The irregular firing properties of thalamic head direction cells mediate turn-specific modulation of the directional tuning curve

Take-home message: Anterior thalamic head direction cells are interesting in all sorts of ways. Here, we show that head direction cells remain active during sleep (how interesting is that?!), replicate the finding that these cells fire at different rates depending on whether the head makes clockwise or counterclockwise movements, and that the origin of this difference might lie in the intrinsic firing properties of these neurons. [Download the paper]

The irregular firing properties of thalamic head direction cells mediate turn-specific modulation of the directional tuning curve

Marian Tsanov , Ehsan Chah , Muhammad S. Noor , Catriona Egan , Richard B. Reilly , John P. Aggleton , Jonathan T. Erichsen , Seralynne D. Vann , Shane M. O’Mara
Journal of Neurophysiology

Published 13 August 2014

Equivalent circuit for the cell membrane in th...

Equivalent circuit for the cell membrane in the Hodgkin-Huxley model (Photo credit: Wikipedia)

Vol. no. DOI: 10.1152/jn.00583.2013

ABSTRACT

Head-direction cells encode an animal’s heading in the horizontal plane. However, it is not clear why the directionality of a cell’s mean firing rate differs for clockwise, compared to counter-clockwise head turns (this difference is known as the ‘separation angle’) in anterior thalamus. Here we investigated, in freely-behaving rats, if intrinsic neuronal firing properties are linked to this phenomenon. We found a positive correlation between the separation angle and the spiking variability of thalamic head-direction cells. To test whether this link is driven by hyperpolarisation-inducing currents, we investigated the effect of thalamic reticular inhibition during high-voltage spindles on directional spiking. While the selective directional firing of thalamic neurons was preserved, we found no evidence for entrainment of thalamic head-direction cells by high-voltage spindle oscillations. We then examined the role of depolarisation-inducing currents in the formation of separation angle. Using a single-compartment Hodgkin-Huxley model, we show that modelled neurons fire with higher frequencies during the ascending phase of sinusoidal current injection (mimicking the head-direction tuning curve), when simulated with higher high-threshold calcium channel conductance. These findings demonstrate that the turn-specific encoding of directional signal strongly depends on the ability of thalamic neurons to fire irregularly in response to sinusoidal excitatory activation. Another crucial factor for inducing phase lead to sinusoidal current injection was the presence of spike-frequency adaptation current in the modelled neurons. Our data support a model in which intrinsic biophysical properties of thalamic neurons mediate the physiological encoding of directional information.

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SfN removes exclusive license requirement for eNeuro

Originally posted on Erin C. McKiernan:

Using the open letter to the AAAS as a template, this last Saturday (August 16), I drafted a letter to the Society for Neuroscience about their new open access journal, eNeuro. As with the AAAS letter, the letter to SfN is open for anyone to read, comment on, or sign. Early in the editing process, Fabiana Kubke (@Kubke) brought it to my attention that eNeuro‘s policies stated that while authors would retain copyright, they would be required to grant an exclusive license to SfN as part of their publishing agreement. SfN would then publish articles under a Creative Commons license. Together*, we wrote a paragraph objecting to the requirement for an exclusive license:

Our first concern relates to the copyright policy of eNeuro. The journal’s policy states that authors will retain copyright but must grant the Society an exclusive license to publish. An exclusive license…

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Savagery Explained: 5 Reasons Humans Become Inhuman

Originally posted on The Winner Effect:

As Islamic State militants in Iraq and Syria butcher thousands of “infidels” and carry off their women and children into slavery, many in the West are inclined to see this as an unique outcrop of Islamic fundamentalism. Yet after over-running a Bosnian town on 11th July 1995, Bosnian Serb – ostensibly Christian – forces, cold-bloodedly massacred 8,000 Bosnian Muslims at Srebrenica. Hutu genocide of Tutsi in Rwanda, Khmer Rouge mass-murder of Cambodian city-dwellers, Nazi genocide of Jews, Gypsies and the disabled….the list of savagery is as long as it is profoundly depressing.

Isis Execution

Savagery begets Savagery

What, then are the origins of savagery, if they cannot be ascribed to a single religion or ideology? The first part of an answer may be horribly simple: savagery begets savagery. Callousness, aggression and lack of empathy are common responses by people who have been harshly treated themselves. In the Nazi concentration camps…

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How split memories help us perform tasks much better the second or third time around

Originally posted on Quartz:

Now we know what’s happening in our brains when we correctly pull a door that we once (embarrassingly) pushed.

Researchers at Johns Hopkins University have concluded that we learn motor commands faster when we revisit a task because we create two separate memories—the muscle memory of how to perform the task, and the memory of the errors we made the first time around. The brain recognizes the errors it made before, and makes corrections.

Reza Shadmehr, a professor of biomedical engineering at Johns Hopkins and leader of the research team, likens our brain’s ability to critique our mistakes to that of a coach. “Learning the next similar task goes faster, because the coach knows which errors are most worthy of attention,” he said in a release about the study. “In effect, this second process leaves a memory of the errors that were experienced during the training, so the re-experience of those errors makes the…

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The Morality Of Brain Science

Originally posted on The Dish:

by Dish Staff

Carey Goldberg interviews Daniel Dennett about how our understanding of neuroscience affects how we view free will. Dennett suggests reframing the debate:

This is a question that’s already millennia old: How can there be free will if everything basically works on cause and effect? So now we have a new layer on that age-old argument, which is that we can see more about the actual workings of the brain. Do you see that adding anything or is it the same-old same-old?

In one sense, it’s the same-old same-old. It doesn’t show that we don’t have free will, but it does show something interesting. And that is: An important element of free will, not often publicly and articulately or explicitly discussed, but an important one, is that we keep our thinking to ourselves. We want to have certain privacy about our thoughts, because if we wear our hearts…

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Metabolic Syndrome and Mental Decline: Is Exercise A Feasible Prevention?

Originally posted on 2014 APA Annual Convention:

Metabolic syndrome (MetS) “is an example of a health variable that may play a causal role in cognitive and language declines with age,” Avron Spiro III, PhD, said at a symposium Aug. 7 at the convention.

A constellation of five interrelated risk factors (a large waistline, a high triglyceride level, a low HDL cholesterol level, high blood pressure and high fasting blood sugar; three are needed to be diagnosed with MetS), MetS is known to increase an individual’s risk of cardiovascular disease, stroke and diabetes. Recent research has also linked cardiovascular and metabolic declines to decreases in different cognitive abilities among older adults, showing reduced cognitive speed, executive functions, memory, and language functioning (i.e., word finding, sentence processing).

obesity1Concurrently, we also know the lack of physical activity is closely linked to metabolic syndrome, and that regular exercise can help to control weight, reduce the risk of cardiovascular disease, Type 2 diabetes and…

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The Conscious Claustrum

Originally posted on NeuWrite San Diego:

Consciousness and Crick

The definition of consciousness, as a biological phenomenon, remains contested. Some definitions consider language necessary for consciousness, while for others, more basic aspects of experience suffice. Only recently has the study of consciousness been broached by “respectable neuroscientists”, where it had previously been the realm of more philosophical disciplines. For the purposes of this article, we will define consciousness as the experience of awareness of our own thoughts and internal state, in response to, and in interaction with the world around us. What can neurobiology tell us about the source of this experience?


The idea that the claustrum might be the seat of consciousness in the brain was strongly advocated by the same man, Francis Crick, who is credited with the discovery of DNA and its function. In a Nature Review, Charles Stevens suggests that Crick’s belief in the importance of this brain structure “bordered on…

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