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December 4, 2011

This Proves We're Obsessed with Shiny Things


How does a predator within 4 seconds of scanning an environment map it, memorize it, and sort out all unnecessary information from the info needed to be able to survive? Many theories have to do with the difference between top down and bottom up visual processing. Top down processing refers to the slower, executive cognition behind vision while bottom up is fast and not consciously driven and heavily influenced by environmental cues. Those environmental cues have been studied as to their effect and also as to what exactly grants them salience, or the property that allows the stimulus to stand out against its backdrop. While many studies have already been done studying the effect of salience on such things as saccade movements in the eyes to fixation periods to mapping brain location, little to no experiments have been done trying to illuminate salience and its relationship to memory.
A simple task was devised consisting of having 12 participants focus on a scene for a brief period of time. The view is then removed from the participants and they are subjected to a wait period. Once that time is completed the participants are asked to recall the position of several figures in the scene to test their memory. They varied the difficulty of the scenes and the salience of the objects to see if there was any correlation between the two, and as it turns out there was indeed. The salience of the object was directly correlated with the performance of the participants meaning they were more successful at recalling the objects exhibiting greater degrees salience than they were recalling inconsequential items. Furthermore, they tested this with varying degrees of difficulty and found that the more difficult the recollection task was, the greater the positive effect of salience had on the performance of the participants. While one could argue that they perhaps were drawn to those items and they simply focused on those items more than the others thus increasing the chances of memorization, they mapped and timed their eye movements to measure any fixation times on the items and found no difference in the fixation times between the salient objects and the non-salient objects meaning that they spent the same amount of time memorizing each object.
To summarize the findings, they showed that human�??s ability to recall objects within a certain space is positively dependent upon the salience of the object, and it is not due to any differences in memorization periods. A positive correlation between the increasing difficulty of the task and the positive effect of salience on memorization suggests that perhaps the brain may use salience to identify objects of value and omit objects deemed unimportant when the brain is forced to compromise.
They did make sure to mention another study with conflicting results. The study opted for a test involving people to assess whether a certain object was in a scene. They authors asserted that the difference in the findings could be attributed to the inherent difference in the tests, as one dealt with object identification and another with object location and spatial memory. They conclude that salience of an object and the effect it has on memory needs to be studied on a brain system to brain system basis, analyzing which systems are involved and what that would then imply.
This study provides more insight into the evolution of sight and how vision has been used and fine tuned throughout evolution. Recognition of the salience of an object is conserved throughout most species and clearly plays a pivotal role in the utility of vision as a whole. The ability to quickly asses an environment for all the information essential for survival is something that if without many animals would fall prey much more often due to lack of attention. This often taken-for-granted aspect of our vision that we are mostly unaware of is something that most certainly needs to be studied further and fully understood.
Original Article: http://www.jneurosci.org/content/29/25/8016.full
Posted by      Christopher R. at 10:37 PM MST

December 3, 2011

Drinking on the Job: How Flies get Drunk


Thursday, Friday, and Saturday night... I know what you're thinking. No class till Monday, no work, what a great night to get ahead on studying and up to date with all the problems in the world. However, I must point out this plan is not the first thing that pops into everyone else's mind (at least those outside the world of the poor soul who is reading this neuroscience blog). Much of western society is based around the beverage/drug/poison we've come to know as alcohol. It has come to the attention of neuroscientist that our race is not the only one that takes pleasure in consuming firewater. It turns out some researchers were playing with the old 160 proof lab ethanol when they came upon an astounding discovery.

It all started when one turned to the other and croaked, "I'm drunkk frog haha." The other slurred back, "weelll thenn, gooood thing I'm not a fly huh?" That's when it hit them. "Eureka!" piped the first. "Oh my god!" yelled the second. "Let's" get the flies wasted!" the second hollered back. They quickly spun off their lab stools and bustled for the fly room stumbling and tripping the whole way. When they got to the room they immediately grabbed the first beaker of flies, ripped out the cork and filled it full of the powerful booze, instantly killing all the flies inside. Once they realized the horrendous massacre they had just committed in front of all the hundreds of thousands of other flies in the room their drunken smiles slipped off. The beaker was placed on the counter as the two somber scientists held each other with silent tears streaming down their cheeks. Then one started laughing; irritated, the other muttered, "How can you laugh at a time like this? We just killed them, in front of their families... drowned them, squashed them like flies... "Look, that one's drunk," the other researcher pointed at a fly that was clearly not adhering to the standard sober drosophila flight pattern. They watched the fly for nearly two hours, they sat on the fly room floor entranced by the fly's drunken escapades. Then as its flight pattern began to return to normal it headed back to the beaker full of booze, and began gulping down, without a thought to the dead brothers, sisters, cousins and children floating on top. Gleeful laughter burst from the researchers as they cheersed and began taking large quaffs of their own. Quickly forgetting their bloody hands they then began pulling the corks of the other beakers, filling up petri dishes with ethanol, and pipetting small volumes of ethanol in for the larvae--so no one was left out. They spent the whole night at the lab with their new found drinking buddies and had a gay old time. A few days later after their handover was gone they decided to write a paper.

It was determined drosophila liked the inebriation caused by excessive consumption of ethanol. Like us, the flies were experiencing their pleasure through the activation of the dopamine pathway. Activating this pathway induced LTP in the flies. Looking further into the flies' neural circuitry the researchers determined the rewarding memories the flies experienced (or the lack of memory if they got too plastered from not getting enough sugar before) were localized, accessed and retrieved with a distinct set of neurons in the mushroom body. With the vast number of flies they got drunk the researchers' found some flies didn't come back to drink. The experimenters were obviously offended and quickly squashed them. However, they didn't stop there; they proceeded to analyze the DNA so they could breed out the bad gene and make sure no other flies would be lame. They found mutations in scabrous were responsible. They commonly call it the party pooper gene around the lab. "This gene encodes a fibrinogen-related peptide that regulates Notch signaling, disrupted the formation of memories for ethanol reward" (Kaun, 2011). The experimenters have been thought to have had a little bit too much fun drinking with the flies, but they have felt the public pressure. Now they're looking into how this research will help their own species and we will undoubtedly be hearing more from them soon.

Hope you enjoyed the read, sincerely Charlie Stewart

"A Drosophila model for alcohol reward"
Karla R Kaun, Reza Azanchi, Zaw Maung, Jay Hirsh & Ulrike Heberlein
Nature Neuroscience April 17th 2011
Posted by      Charlie S. at 8:15 PM MST
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December 1, 2011

Seeing With Your Mind.


When asked to imagine a particular object the mind seems to conjure the image instantly and you can observe it's many features with your mind's eye. Given that we all do this dozens of times a day it seems like a fairly boring and menial occurrence. However if you stop to think of the mental processes that underlay this phenomena you'll see how complex and important it is.

To first test the manner in which mental images are formed participants were shown an empty grid with a lower case letter beneath it. They were asked to imagine the corresponding uppercase letter in the grid as quickly as possible and state whether the letter would cover a particular block in the grid. As the letters became more complex (containing more segments) the response time increased. This finding led the researchers to believe that an image was not formed all at once, but rather as individual parts. (the letter F should take longer to recall because you must recall three parts as opposed to an L which contains only two parts). It also appears as if the parts were imaged in almost the same order in all cases. This is based off the fact that when the subjects were asked to draw individual letters they were imaged in the same sequence at least 75% of the time.

These findings were further supported by auxiliary evidence of the brain forming patterns. For example ------ is viewed as a straight line, not six dashes. Similarly XXX XXX is viewed as two groups not six X's as is XXXooo. Thus the brain is predisposed to organizing things as parts or "perceptual units." Given this it seems likely that the brain stores the letter F by its three individual parts rather than as a whole, and when the letter is recalled it is imaged a part at a time based off previously stored perceptual units.

Why is this the case? Why not simply remember something as a whole rather than by its parts? The answer comes via the limitations of the brain.

Previous research has shown that it is more difficult to hold onto a mental image while you are paying attention to actual visual stimulation. This would seem to say that some of the cortices involved in visual sensory input are implicated in mental imagery. To test why the things are organized by parts the researchers look at the processing of visual stimuli.

The two primary visual cortices are located in the inferior temporal lobe and the parietal lobe. Ablations in monkeys of the inferior temporal lobe causes the monkey difficulty in discriminating against patterns and shapes but have no difficulties in object location. The reverse is true in animals with ablations of the parietal lobe indicating that each lobe has a different functional relevance in visual processing. Thus the observation of "what" and "where" are processed separately.

This explains why we image things sequentially. The shape of a part is stored separately from it's location relative to other parts. For example an F is composed of vertical bar connected on top and in the middle to two horizontal bars. Given that 94% of the participants drew an F by drawing the vertical line first then top and bottom shows that there are parts prerequisite to other parts and thus must be imaged one part at a time.

This division of objects into parts has great importance. It is why we are able to recognize letters in different fonts. Rather than memorizing how an F looks in every form and being confused upon seeing a new font we merely have to know the parts of an F and how they relate to each other. This can be further extrapolated out away from the simplicity of letters. A person can assume many forms. We can stand, sit, curl in the fetal position and still we are able to recognize it as a person because we recognize the parts and how they are connected to one another, as opposed to knowing exactly how a person looks when they are curled.

This division relieves us of having to know much more specific information thus freeing up brain power so we can say, know how to write a blog.

Aspects of a Cognitive Neuroscience of Mental Imagery. Kosslyn et al. Science Journal.
http://wjh-www.harvard.edu/~kwn/Kosslyn_pdfs/1988Kosslyn_Science240_Aspects.pdf
Posted by      Zach I. at 4:22 PM MST
displaying most recent comments (1 ommitted) | Comments (4)
  Zach Irell  says:
Yeah I was wondering the same thing...they don't mention it at all in the paper most likely because they don't have a good answer. I think that there is definitely merit in that answer but from an evolutionary stand point it makes more sense for us to encode things in the way presented by these researchers. The letters are a very simplistic way for them to explain this and thats why we can call it into question but I think the results and direction of the paper point to things on a much larger and more complicated scale.
Posted on Sun, 4 Dec 2011 4:51 PM MST by Zach I.
  Christina Uhlir  says:
Did the paper get into templates and expectations? By templates I'm referring to mental representations of objects, people, scenes that act as a prototype that influences a person's perceptual experience (e.g. drawing from memory a letter and comparing it to the one you see in front of you) and based on that, the expectation a person has about the stimulus, and problematic interactions that could result.
Posted on Sun, 4 Dec 2011 5:04 PM MST by Christina U.
  Zach Irell  says:
This paper refers to how mental representation of objects, people and scenes are stored and how we recall them.
Posted on Thu, 8 Dec 2011 8:42 PM MST by Zach I.

October 23, 2011

Flies Like to Get Drunk As Well?


Well, it is unclear whether they get "drunk" or not but they do display hyperactivity after being exposed to intoxicating vapors of ethanol which is similar to that of what humans do after drinking too much. A recent study done by Karla R. Kaun et al shows that flies are attracted to ethanol just as much as humans are. Although humans have various reasons for ingesting alcohol, flies on the other hand, are attracted the rewarding effects that ethanol has on the brain. This attraction towards ethanol and the rewarding effects are so great; one could say that they are addiction to ethanol.
In the study done by Karla R. Kaun et al, they wanted to test whether or not flies displayed addition like behavior such as that in humans. They conditioned flies to be attracted ethanol by various means and tested them for addition like behavior by administering 100 V and 120 V shocks. They found that even after administering shocks to the flies, they were drawn to ethanol. Another test was done with the same voltages except ethanol was replaced with sucrose. This time, the flies only tolerated the 100 V shock and not the 120 V shock. This higher tolerance towards ethanol than sucrose could mean that they associate ethanol as giving them a more rewarding feeling than sucrose and that ethanol is worth the pain.
The flies were, as one could say, addicted to ethanol but why was this? Well, as we know, dopamine plays a role in the reward system and "ethanol amplifies the dopaminergic responses to natural reward and reward-related environmental cues" which causes this attraction and who can blame them, we all like to feel good (Karla R. Kaun et. al, pg. 3). Not only does dopamine play a role in the reward system, but so does memory of that good feeling. Karla R. Kaun et. al also found that the mushroom body and scabrous gene were required for the ethanol reward memory. By blocking various synaptic transmissions in the mushroom body, they found that the formation of ethanol reward memory "may be mediated by dopaminergic innervations of the αβ neurons (Karla R. Kaun et al, pg 5)." Karla R. Kaun et al also found that within the mushroom body, there was the scabrous gene that was required for the ethanol reward memory. It plays a role in this reward memory in that scabrous sends signals to Notch in which Notch mediates the reward memory. And so with the brain releasing chemicals that make you feel good and memories of that good feeling, who wouldn't be addicted to something that made you feel this way?
So why does studying flies and their addiction towards ethanol matter? Well, by studying flies and what influences them in their addictions, it could help researchers better understand human addiction and possibly allow researchers to find ways to help people with these addiction such as finding genes or circuits that makes a person more susceptible to being more addictive to various substances. By being able to identify these factors that influence a person's addiction, there will be better ways of treating a patient who has a drug abuse/addiction problem and better ways of treating the side effects of going off the drug such as withdrawal.

Source:https://cuvpn.colorado.edu/neuro/journal/v14/n5/pdf/,DanaInfo=www.nature.com+nn.2805.pdf
Posted by      Kou X. at 3:14 PM MDT
  Christina Uhlir  says:
Kou,

What is the mushroom body, scabrous gene, and Notch?
Posted on Sun, 23 Oct 2011 5:48 PM MDT by Christina U.

True or False: Emotions and Electrons Are Alike (Answer: true)


Remember that one time your girlfriend or boyfriend got ketchup on their nose while eating French fries and you thought it was hilarious, but immediately afterwards you felt guilty because they glared at you and growled for a napkin?

There is a word for that: ambivalence. The word ambivalence means that you feel two contradictory emotions (hilarity and guilty) simultaneously. Look a little more closely at the word ambivalence and you can probably guess what electrons and emotions have in common: valences. Emotional valences, like valence electrons, are shown outwardly on a persons face and they either attract (positive valence) or repel (negative valence) the person at which they are directed.

Many studies, since the advent of the fMRI, have examined the underlying circuitry involved in the expression and perception of emotion, especially negative valence emotions such as anger, sadness, and fear. The paper I analyzed is no exception to this rule: researchers from Kings College London, University College London, and the University of Zürich worked together to a) ascertain the circuitry that underlies the processing of emotionally negative facial expressions, and b) determine whether or not the amygdala is involved in the conscious processing of emotive faces. Basically, they wanted to know if our first response to facial expressions is to think or react.

In the study, a pool of 40 subjects (selected based on a range of nonspecific qualities) were shown a set of 60 faces and a corresponding number of fixation crosses (an image of a white screen on which a + is superimposed), while in an fMRI. Each of the 60 faces displayed either a neutral expression or a negative expression (anger, fear, or sadness) and the subjects used a clicker to indicate whether the face did or did not show an emotion. For each face, the response time and accuracy was recorded and was used in concert with the data provided by the fMRI images. In addition to the tests performed using the fMRI, a battery of statistical tests corrected for noise and anatomical dissimilarities among participants.

The findings are significant: the amygdala is not the only cranial structure that modulates facial processing. To be more specific, their results show that while the amygdala is involved in the processing of facial affect(Dima et al 1) there are also pathways to and from the fusiform gyrus, the inferior occipital gyrus, and the ventrolateral prefrontal cortex, which do not involve the amygdala. Most notably, anger was mediated by the inferior occipital gyrus and ventrolateral prefrontal cortex, not the amygdala.

What does all of that mean?

Basically, our brains have evolved for cognition for so long that we now respond to physical or emotional danger (anger in this case) in a cognitive fashion. We think before we react to a potentially harmful event.

Now think back for a second to your girlfriend or boyfriend with ketchup all over their nose. If this research holds, you will not immediately react and give them the napkin; you will, in fact, think about the potential harm that could come to you if you do not (minimal: they probably will not punch you), and the potential benefits you will reap if you do not (photographic evidence of the event). As far as I am concerned this decision is easy: memory is leaky; emotions are transient; but a picture lasts a lifetime.

What would you do?

Source: https://cuvpn.colorado.edu/content/31/40/,DanaInfo=www.jneurosci.org+14378.full.pdf+html?sid=20ba56d1-84f2-4fdb-b108-83aed6437270
Edited by      Christina U. at 2:03 PM MDT

October 21, 2011

A Mechanism of Auditory Processing


Ever wondered how you're able to distinguish between different sounds and words in conversation? In order to understand the world around you, you not only have to hear all of the sounds together, but you also have to be able to hear the silence between the sounds. But all of this has to occur very quickly, or else you would be stuck having people repeat themselves slowly every time they said something. So, how does it work? The answer is: rapid changes in concentration of ions from cells that are firing electrical signals and turning off.

Previous research has implicated two structures in the brain that are critical in recognizing sounds and silences, namely the superior paraolivary nucleus (SPN, sometimes spelled superior periolivary nucleus) and the medial nucleus of trapezoid body (MNTB), both of which are part of the superior olive in the brainstem. A more current research article ("The Sound of Silence: Ionic Mechanisms Encoding Sound Termination" by Kopp-Scheinpflug, et al.) looks at how these two structures connect to one another and what mechanisms they use for distinguishing sounds.

In general, when a neuron is not being activated, it sends electrical signals at a specific rate, called its basal firing rate. Stimulation can increase or decrease the neuron's firing, and when the stimulation is removed, the firing rate eventually returns to its basal level.

When a sound stimulus is presented, the MNTB neurons continuously fire for the entire stimulation, and then not only cease firing when the stimulation has ended, but also reduce firing to below their normal rate, and return back to normal after a short period of time. On the other hand, SPN neurons have little to no firing when a sound stimulus is presented, and when it stops, the neurons rapidly fire, corresponding to the intensity of the stimulus and then deplete the firing to their normal rate.

The signaling pathways for both SPN and MNTB also involve chloride ions (and possibly potassium ions). The flow of chloride ions into neurons inhibits firing, and is important for recognizing sound in the MNTB, but recognizing silence in the SPN.

The main idea here is that there are multiple mechanisms involved in how we process language and other sounds every day. Without these two brain regions and the chloride signaling between them, we wouldn't be able to communicate. It is necessary to have mechanisms in our brains not only for recognizing sound, but also for recognizing silence, both of which need to communicate with one another to be processed together. This is a very important finding for learning how we acquire language and learn to differentiate syllables and words so readily and easily in early childhood, and more research could possibly help with understanding different speech disorders.

Source: http://www.sciencedirect.com/science/article/pii/S0896627311005587
Posted by      Anna G. at 10:54 PM MDT
  Christina Uhlir  says:
Anna,

Thank you for spelling it out so simply, I understood that we process continuous sounds as discrete but I couldn't understand how that was accomplished, so thank you for elucidating that point for me.
Posted on Sun, 23 Oct 2011 7:44 PM MDT by Christina U.

October 19, 2011

Well that's Surprising...ly Negative


Have you ever been surprised to be let down? Or in other words, have you ever expected a certain outcome only to be surprisingly disappointed? Well if you have, ladies and gentlemen, then do not fear; for your dorsal anterior cingulate cortex is functioning properly! And what's that? There's unified model for the long disputed function of the dorsal anterior cingulate cortex? That's right! Both of these birds were hit by the same stone recently when Alexander and Brown produced a computational model "tour de force" to illustrate how negative surprise signals drive dACC (dorsal anterior cingulate cortex) and mPFC (medial prefrontal cortex) responses.
Many theories have been concocted as to what the dorsal anterior cingulate cortex may be responsible for, such as error detection, error likelihood prediction, and conflict monitoring primarily, and even more such as reinforcement-guided decision making, negative reinforcement learning signals, and action value prediction error. Could the dACC be responsible for all of this in the brain? Well, Alexander and Brown's model seems to narrow our spectrum a bit and put an end to this controversy.
While their model agrees with previous theories that the dACC and mPFC predict action-outcome situations, it is uniformly different in the sense that these regions are responsible for multiple predictions for action-outcome situations in parallel, and then these predictions are scaled to their probability of their occurrence. When the predicted outcome doesn't happen, learning rates are modified in order to update action-outcome predictions to the degree necessary to learn from mistakes and find a better solution.
Another important point of this model's representation of multiple predictions of action-outcomes is that different ongoing predictions could account for heterogeneity of neural responses usually observed in single-unit studies. So basically, the dorsal anterior cingulate cortex and medial prefrontal cortex can encode different outcomes simultaneously for the same situation that are being encoded in different groups of neurons! Pretty impressive eh?
So let's just recap. The dorsal anterior cingulate cortex analyzes a particular action, predicts an outcome for this action, and if the action-outcome prediction is negated, then the dACC modifies learning rates so that the brain can learn from its mistakes. And the dACC and mPFC can do this multiple times at once!
So while Alexander and Brown's model is reasonable and presents much more concise data, it is obviously provoking new questions and controversy. Seeing as how consequences of positive and negative surprises are the same according to this new model, what makes a negative surprise more significant or important than a positive surprise? If the dorsal anterior cingulate cortex is responsible for negative surprise predictions and reactions, what is responsible for positive surprise monitoring? As for these questions, we shall see what new models of these mysterious brain regions are presented and what will be discovered for the tasks we perform in daily life. Regardless of what is discovered in the future, we'll all be surprised!

main article:http://www.nature.com/neuro/journal/v14/n10/full/nn.2932.html
Posted by      Mark A. at 4:19 PM MDT
  Christina Uhlir  says:
Mr. Alsberg,

Could you kindly explain the mechanism by which the "tour de force" operates?
Posted on Sun, 23 Oct 2011 2:20 PM MDT by Christina U.




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