On Theta Waves and LTP

Theta waves are low-frequency large-amplitude oscillations (6-7/s) recorded in and around the hippocampus in a variety of mammals, notably rodents, rabbits, and marsupials. Theta rhythms appear to correlate with motor activity, such that their timing coincides with whisker movement and sniffing. These waves are typically investigated with respect to their ostensible involvement in memory, as their power correlates with impairments in memory-related tasks (e.g. spatial alternation, spatial reversal) in lesion studies of the fornix and septum.

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The (Un)surprising Empathic Abilities of Rodents

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Regrettably, it has taken a very long time for psychologists and neuroscientists to take the leap towards investigating empathy in non-primate mammals. Of course, why should sociobiology get in the way of politics and religion?

The study that had perhaps the biggest impact in this field, was conducted by Langford et al. (2006), entitled "Social modulation of pain as evidence of empathy in mice". The simple yet ingenious design included placing two mice, which were either strangers or cage mates, into transparent Plexiglas cylinders, such that they could see one another. Either one or both mice received an injection of 0.9% acetic acid into the stomach cavity and their pain response (writhing behavior) was measured. Remarkably, mice appeared to be in more pain when they saw another mouse also in pain, but only when that mouse was their cage mate or sibling, not when it was a stranger. Their pain was amplified by seeing familiar individuals in pain.

Molecular Underpinnings of Sexual Dimorphism in the CNS

Sexual dimorphism, as a topic, has been investigated extensively by neuroscientists at the level of brain structures, but the molecular underpinnings of these sex differences have received much less attention. Below is a short post summarizing the state of affairs in this regard. The information is derived from an excellent 2010 review by Jazin & Cahill published in Nature Reviews: Neuroscience.

Perhaps the most fascinating development in molecular studies of CNS sexual dimorphism is the focus on sex-biased gene expression. Gene expression differences which appear to be independent of hormone action have been found in rodents and in certain invertebrates, notably the fruitfly, D. melanogaster, and the nematode, C. elegans. In the latter two, there are even sex-specific neuronal networks governing mating/courtship behaviors. 

Schizophrenia 3.0: Salience dysregulation.

This post is prompted by an article published in this February’s Trends in Neurosciences under the title “Dopaminergic Basis of Salience Dysregulation inPsychosis” by Winton-Brown, Fusar-Poli, Ungless, & Howes (2014) and an earlier paper in the Schizophrenia bulletin entitled “The dopamine hypothesisof schizophrenia: version II – the final common pathway” (Howes & Kapur, 2009). As stated in the first title, Winton-Brown et al.’s work reviews extensively what they consider to be evidence of the dopaminergic basis of salience dysregulation and more briefly consider the argument for salience dysregulation as a causal force in the etiology of schizophrenia. Their work was building on an argument made by Howes & Kapur who suggested that a panoply of genetic and environmental risk factors all converge on increased striatal dopaminergic function, producing aberrant salience and thereby psychosis.

Pain, Rejection, and the Optimal Calibration Hypothesis

A paper by Chester et al. was published in the July 2012 issue of Frontiers in Evolutionary Neuroscience under the title:

"The optimal calibration hypothesis: how life history modulates the brain's social pain network."

This work presents a novel way of looking at adaptations in the sensitivity of the "social pain network" throughout the human lifespan.

The authors start out by reviewing the evidence of overlap between the brain networks involved in pain perception, and the neural substrates of the affective response to social threats, such as rejection. Reviewed are the two neocortical structures which appear to be involved in both. The anterior cingulate cortex (ACC) is thought to support the affective features of pain, but activation in this region is also observed in response to perceived social rejection. Similarly, the anterior insula appears to be involved in affective responses to both physical pain and social rejection.