Posts tagged neuroscience

The idea that an individual might suffer from a sexual addiction is great fodder for radio talk shows, comedians and late night TV. But a sex addiction is no laughing matter. Relationships are destroyed, jobs are lost, lives ruined.

Yet psychiatrists have been reluctant to accept the idea of out-of-control sexual behavior as a mental health disorder because of the lack of scientific evidence.

Now a UCLA-led team of experts has tested a proposed set of criteria to define “hypersexual disorder,” also known as sexual addiction, as a new mental health condition.

Rory Reid, a research psychologist and assistant professor of psychiatry at the Semel Institute of Neuroscience and Human Behavior at UCLA, led a team of psychiatrists, psychologists, social workers, and marriage and family therapists that found the proposed criteria to be reliable and valid in helping mental health professionals accurately diagnose hypersexual disorder.

The results of this study — reported in the current edition of the Journal of Sexual Medicine — will influence whether hypersexual disorder should be included in the forthcoming revised fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), considered the “bible” of psychiatry.

The importance of the study, Reid said, is that it suggests evidence in support of hypersexual disorder as a legitimate mental health condition.

"The criteria for hypersexual disorder that have been proposed, and now tested, will allow researchers and clinicians to study, treat and develop prevention strategies for individuals at risk for developing hypersexual behavior," he said.

(Source: newsroom.ucla.edu)

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The Who asked “who are you?” but Dartmouth neurobiologist Jeffrey Taube asks “where are you?” and “where are you going?” Taube is not asking philosophical or theological questions. Rather, he is investigating nerve cells in the brain that function in establishing one’s location and direction.

Taube, a professor in the Department of Psychological and Brain Sciences, is using microelectrodes to record the activity of cells in a rat’s brain that make possible spatial navigation — how the rat gets from one place to another — from “here” to “there.” But before embarking to go “there,” you must first define “here.”

Survival Value

"Knowing what direction you are facing, where you are, and how to navigate are really fundamental to your survival," says Taube. "For any animal that is preyed upon, you’d better know where your hole in the ground is and how you are going to get there quickly. And you also need to know direction and location to find food resources, water resources, and the like."

Not only is this information fundamental to your survival, but knowing your spatial orientation at a given moment is important in other ways, as well. Taube points out that it is a sense or skill that you tend to take for granted, which you subconsciously keep track of. “It only comes to your attention when something goes wrong, like when you look for your car at the end of the day and you can’t find it in the parking lot,” says Taube.

Perhaps this is a momentary lapse, a minor navigational error, but it might also be the result of brain damage due to trauma or a stroke, or it might even be attributable to the onset of a disease such as Alzheimer’s. Understanding the process of spatial navigation and knowing its relevant areas in the brain may be crucial to dealing with such situations.

The Cells Themselves

One critical component involved in this process is the set of neurons called “head direction cells.” These cells act like a compass based on the direction your head is facing. They are located in the thalamus, a structure that sits on top of the brainstem, near the center of the brain.

He is also studying neurons he calls “place cells.” These cells work to establish your location relative to some landmarks or cues in the environment. The place cells are found in the hippocampus, part of the brain’s temporal lobe. They fire based not on the direction you are facing, but on where you are located.

Studies were conducted using implanted microelectrodes that enabled the monitoring of electrical activity as these different cell types fired.

Taube explains that the two populations — the head direction cells and the place cells — talk to one another. “They put that information together to give you an overall sense of ‘here,’ location wise and direction wise,” he says. “That is the first ingredient for being able to ask the question, ‘How am I going to get to point B if I am at point A?’ It is the starting point on the cognitive map.”

The Latest Research

Taube and Stephane Valerio, his postdoctoral associate for the last four years, have just published a paper in the journal Nature Neuroscience, highlighting the head direction cells. Valerio has since returned to the Université Bordeaux in France.

The studies described in Nature Neuroscience discuss the responses of the spatial navigation system when an animal makes an error and arrives at a destination other than the one targeted — its home refuge, in this case. The authors describe two error-correction processes that may be called into play — resetting and remapping — differentiating them based on the size of error the animal makes when performing the task.

When the animal makes a small error and misses the target by a little, the cells will reset to their original setting, fixing on landmarks it can identify in its landscape. “We concluded that this was an active behavioral correction process, an adjustment in performance,” Taube says. “However, if the animal becomes disoriented and makes a large error in its quest for home, it will construct an entirely new cognitive map with a permanent shift in the directional firing pattern of the head direction cells.” This is the “remapping.”

Taube acknowledges that others have talked about remapping and resetting, but they have always regarded them as if they were the same process. “What we are trying to argue in this paper is that they are really two different, separate brain processes, and we demonstrated it empirically,” he says. “To continue to study spatial navigation, in particular how you correct for errors, you have to distinguish between these two qualitatively different responses.”

Taube says other investigators will use this distinction as a basis for further studies, particularly in understanding how people correct their orientation when making navigational errors.

(Source: sciencedaily.com)

A research team from Stanford University has found that injecting the blood of young mice into older mice can cause new neural development and improved memory. Team lead Saul Villeda presented the groups’ findings at this year’s Society for Neuroscience conference.

The researchers were following up on work by another team also led by Villeda that last year found that when younger mice were given transfusions of blood from older mice, their mental faculties aged more quickly than non transfused young mice. In their paper published in the journal Nature, the team also noted that the reverse appeared to be true as well, namely that the older mice derived a degree of mental benefit from the transfusions.

In this new research, the team connected the bloodstreams of an older mouse and a younger mouse, allowing their blood to comingle. Subsequent brain scans found that the number of neural stem cells in the brains of the older mice increased by 20 percent after just a few days, indicating that new neural connections were being made – a necessary occurrence for increased memory retention.

To find out if such differences could be measured in a behavioral sense, the team gave transfusions of blood plasma from young mice to older mice and then tested them in a standard water maze; one that requires strong memory skills. The team found that the transfused mice were able to perform as well as much younger mice, while a similar group of older mice that did not get transfusions were much less successful at solving the maze.

Villeda pointed out in his talk that his team’s findings don’t indicate that older people should try to obtain transfusions from younger people to stave off dementia or Alzheimer’s disease, as it’s not yet known if the same results might be had. What needs to happen, he said, is for researchers to look more closely at young mouse blood compared to the blood of older mice to discover what differences in it might account for the increased neural buildup it offers to older mice.

(Source: medicalxpress.com)

Neurobiologists at the Research Institute of Molecular Pathology (IMP) in Vienna investigated how the brain is able to group external stimuli into stable categories. They found the answer in the discrete dynamics of neuronal circuits. The journal Neuron publishes the results in its current issue.

How do we manage to recognize a friend’s face, regardless of the light conditions, the person’s hairstyle or make-up? Why do we always hear the same words, whether they are spoken by a man or woman, in a loud or soft voice? It is due to the amazing skill of our brain to turn a wealth of sensory information into a number of defined categories and objects. The ability to create constants in a changing world feels natural and effortless to a human, but it is extremely difficult to train a computer to perform the task.

At the IMP in Vienna, neurobiologist Simon Rumpel and his post-doc Brice Bathellier have been able to show that certain properties of neuronal networks in the brain are responsible for the formation of categories. In experiments with mice, the researchers produced an array of sounds and monitored the activity of nerve cell-clusters in the auditory cortex. They found that groups of 50 to 100 neurons displayed only a limited number of different activity-patterns in response to the different sounds.

The scientists then selected two basis sounds that produced different response patterns and constructed linear mixtures from them. When the mixture ratio was varied continuously, the answer was not a continuous change in the activity patters of the nerve cells, but rather an abrupt transition. Such dynamic behavior is reminiscent of the behavior of artificial attractor-networks that have been suggested by computer scientists as a solution to the categorization problem.

The findings in the activity patters of neurons were backed up by behavioral experiments with mice. The animals were trained to discriminate between two sounds. They were then exposed to a third sound and their reaction was tracked. Whether the answer to the third tone was more like the reaction to the first or the second one, was used as an indicator of the similarity of perception. By looking at the activity patters in the auditory cortex, the scientists were able to predict the reaction of the mice.

The new findings that are published in the current issue of the journal Neuron, demonstrate that discrete network states provide a substrate for category formation in brain circuits. The authors suggest that the hierarchical structure of discrete representations might be essential for elaborate cognitive functions such as language processing.

(Source: alphagalileo.org)