Does hemispheric lateralization influence functional and cardiovascular outcomes after stroke?: an analysis of placebo-treated patients from prospective acute stroke trials

<p><b>Background and Purpose:</b> The influence of stroke lateralization on functional and cardiovascular outcome after stroke is not well established. We evaluated the influence of hemispheric lateralization among patients enrolled in prospective acute stroke trials.</p> <p><b>Methods:</b> We obtained data from the VISTA database for acute stroke trials which reported lateralization. Baseline data, cardiac adverse events, and 90-day outcomes were compared between right and left hemisphere stroke patients. A "hemisphere unbiased" subscore of the NIHSS which omitted items strongly associated with lateralized cognitive deficits was also compared for trials which reported individual NIHSS item scores. A multivariable analysis of outcome predictors was performed.</p> <p><b>Results:</b> Three acute stroke trials met the prespecified inclusion criteria. 1644 placebo-treated patients with documented hemispheric lateralization were included in the analysis. Baseline NIHSS was higher for left hemisphere patients (mean 16.2, versus 12.8 right, P < 0.001); there was no difference in the "hemisphere unbiased" NIHSS subscore (10.88 left, 11.08 right, n=687, P= 0.49). There was no difference between hemispheres in 90-day modified Rankin Score (3.43 left, 3.29 right, P=0.13), mortality (22.1% left, 19.5% right, P=0.20), or cardiac adverse events (P=0.71). Hemispheric lateralization was not an independent predictor of outcome in the multivariable analysis after controlling for the hemispheric bias intrinsic to the NIHSS.</p> <p><b>Conclusions:</b> There is no difference in functional outcome between patients with right or left hemisphere stroke. Use of the baseline NIHSS score to predict stroke outcome must take hemispheric lateralization into account. Stroke lateralization is not an important predictor of cardiac adverse events or 90-day mortality.</p&gt

When does right functional hemispheric lateralization arise? Evidence from preterm infants

In recent years, magnetic resonance imaging (MRI) has allowed researchers to individuate an earlier morphological development of the right hemisphere compared to the left hemisphere before birth. Anatomical asymmetry, however, does not necessarily mean functional asymmetry and whether the anatomical differences between hemispheres at this early age are paralleled by functional specializations is still unknown. Here we show electrophysiological evidence of an early functional right lateralization for pitch processing arising by 30 gestational weeks, not before, in preterm newborns

Development of lateralization of the magnetic compass in a migratory bird

The magnetic compass of a migratory bird, the European robin (Erithacus rubecula), was shown to be lateralized in favour of the right eye/left brain hemisphere. However, this seems to be a property of the avian magnetic compass that is not present from the beginning, but develops only as the birds grow older. During first migration in autumn, juvenile robins can orient by their magnetic compass with their right as well as with their left eye. In the following spring, however, the magnetic compass is already lateralized, but this lateralization is still flexible: it could be removed by covering the right eye for 6 h. During the following autumn migration, the lateralization becomes more strongly fixed, with a 6 h occlusion of the right eye no longer having an effect. This change from a bilateral to a lateralized magnetic compass appears to be a maturation process, the first such case known so far in birds. Because both eyes mediate identical information about the geomagnetic field, brain asymmetry for the magnetic compass could increase efficiency by setting the other hemisphere free for other processes

Abnormal lateralization of functional connectivity between language and default mode regions in autism

Background: Lateralization of brain structure and function occurs in typical development, and abnormal lateralization is present in various neuropsychiatric disorders. Autism is characterized by a lack of left lateralization in structure and function of regions involved in language, such as Broca and Wernicke areas. Methods: Using functional connectivity magnetic resonance imaging from a large publicly available sample (n = 964), we tested whether abnormal functional lateralization in autism exists preferentially in language regions or in a more diffuse pattern across networks of lateralized brain regions. Results: The autism group exhibited significantly reduced left lateralization in a few connections involving language regions and regions from the default mode network, but results were not significant throughout left- and right-lateralized networks. There is a trend that suggests the lack of left lateralization in a connection involving Wernicke area and the posterior cingulate cortex associates with more severe autism. Conclusions: Abnormal language lateralization in autism may be due to abnormal language development rather than to a deficit in hemispheric specialization of the entire brain

Space representation for eye movements is more contralateral in monkeys than in humans

Contralateral hemispheric representation of sensory inputs (the right visual hemifield in the left hemisphere and vice versa) is a fundamental feature of primate sensorimotor organization, in particular the visuomotor system. However, many higher-order cognitive functions in humans show an asymmetric hemispheric lateralization—e.g., right brain specialization for spatial processing—necessitating a convergence of information from both hemifields. Electrophysiological studies in monkeys and functional imaging in humans have investigated space and action representations at different stages of visuospatial processing, but the transition from contralateral to unified global spatial encoding and the relationship between these encoding schemes and functional lateralization are not fully understood. Moreover, the integration of data across monkeys and humans and elucidation of interspecies homologies is hindered, because divergent findings may reflect actual species differences or arise from discrepancies in techniques and measured signals (electrophysiology vs. imaging). Here, we directly compared spatial cue and memory representations for action planning in monkeys and humans using event-related functional MRI during a working-memory oculomotor task. In monkeys, cue and memory-delay period activity in the frontal, parietal, and temporal regions was strongly contralateral. In putative human functional homologs, the contralaterality was significantly weaker, and the asymmetry between the hemispheres was stronger. These results suggest an inverse relationship between contralaterality and lateralization and elucidate similarities and differences in human and macaque cortical circuits subserving spatial awareness and oculomotor goal-directed actions

Alterations in functional brain network structure induced by subchronic phencyclidine (PCP) treatment parallel those seen in schizophrenia

Abstract of poster presentation shown at the 2nd Biennial Schizophrenia International Research Conference on Alterations in functional brain network structure induced by subchronic phencyclidine (PCP) treatment parallel those seen in schizophrenia

Neural Dynamics of Phonological Processing in the Dorsal Auditory Stream

Neuroanatomical models hypothesize a role for the dorsal auditory pathway in phonological processing as a feedforward efferent system (Davis and Johnsrude, 2007; Rauschecker and Scott, 2009; Hickok et al., 2011). But the functional organization of the pathway, in terms of time course of interactions between auditory, somatosensory, and motor regions, and the hemispheric lateralization pattern is largely unknown. Here, ambiguous duplex syllables, with elements presented dichotically at varying interaural asynchronies, were used to parametrically modulate phonological processing and associated neural activity in the human dorsal auditory stream. Subjects performed syllable and chirp identification tasks, while event-related potentials and functional magnetic resonance images were concurrently collected. Joint independent component analysis was applied to fuse the neuroimaging data and study the neural dynamics of brain regions involved in phonological processing with high spatiotemporal resolution. Results revealed a highly interactive neural network associated with phonological processing, composed of functional fields in posterior temporal gyrus (pSTG), inferior parietal lobule (IPL), and ventral central sulcus (vCS) that were engaged early and almost simultaneously (at 80–100 ms), consistent with a direct influence of articulatory somatomotor areas on phonemic perception. Left hemispheric lateralization was observed 250 ms earlier in IPL and vCS than pSTG, suggesting that functional specialization of somatomotor (and not auditory) areas determined lateralization in the dorsal auditory pathway. The temporal dynamics of the dorsal auditory pathway described here offer a new understanding of its functional organization and demonstrate that temporal information is essential to resolve neural circuits underlying complex behaviors

Brain asymmetries related to language with emphasis on entorhinal cortex and basal forebrain

Anatomical asymmetries of the human brain are important in at least four respects: 1) they can serve as potential indicators of the evolutionary foundations of language, 2) they can be used for comparative analysis of neural specializations for communication in primates, 3) they may provide underlying structural correlates for functional imaging (fMRI, PET) and genetic studies, and finally 4) they can be used for studying disorders which are suspected to result from either disturbed development of cerebral asymmetry or asymmetric damage to the brain. In the first part of this review, we give a general framework of this field through the brief descriptions of the milestone discoveries and major conceptual advances as they emerged throughout the last 150 years. In the second part, we provide a more detailed view on the functional relevance that asymmetries of the entorhinal cortex and basal forebrain may have on the language

The mind body problem, part three: ascension of sexual function to cerebral level

Physiologically, the somatic nervous system intervenes in external interaction between the body and environment, while autonomic nervous system ensures the functioning of internal organs. We present in this paper a psycho-physiological perspective suggesting that mental function (somatic in nature, because coordinates environmental interaction) is closer to and more aligned with the physiologic functioning of autonomic nervous system (due to autonomy, duality, etc.). At opposite end, sexual function (autonomic in nature, erection for example being a parasympathetic vasodilatory reflex) seems to be compatible and even dependent by a somatic participation (erectile response is rather induced by environmental stimuli than internal visceral stimuli). The perspective presented here is that the mind and sexuality are two distinct relational processes which, being related to the same environmental stimuli/ peripheral afferents, should be supported by a common (somatic-autonomic) neurobiological substrate