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[Man and his brain].

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Animals↗
PubMed1977

An anthropological perspective on the evolution and lateralization of the brain.

The purpose of this paper is to review the anthropological evidence relating to the cultural determinants of the right-hand first postaulted by Hertz in his classic study. Also a genetic/cultural conformity model of handedness is presented that postulates that the incidence of handedness in a society is held to result both from the genetic expression of handedness interacting with cultural pressures towards conformity. The evolutionary basis for the hemispheric functional organization into cognitive and perceptual hemispheric functions is discussed in terms of "right-handed dominant homozygotes, DD," "heterozygotes, DR," mixed-handers, and "left-handed recessive homozygotes, RR." The cross-cultural distribution of handedness provides support for this model since the more conforming agriculturalists as measured by the Asch Test have a significantly lower incidence of left-handedness (0.59%, 1.5% and 3.4%), while the more permissively socialized Eskimo and Arunta hunters, who are seen to be more independent on the Asch Test, have 11.3% and 10.5% left-handers, respectively. Also, due to the greater pressures for females to conform in agricultural societies, the incidence of female left-handedness in agricultural societies is 0% out of 330 female Ss, with 3.8%, 0.79%, and 2.5% in agricultural males, as contrasted with the Eskimo hunters who have 12.5% left-handed males and 10.3% left-handed females, showing no significant sex difference. A further Hong Kong-English study also supports the genetic/cultural conformity model with a significantly lower incidence of Hong Kong Chinese left-handers (RR: male = 2.7%, and female = 4.2%). The next section, concerned with the neonatal sex-hormone differentiation and lateralization processes, provides a neuropsychologic theory relating to spatial and linguistic skills that is relevant to the following section, which deals with relationships between laterality and cognitive style. The results are also presented for the Alaskan Eskimo in relation to hand, eye, auditory dominance and cognitive style. The analysis of Eskimo fixed-versus mixed-laterality data also confirms, as predicted, that both within and across a modality (e.g., right hand/right eye/right ear) fixed right-dominance Eskimo Ss are more field-independent than mixed-dominance Ss, while the fixed left-dominance Ss are the most field-dependent and have lower spatial skills. The discussion section reviews the papers relating to the genetic/conformity model of handedness, as well as laterality and cognitive style. The evolutionary adaptive significance of sex differences in gonadal differentiation and lateralization of the brain on spatial and linguistic skills are also reviewed. The conclusions are concerned with the implications for biosocial theory and the rapidly changing incidence of left-handedness due to accompanying changes in cultural pressures both within and across cultures.

Adult↗
PubMed2003

The self: clues from the brain.

Can we find a way of thinking about the self that is compatible with modern neuroscience? I think we can. First of all, we have to recognize that "the self" is not the same as "the conscious self," since much of who we are as individuals takes place out of conscious awareness. Second, we have to accept that some aspects of the self, especially the unconscious aspects, occur in and can be studied in other species, allowing us to relate these aspects of the self to detailed brain mechanisms. Finally, it also helps to think of the self in terms of memory. Obviously, much of who we are is based on memories learned through personal experience, including both conscious or explicit memories and unconscious or implicit memories. This is particularly important since much progress has been made in relating memory to the cells and synapses of the brain. By viewing the self as a network of memories the effort to relate the self to the brain can build on this progress. Emphasizing memory and experience does not take away from the fact that our genetic history also contributes to who we are. In fact, genes and experience, or nature and nurture, are, in the end, not different things, but different ways of doing the same thing-wiring the synapses of our brain. In many ways, the self is synaptic. This synaptic view of the self is not meant as a challenge to other views, such as spiritual, cultural, or psychological views. It is instead, just a way of understanding how these other aspects of who we are relate, deep down, to the brain.

Animals↗
PubMed1998

Endoscope-assisted brain surgery: part 1--evolution, basic concept, and current technique.

RATIONALE: The evolution of neurosurgical techniques indicates the effort to reduce surgery-related traumatization of patients. The reduction of traumatization contributes to better postoperative outcomes. The improvement of diagnostic imaging techniques facilitates not only the precise localization of lesions but also the accurate determination of topographical relations of specific lesions to individual anatomic variations of intracranial structures. This precision of diagnostic imaging should be used to perform individual surgical procedures through so-called keyhole approaches. Keyhole craniotomies are afflicted with a reduction of light intensity in the depth of the operating field, and they provide rather narrow viewing angles. Thus, objects located directly opposite the approach entrance are more visible than those in the shadow of the microscope beam. These two deficiencies of keyhole craniotomies can be compensated for by the intraoperative use of rigid rod lens endoscopes, the shaft of which remains easily controllable through the surgical microscope. CONCEPT: Endoscope-assisted microsurgery, like all routine microsurgical procedures, is performed with both hands; the endoscope is fixed in its desired position via a mechanical arm to the headholder. Because of their superior optical quality and maneuverability, only rigid lens scopes are used for endoscope-assisted brain microsurgery. There are five ways of observing the endoscopic and microscopic images at the same time: 1) observation of the microscopic image through the oculars of the microscope and observation of the endoscopic image on a video screen placed in front of the surgeon, 2) observation of the microscopic image through the oculars of the microscope and display of the endoscopic image on a head-mounted LCD screen, 3) projection of both microscopic and endoscopic images on one screen in a picture-in-picture mode, 4) projection of both microscopic and endoscopic images into specially designed microscope oculars, and 5) transmission of both microscopic and endoscopic images into a head-mounted LCD screen. DISCUSSION: With the knowledge of almost all individual anatomic and pathoanatomic details of a specific patient, it is possible to target the individual lesion through a keyhole approach using the particular anatomic windows. As the light intensity and the depiction of important anatomic details are improved by the intraoperative use of lens scopes, endoscope-assisted microsurgery during keyhole approaches may provide maximum efficiency to remove the lesion, maximum safety for the patient, and minimum invasiveness.

Brain↗
PubMed1990

Cerebral blood flow and edema in perinatal hypoxic-ischemic brain damage.

The relationship between cerebral blood flow (CBF) and the evolution of brain edema was investigated in an experimental model of perinatal hypoxic-ischemic brain damage. Seven-d postnatal rats were subjected to unilateral common carotid artery ligation followed by 3 h of hypoxia with 8% oxygen at 37 degrees C. This insult produces neuronal necrosis and/or infarction only in the cerebral hemisphere ipsilateral to the arterial occlusion in the majority of animals; hypoxia alone produces no damage. CBF, measured by the indicator diffusion technique using iodo[14C]-antipyrine, and tissue water content were determined concurrently in both cerebral hemispheres at specific intervals during recovery from cerebral hypoxia-ischemia. Water contents in the ipsilateral cerebral hemisphere were 89.1, 89.6, 89.7, 91.0, and 88.3% at 30 min, 4 h, 24 h, 3 d, and 6 d, respectively (p less than 0.001); whereas the percent tissue water in the contralateral hemisphere was unchanged from values in nonligated, hypoxic control rats (87.7%). CBF was similar in both cerebral hemispheres at 30 min, 4 h, and 24 h of recovery (50-65 mL/100 g/min) and not different from age-matched controls. At 3 and 6 d, CBF in the ipsilateral cerebral hemisphere was 30 and 26% of the contralateral hemisphere and 23 and 29% of the control animals, respectively (p less than 0.001). No inverse correlation existed between the changes in brain water content and CBF at any interval until 6 d of recovery. Thus, an early hypoperfusion does not follow perinatal cerebral hypoxia-ischemia, as occurs in adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Coevolving avian eye size and brain size in relation to prey capture and nocturnality.

Behavioural adaptation to ecological conditions can lead to brain size evolution. Structures involved in behavioural visual information processing are expected to coevolve with enlargement of the brain. Because birds are mainly vision-oriented animals, we tested the predictions that adaptation to different foraging constraints can result in eye size evolution, and that species with large eyes have evolved large brains to cope with the increased amount of visual input. Using a comparative approach, we investigated the relationship between eye size and brain size, and the effect of prey capture technique and nocturnality on these traits. After controlling for allometric effects, there was a significant, positive correlation between relative brain size and relative eye size. Variation in relative eye and brain size were significantly and positively related to prey capture technique and nocturnality when a potentially confounding variable, aquatic feeding, was controlled statistically in multiple regression of independent linear contrasts. Applying a less robust, brunching approach, these patterns also emerged, with the exception that relative brain size did not vary with prey capture technique. Our findings suggest that relative eye size and brain size have coevolved in birds in response to nocturnal activity and, at least partly, to capture of mobile prey.

Animals↗
PubMed2002

How does the brain control lifespan?

There is generally a positive correlation between brain/body size ratio and lifespan, particularly among mammals, suggesting a role for the brain in determining lifespan. Recent studies in diverse organisms including nematodes, flies and rodents have provided evidence that, indeed the brain may control lifespan. Signaling pathways involved in both central nervous system and peripheral stress responses and regulation of energy metabolism may play important roles in lifespan determination. Indeed, genetic and environmental manipulations of these systems can greatly affect lifespan by changing levels of hormones that modulate energy metabolism, stress resistance and regenerative capacity of cells throughout the body. A signal transduction pathway in neurons involving receptors coupled to phosphatidylinositol-3-kinase, Akt and glycogen synthase kinase-3beta appears to play a key role in regulation of longevity by the brain. Mutations in genes that encode proteins in the insulin signaling pathway can increase lifespan in C. elegans and Drosophila, this signaling pathway in neurons in the brain may be particularly important in limiting lifespan. Dietary restriction results in the upregulation of brain-derived neurotrophic factor (BDNF) in the brain, which may increase the resistance of neurons to aging. Interestingly, BDNF signaling in the brain can increase peripheral insulin sensitivity, suggesting a mechanism whereby the brain can control lifespan. We speculate that during evolution the brain took on the task of monitoring and controlling peripheral energy metabolism, and thereby regulating lifespan in the context of food availability. Roles for other evolutionarily conserved brain signaling pathways in lifespan determination are likely to be discovered in the near future.

Aging↗
PubMed1997

Neurotoxicity to the basal ganglia shown by magnetic resonance imaging (MRI) following poisoning by methanol and other substances.

OBJECTIVE: To define specific brain magnetic resonance features in methanol intoxicated patients and to evaluate the clinical relevance of monitoring these features. BACKGROUND: During the past decade magnetic resonance imaging has proven to be an exquisitely sensitive modality in depicting subtle water changes in diseased areas of the brain, allowing the definition of high-risk structures in numerous pathological conditions. METHOD: Four patients admitted to our institution for acute methanol intoxication were repeatedly evaluated by brain magnetic resonance imaging or a combination of computed tomography and magnetic resonance imaging. Common features of initial brain status were shown in all four cases and compared to those of patients presenting with other intoxications or critical deprivation states. RESULTS: Preferential localization of methanol-induced lesions within the putamina was observed in all four cases. This finding is specific compared to intoxication by other substances like carbon monoxide, or in the critical phase of metabolic disorders. The striking regression of the putaminal lesions on follow-up magnetic resonance examinations correlated with complete neurological recovery and the absence of extrapyramidal disturbance. Two patients exhibited discrete symmetric additional lesions in the medial areas of the parieto-occipital lobes. In a third one, the occipital lesions were severe. All three suffered from permanent visual impairment. The fourth patient, in whom magnetic resonance examinations failed to reveal any occipital lesion, never complained of visual disturbance though signs of optic neuropathy were detected in the visual evoked potentials. CONCLUSION: Magnetic resonance imaging appeared as a well suited neuroimaging modality in methanol intoxicated patients both in revealing a specific pattern of brain lesions and in demonstrating valuable correlation between evolution of brain changes on magnetic resonance images and clinical outcome.

Adult↗
PubMed1991

Arteriovenous malformations. Locations and evolution in the fetal brain.

Almost all cerebral arteriovenous malformations in the fetus involve the vein of Galen, although occasionally they may involve the frontal area of the brain instead. In all reported cases arteriovenous malformations have presented some time after 30 weeks as a sonolucent oval lesion located in the midline behind the third ventricle. Previous scans have been normal. Evidence of high output failure such as cardiomegaly, enlarged neck veins, or hydrops predicts a poor outcome.

Aneurysm↗