TMS brings “shock” to science of memory loss

TMS brings “shock” to science of memory loss

By SAMHITA ILANGO
Published: September 4th, 2014
Views: 8 views

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UQ.EDU.AU

With a few shocks to the brain, scientists have made it possible to never forget a friend’s birthday, lose track of keys or have to deal with uncomfortable encounter of forgetting an acquaintance’s name. A research team at Northwestern University’s Feinberg School of Medicine has used this knowledge for more than just key tracking but for enhancing the retention network of memory-impaired individuals. 

The Transcranial Magnetic Stimulation (TMS) is a noninvasive method to depolarize or hyperpolarize neurons in the brain through electromagnetic induction. Essentially, the treatment will control neurons to be stronger or weaker in an individual. This recent study covers the therapeutic uses of TMS. Joel Voss, assistant professor of medical social sciences at Northwestern University, and his team worked on this project. 

“I am most interested in my research because it has at least some promise for helping individuals with memory impairments,” Voss said. “I’ve spent a lot of time with people after their lives have been essentially destroyed by severe memory impairment, and the desire to figure out some way to improve their lot is what gets me going in the morning.” 

They tested TMS’s impact on memory by understanding the memory-related regions of the brain. Voss and his team tested 16 healthy individuals without memory impairment with an MRI and looked at the treatment’s influence on the regions. This established a standard for proper cognitive function. Afterwards, the same test subjects were brought in for memory tasks over a span of five days with 20 minutes of TMS each time, while an MRI mapped their brain functions. The final analysis of the study revealed that the five days of TMS treatment resulted in the different regions working better together than how they worked at the standard level.

Further analysis sets hopes for this treatment to be able to be used on stroke victims and Alzheimer’s patients.

“I imagine — or rather hope — that in the near future, we devise a superior method for controlling brain function noninvasively,” Voss said. “When I imagine the effects of TMS on neurons, what comes to mind is trying to thread a needle with a shotgun. We will need better if we are to achieve a sophisticated understanding of brain function.”

Chirag Mehra, a neurodevelopment research fellow at the Kennedy Krieger Institute, gave his input on the present and the future of TMS.

“TMS, while stimulating brain regions in this study, is often used to suppress brain regions for research purposes. So far, no long term consequences have been found secondary to this suppression — the suppression ends when the TMS probe is removed,” Mehra said.

He further discussed the prospects of this treatment.

“Perhaps in the future we could apply TMS to treating psychiatric and neurological disorders. For this, we might need to create a much smaller TMS device that remains in our bodies, providing stimulation — intermittently or continuously — on a long term basis, analogous to a pacemaker used to treat cardiac arrhythmias.” 

With the speed at which current neuroscience advancements are occurring, the next 50 years are unpredictable.

“Honestly, advancement is such a moving target that it is impossible to predict very far into the future, much like the weather,” Voss said.

http://www.jhunewsletter.com/2014/09/04/tms-brings-shock-to-science-of-memory-loss-53971/

Who'd have thunk it? Overthinking handicaps human performance

9 August 2013
Who'd have thunk it? Overthinking handicaps human performance
by Will Parker

Appearing in the Journal of Neuroscience, a new University of California - Santa Barbara study reveals why under certain circumstances paying full attention and trying hard can actually impede performance.

The study's lead author, Taraz Lee, explained that there are two kinds of memory: implicit, long-term memory not requiring conscious thought and expressed by means other than words; and explicit, long term memory formed consciously that can be described in words.

Long-term memory is supported by various regions in the prefrontal cortex, the newest part of the brain in terms of evolution and the part of the brain responsible for planning, executive function, and working memory. "A lot of people think the reason we're human is because we have the most advanced prefrontal cortex," noted Lee.

Previous brain studies have shown that taxing explicit memory resources improved recognition memory without awareness. These results suggest that implicit perceptual memory can aid performance on recognition tests, so Lee decided to test whether the effects of the attentional control processes associated with explicit memory could directly interfere with implicit memory.

To investigate, Lee used continuous theta-burst transcranial magnetic stimulation (TMS) to temporarily disrupt the function of two different parts of the prefrontal cortex, the dorsolateral and ventrolateral. The dorsal and ventral regions are close to each other but have slightly different functions. Disrupting function in two distinct areas provided a direct causal test of whether explicit memory processing exerts control over sensory resources - in this case, visual information processing - and in doing so indirectly harms implicit memory processes.

Participants in the experiment were shown a series of kaleidoscopic images for about a minute, then had a one-minute break before being given memory tests containing two different kaleidoscopic images. They were then asked to distinguish images they had seen previously from the new ones. "After they gave us that answer, we asked whether they remembered a lot of rich details, whether they had a vague impression, or whether they were blindly guessing," explains Lee. "And the participants only did better when they said they were guessing."

The results of disrupting the function of the dorsolateral prefrontal cortex shed light on why paying attention can be a distraction and affect performance outcomes. "If we ramped down activity in the dorsolateral prefrontal cortex, people remembered the images better," said Lee.

When the researchers disrupted the ventral area of the prefrontal cortex, participants' memory was just slightly worse. "They would shift from saying that they could remember a lot of rich details about the image to being vaguely familiar with the images," Lee said. "It didn't actually make them better at the task."

Lee now plans to focus on dissecting the process of choking under pressure. For this, he'll use brain scans to examine why people who are highly incentivized to do well often succumb to pressure and how the prefrontal cortex and these attentional processes interfere with performance.

"I think most researchers who look at prefrontal cortex function are trying to figure out what it does to help you and how that explains how the brain works and how we act," said Lee. "I look at it at the opposite. If we can figure out the ways in which activity in this part of the brain hurts you, then this also informs how your brain works and can give us some clues to what's actually going on."

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http://www.scienceagogo.com/news/20130709113343data_trunc_sys.shtml

1.Deep brain stimulation: a fix when the drugs don’t work

14 May 2013, 6.09am EST

1. Deep brain stimulation: a fix when the drugs don’t work

   Author

   1. 

      Amy Reichelt

      Research Fellow in Neuroscience at University of New South Wales

   Disclosure Statement

   Amy Reichelt does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

   University of New South Wales does not contribute to the cost of running The Conversation. Find out more.

   
   
2.  

   The Conversation is funded by CSIRO, Melbourne, Monash, RMIT, UTS, UWA, Canberra, CDU, Deakin, Flinders, Griffith, JCU, La Trobe, Massey, Murdoch, Newcastle. QUT, Swinburne, UniSA, USC, USQ, UTAS, UWS and VU.

   

   Implanted electrodes can alleviate symptoms of Parkinson’s and Alzheimer’s, and help treat addiction. Wikimedia Commons

   
   

   Neurological disorders can have a devastating impact on the lives of sufferers and their families.

   
   
3. 
   Symptoms of these disorders differ extensively – from motor dysfunction in Parkinson’s disease, memory loss in Alzheimer’s disease to inescapable cravings in drug addiction.

   
   
4. 
   Drug treatments are often ineffective in these disorders. But what if there was a way to simply switch off a devastating tremor, or boost a fading memory?

   
   
5. 
   Recent advances using Deep Brain Stimulation (DBS) in selective brain regions have provided therapeutic benefits and have allowed those affected by these neurological disorders freedom from their symptoms, in absence of an existing cure.
   

   A pacemaker for the brain

   Artificial cardiac pacemakers are typically associated with controlling and resynchronising heartbeats by electrical stimulation of the heart muscle.
   

   

   Schematic of deep brain stimulation. stutteringmedia

   Click to enlarge

   
   In a similar manner, DBS sends electrical impulses to specific parts of the brain that control discrete functions. This stimulation evokes control over the neural activity within these regions.
   Prior to switching on the electrical stimulation, electrodes are surgically implanted within precise brain regions to control a specific function.

   
   
6. 
   The neurosurgery is conducted under local anaesthetic to maintain consciousness in the patient. This ensures that the electrode does not damage critical brain regions.

   
   
7. 
   The brain itself has no pain receptors so does not require anaesthetic.

   
   
8. 
   Following recovery from surgery the electrodes are activated and the current calibrated by a neurologist to determine the optimal stimulation parameters.

   
   
9. 
   The patient can then control whether the electrodes are on or off by a remote battery-powered device.
   

   
   

   
   
10. Deep Brain Stimulation surgery.

    
    

    Turning off tremors

    Perhaps the most documented success of DBS is in the control of tremors and motor coordination in Parkinson’s disease.

    
    
11. 
    This is caused by the degeneration of neurons in an area of the brain called the substantia nigra. These neurons secrete the neurotransmitter dopamine.
    

    

    Basal ganglia circuits, including substantia nigra. Wikimedia Commons

    Click to enlarge

    
    Deterioration of these neurons reduces the amount of dopamine available to be released in a brain area involved in movement, the basal ganglia.

    
    
12. 
    Drug therapy for Parkinson’s disease involves the use of levodopa (L-DOPA), a form of dopamine that can cross the blood brain barrier and then be synthesised into dopamine.

    
    
13. 
    The administration of L-DOPA temporarily reduces the motor symptoms by increasing dopamine concentrations in the brain. However, side effects of this treatment include nausea and disordered movement.

    
    
14. 
    DBS has been shown to provide relief from the motoric symptoms of Parkinson’s disease and essential tremors.

    
    
15. 
    For the treatment of Parkinson’s disease electrodes are implanted into regions of the basal ganglia – the subthalamic nucleus or globus pallidus, to restore control of movement.

    
    
16. 
    These are regions innervated by the deteriorating substantia nigra, therefore the DBS boosts stimulation to these areas.

    
    
17. 
    Patients can then switch on the electrodes, stimulating these brain regions to enhance control of movement and diminish tremors.
    

    Restoring fading memories

    Recently, DBS has been used to diminish memory deficits associated with Alzheimer’s disease, a progressive and terminal form of dementia.
    

    

    British author Terry Pratchett has been diagnosed with Alzheimer’s Disease. Bolt of Blue

    
    The pathologies associated with Alzheimer’s disease involve the formation of amyloid plaques and neurofibrillary tangles within the brain leading to dysfunction and death of neurons.

    
    
18. 
    Brain regions primarily affected include the temporal lobes, containing important memory structures including the hippocampus.

    
    
19. 
    Recent clinical trials with DBS involve the implantation of electrodes within the fornix – a structure connecting the left and right hippocampi together.

    
    
20. 
    By stimulating neural activity within the hippocampi via the fornix, memory deficits associated with Alzheimer’s disease can be improved, enhancing the daily functioning of patients and slowing the progression of cognitive decline.
    

    Deactivating addiction

    Another use of DBS is in the treatment of substance abuse and drug addiction. Substance-related addictions constitute the most frequently occurring psychiatric disease category and patients are prone to relapse following rehabilitative treatment.

    
    
21. 
    Persistent drug use leads to long term changes in the brain’s reward system.

    
    
22. 
    Understanding of the reward systems affected in addiction has created a range of treatment options that directly target dysregulated brain circuits in order to normalise functionality.

    
    
23. 
    One of the key reward regions in the brain is the nucleus accumbens and this has been used as a DBS target to control addiction.

    
    
24. 
    Translational animal research has indicated that stimulation of the nucleus accumbens decreases drug seeking in models of addiction. Clinical studies have shown improved abstinence in both heroin addicts and alcoholics.
    

    

    Diagram of a rat self-administering morphine. Wikimedia Commons

    Click to enlarge

    
    Studies have extended the use of DBS to potentially restore control of maladaptive eating behaviours such as compulsive binge eating.

    
    
25. 
    In a recent study, binge eating of a high fat food in mice was decreased by DBS of the nucleus accumbens. This is the first study demonstrating that DBS can control maladaptive eating behaviours and may be a potential therapeutic tool in obesity.

    
    
26. 
    Despite its therapeutic use for more than a decade, the neural mechanism of DBS is still not yet fully understood.

    
    
27. 
    The remedial effect is proposed to involve modulation of the dopamine system – and this seems particularly relevant in the context of Parkinson’s disease and addiction.

    
    
28. 
    DBS potentially has effects on the functional activity of other interconnected brain systems. While it can provide therapeutic relief from symptoms of neurological diseases, it does not treat the underlying pathology.

    
    
29. 
    But it provides both effective and rapid intervention from the effects of debilitating illnesses, restoring activity in deteriorating brain regions and aids understanding of the brain circuits involved in these disorders.

    
    

J Nat Sci Biol Med. 2013 Jan;4(1):8-13. doi: 10.4103/0976-9668.107254.

Vagal nerve stimulator: Evolving trends.

Ogbonnaya S, Kaliaperumal C.

Source

Department of Neurosurgery, Cork University Hospital, Cork, Ireland.

Abstract

Over three decades ago, it was found that intermittent electrical stimulation from the vagus nerve produces inhibition of neural processes, which can alter brain activity and terminate seizures. This paved way for the concept of vagal nerve stimulator (VNS). We describe the evolution of the VNS and its use in different fields of medicine. We also review the literature focusing on the mechanism of action of VNS producing desired effects in different conditions. PUBMED and EMBASE search was performed for 'VNS' and its use in refractory seizure management, depression, obesity, memory, and neurogenesis. VNS has been in vogue over for the past three decades and has proven to reduce the intensity and frequency of seizure by 50% in the management of refractory seizures. Apart from this, VNS has been shown to promote neurogenesis in the dentate gyrus of rat hippocampus after 48 hours of stimulation of the vagus nerve. Improvement has also been observed in non-psychotic major depression from a randomized trial conducted 7 years ago. The same concept has been utilized to alter behavior and cognition in rodents, and good improvement has been observed. Recent studies have proven that VNS is effective in obesity management in patients with depression. Several hypotheses have been postulated for the mechanism of action of VNS contributing to its success. VNS has gained significant popularity with promising results in epilepsy surgery and treatment-resistant depression. The spectrum of its use has also extended to other fields of medicine including obesity, memory, and neurogenesis, and there is still a viable scope for its utility in the future.

KEYWORDS:

Depression, neurogenesis, obesity, seizure, vagus nerve stimulator

PMID:

23633829

[PubMed - in process]

http://www.ncbi.nlm.nih.gov/pubmed/23633829