Spreading depolarizations (SD) are waves of abrupt, near-complete breakdown of neuronal transmembrane ion gradients, are the largest possible pathophysiologic disruption of viable cerebral gray matter, and are a crucial mechanism of lesion development. Spreading depolarizations are increasingly recorded during multimodal neuromonitoring in neurocritical care as a causal biomarker providing a diagnostic summary measure of metabolic failure and excitotoxic injury. Focal ischemia causes spreading depolarization within minutes. Further spreading depolarizations arise for hours to days due to energy supply-demand mismatch in viable tissue. Spreading depolarizations exacerbate neuronal injury through prolonged ionic breakdown and spreading depolarization-related hypoperfusion (spreading ischemia). Local duration of the depolarization indicates local tissue energy status and risk of injury. Regional electrocorticographic monitoring affords even remote detection of injury because spreading depolarizations propagate widely from ischemic or metabolically stressed zones; characteristic patterns, including temporal clusters of spreading depolarizations and persistent depression of spontaneous cortical activity, can be recognized and quantified. Here, we describe the experimental basis for interpreting these patterns and illustrate their translation to human disease. We further provide consensus recommendations for electrocorticographic methods to record, classify, and score spreading depolarizations and associated spreading depressions. These methods offer distinct advantages over other neuromonitoring modalities and allow for future refinement through less invasive and more automated approaches.

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The cetacean brain has long been of scientific interest, not only because of its large size -the largest in the animal kingdom -but also because of its high gyrification. It shows several adaptations to the aquatic environment, especially in the cortical arrangements of functional areas. To study structural aspects of the mysticete brain we estimated neocortical features in the common minke whale using stereological methods. The neocortex was surprisingly thick, equal to that in humans. The total neocortical neuron number was 12.8 3 10 9 , and the total neocortical glia number 98.2 3 10 9 . Total cell numbers in the auditory and visual cortex were also estimated, and showed that the auditory cortex contained more cells than the visual cortex. In this small sample, no sexual dimorphism was seen within the neocortex of the common minke whale. Our aim was to estimate the total cell number, cortical volume and cell density in the entire mysticete neocortex and compare the total cell number in the auditory cortex with that of the visual cortex using stereological methods. Here, we used the common minke whale as a model of all mysticetes. We wanted to compare these neocortical features to those of other mammals to forward understanding of the evolution of the mammalian brain. Anat Rec, 290:83-95, 2007. 2006 Wiley-Liss, Inc. Key words: mysticete; neocortex; cell numberThe number of neurons and their relative abundance in different parts of the brain is at least partly a determinant of neural functions and consequently also a determinant of behavior. The neurons and glia in the neocortex in particular are involved in important brain processes, and it is assumed that neurons are somehow responsible for the evolution of intelligence, since phyla with larger brains and more neurons more easily adapt to environmental change with a greater range and versatility of behavior (Jerison, 1985). Cetaceans possess complex behaviors and social patterns, such as cultural transmission of vocal and behavioral traits (Payne and Payne, 1985;Rendall and Whitehead, 2001), and bottlenose dolphins have shown that they are capable of selfrecognition (Reiss and Marino, 2001), cooperation, and tool use (Krutzen et al., 2005). Moreover, they also have the largest brain in the animal kingdom in absolute size, but not in relation to body size [here expressed as encephalization quotient, EQ (Jerison, 1973)]. Odontocetes (toothed whales) possess above-average encephalization levels compared to other mammals, second only to humans, whereas the encephalization level of the mysticete (baleen whales) is much lower, because of nonlinearities in EQ for very large animals (Marino, 2002(Marino, , 2004. However, the large absolute size and high degree of cortical gyrification show that the mysticete brain has undergone substantial enlargement and elaboration during the course of evolution (Oelschlä ger and Oelschlä ger, 2002).The cetacean brain differs from the terrestrial mammalian brain in many ways. It has a very high level of gyrification, an...