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 Optogenetics..... wholy crap!

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PostSubject: Optogenetics..... wholy crap!   Sat 01 Oct 2011, 4:23 pm

Here Joe LaDoux talks about some "great" discoveries. Listen closely as he describes how they send signals directly into a rats brain via laser light, bypassing the brains own signal processes, ultimately allowing them to control behaviour and emotional response via external stimuli. I guess we will learn to love our servitude after all, just as Bertrand Russell said.



Scared by the Light
http://scienceblogs.com/neurophilosophy/2010/07/scared_by_the_light.php



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.


Fear conditioning typically involves associating an innocuous stimulus such as an audible tone with an aversive stimulus such as electric shock. With repeated pairings, the animal quickly learns an association between the two, and subsequently expects to receive a shock whenever it hears the tone[/b]. As a result, it will exhibit a fear response (freezing) when the innocuous stimulus is presented alone. The initial association between the two stimuli is thought to be due to synaptic plasticity in the amygdala - the inputs related to each stimulus converge on the same group cells, causing the connections between them to be strenthened. As a result, a memory associating the innocuous stimulus with the aversive one is encoded, but this quickly fades, or becomes extinct, if the innocuous stimulus is then repeatedly presented alone.

Johansen and his colleagues substituted the electric shock with pulses of laser light, delivered to the lateral nucleus of the amygdala through a fibre optic cable. This was done in three groups of rats - in one, the light pulses were delivered at the same time as a tone; in another, just before; and in the third, just after. 24 hours later, they played the tone back, and tested the animals' responses to it. The first group of rats froze when they heard it, biut the other two did not, showing that the light pulses were sufficient to induce fear conditioning, but only when delivered at the same time as the tone. This supports the view that associative learning occurs when inputs representing the two stimuli coincide on the same neurons.

The observed fear responses were, however, significantly smaller than those seen when electric shocks are used, or when the central nucleus of the amygdala is electrically stimulated. This might be because the optical stimulation activated cells in the lateral nucleus indiscriminately, interfering with proper encoding of the memory. A more likely explanation is that the lateral amygdala alone is insufficient to generate a full fear response, and that other components of the brain's fear circuitry are also required. One of these other components is the central nucleus of the amygdala, whose role in fear conditioning overlaps with, but is distinct from, that of the lateral mucleus.

"The central nucleus is especially involved in controlling responses," says senior author Joseph LeDoux, "while the lateral nucleus is especially involved in sensory processing and association [between the two stimuli], and is the initial site of plasticity. The central nucleus is also a site of plasticity, but seems to be downstream, which is why we focused on the lateral nucleus." LeDoux's group is now introducing ChRs into different cell types in the amygdala, in order to examine the contribution of each to fear conditioning. They are also investigating the effects of various neuromodulators on synaptic plasticity in the amygdala.

Optogenetics is still in its infancy, and will undoubtedly become more advanced with time, enabling researchers to probe the cellular mechanisms of fear conditioning in greater detail. Indeed, a group from the Howard Hughes Medical Institute has just reported using the technique in combination with two-photon microscopy, not only to target single cells in the hippocampus, but also to selectively activate distinct subcellular compartments such as the axon and dendrites. Such advances will eventually provide a more detailed understanding of how the amygdaloid nuclei are connected to one another and to other parts of the fear circuit, as well as how information related to fear conditioning is processed by individual cells and neural networks.



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PostSubject: Re: Optogenetics..... wholy crap!   Sat 01 Oct 2011, 4:31 pm

Optogenetics Discovers Brain Anxiety Circuit
Written by Dr. Z in Clinical, Stress & Health
http://www.stresshacker.com/2011/03/optogenetics-discovers-brain-anxiety-circuit/

The state of heightened apprehension and high arousal in the absence of immediate threat—commonly labeled as acute stress or anxiety—can be a severely debilitating condition. Over 28% of the population suffers from anxiety disorders that contribute to the development of major depressive disorder and substance abuse. Of all the structures of the limbic system, the seat of emotion processing, the amygdala plays a key role in anxiety, although by what exact mechanism still remains unclear. Newly published research carried out by a group of neuroscientists at Stanford University using the novel technique of optogenetics with two-photon microscopy has permitted a much closer exploration of the neural circuits underlying anxiety than ever before. The optogenetics approach facilitates the identification not only of cell types but also the specific connections between cells. The researchers noticed that timed optogenetic stimulation of the basolateral amygdala (BLA) terminals in the central nucleus of the amygdala (CeA) produced a significant, acute, and reversible anxiety-reducing effect. Conversely, selective optogenetic inhibition of the same projection resulted in increased anxiety-related behaviors. These results indicate that specific BLA–CeA projections are the critical circuit elements for acute anxiety control in the brain. The results were published in the March 17 issue of the scientific journal Nature.
A Closer Look at the Amygdala’s BLA and CeA Regions

The amygdalae (amygdaloid nucleus) are two identical almond-shaped brain structures located in each temporal lobe. Each amygdala receives input from the olfactory system, as well as from visceral structures. The amygdala in humans has been confirmed by functional MRI imaging to be the area of the brain that is best correlated with emotional reactions and plays a key role in the brain’s integration of emotional meaning with perception and experience. The emotional aspect of the response of the individual is passed on to the frontal cortex, where “decisions” are made regarding possible responses. In this way, the response of the individual can take into account the emotional aspect of the situation.

Additionally, the amygdala coordinates the actions of the autonomic and endocrine systems and prompts release of adrenaline and other excitatory hormones into the bloodstream. The amygdala is involved in producing and responding to nonverbal signs of anger, avoidance, defensiveness, and fear. The amygdala has been implicated in emotional dysregulation, aggressive behavior, and psychiatric illnesses such as depression. It has also been shown to play an important role in the formation of emotional memory and in temporal lobe epilepsy.

The basolateral amygdala, one of the two structures studied in the recent Stanford research, receives extensive projections from areas of the brain cortex that are specialized for recognizing objects such as faces in central vision. Extensive intrinsic connections within the amygdala
promote further coordination of sensory information.

Biological effects initiated by amygdala include increases or decreases in arterial pressure and heart rate, gastrointestinal motility and secretion, evacuation, pupillary dilation, piloerection, and secretion of various anterior pituitary hormones, especially the gonadotropins and
adrenocorticotropic hormone, which are key agents in the stress reaction. Interestingly, amygdala stimulation can also cause several types of involuntary movement, such as raising the head or bending the body, circling movements, occasionally rhythmical movements, and movements
associated with taste and eating, such as licking, chewing, and swallowing.

The findings also show the involvement of the amygdala’s CeA region in mediating threat-related anxiety and acute fear-related behavioral and hormonal responses. Earlier studies had shown that stimulation of this same area reduces snake fear and pituitary-adrenal activity and that CeA lesions resulted in decreased expression of threat-induced freezing. Additionally, the CeA region of the amygdala was reported as being significantly involved in the consolidation of contextual fear memory, i.e., what permits us to remember so vividly and persistently objects or situations that have caused fear in us in the past.

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PostSubject: Re: Optogenetics..... wholy crap!   Sun 02 Oct 2011, 11:49 am

"Wholy crap!" indeed - these guys are SUCH sickos
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in "That Hideous Strength"!!
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