April 20, 2011

Addiction and Brain Circuits

From Brain Briefings:

Humans have always struggled with addictions to mind-altering substances. Yet, only in the past few decades have neuroscientists begun to understand precisely how these substances affect the brain — and why they can quickly become a destructive and even deadly habit. 

For a long time, society viewed addiction as a moral failing. The addict was seen as someone who simply lacked self-control. Today, thanks to new advances in brain imaging and other technologies, we know that addiction is a disease characterized by profound disruptions in particular routes — or circuits — in the brain.

Scientists are learning how genetics and environmental factors, such as stress, contribute to these neural disruptions and increase the risk of addiction. This ongoing research is allowing researchers to:

  • Understand how addictive substances affect the brain’s reward system.
  • Develop more effective therapies for treating drug abuse and addiction.
  • Establish better methods of detecting people at risk of developing addictions.

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February 23, 2011

Scientists look to new imaging techniques to measure metals in the brain

From the Globe and Mail:

We are metal heads. Our brains need iron, copper, manganese and zinc to function, yet there is growing evidence that these metals may play a role in Alzheimer’s disease, Parkinson’s disease multiple sclerosis and other illnesses.

Canadian scientists are developing new imaging techniques to accurately map and measure metals in the brain, a crucial step toward learning more about why they are so essential, as well as understanding the damage they can cause under some circumstances.

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February 21, 2011

Former CFL players’ brains used to study link between concussions and disease

From the Globe and Mail:

Concussion stories from Bobby Kuntz’s days with the Toronto Argonauts and the Hamilton Tiger-Cats made for family football folklore until a decade ago when they suddenly seemed bittersweet.

Mr. Kuntz, who suffered as many as 20 concussions playing football in the 1950s and 60s, developed a tremor and started to forget things. His golf game went and he had to give up his position as president and chief executive officer of his family’s metal finishing business.

His symptoms were progressive, yet difficult to diagnose. His wife, Mary, took him down to the Mayo Clinic – he was in his late 60s – and doctors suggested Lewy Body dementia and Parkinson’s.

“The only way you’ll ever find out if its Lewy Body disease is to have an autopsy,” Mrs. Kuntz recalled the Mayo Clinic doctors telling her about a decade ago.

She had always planned on having her husband autopsied as she was concerned about whether her five living children were at risk of inheriting his brain disease. Ms. Kuntz wants to know if there is a link between repeated concussions and his Lewy Body disease, a progressive form of dementia, or Parkinson’s, a degenerative disorder of the central nervous system with similar characteristics.

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November 9, 2009

Wired for Hunger: The Brain and Obesity

From the Dana Foundation:For most of human history, food was not readily available; storing energy helped ensure survival. Humans thus evolved to eat whenever food is at hand-a tendency that in the modern world may contribute to widespread obesity. Researchers are starting to determine the brain circuitry responsible for this default “eat” message. Marcelo Dietrich and Tamas Horvath tell the story of false starts and measured successes in obesity research. They propose that developing successful obesity therapy may require combining drug therapy with psychological or psychiatric approaches, as well as exercise. In the sidebar, they examine the opposite of obesity: anorexia nervosa.

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November 24, 2008

Real-time chemical responses in the nucleus accumbens differentiate rewarding and aversive stimuli

neurochemistry,neuroscience,perception — alice @ 1:28 am

Mitchell F Roitman, Robert A Wheeler, R Mark Wightman and Regina M Carelli
Article in Nature Neuroscience

Abstract
Rewarding and aversive stimuli evoke very different patterns of behavior and are rapidly discriminated. Here taste stimuli of opposite hedonic valence evoked opposite patterns of dopamine and metabolic activity within milliseconds in the nucleus accumbens. This rapid encoding may serve to guide ongoing behavioral responses and promote plastic changes in underlying circuitry.

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Gamma oscillations mediate stimulus competition and attentional selection in a cortical network model

Christoph Börgers, Steven Epstein, and Nancy J. Kopell
Article in Proceedings of the National Academy of Science, USA

Abstract
Simultaneous presentation of multiple stimuli can reduce the firing rates of neurons in extrastriate visual cortex below the rate elicited by a single preferred stimulus. We describe computational results suggesting how this remarkable effect may arise from strong excitatory drive to a substantial local population of fast-spiking inhibitory interneurons, which can lead to a loss of coherence in that population and thereby raise the effectiveness of inhibition. We propose that in attentional states fast-spiking interneurons may be subject to a bath of inhibition resulting from cholinergic activation of a second class of inhibitory interneurons, restoring conditions needed for gamma rhythmicity. Oscillations and coherence are emergent features, not assumptions, in our model. The gamma oscillations in turn support stimulus competition. The mechanism is a form of “oscillatory selection,” in which neural interactions change phase relationships that regulate firing rates, and attention shapes those neural interactions.

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