Press releases
Please quote Nature Neuroscience as the source of these items.
The April 2008 issue of Nature Neuroscience is available online.
April 2008
Adapting brain and behaviour to match the environment
Nature Neuroscience pp 423 - 425
Zones in a specific brain area change size depending on whether rats experience a calm or stressful environment, suggests a paper online in Nature Neuroscience this week. The observed size changes happen in a brain area involved in producing avoidance and approach behaviour.
An area deep in the brain known as the nucleus accumbens shell is subdivided into zones — stimulating a zone towards the front of the accumbens shell causes rats to seek out food and mates, known as appetitive behaviour. Stimulating a zone towards the back of the accumbens causes rats to behave as if they are scared.
Sheila Reynolds and Kent Berridge now show that the size of these zones can be changed by the kind of environment in which the rats live. Rats feel safe in quiet, dark places and when rats were placed in such an environment, the area where electrical stimulation later resulted in appetitive behaviour expanded from the front of the accumbens shell to cover the back as well. About 90% of the accumbens shell became an appetitive behaviour generating zone in this condition. The size of the area where stimulation resulted in fearful behaviour shrank considerably.
In comparison rats find loud and bright environments very stressful. When rats were placed in a well-lighted room and made to listen to loud music, about 90% of the accumbens shell became a fearful behaviour generating zone. Stimulation in most places in this area resulted in fearful behaviour, and the area where stimulation resulted in appetitive behaviour shrank to the very front of the accumbens shell.
These findings suggest an explanation for how animals adjust their behaviour to match their environments.
Emotional environments retune the valence of appetitive versus fearful functions in nucleus accumbens
pp 423 - 425
Sheila M Reynolds & Kent C Berridge
Published online: 16 March 2008 | doi10.1038/nn2061
How synaptic activity protects neurons
Nature Neuroscience pp 476 - 487
Scientists have identified a key signalling pathway that could protect areas of the brain at risk of damage from ageing and neurodegenerative diseases. The study, published online in Nature Neuroscience this week, reports that activation of NMDA receptors increases the expression of enzymes that protect neurons from damage by molecules called free radicals, which disrupt many normal cellular functions. Because these receptors are activated by events, including strokes, that increase the risk of such damage, this signalling pathway could serve to target the protective response to areas of the brain that need it most.
Giles Hardingham and colleagues report that the same receptor type also increases the effectiveness of cellular defences against free radicals. Activation of NMDA receptors at synapses increases the transcription of several enzymes that detoxify free radicals. Interfering with these enzyme systems made cells more susceptible to damage by free radicals. The authors also showed that some of these enzymes can reverse a chemical reaction that increases neural vulnerability; such reversal was not known to be possible in mammalian cells. Thus, this research may have identified a new potential target for therapies to decrease or reverse damage due to aging and neurodegenerative diseases.
Synaptic NMDA receptor activity boosts intrinsic antioxidant defenses pp 476 - 487
Sofia Papadia, Francesc X Soriano, Frédéric Léveillé, Marc-Andre Martel, Kelly A Dakin, Henrik H Hansen, Angela Kaindl, Marco Sifringer, Jill Fowler, Vanya Stefovska, Grahame Mckenzie, Marie Craigon, Roderick Corriveau, Peter Ghazal, Karen Horsburgh, Bruce A Yankner, David J A Wyllie, Chrysanthy Ikonomidou & Giles E Hardingham
Published online: 23 March 2008 | doi10.1038/nn2071
Smokers insensitive to what might have been
Nature Neuroscience pp 514 - 520
Chronic cigarette smokers consider the consequences of their choices differently than non-smokers according to a study in the April issue of Nature Neuroscience. In particular, smokers' decisions are not influenced by the outcome that would have followed an alternative choice.
Read Montague and colleagues asked people to play a game in which they repeatedly decided how much of their money to invest in an artificial stock market. After each investment decision, the change in the market was revealed and the subjects found out how much money they won. The authors could predict subsequent choices for non-smokers based on the difference between the amount of money the subjects won and the amount of money they could have won by making the largest possible bet. In contrast, for smokers, this difference had little influence on their subsequent choices. This suggests that smokers may make poor decisions because they ignore alternative outcomes that could have been achieved.
Even though smokers and non smokers made different choices, brain activity measured during this task in all participants was correlated with the difference between what actually happened and what might have been. Thus, the authors conclude that smokers' brains have information about what might have happened, but ignore it in deciding how to act.
Smokers' brains compute, but ignore, a fictive error signal in a sequential investment task pp 514 - 520
Pearl H Chiu, Terry M Lohrenz & P Read Montague
Published online: 2 March 2008 | doi10.1038/nn2067
