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My wife and also I save pet rabbits. Observe their cuteness:

We feed Jackchild (he"s the black one) and also Dutchess (she"s the significant one) once each morning and once each night, and normally give them a couple of treats in between. A month or so earlier, we noticed that as soon as we open the refrigerator door they hop up from wherever before they are and also run right over to us, necks craned to see what we"re going to pull out. More newly, Dutchess has taken to standing up and also placing her front paws on my leg whenever before I"m holding a bag of treats. I think this is incredibly cute, so I offer her treats as soon as she does it.

You are watching: Animals behave in order to satisfy needs

If you"ve ever before had a pet, you"ve almost definitely seen habits favor this. A good trainer can teach an pet to perdevelop all sorts of tricks using food as a reward. A bad trainer deserve to rotate the same animal into a nuisance (albeit, an adorable one) who persistently begs and also butts in wright here it"s not wanted. We are of the second form, though by some magnificent grace our rabbits have actually turned out simply as sweet as deserve to be.

Jackboy and Dutchess seem to know that tright here is an excellent chance that they will obtain food as soon as they see me open the refrigerator - at least, they act choose it. They seem to really want the treats, and also because of this we deserve to infer that they should really like to eat the treats. This all seems extremely simple and also intuitive, however the field of behavior neuroscientific research, which researches how the brain contributes to and controls an animal"s behavior, has actually a long history of studying the not-so-straightforward means that the brain makes animals - humans had - prefer and want things.

A basic question

Let"s action ago for a minute.

The main question of scientific research is: why carry out things happen? More particularly, why carry out things occur the way they perform, instead of happening in an additional of the boundless means they can possibly happen? For instance, physicists ask questions like: "as soon as we drop something, why does it move dvery own rather of up, or some direction in between?" They can then perform experiments and come up with theories (choose the concept of gravity) to figure out just what it is around the people that renders this certain occasion - an item falling - happen the method it does. If we"re talking about animals, the question instantly becomes even more specific: "why carry out animals carry out things?"

We are now in the realm of behavioral neuroscientific research. Behavidental neuroscientific research is a branch of psychology that is concentrated of describing just how assorted arrangements of neurons (the cells that consist of the brain, spinal cord, and nerves) add to the miscellaneous things that animals do. Now we have an even tighter watch of the problem: "just how carry out animals" nervous systems cause them to do things?"

The first action in answering this question is to look at some of our basic presumptions around behavior. We might say that actions is ssuggest what an animal does. This appears to be an okay definition at challenge worth, but it misses something. Is the beating of a heart "behavior"? What about the movement of a white blood cell? A much better definition could encompass the concept that behavior is an answer to some part of an animal"s atmosphere - it involves the animal sensing some component of their atmosphere and also reacting to it.

With this definition, we see that tright here is always some aspect of choice involved. In any kind of situation, an animal is physically capable of doing many kind of different things - the thing it chooses to carry out is its habits. Its nervous system somejust how helps it select which habits is best for each situation. Our question has now been refined yet again: why an animal does one habits at a details time instead of one more behavior?

For instance, let"s expect that Jackkid is pleasantly snoozing on the floor, prefer so:

At this suggest, he could perform a number of things - he can save snoozing, he might groom himself, he could relocate about, he might groom Dutchess, he might uncover and also eat some food, he might drink water, he might play with playthings, and also so forth. Because he is snoozing, we have the right to say that he is absolutely not grooming himself, eating, running in the direction of me, or doing anything else. When I open up the refrigerator door, yet, he hops right up and also shuffles over to me as conveniently as his tiny bunny legs will carry him. A decision has just been made - it is the job of behavior neuroscience to describe just how Jackson"s brain has actually chose that this is what he must do at this moment.

One have the right to divide the answers to this question into 2 categories: proximate reasons and ultimate reasons. Proximate causes are the events that directly precede a behavior (ie. Jackboy runs and also hides bereason I have dropped a frying pan on the ground and also made an extremely loud sound, which nerve cells in his inner ear sensed and also which was then turned right into a signal in his brain that told his muscles to move in a certain way.)

Ultimate causes, on the other hand also, define the factor an organism does the actions in the initially place: it"s goal (ie. Jackson hides because, if he were in a dangerous atmosphere, it would certainly be much safer for him to be far ameans from the resource of a loud noise, which is most likely to have actually come from a bigger animal or some other source of danger.)

The ultimate reasons of habits are mainly well-known. Sure, examples pop up eincredibly currently and aget that defy current theories, but we know what most actions perform for the animal: hunting and also foraging uncover food, fighting defends territory or resources from intruders, social interactivity and also bonding promote safety and security and opportunities to mate, and so forth.

How about the proximate reasons of behavior? We know that the brain sends out electric signals dvery own the spinal cord to muscle fibers, which is what actually reasons an animal"s muscles to relocate. To look at the means habits is controlled in its entirety, we deserve to look at the brain. Tbelow are some locations of the brain that regulate particular actions - for example, the locations of the brain that are crucial for speaking and also expertise language in human beings have been stupassed away for a lengthy time, and some areas of the rodent brain that manage repeated behaviors like grooming and also licking have been pretty broadly studied. In general, we have the right to say that pets carry out specific complicated habits bereason particular components of their brain are energetic.

This is an imexact answer, yet it offers us a place to look. Of course, any type of particular behavior will be caused by specific areas of the brain, we must look at each of these in turn to understand how the brain creates actions all at once.

We still require some connection in between the proximate reasons and also the ultimate causes of behavior; some procedure that web links reason an animal does something through the components of the animal"s brain that make its body move in a details way. The crucial component of this link is incentive.

By "inspiration," I don"t intend what you get from your friend that does Tai-Bo through you and also tells you exactly how good you are at it (although I completely dig that sort of impetus, and I love that friend). I"m talking about the procedures in the brain that tell an pet just how urgently it requirements to perform different points. When we say an pet is hungry or thirsty, we intend that tbelow is somepoint about the state of animal"s nervous system that makes it even more most likely to percreate certain behaviors than others.

Often this have the right to be described by looking at what has taken place to the animal in the previous. For example, Dutchess is much more likely to drink when she has actually not had anypoint to drink in a while, or when it is a specifically hot and also dry day and also she is losing water quicker than normal. Similarly, she will run to the refrigerator even more easily and excitedly if she has actually not consumed for a while - in mental jargon, we would say that she is very urged to get food; she is hungry. We would certainly additionally say that the food is incredibly rewarding to her, and so it urges her to repeat whatever before actions preceded it (in this instance, jumping up my leg.) Here, we view Dutchess in simply such a strongly urged state, trying to get a item of food from my hand:

Now that we"ve come up via a simple answer to the question of why animals do points ("it"s the brain!"), we have the right to work-related on an extra complete answer. Ideally, we desire to describe precisely which components of the brain recognize what is most necessary for an animal to carry out at a particular time. This transforms out to be an overwhelming and complicated problem.

A straightforward answer?

To make the case much easier, let"s move from the fairly complicated people of a pet to the well-controlled human being of a clinical laboratory. A rat (prefer we could study in a mental laboratory) quickly learns to perform a few points as it creates - he deserve to walk, eat food, groom himself, have sex, fight via various other rats, and also so forth. He does not need to learn a lot around these behaviors - he have the right to do them pretty well, though not perfectly, the initially time he tries (provided that he is physically able to.) Other points, though, he have to learn how to execute.

Imagine that we have actually a rat who leads a pretty drab life - we save him in an opaque box, and feed him pellets each day via a slot in the top of the box. One day, we put him in a new box, one through a switch in the facility of the floor. Whenever the rat actions on the switch, a piece of food drops into among the corners of package. The initially time this happens, it happens by accident - the rat has sindicate stumbled on to the button. However, he eagerly eats the food, and also at a particular place in his brain a set of electrical impulses fire (most theories say this happens in a set of frameworks described as the basal ganglia, including structures choose the ventral tegmental location and the nucleus accumbens.) These impulses say to the rest of the brain, albeit in code, that something great has actually simply occurred.

At the exact same time, locations of the rat"s brain that are responsible for memory are active. Over numerous centuries of advancement, brains have actually become extremely logical (at least as soon as it involves acquiring food, or anypoint else that we"d speak to "pleasurable" or "rewarding",) and also so the brain tries to number out what it deserve to execute to gain even more food. Since the last thing the rat did was action on the switch, a collection of transforms happen in the rat"s brain cells that web links the activity of stepping on the button through the goodness of the food. A single repetition of this cycle is not normally sufficient for learning to take area, given that the changes that take location after a solitary event are most likely fairly subtle, however after even more and more cycles of stepping on the button and also eating the resulting food, our rat pertains to learn that one occasion causes the other. At this allude, the brain signals that go together with the act of stepping on the switch and also those that go along with the pleasurable experience of eating become linked to each other - a "memory trace" has actually been developed, and the animal"s habits in the future will reflect this (importantly, he will eat even more tasty food.)

We now have a way of measuring just how a lot the rat desires to obtain food at any kind of specific time - exactly how motivated he is. Suppose that we rise the number of times he needs to push the button to gain some food - he gets food after the first push, however then it has to press the button twice for a solitary morsel, then 4 times, then eight times, then sixteen times, and also so on. We can figure out just how encouraged our rat is to eat by just how much he goes before he decides that it"s not worth it to store trying to acquire the food. If we force-fed our rat, we would find him unwilling to perform any kind of button-pushing to get food; he would certainly simply not be hungry sufficient. If we starved our rat, we would uncover him incredibly eager to press the button.

Variations of this approach have actually been offered to study discovering and impetus in vertebprices for many years - by this point, we have actually a unstable understanding of which structures and chemicals execute what in this procedure. We know that components of the cortex, the wrinkled outermost component of the brain, are connected in making decisions, planning movements, and then sending electric signals to muscles to actually execute the activities. These parts of the cortex have actually several relations with deeper parts of the brain that attend to miscellaneous parts of the decision-making procedure - the limbic device, which is involved in emovement, the hippocampus and amygdala, which are connected in memory and also emovement, and also the basal ganglia, which are associated in learning and the control of activity. All of these devices act together to come up via a arrangement of action in response to a certain setting, which is then sent out to the muscles and also turned into a behavior.

To make the job of explaining how these decisions happen a bit much easier on ourselves, let"s leave out decisions that are based upon most assumed, like selecting a career path or deciding which insurance arrangement to buy. Let"s stick to simple decisions - say, ordering dinner off of a restaurant food selection. If I were at dinner through you, and also I asked you how you decided on a details dish, you hopecompletely wouldn"t describe that uttering the expression "I"ll have the southwestern omelet" had actually been very closely adhered to by rewarding experiences sufficient times in the previous that you had actually learned that this is the best thing to say to a server if you are hungry. Rather, you would say somepoint prefer "It tastes great," or "I like to eat eggs." Your answer would be around pleasure, and particularly around which food you think will carry you the the majority of pleasure.

This appears intuitive - we execute points that make us feel great. In terms of the nervous system, we seem to execute points because they stimulate parts of the brain which, once stimulated, make us feel some sort of pleasure. In the exact same means that you eat a certain food because it brings you more pleasure than an additional, Jackson digs with his food bowl and eats the tastiest pieces first, presumably because they cause specific components of his brain to be active in a means that ends up being pleasurable to him. Let"s take a minute to observe this process before continuing (for the sake of scientific research, of course):

What"s the brain gained to do with it?

Behavioral neuroresearchers have actually been working to number out just how the brain controls motivated behavior for many years. In 1957, 2 psychologists named James Olds and Peter Milner publiburned a report on their exploration that, if they put electrodes in a particular component of a rat"s brain (the medial septum) so that they can stimulate it through electrical energy, the rat would work to receive this stimulation in the exact same way it would job-related to receive food or water. They had found what seemed to be a facility for reward (and/or pleasure) in the brain. Stimulation here appears to signal to animals once somepoint is excellent and also should be sought out.

Later, they found that the same impact occurred once the electrode was inserted right into a group of nerve fibers in the brain dubbed the medial forebrain bundle, which connects the ventral tegpsychological area (a little area in the middle of the brain) to the nucleus accumbens (an additional small location in the middle of the brain.) This stimulation causes signals to be sent out to the nucleus accumbens, wright here the chemical dopamine is released. Since a rat will work-related for this type of stimulation, we recognize that the stimulation is rewarding to the rat; it has actually some home that makes the rat desire even more of it.

To gain a much better handle on what we"re talking about, let"s zoom in on the appropriate component of the brain first.

This is an MRI image that reflects a slice through the middle of somebody"s head. That green spot is the approximate location of the ventral tegpsychological area, or VTA. It receives relationships from many kind of various other locations of the brain. It also sends connections out to many type of areas of the brain, consisting of the nucleus accumbens, or NAc - that green line represents these fibers, the ones in which stimulation deserve to be rewarding.

The nucleus accumbens (its place is shown in pink) receives relations from the ventral tegmental area and the cortex and various other areas of the brain, and sends relationships out the basal ganglia (their approximate place is highlighted in yellow), which manage movement, and these relationships eventually gain to the prefrontal cortex (outlined in blue), which is connected in planning and also decision making. The nucleus accumbens can be divided into a core and also a shell (via the shell wrapped around the core, favor a boiled egg"s white is wrapped about the yolk.) We"ll come back to this in a little bit.

So we know that we execute points because they tend to cause a details sort of task in specific areas of the brain. It appears obvious that we do things bereason they make us feel good. It seems reasonable that the brain activity that encourages us to carry out things additionally plays a function in making us feel great. In fact, the circuits that the nucleus accumbens is part of seem to be central to both the pleacertain we feel and the motivated behavior that it persuades us to perform (choose getting approximately reduced the evening"s 3rd piece of pie while you"re in the middle of composing a blog post, bereason it just tastes so excellent.)

This strikes me as a fairly profound area of clinical research study for a couple of of reasons. For starters, it represents a type of triumph in science"s search to address substantial, important inquiries (like "What makes us happy?", and "Why do we execute the points we do?") While the many type of questions raised in this field aren"t all answered yet, the reward device has been and also proceeds to be a abundant ground for coming up through new methods to study and also think about the brain.

Secondly, researching pleasure, reward and impetus gives us a language via which to talk about not just the habits but the experiences of animals. It"s vital, if we are to share a world with organisms that we cannot talk to, to be able to understand also exactly how they feel points and also why they feel them and why they behave the method that we carry out.

Lastly, pleacertain and incentive are central to living, and also especially central to living an excellent life. Undoubtedly pleasure is not tantamount to happiness, however it is difficult to imagine happiness existing without pleasure. It is pleacertain (and also displeasure) that provides texture and also humankind to what would otherwise be a machine-prefer, pucount practical existence. To imagine a civilization wbelow civilization lacked the capability to favor and disprefer things is, in reality, imagining a people devoid of world as we know them - the abilities to prefer and also to desire are what provide life interpretation. It is uniquely humbling to realize that something so main to huguy experience as pleacertain arises from the task of neurons, from an excellent, complex, mostly-unfound dance of energy and molecules inside each of our heads.

All that sentipsychological stuff aside, we"ve pertained to a problem. If "pleasure" (a subjective feeling) and also "reward" (a signal that teaches us to perform things) both cause the exact same actions, and also both aincrease from the very same sort of task in the same part of the brain, are they various at all? Why carry out we should talk about "pleasure" at all, especially when we"re talking about animals (prefer my pet rabbits, that can"t talk to us and also tell us what they feel, no issue exactly how a lot I may wish they could)? Why talk about pets "experiencing" things as soon as it"s so much simpler to talk about pets "responding"?

Psychology has actually a lengthy background of about pleasure and also reward as the same point, accidentally or not. For psychologists who were (and are) came to mainly through measuring actions, it regularly seems unessential or also absurd to talk about pleacertain, once "reward" explains the exact same thing yet does not suggest that the actions you are studying count on anything as etheactual as a "feeling". Even if you recognize that the organism most likely feels somepoint that goes together with reward, "pleasure" and "reward" appear to be so close to the exact same point that tbelow is no clear way to sepaprice them - they have the very same impacts, they are resulted in by the same stimuli, and they also (utilizing some straightforward measurements) appear to aclimb from the very same structures in the brain.

The story, it transforms out, is not so easy.

Liking, wanting, and also the nucleus accumbens

Three researchers (Kent Berridge, Terry Robinkid, and also J. Wayne Aldridge) freshly publimelted a record summarizing a line of research they and many others have been functioning on given that at least the early 1980"s. Their findings argue that liking somepoint and also wanting something are actually dissociable in the brain - that they rely on the task of different neurons, so you can have one without the other. As they say in the 2009 research report: "Generally a mind "likes" the rewards that it "wants". But periodically it might simply "want" them."

A corollary to this is: "Sometimes the brain might simply "like" points," a concept which has led some to propose that the people would certainly be better if we all had actually electrodes inside of our head that would stimulate our brains in a pleasurable way. It transforms out, as Berridge and Morten Kringelbach cite in a later publication, that the few ethically questionable experiments that have been done making use of brain self-stimulation in people did not seem to develop happy human being - occasionally they developed human being that were very encouraged to push a switch to get brain stimulation, and also sometimes (as is the instance through even more current studies of brain stimulation for depression) they have helped human being to not feel fairly as poor as they did.

Besides being amazing to philosophers and also utopian dreamers, this area of study is of interemainder to healthtreatment practitioners and also their patients because figuring out what renders somebody "like" doing something and also what renders them "want" to perform something might assist us treat disorders in which these processes go wrong - for example, in depression, obsessive compulsive disorder, and also drug addiction.

Before we acquire as well worried about the implications of this idea, though, let"s watch what kind of evidence tbelow is to earlier it up.

First, the researchers required a means to meacertain exactly how a lot pleacertain an pet gets from somepoint. More importantly, they needed to measure exactly how a lot an pet likes something without measuring motivation - that is, in a way that doesn"t rely on the pet seeking out or consuming that point. To show the difficulty, think of our button pushing rat - in that design, we are measuring how a lot the pet desires the food. It may seem that an pet would only work for things it likes, yet if we want to display that wanting and liking have the right to be separated from each other, we need an independent measurement of each.

It turns out that it"s straightforward to measure exactly how much an individual likes somepoint, if you usage the ideal type of thing. Tastes turn out to be well-suited for this. Think around it: a good method to determine whether somebody likes or dislikes the taste of somepoint is to watch its face as it tastes the substance. It transforms out that this approach have the right to be supplied (even more or less efficiently, relying on that you ask) to recognize whether humale babies, primate infants, and also rats like or dislike a taste. Of course, the Youtube-watching public is currently familiar with the use of this approach in humans:

Somejust how, I doubt this would be a beneficial method to usage through my rabbits, whose deals with seem to be permanently solved in a single expression: grumpy.

Berridge, Robinkid, and Aldridge argue that huguy infants, some primates, and also rats make comparable encounters once they like or dislike a taste, and also that these encounters can quantified in a means that produces beneficial clinical data. Using this measurement, as well as even more standard dimensions of exactly how difficult pets will certainly job-related for a reward, they and also other researchers have displayed that there are instances in which an animal"s noticeable "like" of a food item deserve to be separated from its "want" for that food.

For example, in one experiment Berridge and also his collaborator Elliot Valenstein investigated why a specific form of electric brain stimulation reasons pets to eat. When they provided rats this kind of stimulation (of the lateral hypothalamus) it brought about some of the rats to seek food more strongly than rats that didn"t get the stimulation. After selecting a team of rats in whom this stimulation caused feeding, the researchers tested whether that stimulation influenced the faces they made in response to various tastes.

If pleacertain and inspiration constantly go together, one would expect that as the animals were more urged to eat food, good-tasting points would also taste much better to them. In fact, the rats" facial reactions to sweet tastes did not markedly change while they were receiving brain stimulation. Their responses to sour tastes did change in some instances, indicating that bad tastes actually tasted worse in the time of the brain stimulation. It appeared that the stimulation made the rats "want" the food, but it did not make them "like" the food any kind of more.

In another examine Berridge and also his coworker Susana Pecina wanted to know if liking and wanting were brought about by various teams of brain cells. Opiate drugs (favor morphine, which Berridge and also Pecina supplied in their study) both feel great and also are rewarding - they affect both pleasure and motivation. Prior to this study, it had actually been displayed that once opiate drugs are put right into any kind of component of the nucleus accumbens, they encourage rats to eat - they made the rats even more urged to eat. The experimenters wanted to find out, though, what kind of result the very same drugs had actually on the pleasure (or the "hedonic impact") of eating once injected right into the nucleus accumbens.

Their procedure was elegant: they implanted needles into the nucleus accumbens of rats, then provided them injections of morphine directly into the nucleus accumbens just prior to giving them either sugar or quinine, a bitter chemical discovered in tonic water. By varying the place of the implanted needle, they built up a map of nucleus accumbens showing the places wbelow morphine influenced how a lot the rats chosen or disfavored the tastes. Using a procedure wbelow rats got morphine injections simply before being permitted to push a lever to receive food, they gathered another map mirroring where in the nucleus accumbens the morphine made the rats desire the food even more.

When morphine was injected almost everywhere in the nucleus accumbens, it made the rats spfinish more time finding, manipulating, and eating food - it boosted their incentive to attain and also eat food. It was only as soon as morphine was injected right into a smaller sized area in the facility of the nucleus that the rats showed even more positive reactions to sweet tastes, though. This suggests that in a specific location in the shell of the nucleus accumbens, morphine injections made the rats want food more, but didn"t make them choose the taste of it any type of more.

These results make the situation that liking and also wanting have the right to be separated from each various other both in habits and in the anatomy of the brain. It"s amazing to note that tbelow was no area of the nucleus accumbens in Berridge and Pecina"s map that was solely responsible for the pleasure-enhancing impacts of morphine - they could acquire wanting without liking, however not the various other method around.

In fact, pleasure and also catalyst appear to be distinct procedures in many kind of more methods than this, even if they are linked through each other both in everyday life and in the anatomy of the brain. Berridge"s functions define "hotspots" of pleasure in the brain, which are certain locations where certain kinds of task or drugs produce pleacertain in means that may or might not be linked via alters in incentive - these encompass the nucleus accumbens and also VTA, as I stated over, yet also parts of the cortex and also other frameworks in the brain. By perdeveloping many kind of experiments investigating the attributes of many kind of locations of the brain, researchers are structure maps that explain wright here, why, and also just how our brains identify our actions. These maps recurrent the initially procedures in answering that deceptively straightforward question: why execute we execute what we do?

Filling in the holes

It is excellent to save in mind that the findings I"ve debated are infinish - it turns out that many type of of the brain"s “pleasure centers” have a range of attributes, namong which are as simple as I"ve made out the duty of nucleus accumbens in pleasure to be. In addition, pleacertain and also reward, prefer the majority of features of the brain, show up to arise from extremely complicated arrangements of cells spcheck out throughout the brain. It is impossible to take exceptionally complicated behaviors (choose pursuing objectives and also enjoying getting to them) and also collapse them down right into a details sort of task of a little structure in the brain.

Tright here is so much research study going on in this location of neuroscience that it"s difficult for me to tell the entirety story - I hope I have conveyed some of the excitement of it, though. These research studies stand also as a proof-of-principle that wanting somepoint and also liking it may be very various procedures. If nothing else, the trouble of differentiating pleasure from reward serves as an instance that also the a lot of intuitively sensible concepts around behavior are likely to be wrong in some means, or are at leastern worth looking at critically.

As even more research studies have been (and also continue to be) publiburned, such results are disputed, suggested over, expanded, and corrected. The initially hundred-some years of neuroscientific research have actually left us with a fragmented and rapidly altering picture of just how motivation functions, and also I suspect that the research study done in the next a century will continue to fill in the holes in our map of the brain, also if it"s never completed.

Nevertheless, I still have actually that prodiscovered, romantic feeling around the research of inspiration and also pleacertain. It offers me many kind of tiny moments of awe to think about all the complex things that go into impetus, whether it"s a toddler standing on her tip-toes to reach the optimal shelf of the refrigerator wright here the cocoa milk is, a shopper deciding which automobile to buy, a rablittle begging for a treat, a rat pushing a button, or myself deciding what to eat. Many of all, it reminds me of the factor that I was drawn to study neuroscience in the initially place: to understand humankind, to understand also why we execute what we execute, we should understand also the body, and most of all the brain.

See more: Which Statement Explains The Difference Between Multiple Alleles And Polygenic Inheritance?

OLDS J, & MILNER P (1954). Hopeful reinforcement produced by electrical stimulation of septal area and also other areas of rat brain. Journal of comparative and also physiological psychology, 47 (6), 419-27 PMID: 13233369

Berridge KC, Robinkid TE, & Aldridge JW (2009). Dissecting components of reward: "liking", "wanting", and also discovering. Current opinion in pharmacology, 9 (1), 65-73 PMID: 19162544

Berridge, K. (1996). Food reward: Brain substprices of wanting and liking Neuroscience & Biobehavioral Reviews, 20 (1), 1-25 DOI: 10.1016/0149-7634(95)00033-B

Berridge, K., & Valenstein, E. (1991). What mental procedure mediates feeding evoked by electrical stimulation of the lateral hypothalamus? Behavidental Neuroscience, 105 (1), 3-14 DOI: 10.1037//0735-7044.105.1.3

Peciña S, & Berridge KC (2005). Hedonic warm spot in nucleus accumbens shell: where carry out mu-opioids reason enhanced hedonic affect of sweetness? The Journal of neuroscience : the main journal of the Society for Neuroscientific research, 25 (50), 11777-86 PMID: 16354936

PECINA, S. (2008). Opioid reward "liking" and also "wanting" in the nucleus accumbens Physiology & Behavior, 94 (5), 675-680 DOI: 10.1016/j.physbeh.2008.04.006

Image credits: All photos except for the MRI photo (which was released under an Creative Commons Attribution-Shareachoose 2.0 generic license by Flickr user everyone"s idle ) were taken by Michael Lisieski, and also are licensed under a Creative Commons Attribution-NonCommercial0ShareAfavor 3.0 Unported License.

About the Author: Michael Lisieski is an undergraduate student pursuing degrees in Pharmacology and Psychology in Buffalo, New York, where he resides with his wife, three rabbits, and also a leopard gecko. His major expert interests are in examining and also dealing with drug addiction. He writes around cephalopods in science and also society at Cephalove, and also tweets around whatever else as