To sleep: perchance to learn

The dreaming brain can produce complex language output.

To sleep: perchance to learn
Robert Stickgold
Nature Neuroscience  (September 2012) 15, 1322–1323
http://www.nature.com/neuro/journal/v15/n10/full/nn.3223.html

Not only can the sleeping brain perceive sensory information, it can learn from this information, leading to changed behaviors the next day: it can come to associate a sound with a pleasant or unpleasant odor and react, both while still asleep and after waking, with a deeper or shallower breath. But classic ‘sleep learning’ remains just a dream.

related:
Sounds during sleep may help you remember
2009
http://www.npr.org/templates/story/story.php?storyId=120573613

Orbitofrontal cortex and decision-making

Cross-species studies of orbitofrontal cortex and value-based decision-making
Jonathan D Wallis
Nature Neuroscience  15, 13–19 (2012)
http://www.nature.com/neuro/journal/v15/n1/full/nn.2956.html

Recent work has emphasized the role that orbitofrontal cortex (OFC) has in value-based decision-making.

However, it is also clear that a number of discrepancies have arisen when comparing the findings from animal models to those from humans. Here, we examine several possibilities that might explain these discrepancies, including anatomical difference between species, the behavioral tasks used to probe decision-making and the methodologies used to assess neural function.
Understanding how these differences affect the interpretation of experimental results will help us to better integrate future results from animal models.
This will enable us to fully realize the benefits of using multiple approaches to understand OFC function.

Unconscious determinants of free decisions (2008)

Unconscious determinants of free decisions in the human brain
Nature Neuroscience 11, 543 – 545 (2008)
http://www.nature.com/neuro/journal/v11/n5/full/nn.2112.html
Chun Siong Soon, … John-Dylan Haynes

There has been a long controversy as to whether subjectively ‘free’ decisions are determined by brain activity ahead of time.
We found that the outcome of a decision can be encoded in brain activity of prefrontal and parietal cortex up to 10 s before it enters awareness.
This delay presumably reflects the operation of a network of high-level control areas that begin to prepare an upcoming decision long before it enters awareness.

cited by:
Introduction to Neuroeconomics: how the brain makes decisions
Coursera. July 2014
https://www.coursera.org/course/neuroec

cf:
Wilheml Wundt
structuralist
structuralism
introspection
{Understanding Psychology © 2014. p. 8}

related:
https://franzcalvo.wordpress.com/2014/08/18/time-flew-we-must-have-been-having-fun

Maintenance of neuronal identity

Maintenance of postmitotic neuronal cell identity
Evan S Deneris, et al.
Nature Neuroscience  17, 899–907 (July 2014)
http://www.nature.com/neuro/journal/v17/n7/full/nn.3731.html

The identity of specific cell types in the nervous system is defined by the expression of neuron type–specific gene batteries.
How the expression of such batteries is initiated during nervous system development has been under intensive study over the past few decades.

However, comparatively little is known about how gene batteries that define the terminally differentiated state of a neuron type are maintained throughout the life of an animal.

Here we provide an overview of studies in invertebrate and vertebrate model systems that have carved out the general and not commonly appreciated principle that neuronal identity is maintained in postmitotic neurons by the sustained, and often autoregulated, expression of the same transcription factors that initiate terminal differentiation in a developing organism.
Disruption of postmitotic maintenance mechanisms may result in neuropsychiatric and neurodegenerative conditions.

============

Serotonergic transcriptional networks …
2012
http://www.nature.com/neuro/journal/v15/n4/full/nn.3039.html

Caffeine enhances memory consolidation

Caffeine enhances discrimination performance 24 h after study.

Post-study caffeine administration enhances memory consolidation in humans
Nature Neuroscience (2014). Published online 12 January 2014
http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.3623.html
Daniel Borota, et al.

It is currently not known whether caffeine has an enhancing effect on long-term memory in humans.
We used post-study caffeine administration to test its effect on memory consolidation using a behavioral discrimination task.

Caffeine enhanced performance 24 h after administration according to an inverted U-shaped dose-response curve; this effect was specific to consolidation and not retrieval.

We conclude that caffeine enhanced consolidation of long-term memories in humans.

Targeting neurons and photons for optogenetics

Targeting neurons and photons for optogenetics
Nature Neuroscience 16, 805–815 (July 2013)
http://www.nature.com/neuro/journal/v16/n7/full/nn.3427.html

optogenetic probes

dream experiments will become possible with the application of these new approaches

Caenorhabditis elegans has 302 neurons, and the morphology of every neuron is known.

mammalian retina: the functional unit is often considered to be a mosaic of cells with the same properties, referred to as cell type.

cell type” refers to a population of neurons that cannot practically be divided into smaller units

cell class” refers to a population of neurons that is defined by some common property but which can be further divided into smaller populations.

a single retinal ganglion cell mosaic

Targeting the right neurons is still a largely unsolved problem, especially in species, such as non-human primates, where genetic manipulations are often not feasible.

approaches for targeting optogenetic probes, focusing on using viruses, alone or in combination with transgenics.

the virus used most frequently for targeting, the adeno-associated virus (AAV), has a coat protein that exists in 100 different variants in nature … changing the entry site from axons to soma or dendrites.

The thousands of viruses made by nature and the many variants made by researchers can therefore be thought of as a ‘Legoland’ for neuroscientists performing optogenetics experiments

the way viruses are made is highly modular: the different properties are stored in different plasmids, and by mixing these plasmids and adding them to cells the virus is self-assembled.

Replication-competent viruses are toxic to varying degrees

the genetic identity of these neurons (for example, expression of parvalbumin)

Virus targeting based on genetic identity.
The morphology and function of different cell types is to a large extent defined by the pattern of genes they express.
Past work has used the fact that some classes of neurons uniquely express particular signature genes—for instance, a large class of fast-spiking interneurons expresses parvalbumin

molecular tools, such as site-specific recombinases (for example, Cre or Flp) can be used to drive the expression of optogenetic probes from viruses infecting these cells.
Such conditional viruses can be made from DNA viruses, such as AAV or herpesviruses

The main drawback of the conditional virus approach is that it requires expression of a site-specific recombinase, typically using a transgenic animal.
The generation of a transgenic animal for a target neuronal type is both time consuming and unpredictable

Rabies– and herpesvirus-based retrograde labeling methods, while suitable for short-term studies over days, are too toxic for studies in which long-term expression is needed.

AAVs are excellent tools for anterograde delivery; however, existing AAVs are not exclusively anterograde, and further development of nontoxic, exclusively anterograde vectors is needed.

single-cell electroporation of a postsynaptic neuron and the subsequent initiation of a retrograde virus from only the electroporated neuron.

high-level, long-term expression has been shown to cause abnormal axonal morphology

This involves using two-photon microscopy to target a plasmid-filled patch pipette to individual neurons in vivo, followed by electroporation to deliver the plasmid to the cell under visual control.
Neurons can be targeted in this way on the basis of

  • their somatodendritic morphology (using ‘shadowimaging’30),
  • their genetic identity (using GFP expression as a marker) or
  • their functional properties (such as tuned responses to sensory stimuli) for subsequent optogenetic activation.

===================

Optogenetics: controlling cell function with light
Nature Methods 8, 24–25 (2011)
http://www.nature.com/nmeth/journal/v8/n1/full/nmeth.f.323.html
http://www.stanford.edu/group/dlab/papers/moynature2010.pdf

Brain responses to angry prosody

prosodyThe voices of wrath: brain responses to angry prosody in meaningless speech
Nature Neuroscience 8, 145 – 146 (2005)
Didier Grandjean, et al.
http://www.nature.com/neuro/journal/v8/n2/full/nn1392.html

emotional enhancement was voice specific, unrelated to isolated acoustic amplitude or frequency cues in angry prosody, and distinct from any concomitant task-related attentional modulation.
Attention and emotion seem to have separate effects on stimulus processing, reflecting a fundamental principle of human brain organization shared by voice and face perception.

voice perception