides the first large scale opportunity to gain meaningful insights into the concordance or discordance in micro– and macroscopic structure and function. The philosophy, strategy, algorithm development, data acquisition techniques and validation methods are described in this report along with database structures. Examples of results are described for the normal adult human brain as well as examples in patients with Alzheimer's disease and multiple sclerosis. The ability to quantify the variance of the human brain as a function of age in a large population of subjects for whom data is also available about their genetic composition and behaviour will allow for the first assessment of cerebral genotype–phenotype–behavioural correlations in humans to take place in a population this large. This approach and its application should provide new insights and opportunities for investigators interested in basic neuroscience, clinical diagnostics and the evaluation of neuropsychiatric disorders in patients.

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A probabilistic atlas and reference system for the human brain: International Consortium for Brain Mapping (ICBM)

A model of the effects of aging on brain activity during cognitive performance is introduced. The model is called HAROLD (hemispheric asymmetry reduction in older adults), and it states that, under similar circumstances, prefrontal activity during cognitive performances tends to be less lateralized in older adults than in younger adults. The model is supported by functional neuroimaging and other evidence in the domains of episodic memory, semantic memory, working memory, perception, and inhibitory control. Age-related hemispheric asymmetry reductions may have a compensatory function or they may reflect a dedifferentiation process. They may have a cognitive or neural origin, and they may reflect regional or network mechanisms. The HAROLD model is a cognitive neuroscience model that integrates ideas and findings from psychology and neuroscience of aging.

Hemispheric asymmetry reduction in older adults: the HAROLD model.

Part two of this three-part series commences with anomalous dominance and special talents. Part one appears in a previous issue of theArchives. 1 ANOMALOUS DOMINANCE AND SPECIAL TALENTS According to our hypothesis, slowed growth within certain zones of the left hemisphere is likely to result in enlargement of other cortical regions, in particular, the homologous contralateral area, but also adjacent unfaffected regions. The influences that favor anomalous dominance may thus favor talents associated with superior development of certain regions either in the right hemisphere or in adjacent parts of the left hemisphere. Even with excessive retardation of growth and the resultant migration abnormalities and learning disorders (LD), high talents may exist as a result of compensatory enlargement of other cortical regions. Several types of data are in concordance with these conclusions. Several studies have claimed that the average level of spatial talents is higher in male subiects. 2 Hier

https://jamanetwork.com/journals/jamaneurology/articlepdf/584161/archneur_42_5_008.pdf

Cerebral lateralization. Biological mechanisms, associations, and pathology: II. A hypothesis and a program for research.

Dual functional brain asymmetry refers to the notion that in most individuals the left cerebral hemisphere is specialized for language functions, whereas the right cerebral hemisphere is more important than the left for the perception, construction, and recall of stimuli that are difficult to verbalize. In the last twenty years there have been scattered reports of sex differences in degree of hemispheric specialization. This review provides a critical framework within which two related topics are discussed: Do meaningful sex differences in verbal or spatial cerebral lateralization exist? and, if so, Is the brain of one sex more symmetrically organized than the other? Data gathered on right-handed adults are examined from clinical studies of patients with unilateral brain lesions; from dichotic listening, tachistoscopic, and sensorimotor studies of functional asymmetries in non-brain-damaged subjects; from anatomical and electrophysiological investigations, as well as from the developmental literature. Retrospective and descriptive findings predominate over prospective and experimental methodologies. Nevertheless, there is an impressive accummulation of evidence suggesting that the male brain may be more asymmetrically organized than the female brain, both for verbal and nonverbal functions. These trends are rarely found in childhood but are often significant in the mature organism.

Sex differences in human brain asymmetry: a critical survey

Brain asymmetry has been observed in animals and humans in terms of structure, function and behaviour. This lateralization is thought to reflect evolutionary, hereditary, developmental, experiential and pathological factors. Here, we review the diverse literature describing brain asymmetries, focusing primarily on anatomical differences between the hemispheres and the methods that have been used to detect them. Brain-mapping approaches, in particular, can identify and visualize patterns of asymmetry in whole populations, including subtle alterations that occur in disease, with age and during development. These and other tools show great promise for assessing factors that modulate cognitive specialization in the brain, including the ontogeny, phylogeny and genetic determinants of brain asymmetry.

http://brainimaging.waisman.wisc.edu/~chung/asymmetry/asymmetry.thompson.pdf

Mapping brain asymmetry

Structural asymmetries between the hemispheres are found in the human brain. Asymmetries in the auditory regions and in the Sylvian fissures are present even in the fetus. The Sylvian asymmetries may have existed in Neanderthal man and are found consistently in some apes. They may relate to right-left differences infunction. Thus, the striking auditory asymmetries could underlie language lateralization. The asymmetries in the frontal and occipital lobes and the lateral ventricles are correlated with hand preference. Anatomical asymmetries may help to explain the range of human talents, recovery from acquired disorders of language function, certain childhood learning disabilities, some dementing illnesses of middle life, and the evidence for behavioral lateralization in nonhuman primates.

https://science.sciencemag.org/content/sci/199/4331/852.full.pdf

Right-left asymmetrics in the brain

We used a psychophysical task to measure sensitivity to motion direction in 50 stroke patients with unilateral brain lesions and 85 control subjects. Subjects were asked to discriminate the overall direction of motion in dynamic stochastic random dot displays in which only a variable proportion of the spots moved in a single direction while the remainder moved randomly. Behavioural and neurophysiological evidence shows that the middle temporal (MT/V5) and middle superior temporal (MST) areas in the macaque monkey are indispensably involved in the perception of this type of motion. In human subjects too, lesions in the same region disrupt performance on this task. Here we assessed more extensively the correlation between direction sensitivity for global motion and the anatomical locus of the lesion. Thresholds for perceiving the direction of global motion were impaired in the visual field contralateral to the lesion in patients with lesions in the occipitoparietal and parietotemporal areas involving the human analogue of areas MT/V5 and MST, but not by lesions in the occipito-temporal or anterior frontal areas. Patients with lesions involving the anterior temporal or parietal lobes displayed poor performance for stimuli presented in either visual field, which is consistent with the large and bilateral receptive fields in these areas in monkeys. The perception of global motion was also more impaired in the centripetal than the centrifugal direction in the hemifield contralateral to the MT/V5 lesion. Surprisingly, thresholds were normal in all patients when the displays contained static but not dynamic visual noise, suggesting that their deficit reflects an inability to filter out dynamic noise. Although frequent repeated testing of some patients whose lesion involved the human homologue of MT was accompanied by an improvement in performance, this was no greater than in other patients who received training on different motion tasks.

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Regional cerebral correlates of global motion perception: evidence from unilateral cerebral brain damage.

Thirteen monkeys with catheter reservoir systems for cerebral x- irradiation at 250 lVp. 30 mA, in a single dose to the right weeks after irradiation, reflected by cerebral spinal fluid pressure 3 to 4 times baseline, with absence of visual evoked response and behavioral blindness in four, and unilateral visual evoked response depression in the other four. After the intravenous injection of Evans Blue, seven monkeys, sactificed between 20 and 36 weeks, showed proliferative and degenerative changes in the right occipital lobe which was deeply stained with dye. The swelling extended throughout the right hemisphere with distortion in brain structures. One sacrificed at 52 weeks, after resolution of increased pressure, had a fibrotic, nonstained occipital lesion with atrophic changes in both hemispheres. In five there were less pronounced functional and structural changes. Two nonirradiated controls remained within normal limits. The cause for the delayed brain swelling was a breakdown in the blood brain barrier accompanying the delayed radiation lesion, with extravasation of fluid into brain parenchyma. The impaired function was related to local destruction in the right visual cortex and swelling or compression of the visual pathways by the vasogenic edema.

Delayed brain swelling and functional derangement after X-irradiation of the right visual cortex in the Macaca mulatta.

CLINICAL and electrocortical observations (Caveness, 1969; and Caveness et al., 1973) have indicated significant differences in the development and propagation of focal seizure activity induced by penicillin injection into the face-hand area of the motor cortex of the Macaca mulatto at birth and at 24 months of age. From histoanatomical study of the cerebra of the newborn and 24-month-old monkeys, Yakovlev (1962) concluded that these differences correlate with the early maturation of cortico-subcortical-cortical connexions and the later elaboration of the intracortical connexions. This interpretation has been further supported by recent electrophysiological experiments of Caveness et al. (1973) which showed that when the subcortical connexions of the face-hand area of the motor cortex of the newborn monkey were interrupted by undercutting the cortex prior to the injection of penicillin, there was no or only minimal spread of seizure activity. In contrast, subpial circumsection of the intracortico-cortical connexions of the face-hand area of the motor cortex without cortical undercutting did not prevent the spread of the penicillin-induced seizure activity to either the ipsilateral or contralateral hemisphere. The present study was undertaken to extend the earlier histoanatomical observations of Yakovlev and experimental studies of Caveness referred to, with special attention to the development of the dendritic arbours and postsynaptic spines of the individual neurons of the motor cortex in relation to age.

Thomas L. Kemper

Papers

Right-left asymmetrics in the brain

Regional cerebral correlates of global motion perception: evidence from unilateral cerebral brain damage.

Delayed brain swelling and functional derangement after X-irradiation of the right visual cortex in the Macaca mulatta.

The neuronographic and metric study of the dendritic arbours of neurons in the motor cortex of Macaca mulatta at birth and at 24 months of age.

The propagation of focal paroxysmal activity in the macaca mulatta at birth and at 24 months