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. (shrink)

Recent findings indicate that frontal brain asymmetry may be a marker of for depression. However, the psychological predispositions that account linkage between frontal brain asymmetry and depression are unclear. approach-withdrawal hypothesis is the primary framework that has been to account for the linkages between frontal brain asymmetry and or emotional disorders. We review evidence consistent with this and suggest several directions for its extension. One such direction is to constrain the approach-withdrawal hypothesis by linking (...) frontal asymmetry to the known functions of the prefrontal cortex. On this we propose that frontal brain asymmetry may be preferentially linked processes that promote the temporal continuity and shifting of or emotional priorities and the suppression of interference by sources of motivation or emotion. We review evidence from and neurobiological studies of depression that is broadly consistent with these predictions. We emphasise the need for future studies testing our hypotheses. (shrink)

Similar to directional asymmetries in animals, language lateralization in humans follows a bimodal distribution. A majority of individuals are lateralized to the left and a minority of individuals are lateralized to the right side of the brain. However, a biological advantage for either lateralization is lacking. The scenario outlined by Vallortigara & Rogers (V&R) suggests that language lateralization in humans is not specific to language or human speciation but simply follows an evolutionarily conserved organizational principle of the brain.

Although brain size and the concept of intelligence have been extensively used in comparative neuroscience to study cognition and its evolution, such coarse-grained traits may not be informative enough about important aspects of neurocognitive systems. By taking into account the different evolutionary trajectories and the selection pressures on neurophysiology across species, Logan and colleagues suggest that the cognitive abilities of an organism should be investigated by considering the fine-grained and species-specific phenotypic traits that characterize it. In such a way, (...) we would avoid adopting human-oriented, coarse-grained traits, typical of the standard approach in cognitive neuroscience. We argue that this standard approach can fail in some cases, but can, however, work in others, by discussing two major topics in contemporary neuroscience as examples: general intelligence and brain asymmetries. (shrink)

I do not disagree with the argument that human-population right-handedness may in some way be a consequence of the population-level left-lateralization of language. But I suggest that the human functional lateralization is not dependent on the structural left-right brain asymmetries to which Corballis refers.

The aim of this study was to verify whether chimpanzees demonstrate an auditory laterality during the orientation reaction, and which hemisphere is responsible for processing the emotional stimuli and which for the species-specific vocalizations. The study involved nine chimpanzees from the Warsaw Municipal Zoological Garden. They were tested individually in their bedrooms. Chimpanzees approached a tube filled with food, located in the centre of the cage. Randomly selected sounds were played from the speakers when the subject was focused on getting (...) food. Individual reactions were observed and outcomes reported. The four types of sound used: thunderstorm, dog barking, chimpanzee vocalization and a zookeeper’s voice. To test whether chimpanzees demonstrate auditory laterality we used a single sample X2 test. The existence of auditory laterality has been confirmed. The sound of the storm caused the orientation reaction to the left, while chimpanzee vocalization - to the right. On this basis we can conclude that among chimpanzees, arousing stimuli are being processed by the right hemisphere, and species-specific vocalizations by the left. However, the set of stimuli was limited so the study did not unequivocally resolve this issue. (shrink)

BackgroundThe preferable position of Deep Brain Stimulation electrodes is proposed to be located in the dorsolateral subthalamic nucleus to improve general motor performance. The optimal DBS electrode localization for the post-operative improvement of balance and gait is unknown.MethodsIn this single-center, retrospective analyses, 66 Parkinson’s disease patients were assessed pre- and post-operatively by using MDS-UPDRS, freezing of gait score, Giladi’s gait and falls questionnaire and Berg balance scale. The clinical outcome was related to the DBS electrode coordinates in x, y, (...) z plane as revealed by image-based reconstruction. Binomial generalized linear mixed models with fixed-effect variables electrode asymmetry, parkinsonian subtype, medication, age class and clinical DBS induced changes were analyzed.ResultsSubthalamic nucleus-deep brain stimulation improved all motor, balance and FoG scores in MED OFF condition, however there were heterogeneous results in MED ON condition. DBS electrode reconstructed coordinates impacted the responsiveness of axial symptoms. FoG and balance responders showed slightly more medially located STN electrode coordinates and less medio-lateral asymmetry of the electrode reconstructed coordinates across hemispheres compared to non-responders.ConclusionDeep brain stimulation electrode reconstructed coordinates, particularly electrode asymmetry on the medio-lateral axis affected the post-operative responsiveness of balance and FoG symptoms in PD patients. (shrink)

BackgroundIn Parkinson's disease, the side of motor symptoms onset may influence disease progression, with a faster motor symptom progression in patients with left side lateralization. Moreover, worse neuropsychological outcomes after subthalamic nucleus deep brain stimulation have been described in patients with predominantly left-sided motor symptoms. The objective of this study was to evaluate if the body side of motor symptoms onset may predict motor outcome of bilateral STN-DBS.MethodsThis retrospective study included all consecutive PD patients treated with bilateral STN-DBS at (...) Grenoble University Hospital from 1993 to 2015. Demographic, clinical and neuroimaging data were collected before and 1 year after surgery. The predictive factors of motor outcome at one-year follow-up, measured by the percentage change in the MDS-UPDRS-III score, were evaluated through univariate and multivariate linear regression analysis.ResultsA total of 233 patients were included with one-year follow-up after surgery [143 males ; 121 right body onset; 112 left body onset; mean age at surgery, 55.31 ± 8.44 years; mean disease duration, 11.61 ± 3.87]. Multivariate linear regression analysis showed that the left side of motor symptoms onset did not predict motor outcome.ConclusionsIn this retrospective study, the body side of motor symptoms onset did not significantly influence the one-year motor outcome in a large cohort of PD patients treated with bilateral STN-DBS. (shrink)

The most developed and the latest-to-mature mental skills represented in the creation of mono- versus polysemantic contexts are related respectively to the left and right frontal lobe. A polysemantic way of thinking is responsible for the subject's successful integration in the polydimensional world. The functional insufficiency of this right-hemispheric way of thinking displays a predisposition toward the development of mental disorders, including schizophrenia.

I agree with Burns that an evolutionary theory is required, but I question his multifactorial premise. The arguments for an evolutionary theory are stronger, and one that is more precise than that presented by Burns has already been formulated. This theory, that schizophrenia is “the price that Homo sapiens pays for language,” (Crow 1997a; 2000b, 2004c), generates testable predictions absent from Burns' presentation.

The main aspects of interdisciplinary ICT technology of educational process based on the concept of functional asymmetry of the cerebral hemispheres, which reflect space-time asymmetry of the Universe and constitute a certain psychophysiological focus of human organism, are presented in the article. Its urgency stems from the tendencies of contemporary world, evolving towards the information society and influencing the development of modern education, becoming increasingly multimedia-rich and psychologised. The authors consider the major peculiarities of cognitive strategies of (...) class='Hi'>brain’s hemispheres, which should be taken into account in modern educational systems that apply versatile multimedia means in teaching different academic disciplines. It is shown that training information offered to the students can be differentiated by the right and left video sequences, which corresponds to hemispheric information processing strategies and promotes the synergetic state of synchronization of the hemispheres functions. And the encephalographic studies show that such functional synchronization, revealing the medication state of human brain, presupposes the integration of two information processing strategies, leading to harmonization of the processes of the first and second signalling systems. The algorithms of the most effective influence of multimedia presentations of teaching materials on a student based on the concept of functional asymmetry of human brain are substantiated. These algorithms presuppose combining the "left" and "right" information in such a way that the volumes of two types of information would form a harmonious proportion. (shrink)

In the First Meditation, the Cartesian meditator temporarily concludes that he cannot know anything, because he cannot discriminate dreaming from waking while he is dreaming. To resist the meditator’s conclusion, one could deploy an asymmetry argument. Following Bernard Williams, one could argue that even if the meditator cannot discriminate dreaming from waking while dreaming, it does not follow that he cannot do it while awake. In general, asymmetry arguments seek to identify an asymmetry between a bad case (...) that is entertained as a ground for doubt and a good case in which one takes oneself to know something. My aim in this paper is to consider how effective asymmetry arguments are as an anti-skeptical strategy. I conclude that although asymmetry arguments provide an effective response to dreaming skepticism, they fail as a response to brains-in-a-vat skepticism. (shrink)

Drug resistant epilepsy is one of the most complex, multifactorial and polygenic neurological syndrome. Besides its dynamicity and variability, it still provides us with a model to study brain-behavior relationship, giving cues on the anatomy and functional representation of brain function. Given that onset zone of focal epileptic seizures often affects different anatomical areas, cortical but limited to one hemisphere, this condition also let us study the functional differences of the left and right cerebral hemispheres. One lateralized function (...) in the human brain is emotional prosody, and it can be a useful ictal sign offering hints on the location of the epileptogenic zone. Besides its importance for effective communication, prosody is not considered an eloquent domain, making resective surgery on its neural correlates feasible. We performed an Electronic databases search (Medline and PsychINFO) from inception to July 2017 for studies about prosody in epilepsy. The search terms included “epilepsy,” “seizure,” “emotional prosody,” and “vocal affect.” This review focus on emotional prosody processing in epilepsy as it can give hints regarding plastic functional changes following seizures (preoperatively), resection (post operatively), and also as an ictal sign enabling the assessment of dynamic brain networks. Moreover, it is argued that such reorganization can help to preserve the expression and reception of emotional prosody as a central skill to develop appropriate social interactions. (shrink)

Recent evidence in natural and semi-natural settings has revealed a variety of left-right perceptual asymmetries among vertebrates. These include preferential use of the left or right visual hemifield during activities such as searching for food, agonistic responses, or escape from predators in animals as different as fish, amphibians, reptiles, birds, and mammals. There are obvious disadvantages in showing such directional asymmetries because relevant stimuli may be located to the animal's left or right at random; there is no a priori association (...) between the meaning of a stimulus (e.g., its being a predator or a food item) and its being located to the animal's left or right. Moreover, other organisms (e.g., predators) could exploit the predictability of behavior that arises from population-level lateral biases. It might be argued that lateralization of function enhances cognitive capacity and efficiency of the brain, thus counteracting the ecological disadvantages of lateral biases in behavior. However, such an increase in brain efficiency could be obtained by each individual being lateralized without any need to align the direction of the asymmetry in the majority of the individuals of the population. Here we argue that the alignment of the direction of behavioral asymmetries at the population level arises as an “evolutionarily stable strategy” under “social” pressures occurring when individually asymmetrical organisms must coordinate their behavior with the behavior of other asymmetrical organisms of the same or different species. Key Words: asymmetry; brain evolution; brain lateralization; development; hemispheric specialization; laterality; lateralization of behavior; social behavior; theory of games. (shrink)

The possibility that two forms of asymmetry underlie handedness is considered. Corballis has proposed that right-handedness developed when gesture encountered lateralized vocalization but may have been superimposed on a preexisting two-thirds dominance. Evidence is reviewed here which suggests that the baseline asymmetry is even more substantial than this, with possible implications for brain anatomy and genetic theories of handedness.

Similar to visual perception, auditory perception also has a clearly described “pop-out” effect, where an element with some extra feature is easier to detect among elements without an extra feature. This phenomenon is better known as auditory perceptual asymmetry. We investigated such asymmetry between shorter or longer duration, and level or falling of pitch of linguistic stimuli that carry a meaning in one language, but not in another. For the mismatch negativity experiment, we created four different types of (...) stimuli by modifying the duration of the first vowel [ɑ] and pitch contour of the stimuli words. The stimuli were synthesized from Estonian words and follow the Estonian language three-way quantity system, which incorporates tonal features together with temporal patterns. This made the meaning of the word dependent on the combination of both features and allows us to compare the relative contribution of duration and pitch contour in discrimination of language stimuli in the brain via MMN generation. The participants of the experiment were 12 Russian native speakers with little or no experience in Estonian and living in Estonia short-term, and 12 Estonian native speakers. We found that participants’ perception of the linguistic stimuli differed not only according to the physical features but also according to their native language, confirming that the meaning of the word interferes with the early automatic processing of phonological features. The GAMM and ANOVA analysis of the reversed design results showed that the deviant with longer duration among shorter standards elicited a MMN response with greater amplitude than the short deviant among long standards, while changes in pitch contour produced neither strong MMN nor asymmetry. Thus, we demonstrate the effect of language background on asymmetric perception of linguistic stimuli that aligns with those of previous studies, and contributes to the growing body of knowledge supporting auditory perceptual asymmetry. (shrink)

In this commentary we suggest that asymmetries in reasoning associated with moral judgment do not necessarily invalidate a theory-theory account of naïve psychological reasoning. The asymmetries may reflect a core knowledge assumption that human nature is prosocial, an assumption that heightens vigilance for antisocial dispositions, which in turn leads to differing assumptions about what is the presumed topic of conversation.

We describe a possible link between coordinated lateralised group behaviour serving species survival in lower vertebrates and a striking lateralisation phenomenon found in human social behaviour: the universal preference for cradling a young infant on the left side. Our exploration offers a different perspective on the role of cerebral asymmetry for the survival of both the individual and the species.