Functional Weight of Somatic and Cognitive Networks and Asymmetry of Compensatory Mechanisms: Collaboration or Divergency among Hemispheres after Cerebrovascular Accident?

The human brain holds highly sophisticated compensatory mechanisms relying on neuroplasticity. Neuronal degeneracy, redundancy, and brain network organization make the human nervous system more robust and evolvable to continuously guarantee an optimal environmental-related homeostasis. Nevertheless, after injury, restitution processes appear dissimilar, depending on the pathology. Following a cerebrovascular accident, asymmetry, within- and across-network compensation and interhemispheric inhibition are key features to functional recovery. In moderate-to-severe stroke, neurological outcome is often poor, and little is known about the paths that enable either an efficient collaboration among hemispheres or, on the contrary, an antagonism of adaptative responses. In this review, we aim to decipher key issues of ipsilesional and contralesional hemispheric functioning allowing the foundations of effective neurorehabilitation strategies.

There are More than Two Sides to Antisocial Behavior: The Inextricable Link between Hemispheric Specialization and Environment

Human functions and traits are linked to cerebral networks serving different emotional and cognitive control systems, some of which rely on hemispheric specialization and integration to promote adaptive goal-directed behavior. Among the neural systems discussed in this context are those underlying pro- and antisocial behaviors. The diverse functions and traits governing our social behavior have been associated with lateralized neural activity. However, as with other complex behaviors, specific hemispheric roles are difficult to elucidate. This is due largely to environmental and contextual influences, which interact with neural substrates in the development and expression of pro and antisocial functions. This paper will discuss the reciprocal ties between environmental factors and hemispheric functioning in the context of social behavior. Rather than an exhaustive review, the paper will attempt to familiarize readers with the prominent literature and primary questions to encourage further research and in-depth discussion in this field.

Bizarre behavior during intracarotid sodium amytal testing (Wada test): are they predictable?

The intracarotid sodium amytal test (ISAT or Wada Test) is a commonly performed procedure in the evaluation of patients with clinically refractory epilepsy candidates to epilepsy surgery. Its goal is to promote selective and temporary interruption of hemispheric functioning, seeking to define language lateralization and risk for memory compromise following surgery. Behavioral modification is expected during the procedure. Even though it may last several minutes, in most cases it is subtle and easily manageable. We report a series of patients in whom those reactions were unusually bizarre, including agitation and aggression. Apart of the obvious technical difficulties (patients required physical restraining) those behaviors potentially promote testing delay or abortion and more importantly, inaccurate data. We reviewed those cases, seeking for features that might have predicted their occurrence. Overall, reactions are rare, seen in less than 5% of the ISAT procedures. The barbiturate effect, patients' psychiatric profiles, hemisphere dominance or selectiveness of the injection were not validated as predictors. Thorough explanation, repetition and simulation may be of help in lessening the risk of those reactions.