Nanomagnetic remote control of animal behaviour

MAGNETIC nanoparticles targeted to nerve cell membranes can be used to remotely control cellular activity and even the simple reflex behaviours of nematode worms, according to research by a team of biophysicists at the University of Buffalo. The new method, which is described in the journal Nature Nanotechnology, could be very useful for investigating how cells interact in neuronal networks, and may eventually lead to new therapies for cancer and diabetes.

Heng Huang and her colleagues synthesized manganese-iron nanoparticles, each just 6 millionths of a millimeter in diameter, and coated with the bacterial protein straptavidin attached to a fluorescent molecule called DyLight549. Strepdavidin binds another molecule, much like a key fits into a lock, enabling specified cells to be targeted, while DyLight549 acts like a molecular thermometer, whose fluoresence intensity changes with temperature.

Tags: bionanotechnology, magnetic nanoparticles, nematode, TRPV1

Scared by the light

WHO could have guessed that a protein isolated from pond scum would transform the way researchers investigate the brain? The protein, called channelrhodopsin (ChR), is found in algae and other microbes, and is related to the molecule in human photoreceptors that captures light particles. Both versions control the electrical currents that constantly flow in and out of cells; one regulates the algae’s movements in response to light, the other generates the nervous impulses sent along the optic nerve to the brain. Unlike its human equivalent, the algal ChR controls the currents directly because it forms a pore that spans the cell membrane. When expressed in neurons, it renders the cells sensitive to light, and they can be switched on or off very precisely using lasers.

This discovery led to the emergence of a new field called optogenetics. Early studies showed that the technique can be used to control the behaviour of small organisms such as nematode worms and fruit flies. Last year, Karl Deisseroth‘s group at Stanford University demonstrated, for the first time, that it can also be used to control reward and motivation behaviours in mice. Josh Johansen of the Center for Neural Science at New York University and his colleagues have now taken this one step further. Working in collaboration with Deisseroth, they show that optogenetics can also be used to induce a simple form of associative learning called fear conditioning.

Tags: amygdala, brain, classical conditioning, fear, optogenetics

Neural basis of spatial navigation in the congenitally blind

FOR most of us, the ability to navigate our environment is largely dependent on the sense of vision. We use visual information to note the location of landmarks, and to identify and negotiate obstacles. These visual cues also enable us to keep track of our movements, by monitoring how our position changes relative to landmarks and, when possible, our starting point and final destination. All of this information is combined to generate a cognitive map of the surroundings, on which successful navigation of that environment later on depends.

Despite the importance of vision for navigation, congenitally blind people – those born blind – can still generate neural representations of space. Exactly how is unclear, but it is thought to be by using a combination of touch, hearing and smell, and some are even known to use echolocation. Spatial navigation in the congenitally blind is therefore thought to involve different brain networks than those engaged in sighted people. A team of Danish researchers  now report, however, that the mechanisms underlying spatial navigation in the blind are much the same as those in sighted people, due to the brain’s remarkable ability to reconfigure itself. 

Tags: blindness, brain, Brainport, fMRI, sensory substitution, spatial navigation, tongue

Touch influences social judgements and decisions

APPLYING for a job? The weight of the clipboard to which your CV is attached may influence your chances of getting it. Negotiating a deal? Sitting in a hard chair may lead you to drive a harder bargain. Those are two of the surprising conclusions of a study published in today’s issue of Science, which shows that the physical properties of objects we touch can unconsciously influence our first impressions of other people and the decisions we make about them.

Josh Ackerman of the Sloan School of Management at MIT, and psychologists Chris Nocera and John Bargh of Harvard and Yale Universities, respectively, performed a series of six experiments designed to investigate whether or not the weight, texture and hardness of objects can influence our judgements of, and decisions about, unrelated events and situations. Their findings provide yet more evidence for the embodied cognition hypothesis, which states that bodily perceptions can exert a strong influence on the way we think.

Tags: embodied cognition, haptics, social psychology, touch

Movable micromotor brain implants

BRAIN implants containing microelectrodes are used widely in the laboratory and clinic, both to stimulate nerve cells and to record their activity. Researchers routinely implant electrode arrays into the brains of rodents to investigate the neuronal activity associated with spatial navigation, or into monkeys’ brains to gain a better understanding of the mechanisms of motor control. As a result, we now have brain-computer interfaces that can help paralysed patients to communicate or control a prosthetic limb. Electrode arrays can also be used to assess vegetative patients, and to treat conditions such as Parkinson’s Disease and depression.

In most instances, keeping the electrodes in place for long periods of time is crucial. But this is difficult, for a number of reasons. In experiments involving freely moving rats, for example, the animal’s movements can cause the electrodes to be displaced, and when they do stay in place, the electrodes become gradually become ensheathed with glial cells, causing the signal to deteriorate with time. The devices have to be re-adjusted regularly, and their decoding algorithms recalibrated, to maintain the signal strength. Implants containing movable electrodes can potentially overcome these problems. The latest such device (described in a new paper in the journal Frontiers in Neuroengineering)  is the most advanced yet. It uses microelectromechanical systems (MEMS) to move the electrodes up and down, and can record stably for up to 6 months.

Tags: brain implant, MEMS, microelectrodes

Obesity linked to brain shrinkage and dementia

THE dangers of obesity are very well known. Being overweight is associated with an increased risk of coronary heart disease and stroke, the two leading causes of death in the Western world. Gout is more common in overweight people, with the risk of developing the condition increasing in parallel with body weight. Obese people are twice as likely to develop type 2 diabetes as those who are not overweight, and being overweight is also associated with several types of cancer. The list goes on…

Less well known is the effect of obesity on the brain. In the past few years, however, it has emerged that being overweight in middle age is linked to an increased risk of Alzheimer’s Disease and other forms of dementia. Two new studies strengthen this association: the first, just published in the Annals of Neurology, shows that abdominal fat is linked to reduced brain volume in otherwise healthy middle-aged adults. The second, published last month in Proceedings of the National Academy of Sciences, shows that this reduction is associated with a common variant of an obesity-related gene.

Tags: body-mass index, brain volume, dementia, obesity

Hair pulling is a neuroimmunological condition

TRICHOTILLOMANIA (or hair pulling) is a condition characterised by excessive grooming and strong, repeated urges pull out one’s own hair. It is classified as an obsessive-compulsive disorder (OCD), and is relatively common, affecting about 2 in 100 people. Sufferers normally feel an increasing sense of tension before pulling out their scalp hair, facial hair, and even pubic hair, eyelashes or eyebrows. This provides gratification, but only briefly.

Hair pulling is usually thought of as being psychological in origin, but an intruiging new study now suggests that it occurs as a result of defects in the immune system. The study, which is published in the journal Neuron, shows that excessive grooming and hair pulling occur in mice because of reduced numbers of microglial cells, which are critical  for the brain’s immune response. It also suggests – very unexpectedly – that bone marrow transplants may be an effective treatment for trichotillomania in humans.

Tags: hair pulling, Hox genes, obsessive-compulsive disorder, OCD, psychiatry, Trichotillomania

Apparent motion steers the wandering mind

DAYDREAMING is a critical component of conscious experience. The mind can perform mental time travel – it occasionally strays from the present moment, to recollect an experience from the near or distant past, or to imagine an event that has not yet taken place. We know that thinking about the future is dependant on memory, because patients with amnesia cannot imagine new experiences. It involves piecing together fragments of past experiences to generate a plausible simulation of what might happen. This may have been an important development in human evolution, as it enables us anticipate a likely outcome and to plan the best possible course of action. 

Space and time are intimately linked in the mind, and this is reflected in our metaphors. We often say that we are thinking back to a past event, or looking forward to one that will take place in the future. But the mind and body are also closely linked: think about a past experience, and you might find yourself moving backwards. A new study suggests that this can be reversed, by showing that apparent motion can influence the direction of the mind’s wanderings. Thus, moving backwards could evoke long lost memories, while moving forward might make you think about the future.

Tags: brain, embodied cognition, memory, space, time

Optogenetic fMRI

OF all the techniques used by neuroscientists, none has captured the imagination of the general public more than functional magnetic resonance imaging (fMRI). The technique, which is also referred to as functional neuroimaging and, more commonly, “brain scanning”, enables us to peer into the human brain non-invasively, to observe its workings and correlate specific thought processes or stimuli to activity in particular regions. fMRI data affect the way in which people perceive scientific results: colourful images of the brain have persuasive power, making the accompanying data seem more credible.

Functional neuroimaging is used widely by researchers, too, with tens of thousands of research papers describing fMRI studies being published in the past decade. Yet, a big question mark has been hanging over the validity of the technique for over a year and, furthermore, the way in which fMRI data are interpreted has also been called into question. Using a novel combination of fMRI and a recently developed state-of-the-art technique called optogenetics, researchers now provide the first direct evidence that the fMRI signal is a valid measure of brain activity.

Tags: BOLD, brain, fMRI, optogenetics

Near misses fuel gambling addiction

GAMBLING is extremely popular, with lottery tickets, casinos, slot machines, bingo halls and other forms of the activity generating revenues of more than £80 billion each year in the UK alone. For most people, gambling is nothing more than an entertaining way to pass the time. But for some, it becomes a compulsive and pathological habit – they spend increasing amounts of time gambling, because tolerance builds up quickly, and experience withdrawal symptoms when they aren’t gambling.

The terms “tolerance” and “withdrawal” are normally associated with drug addiction, and indeed pathological gambling is now considered as being akin to substance abuse. We know, for example, that monetary wins activate the brain’s reward circuitry. In pathological gamblers, however, these responses are dampened, so that increasingly larger wins are needed to produce the same rewarding effects. And according to a new study published in the Journal of Neuroscience, near misses fuel the habit in regular gamblers, because they are almost as rewarding as wins.

Tags: addiction, brain, fMRI, gambling, lottery, reward circuits