Brain size relative to pain?

[Scott]

I heard or read somewhere that the bigger the brain, the more pain the creature would feel, and the smaller, the less pain.

 

I was wondering if this is correct.

[Glider]

Not necessarily. It's going to depend on the systems within the brain/nervous system. Obviously, something with an extremely tiny brain (e.g. invertebrates) is less likley to have the mechanisms required to produce the experience of pain, but mammals all have more or less the same structures to varing degrees, so whilst the brain of a cat is a lot amller than the brain of a human, cats can experience pain very well.

 

The problem is that pain is a psychological state, so the ultimate experience will be determined by the psychology of the organism experiencing it. Humans, for example, have expectancies concerning the meaning and probable outcomes of our situation, which many animals don't have. So, for example, take two male humans, one of whom has been warned by his doctor to quit smoking, lose weight and so-on because he is at risk of a heart attack. The other male has been given a clean bill of health. Both go to a business dinner and both subsequently suffer severe indegestion (i.e. a burning chest pain). Do you think that each of these two will experience the pain in the same way? (hint: No). The one that was warned will suffer a lot more because his pain also includes heightened anxiety, fear (of death) and so on. But they both have brains of the same size.

[birdo118]

The problem with that theory is that pain is based on the number of pain receptors in the body, not on the number of neurons in the brain. Because of this, an animal with many pain receptors will feel more pain. I know people that have had trauma and have lost some pain response. This is caused by the destruction of receptors. As Glider said, an animal must have the proper mechanisms to experience pain, or they will be unable to do so. These mechanisms are the receptors, and the pain is interpreted by the neurons. The receptors "feel" the pain, while the brain interprets it. Becuase of this, the brain just needs to be advanced enough to interpret pain signals from the receptors.

[YT2095]

Curiosity then...

 

IF we KNOW this and truly beleive it, how come stuff can still hurt?

surely there MUST be a way to accept and acknowledge that all it is, is just a purely chemical reaction (for wants of a better word) and the pain should just go?

 

so what ACTUALY hurts???

[Glider]

Well this is where it gets tricky, because here you have to start differentiating between nociception and pain. Nociception refers to the physiological detection, transduction and transmission of noxious stimuli (and nociceptive volleys) to the brain. Pain refers to the ultimate experience. Even then, the experience can be subclassified into to components pain and suffering (for example, morphine, the most effective known analgesic, exerts it greates influence on the suffering component of pain, rather than the nociceptive component).

 

Believe it or not, nociception and pain are not directly linked in a rigid cause/effect relationship. They only correlate. The ultimate experience has been shown to be largely independent of the frequency of nociceptive volleys. In other words, the intensity of the stimulus (higher intensity = higher frequencly nociceptive volleys), is not directly related to the intensity of the experience. Whilst as a general rule, there is a 'working correlation', e.g. the higher the stimulus intensity, the greater the experience of pain, there are too many exceptions to accept a direct causal relationship.

 

Examples of the dissociation exist at both ends of the continuum, e.g. at one end there are examples of pain (real pain) with no organic cause, i.e. no nociceptive activity at all (thelamic pain is an example of this). At the other end, there are examples of significant physical trauma, that does not result in pain, e.g. the Indian hook swinging ceremony, surgery under hypnosis etc.. This latter phenomenon supports YT's contention of 'there must be a way to make it go'. I believe there is, but we haven't found it yet.

 

However, as an aside, the ultimate aim is to control pain, not to abolish it. Pain is absolutely necessary for survival.

[Glider]

The problem with that theory is that pain is based on the number of pain receptors in the body, not on the number of neurons in the brain.

This is not strictly true, partly because of what I explained in my previous post, and partly because there isn't really any such thing as a pain receptor.

 

In humans, there are receptors associated with nociception, but they are not strictly speaking, pain receptors. For example, there are two classes of primary afferent fibres; A-Delta and C fibres. A-Delta are associated with sharp, fast pain (they are small diameter, thinly mielinated fibres). C fibres are associates with slow aching and burning pain (they are small diameter, non-myelinated fibres with slow conduction rates of around 0.5 meters s1). However, C fibres are polymodal, they are triggered by a wide range of stimuli and are particularly associated with detection of temperature change, as well as noxious heat (>~58 degrees C) and cold. Volleys in A-Delta and C fibres are associated with pain, but do not necessarily result in pain as they have other functions.

 

Pain is actually based on neurological interpretation of incoming primary afferent volleys. The experience of pain is a result of the way in which the brain processes and interprets these incoming volleys. Pain itself is a psychological state and as such is sensitive to psychological intervention. Therefore, the ultimate experience of pain is more dependent on the brain and its systems than on the numbers of 'nociceptive' receptors.

[YT2095]

I`m going to stick my neck out now and risk sounding like a complete nutbar.

 

I`ve found that with Some types of pain (Idealy the constant type, not spurious) that Visualisation can actualy remove it, I need to be away from distractions and be relaxed (horizontaly polarised in bed is ideal).

I picture the pain as an entity with a border, maybe like a tennis ball or something, but it`s key to give it a shape and recognise and accept it.

then slowly you can shrink this shape and the pain actualy starts to diminish! at 1`st it`s all to easy to get excited that it`s working and snap back to full pain again, but with practice it works.

eventualy I get the pain down to something so tiny it feels like a pin sticking in me, again I recognise and accept this, I then use a hand and pull this pin out and the pain is totaly gone!

I can stay in this state for as long as I`m undisturbed, often long enough to get to sleep, or even just long enough to enjoy the reprive until I`m ready to face it again and go about my daily life, it always comes back, i`ve not yet found a way to keep it "held" in that position/status.

 

would this be a self hypnosis?

[Glider]

I don't know that much about the mechanisms of hypnosis, but it sounds like it might have elements in common. It actually sounds more analogous to some of the visualisation techniques used in chronic pain management.

[YT2095]

that adds up, I use it mostly when I`m having a bad time with arthritis, I`ve tried it for toothache also, but that doesn`t work as well for some reason?

[Glider]

Toothace and orofacial pain like myalgia aren't subject to central control mechanisms to the same degree as somatic pain. We have our own mechanisms of pain control, which originates in the periaqueductal grey area (PAG; a nucleus around the cerebral aqueduct). This projects down through the raphe magnus nucleus in the brain stem and down the raphespinal tract. It terminates in the dorsal horn of the spinal cord, which is where the incoming primary afferents enter.

 

Stimulation of the PAG has been shown to produce profound analgesia in rats, and has also shown significant effects in humans. However, toothache and other orofacial pain is mediated by cranial nerves V & VII (Trigeminal and Facial) which don't enter the spine, but project straight to the brain, and so are not subject to this central control mechanism.

[Kygron]

I recently dislocated my shoulder (remind me NOT to stray from the subject...). I remember a nurse in the hospital mentioning how much pain I was in. I was really surprized when she said this! I didn't consider myself in pain at all. It was more like extreme discomfort (pain? lol). I was conciously aware that all those feelings came from the fact that my muscles were streched out. If it weren't for simple stretched muscles I knew that I wouldn't be in pain at all.

 

Perhaps this was an example of my mind NOT recognizing pain? Clearly I appeared to be in pain. I was actually facinated (at the time) by the fact that my muscles kept right along with feeling streched instead of pretending for the moment that this was normal.

[Kygron]

that adds up, I use it mostly when I`m having a bad time with arthritis, I`ve tried it for toothache also, but that doesn`t work as well for some reason?

 

don't give up! you can train your brain to do anything!

 

However, as an aside, the ultimate aim is to control pain, not to abolish it. Pain is absolutely necessary for survival.

 

just don't forget to see your dentist

[YT2095]

another pain type question, Why do things seem to hurt more when you`re cold?

 

I`ve noticed that if I`m working outdoors in the cold and maybe my finger gets a light impact (maybe the corner of a peice of wood) nothing that breaks the skin or even scratches it, It really hurts quite a bit, and yet the same thing when I`m hot and I probably wouldn`t even notice it or feel it?

[Glider]

This is because large sensory fibres begin to struggle with transmission at around 7 degrees C, but the primary afferents (associated with pain), particularly C fibres, don't stop until about 4 degrees C. So, put simply, when you're hands/legs whatever are very cold, the only fibres left working efficiently are pain fibres. That's why it hurts so much more to get hit in the leg with a footbal in the winter, than in the summer.

[YT2095]

so it actualy hurts the SAME when both are working in the heat, but part of the signal is tactile and provides "interferance" to the pain signals?

 

somethimes I don`t understand your posts, it`s a little above my head in this area, sorry

[Glider]

That pretty much it. The stimulus of getting hit in the leg with a football will be the same, summer or winter, but in the summer, the large, fast conducting fibres run interference. The signals they conduct dampens the signals from the slower primary afferents associated with pain (Gate Control Theory of Pain; Melzack & Wall). In the winter, when your skin temperatue drops, it knocks out these larger fibres and their dampening effect, so the majority of the signals you get is from pain associated fibres, so though the stimulus is the same, it hurts more.