Posts Tagged ‘neurobiology’

Discovery of Gatekeeper Nerve Cells Explains the Effect of Nicotine on Learning and Memory

December 16, 2012 Leave a comment

Swedish researchers at Uppsala University have, together with Brazilian collaborators, discovered a new group of nerve cells that regulate processes of learning and memory. These cells act as gatekeepers and carry a receptor for nicotine, which can help explain our ability to remember and sort information.

The discovery of the gatekeeper cells, which are part of a memory network together with several other nerve cells in the hippocampus, reveal new fundamental knowledge about learning and memory. The study is published today in Nature Neuroscience.

The hippocampus is an area of the brain that is important for consolidation of information into memories and helps us to learn new things. The newly discovered gatekeeper nerve cells, also called OLM-alpha2 cells, provide an explanation to how the flow of information is controlled in the hippocampus. Read more…

A Glance at the Brain’s Circuit Diagram

December 16, 2012 3 comments

A new method facilitates the mapping of connections between neurons.

The human brain accomplishes its remarkable feats through the interplay of an unimaginable number of neurons that are interconnected in complex networks. A team of scientists from the Max Planck Institute for Dynamics and Self-Organization, the University of Göttingen and the Bernstein Center for Computational Neuroscience Göttingen has now developed a method for decoding neural circuit diagrams. Using measurements of total neuronal activity, they can determine the probability that two neurons are connected with each other.

The human brain consists of around 80 billion neurons, none of which lives or functions in isolation. The neurons form a tight-knit network that they use to exchange signals with each other. The arrangement of the connections between the neurons is far from arbitrary, and understanding which neurons connect with each other promises to provide valuable information about how the brain works. At this point, identifying the connection network directly from the tissue structure is practically impossible, even in cell cultures with only a few thousand neurons. In contrast, there are currently well-developed methods for recording dynamic neuronal activity patterns. Such patterns indicate which neuron transmitted a signal at what time, making them a kind of neuronal conversation log. The Göttingen-based team headed by Theo Geisel, Director at the Max Planck Institute for Dynamics and Self-Organization, has now made use of these activity patterns. Read more…

Researchers Explore How the Brain Perceives Direction and Location

December 16, 2012 Leave a comment

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. Read more…

The Impossible Staircase in Our Heads: How We Visualize the World Around Us

March 28, 2012 1 comment

Our interpretation of the world around us may have more in common with the impossible staircase illusion than it does the real world, according to research published today in the open access journal PLoS ONE.

A ‘Penrose stairs’ optical illusion, or impossible staircase. Image adapted from public domain image shared by Sakurambo on Wikimedia

The study, which was funded by the Wellcome Trust, suggests that we do not hold a three-dimensional representation of our surroundings in our heads as was previously thought.

Artists, such as Escher, have often exploited the paradoxes that emerge when a 3D scene is depicted by means of a flat, two-dimensional picture. In Escher’s famous picture ‘Waterfall’, for example, it is impossible to tell whether the start of the waterfall is above or below its base.

Paradoxes like this can be generated in a drawing, but it is not possible to create such a 3D structure. The illusion is possible because drawings of 3D scenes are inherently ambiguous, so there is no one-to-one relationship between the picture and 3D locations in space.

Most theories of 3D vision and how we represent space in our visual system assume that we generate a one-to-one 3D model of space in our brains, where each point in real space maps to a unique point in our model. However, there is an ongoing debate about whether this is really the case.

To test this idea, researchers at the University of Reading placed participants wearing a virtual reality headset in a virtual room in which they had to judge which of two objects was the nearest. On some occasions, the size of the room was increased four-fold – previous research by the team showed that participants fail to notice this expansion.

In this new study, the researchers found that people’s judgement of the relative depth of objects depended on the order in which the objects were compared. Although the results are readily explained in relation to the expansion of the room, the participants had no idea that the room changed at any stage during the experiment. It is the properties of this stable perception that the experiment tested.

Dr Andrew Glennerster from the University of Reading, who led the study, explains: “In the impossible staircase illusion, you cannot tell whether the back corner is higher or lower than the front one as it depends which route you take to get there. The same is true, we find, in our task. This means that our own internal representations of space must be rather like Escher’s paradoxes, with no one-to-one relationship to real space.”

“Even when the size of the room increases four-fold, people think they are in a stable room throughout the experiment. Their interpretation of the room does not update itself when the room itself changes.

“Does it make sense for their representation of the room to have 3D coordinates, as a proper staircase would? No – there is no way to write down the coordinates of the objects that could explain the judgements people made. Visual space – the internal representation – is much more like the paradoxical staircase than a physically realisable model.”


Wellcome Trust press release
Image Source: image adapted from public domain image with credit to Sakurambo on Wikipedia.
Original Research: Research article “A demonstration of ‘broken’ visual space” by Svarverud E et al. to appear in PLoS ONE 2012