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Re-mapping taste in the brain

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What happens in our brain that makes us experience the sweet taste of a donut or the bitter taste of tonic water? What are the patterns of neural activity responsible for the perception of taste?

A new study from Stony Brook University found that the map of neural responses mediating taste perception does not involve, as previously believed, specialized groups of neurons in the brain, but rather overlapping and spatially distributed populations.

The findings, to be published in Current Biology, counter an influential but controversial theory based on studies suggesting that there is a topographic map in the gustatory cortex that is responsible for our perception of taste. According to this theory, the gustatory cortex has “hot spots” of neurons whose activation leads to the perception of certain tastes. The new study by Stony Brook researchers demonstrates such a simple map of taste does not exist in the cortex of behaving animals.

When we taste food, neural activity propagates from the tongue to the brainstem and up to the cerebral cortex region known as the gustatory cortex. Activation of the gustatory cortex contributes to our perception of taste and flavor. Early imaging experiments provided evidence in favor of the theory of taste coding that postulates the existence of spatially localized clusters of neurons encoding specific tastes.

These clusters, also known as “hot spots” form a map of taste on the gustatory cortex, with an hot spot for “sweet,” one for “bitter,” one for “salty,” and one for “savory.” According to this model of taste function, the activation of one cluster would correspond to the sensation of a specific taste.

“Our experiments demonstrate there is not a map with hot spots in the gustatory cortex of behaving animals,” says Alfredo Fontanini, MD, PhD, lead investigator and Chair of the Department of Neurobiology and Behavior in the College of Arts and Sciences and Renaissance School of Medicine at Stony Brook University.

“Instead, each taste is represented by spatially distributed ensembles of neurons sprinkled across the cortex. Neurons can represent one or many taste sensations and form what is called an ensemble code. Basically, neurons act very much like instruments in an orchestra playing different notes forming a chord.”

The researchers demonstrated this activation repeatedly in behaving mice sampling different tastes from a spout. They used calcium imaging to determine how taste and task-related variables are represented in alert licking mice.

With the experiments they collected data on how various taste stimuli evoke responses from neurons in the gustatory cortex. They found that some neurons respond to a single taste and other to multiple.

An analysis of the distribution of responses over multiple spatial scales demonstrated that taste representations are distributed across the cortex, with no sign of spatial clustering or topography as would be expected with a map of the gustatory cortex corresponding specific taste sensations.

“Our findings are important because they address one of the basic organizing principles of brain function,” explains Dr. Fontanini. “Topographical maps are a pervasive feature of brain organization. Demonstrating that the spatial organization of taste responses is not as simple as previously believed makes us re-evaluate the neurobiological processes underlying taste perception and taste-related brain functions.”

The researchers conclude that their overall data provides evidence for a distributed neurobiological brain process when it comes to taste, a coding scheme differing from the topographical brain organisation of visual, somatosensory and auditory systems and similar to olfaction.

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Magnetic sensor could detect early signs of TBI

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Signs of traumatic brain injury, dementia and schizophrenia could be detected at an earlier stage as a result of the development of a new sensor which measures weak magnetic signals in the brain.

Through the development of the new Optically Pumped Magnetometer (OPM) sensor, scientists are hopeful of enabling a greater understanding of connectivity in the brain, which could have significant benefits in the chances of early diagnosis.

The device, developed by teams of scientists at the University of Birmingham, is currently in trail stage and clinicians at the Queen Elizabeth Hospital Birmingham are involved in its use in pinpointing the site of TBIs.

Its potential to increase diagnostics for neurological injury, neurological disorders such as dementia, and psychiatric disorders such as schizophrenia, has been widely recognised, and the team are now seeking commercial and research partnerships to help advance its development further.

The new sensor has enabled advances in detecting brain signals and distinguishing them from background magnetic noise, when compared to commercially available sensors. By using polarised light, the device can detect changes in the orientation of spin atoms when exposed to a magnetic field.

The team was also able to reduce the sensor size by removing the laser from the sensor head, and made further adjustments to decrease the number of electronic components, in a move that will reduce interference between sensors.

Benchmarking tests have taken place at the University’s Centre for Human Brain Health, and has reported “good” performance in environmental conditions where other sensors do not work.

Specifically, the researchers showed that the new sensor is able to detect brain signals against background magnetic noise, raising the possibility of magnetoencephalography (MEG) testing outside a specialised unit or in a hospital ward.

The research – published in the ‘Detection of human auditory evoked brain signals with a resilient non linear optically pumped magnetometer’ report, Kowalczyk et al (2020) – was led by physicist Dr Anna Kowalczyk.

“Existing MEG sensors need to be at a constant, cool temperature and this requires a bulky helium-cooling system, which means they have to be arranged in a rigid helmet that will not fit every head size and shape,” she says.

“They also require a zero-magnetic field environment to pick up the brain signals. The testing demonstrated that our stand-alone sensor does not require these conditions.

“Its performance surpasses existing sensors, and it can discriminate between background magnetic fields and brain activity.”

The researchers expect these more robust sensors will extend the use of MEG for diagnosis and treatment, and they are working with other institutes at the University to determine which therapeutic areas will benefit most from this new approach.

Neuroscientist Professor Ole Jensen, who is co-director of the Centre for Human Brain Health (CHBH), highlighted the potential of the sensor.

“We know that early diagnosis improves outcomes and this technology could provide the sensitivity to detect the earliest changes in brain activity in conditions like schizophrenia, dementia and ADHD,” he says.

“It also has immediate clinical relevance, and we are already working with clinicians at the Queen Elizabeth Hospital to investigate its use in pinpointing the site of traumatic brain injuries.”

The team at the CHBH has also recently been awarded Partnership Resource Funding from the UK Quantum Technology Hub Sensors and Timing to further develop new OPM sensors.

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Management during a pandemic: what we’ve learned

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As the country faces the second wave of the coronavirus pandemic, the management team at Richardson Care reflect on their experiences so far. Richardson Care has six specialist residential care homes – three for adults with acquired brain injury and three for adults with learning disabilities. Caring for up to 78 people, many of whom are vulnerable brings added responsibilities and pressures, as well as additional skills.

Our experience in supporting people who are rebuilding their lives after brain injury or living with learning disabilities means that we are problem solvers. We support people to overcome challenges every day. Never has this been more important and we’re proud of the way that our management team and staff have responded.

We asked our Homes Managers for their personal views and experiences of the pandemic – from their initial reactions to plans for the future. We discover what we’ve learnt, and how we can change things for the better.

Resilience
‘The capacity to recover quickly from difficulties; toughness’ has been demonstrated by our team throughout the pandemic. Jane Payne, Operational & Clinical Officer at Richardson Care, takes us back to the beginning of the year: “On February 18th 2020 we informed staff that there was a new virus, and preventative measures were put into place; including hourly touch point cleaning, increase in hand washing and an increase in awareness. Ahead of government guidance on March 12th 2020, we took the very tough, necessary decision to close our doors to family and friends to protect service users. We made sure that all staff worked only in one home, so in the event of an infection, it would not be transferred from one home to another by our staff.”

“The management team have become incredibly solid; working as one in supporting each other, as and when each has needed, as we live and work through the rollercoaster that is Covid-19. I am proud to lead; and be part of such a strong group of individuals displaying a sole purpose of ensuring the care, welfare, safety and security of our service users and staff. Richardson Care has shown we are more than resilient, we have become stronger through experience. Care: it’s in our DNA.”

Jacky Johnson, Registered Manager at our Boughton Green Road home for adults with acquired brain injury talks about the realities of dealing with something that no one had ever experienced before. She says: “We were dealing with real disease: a real virus, in real time with real people…The guidance received from various governing and public bodies changed before the ink could dry…The initial fear demonstrated by some staff left others having to broaden their shoulders… taking on extra activities within their daily routines…The expectation on myself as a Manager weighed heavily, it felt like I should know all the answers to the questions they asked… I was clear of my expectations from my team and them of me… Resilience: it’s not about how many times you fall… it’s about how many times you stand up and face another day.”

Teamwork
It was important to create a positive spirit as we knew our response would impact our service users. Central staff were redeployed so each home had enough admin and maintenance support in their team. This means they have been able to form closer relationships with the service users, some have been helping out with maintenance jobs – developing their skills and feeling valued while completing meaningful activities.

The teams within each home became closer, bonding more as they faced challenges together. No job was too big.

Weekly management meetings moved online in February. The Managers have worked more closely together while being socially distanced. Helen Petrie, Manager at The Richardson Mews adds: “No-one has ever been in this position before. We’re all learning together and supporting each other. We’re there to boost morale when it’s needed, sharing experiences and insight to keep our service users and staff happy and safe.”

Resourceful
We’ve found more efficient ways of operating – reducing risk while continuing to help our service users develop their daily living skills. For example, instead of going out to the shops several times a day, there’s just one trip per day. This means planning ahead, so service users have been helping to plan the menus, write shopping lists and prepare for their daily needs. These all require cognitive skills.

We have all become much more tech-savvy, using the internet, apps, photos and video calls as well as phone calls and letters to keep in touch with service users’ family and friends. We’ve also been checking in with each other more too.

Wendy Coleman, Registered Manager at our Duston Road home adds: “For service users, routine is a major part of their life. When their usual activities are no longer possible – no home visits, day services, community activities – staff have shown how well they have supported service users, reassuring them throughout all this. They have also been dealing with more challenging behaviours due to service users’ complex needs and lack of understanding of what is happening. We have created different routines and activities, promoting health and exercise.”

At The Richardson Mews (inspired by Joe Wicks) the day now starts with ‘Morning Motivation’ – exercising to music every day to improve fitness, flexibility and well-being. We’re also making more use of our in-house gym equipment. One service user who has a brain injury thrived during lockdown: he was in a wheelchair in February and now he can walk 70 lengths of the parallel bars.

Although the service users have missed going out, we have had plenty of scope and opportunity to develop in-house activities. Our large gardens and outdoor spaces have been used for gardening, ‘coffee shops’, sports and games, trampolining and treasure hunts. Our indoor communal spaces have hosted quizzes, craft activities, music and karaoke sessions. We’ve celebrated birthdays with gifts, parties and barbecues. We’ve maintained structure when needed, providing mental stimulation, social interaction and fun, while supporting well-being and skills development.

Appreciating each other
“The new normal is valuing and appreciating the simple things in life and each other, focusing on the positives,” adds Wendy Coleman. As we have gone through the months, we’ve noticed positive changes in service users – improved bonding with staff due to them having much more 1-1 time. Individual service user’s communication skills have also improved.

“Staff have done all this whilst dealing with the impact on their own lives. I feel through all this we all have changed our priorities, we have learnt different coping skills, adapted to change, and have gained new skills.

“It is important to show how we value, support and appreciate each other, talk more, respect and most importantly listen to each other. Learning that showing praise and valuing people is so important in these difficult times.”

Never has the responsibility of managing specialist care services been so great. As we prepare for the next phase of the Coronavirus pandemic, we know that we have the experience, skills and resilience to face the challenges ahead.

Richardson Care provides specialist residential care and rehabilitation for adults with acquired brain injury and learning disabilities. An independent family business with a 30-year track record, it has six residential care homes in Northampton. Find out more at www.richardsoncares.co.uk

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The danger of Z-drugs for dementia patients

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Strong sleeping pills known as ‘Z-drugs’ are linked with an increased risk of falls, fractures and stroke among people with dementia – according to research from the University of East Anglia.

Sleep disturbance is common among people with dementia and the impact for patients and their families is significant.

To date there are no proven effective treatments available, however people with dementia are often prescribed Z-drugs (zopiclone, zaleplon, and zolpidem).

But a new study published today reveals that stronger doses of these drugs are linked with an increased risk of adverse effects.

These adverse effects were found to be similar or greater than those for higher dose benzodiazepines or ‘benzos’ – which are also used to treat sleep disturbance, and are known to have several adverse effects.

The team say that patients already taking higher doses of Z-drugs should not stop taking their medication suddenly, however they should seek a review with their GP.

Prof Chris Fox, from UEA’s Norwich Medical School, said: “As many as 90 per cent of people with dementia suffer sleep disturbances and it has a big impact on their mental and physical health, as well as that of their carers.

“Z-drugs are commonly prescribed to help people sleep – however these medicines were never licensed for dementia and they have been associated with adverse events such as falls and fracture risks in older people.

“We wanted to find out how they affect people with dementia, who are frequently prescribed them to help with sleep disturbance.”

The team analysed data from 27,090 patients in England diagnosed with dementia between January 2000 and March 2016. The average age of the patients was 83 and 62 per cent were women.

They looked at the adverse events for 3,532 patients who had been prescribed Z-drugs and compared them to people suffering sleep disturbance who had not been prescribed sedatives, and patients who had been prescribed benzodiazepines.

They also looked to see whether Z-drug dosage played a part in adverse outcomes.

Prof Fox said: “We studied a range of adverse outcomes including fractures, falls, deep vein thrombosis, stroke and death – over two years. And we were particularly interested to see whether higher doses led to worse outcomes.”

Higher dose Z-drugs and benzodiazepines were defined as prescriptions equivalent to ≥7.5mg zopiclone or >5mg diazepam daily.

“For patients prescribed Z-drugs, 17 per cent were given higher doses. And we found that these patients on higher doses were more at risk of falls and fractures, particularly hip fractures, and stroke – compared with patients who were not taking any medication for sleep disturbance,” said Prof Fox.

Those on lower doses however (≤3.75mg zopiclone or equivalent) were not found to have an increased risk of adverse outcomes.

And there were no differences in adverse events for Z-drugs compared to benzodiazepines, except lower mortality rates with Z-drugs.

Prof Fox said: “This research shows us that higher dose Z-drugs should be avoided, if possible, in people living with dementia, and non-pharmacological alternatives preferentially considered.

“Patients already taking higher dose Z-drugs should not stop taking their medication, but we recommend that they should make an appointment to see their GP for a review,” he added.

Prof Clive Ballard, of the University of Exeter Medical School, who collaborated on the study, said: “Our findings serve an important caution regarding the harms of sleeping tablets in people with dementia.

“This research is a very timely and unfortunately necessary reminder that sedative medications are not a helpful way to manage social isolation during Covid-19.

“Our study also highlights the importance of research to develop non-drug approaches to help people with dementia to sleep – whether they are at home or in residential care.”

Dr Ian Maidment, Reader in Clinical Pharmacy at Aston University and lead pharmacist on the study, said: “Z-drugs are widely used to treat insomnia in people living with dementia, but are only recommended as a short-term treatment for the maximum of four weeks. Our work shows the importance of clinicians including GPs and pharmacists reviewing patients on long-term Z-drugs.”

The study was led by UEA, in collaboration with researchers from The Quadram Institute, Aston University, University College London, and the University of Exeter.

‘Adverse effects of Z-drugs for sleep disturbance in people living with dementia: a population-based cohort study’ is published in the journal BMC Medicine on November 24, 2020.

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