Maria Esposito, MA – Brain Blogger http://brainblogger.com Health and Science Blog Covering Brain Topics Wed, 30 May 2018 15:00:03 +0000 en-US hourly 1 https://wordpress.org/?v=4.9.6 Teaching the Brain to Calm Itself http://brainblogger.com/2013/05/11/teaching-the-brain-to-calm-itself/ http://brainblogger.com/2013/05/11/teaching-the-brain-to-calm-itself/#comments Sat, 11 May 2013 11:00:47 +0000 http://brainblogger.com/?p=14586 Estimates of combat-related Post-Traumatic Stress Disorder (PTSD) in U.S. veterans since the Vietnam War ranges from approximately 2& to 17%. Additional studies of combat veterans of more recent wars places the range of Iraq War returnees who suffer from PTSD  between 4% and 17%. Currently, there is no one form of treatment that has been found effective in combating this disorder, but can the brain somehow be encouraged to calm itself down?

PTSD is classified as an anxiety disorder brought on as the result of witnessing a life-threatening event. The individual repeatedly re-experiences distressing memories of the event and this constant repetition eventually alters the composition of the neural networks which process traumatic memories. This memory repetition also initiates:

  • Iterative learning – learning through repetition to fear the traumatic event
  • Top-down activation – expecting to find a certain pattern, the brain focuses attention on finding evidence of that pattern and not processing what is actually there
  • Pruning – eliminating tiny connections between neurons called synapses that don’t receive a lot of activity, further changing the structure of neural networks

Eventually, the PTSD patient is unable to distinguish between similar experiences. Minor threats to their personal safety are perceived as being on the same level as major ones which causes heightened anxiety responses.

Researchers from the Columbia University Medical Center have been experimenting with activating the dentate gyrus – a part of the hippocampus – to relieve stress in PTSD patients and those with similar anxiety disorders. The researchers inserted light-sensitive proteins called opsins into the dentate gyrus of mice models. They used light from a fiber optic strand to alternately activate and silence both portions of the dentate gyrus for three minute intervals while the mice took part in two anxiety tests.

The researchers found that stimulating the dorsal dentate gyrus – the area involved in learning – caused the mice to be more interested in investigating their surroundings, but it inhibited their ability to learn. However, when they stimulated the ventral portion – which is involved in anxiety – the animals’ anxiety levels were decreased without interfering with their ability to learn new things. The researchers also discovered that the effects could be reversed. When the they stopped activating the dentate gyrus, the mice returned to their previous states of anxiety.

From these results, the researchers concluded that there is potential for alleviating anxiety in individuals with anxiety disorders by targeting the ventral dentate gyrus with medication or deep-brain stimulation. The advantage to this kind of targeted therapy is that it makes an immediate impact on behavior and so it could work much faster than current courses of treatment.

References

Kheirbek MA, Drew LJ, Burghardt NS, Costantini DO, Tannenholz L, Ahmari SE, Zeng H, Fenton AA, & Hen R (2013). Differential Control of Learning and Anxiety along the Dorsoventral Axis of the Dentate Gyrus. Neuron, 77 (5), 955-68 PMID: 23473324

McFarlane AC, Yehuda R, & Clark CR (2002). Biologic models of traumatic memories and post-traumatic stress disorder. The role of neural networks. The Psychiatric clinics of North America, 25 (2) PMID: 12136500

Richardson LK, Frueh BC, & Acierno R (2010). Prevalence estimates of combat-related post-traumatic stress disorder: critical review. The Australian and New Zealand journal of psychiatry, 44 (1), 4-19 PMID: 20073563

Image via Oleg Zabielin / Shutterstock.

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Is Obesity Linked to ADHD? http://brainblogger.com/2013/05/05/is-obesity-linked-to-adhd/ http://brainblogger.com/2013/05/05/is-obesity-linked-to-adhd/#comments Sun, 05 May 2013 11:00:49 +0000 http://brainblogger.com/?p=14428 As more and more children consume high-fat diets and become increasingly overweight, the incidences of diseases like type 2 diabetes and high blood pressure have steadily grown among the population. However, these may not be the only health issues linked with this surge in overeating among children. In a recent study from the University of Illinois, researchers have found that high-fat diets may also be associated with impulsivity, depression, anxiety and ADHD.

They used four-week old mice to see if bio-behaviors would be affected by placing the animals on a high-fat diet for one to three weeks. The mice were randomly divided into two groups; the first group ate a diet in which 60% of the calories were from fat, and the second group ate a diet in which only 10% of the calories were from fat. After one week of eating a high-fat diet, the mice in group one exhibited an increase in anxiety levels as evidenced by more time spent burrowing and wheel running. In addition, the mice in group one were hesitant to explore open quadrants of a zero maze. They were also unable to navigate a Y-maze and recognize a new object.

When the researchers analyzed the cortex, hippocampus and hypothalamus for dopamine in the group one mice, they found increased levels of homovanillic acid (HVA) in the hippocampus and cortex. HVA is a byproduct that results when dopamine is metabolized. That means that the dopamine levels in the group one mice were low. Dopamine is important because it is a neurotransmitter that sends impulses from a nerve cell to another nerve, organ or tissue. Low levels of dopamine negatively impact the ability to think, focus and concentrate. It also affects motor coordination. Individuals with Parkinson’s Disease have low levels of dopamine.

Dopamine levels in another part of the brain called the dorsal striatum control an individual’s ability to enjoy rewards like eating. A poorly functioning dorsal striatum in which dopamine cannot signal to the brain that enough food had been consumed would lead to excess consumption, resulting in obesity.

The high level of HVA in the animals’ hippocampus and cortex was associated with a decreased presence of the BDNF gene in the cortex, which means that the levels of the protein it produces were also decreased. This protein helps existing neurons survive and aids in the growth of new neurons. Without those neurons, learning and memory would be affected.

The researchers also discovered that giving the group one mice Ritalin reversed the damage to learning and memory caused by eating the high-fat diet. Giving them the antidepressants Vestra and Norpramin had no effect on the memory and learning impairment.

References

Kaczmarczyk, M., Machaj, A., Chiu, G., Lawson, M., Gainey, S., York, J., Meling, D., Martin, S., Kwakwa, K., Newman, A., Woods, J., Kelley, K., Wang, Y., Miller, M., & Freund, G. (2013). Methylphenidate prevents high-fat diet (HFD)-induced learning/memory impairment in juvenile mice Psychoneuroendocrinology DOI: 10.1016/j.psyneuen.2013.01.004

Stice, E., Spoor, S., Bohon, C., & Small, D. (2008). Relation Between Obesity and Blunted Striatal Response to Food Is Moderated by TaqIA A1 Allele Science, 322 (5900), 449-452 DOI: 10.1126/science.1161550

Image via Fer Gregory / Shutterstock.

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Can Age-Related Forgetfulness be Overcome? http://brainblogger.com/2013/03/26/can-age-related-forgetfulness-be-overcome/ http://brainblogger.com/2013/03/26/can-age-related-forgetfulness-be-overcome/#comments Tue, 26 Mar 2013 11:00:05 +0000 http://brainblogger.com/?p=14303 Most older adults accept forgetfulness as natural part of the aging process. However, a group of Canadian researchers from the University of Toronto and Baycrest Health Services have found that mature adults can boost their memory and even perform as well on memory tests as younger adults through distraction learning. This type of learning uses a senior adult’s ability to associate useless information that distracted them while they were learning something new in order to remember what they learned.

The researchers recruited two groups of participants: students from the University of Toronto who were between the ages of 17 and 27 and older adults who lived in the community who were between the ages of 60-78 years old. All the participants were asked to take three tests. The first was to memorize a list of words and recall those words after only a few minutes. After this first test, there was a fifteen minute period during which the participants worked on an attention task that involved looking at pictures. While they were working on this task, half of the list of words they studied appeared as distractors across the screen they were viewing. The effect was similar to watching television and then suddenly seeing weather information about an upcoming storm streamed across the bottom of the screen. In some instances the words were appeared during the 15 minutes assigned for the picture task and in other instances they appeared at the end of the 15 minute interval. After the picture task was complete, the researchers surprised the participants by asking them to recall the words on that original list.

What the researchers observed during that second recall test was quite amazing. Repeating the words as distractors did not affect how well the young people remembered the words on the list. However,  older adults rarely or never forgot the words that had appeared as distractors. These seniors were 30% more likely to remember the distractor words compared to the words that were not used as distractors. The seniors used hyperbinding, linking the words to the pictures, as a way to remember.

What do these findings mean in terms of improving the quality of life for senior citizens? These results can be used to develop learning techniques for older adults that can help them remember important information like when to take medication or if they are supposed to be somewhere. The most significant aspect to all of this is that the seniors do not even have to be consciously paying attention to the distractors that will act as cues to remembering.

References

Biss RK, Ngo KW, Hasher L, Campbell KL, & Rowe G (2013). Distraction Can Reduce Age-Related Forgetting. Psychological science PMID: 23426890

Image via d13 / Shutterstock.

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This Is Your Brain… This Is Your Brain on Chemotherapy http://brainblogger.com/2013/03/11/this-is-your-brain-this-is-your-brain-on-chemotherapy/ http://brainblogger.com/2013/03/11/this-is-your-brain-this-is-your-brain-on-chemotherapy/#comments Mon, 11 Mar 2013 11:00:11 +0000 http://brainblogger.com/?p=14250 Cancer patients undergoing chemotherapy experience a number of negative side effects; however, the cause of one of those reactions, commonly referred to as “chemobrain,” has never really been understood. The term actually encompasses several different types of mental impairment including a feeling of confusion, difficulty learning new tasks, short attention span, and poor short-term memory. Chemobrain affects about 70 percent of all chemotherapy patients; but until now, no one could explain why it happened.

Researchers from Rutgers University found that there are two conditions caused by prolonged treatment with chemotherapy that travel throughout the body that create chemobrain. First, there is decreased in the growth of new neurons in the hippocampus. The constant proliferation of new brain cells is necessary to maintain the ability to learn, and if the number is decreased, the individual will find it difficult to learn something new. Second, which also occurs in the hippocampus, brain rhythm known as theta activity is inhibited. When a person learns a new task, these brain rhythms aid in communication between similar brain structures that are a distance away from each other. If that communication is disrupted, as it is during chemotherapy, the person is unable to learn that task. The other important discovery these researchers made is that since the hippocampus controls learning, but not long-term memory, the chemotherapy patient will find it hard to learn a new task but will have no trouble replicating tasks that were learned prior to receiving treatment.

The Rutgers team made their findings through an analysis of the behavior of 53 adult male rats bred in the Department of Psychology at the University. The animals were injected with temozolomide (TMZ), a chemotherapy drug that has been used to treat human brain tumors for more than ten years. The rats were treated cyclically, meaning they were given a dose of 2-5 mg per kilogram of body weight once a day for three days followed by four days of recovery, for up to six weeks. The dose and method of treatment mimicked human cancer patient treatment.

The researchers evaluated changes in the rats’ learning and memory by using variations of eyeblink conditioning, a methodology for studying the brain structures that facilitate memory and learning. A classic example of conditioning training is Pavlov’s famous experiment in which he rang a bell and then gave  his dogs food. The food caused the dogs to salivate. After repeating the pairing of a ringing bell followed by food, the dogs began salivating when they heard the bell because they had learned that the bell meant food was coming and they remembered that fact each time they heard the bell.

In this experiment, the number of daily tests and the number of training days for each eyeblink conditioning was determined by the difficulty of the task the researchers tried to teach the rats. The results of these tests showed that the rats had a lot of trouble learning to associate two events if there was a period of time between the tests. However, they could learn a simple tasks if the researchers performed the tasks without any time gap.

References

Nokia MS, Anderson ML, & Shors TJ (2012). Chemotherapy disrupts learning, neurogenesis and theta activity in the adult brain. The European journal of neuroscience, 36 (11), 3521-30 PMID: 23039863

Wada, N., Kishimoto, Y., Watanabe, D., Kano, M., Hirano, T., Funabiki, K., & Nakanishi, S. (2007). Conditioned eyeblink learning is formed and stored without cerebellar granule cell transmission Proceedings of the National Academy of Sciences, 104 (42), 16690-16695 DOI: 10.1073/pnas.0708165104

Image via Juan Gaertner / Shutterstock.

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