<p>Obviously, pain and touch receptors are represented by entirely different receptors in the skin, <em>i.e.</em> <a href="https://en.wikipedia.org/wiki/Nociceptor#:" rel="nofollow noreferrer">nociceptors</a> and <a href="https://en.wikipedia.org/wiki/Cutaneous_receptor" rel="nofollow noreferrer">mechanoreceptors</a>, respectively. Each has physically different afferents that carry the signal to the brain. Pleasant touch is mediated by C-tactile afferents to the brain, represented by low-threshold non-myelinated C-fibers <a href="https://www.sciencedirect.com/science/article/pii/S2452073X18300229" rel="nofollow noreferrer">(Nees <em>et al</em>., 2019</a>. Pain is mainly mediated via Aδ and C fibers <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/pain-receptor#:%7E:text=Pain%20receptors%2C%20also%20called%20nociceptors,and%20most%20of%20visceral%20organs." rel="nofollow noreferrer">(Beissner <em>et al</em>., 2010)</a>. Hence, different afferent pathways to the S1 exist from the periphery to the brain.</p>
<p>Once in the brain, there is no such thing as a single localized 'pain center', as proposed by Descartes in the early days (<a href="https://www.nlc-bnc.ca/obj/s4/f2/dsk1/tape2/PQDD_0033/MQ64365.pdf" rel="nofollow noreferrer">Ha, 2000)</a>. In fact, SI cannot be called the 'pain center', as ablation of this cortical region leads to an altered perception of pain, rather than its disappearance <a href="https://www.sciencedirect.com/science/article/abs/pii/S1082317496800262#:%7E:text=Pages%20174%2D180-,Primary%20somatosensory%20cortex%20and%20pain%20perception%3A%20Yes%20sir%2C%20your%20pain,in%20your%20head%20(Part%20I)&amp;text=This%20Focus%20article%20proposes%20that,as%20any%20other%20novel%20stimulus." rel="nofollow noreferrer">(Backonja, 1996)</a>. Pain perception involves many more brain centers, including S2, and those involved in higher cognitive and emotional-motivational processes, such as the orbitofrontal cortex (OFC), the anterior cingulate cortex (ACC), the ventral striatum (VS), and the insular cortex <a href="https://www.sciencedirect.com/science/article/pii/S2452073X18300229" rel="nofollow noreferrer">(Nees <em>et al</em>., 2019</a>.</p>
<p>In the brain, pleasant touch seems mediated by a set of brain regions overlapping with that of pain, involving the insula, considered to be the primary somatovisceral cortex and connections to the striatum <a href="https://www.sciencedirect.com/science/article/pii/S0376871613003311?casa_token=W1HFjAvr2N4AAAAA:Yx98lsVnynJ93xSuSixyR6nAoCJAAketVI-hwoe7xf97bYujMdMnG5jmyF-oopd0RQkfDtmfsFI" rel="nofollow noreferrer">(Migliorini <em>et al</em>., 2013)</a> and ACC. Interestingly, however, pleasant touch was also shown to activate the nucleus accumbens <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/hbm.23679" rel="nofollow noreferrer">(Kreuder <em>et al</em>., 2017)</a>.</p>
<p>In all, to me it seems the pathways largely overlap centrally, barred the activation of the nucleus accumbens for pleasurable tactile stimuli, which is consistent with it being a <a href="https://en.wikipedia.org/wiki/Nucleus_accumbens" rel="nofollow noreferrer">pleasure center</a>. I think there must be specific connections that are separated very early in the very periphery through a different set of skin receptors that signal to different neurons in brain regions that largely overlap between the two modalities.</p>
<p><sub><strong>References</strong><br />
<strong>-</strong> <a href="https://www.sciencedirect.com/science/article/abs/pii/S1082317496800262#:%7E:text=Pages%20174%2D180-,Primary%20somatosensory%20cortex%20and%20pain%20perception%3A%20Yes%20sir%2C%20your%20pain,in%20your%20head%20(Part%20I)&amp;text=This%20Focus%20article%20proposes%20that,as%20any%20other%20novel%20stimulus." rel="nofollow noreferrer">Backonja, <em>Pain Forum</em> (1996); <strong>5</strong>(3): 174-80</a><br />
<strong>-</strong> <a href="https://www.sciencedirect.com/topics/immunology-and-microbiology/pain-receptor#:%7E:text=Pain%20receptors%2C%20also%20called%20nociceptors,and%20most%20of%20visceral%20organs." rel="nofollow noreferrer">Beissner <em>et al</em>., <em>Encyclopedia of the Neurological Sciences</em> 2<sup>nd</sup> ed., 2014</a><br />
<strong>-</strong> <a href="https://www.nlc-bnc.ca/obj/s4/f2/dsk1/tape2/PQDD_0033/MQ64365.pdf" rel="nofollow noreferrer">Ha, MSc thesis, McGill University, Montreal, 2000</a><br />
<strong>-</strong> <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/hbm.23679" rel="nofollow noreferrer">Kreuder <em>et al</em>., <em>Human Brain Mapping</em> (2017); <strong>38</strong>(9): 4525-34</a><br />
<strong>-</strong> <a href="https://www.sciencedirect.com/science/article/pii/S0376871613003311?casa_token=W1HFjAvr2N4AAAAA:Yx98lsVnynJ93xSuSixyR6nAoCJAAketVI-hwoe7xf97bYujMdMnG5jmyF-oopd0RQkfDtmfsFI" rel="nofollow noreferrer">Migliorini <em>et al</em>., <em>Drug and Alcohol Dependence</em> (2013); <strong>133</strong>(2): 661-8</a><br />
<strong>-</strong> <a href="https://www.sciencedirect.com/science/article/pii/S2452073X18300229" rel="nofollow noreferrer">Nees <em>et al</em>., <em>Neurobiology of Pain</em> (2019); <strong>5</strong>: 100025</a>
</sub></p>

CC BY-SA 4.0
2020-12-17T21:12:45.953Z
2020-12-17T21:12:45.953Z
AliceD
<p>A <a href="https://psychology.stackexchange.com/questions/20736/is-there-a-region-of-the-brain-that-mediates-pain-a-la-mesolimbic-pathway">recent question</a> here  asked about (mostly) how pain and pleasure are differentiated in pathways involving reward/aversion cues. But there was some confusion as to what the question really wanted to ask as it also mentioned &quot;somatosensory mapping&quot;.</p>
<p>A reasonably different but also good question is how are pleasure and pain decoded before it gets to any feedback/reinforcement pathways, i.e. how are pain and pleasure distinguished in the somatosensory cortex. This discussion probably involves considering the way such stimuli are transmitted/encoded from the peripheral nervous system, (e.g. <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/exd.12639" rel="nofollow noreferrer">Lloyd, et al. 2015</a>)</p>
<blockquote>
<p>The skin senses serve a discriminative function, allowing us to manipulate objects and detect touch and temperature, and an affective/emotional function, manifested as itch or pain when the skin is damaged. Two different classes of nerve fibre mediate these dissociable aspects of cutaneous somatosensation: (i) myelinated A-beta and A-delta afferents that provide rapid information about the location and physical characteristics of skin contact; and (ii) unmyelinated, slow-conducting C-fibre afferents that are typically associated with coding the emotional properties of pain and itch. However, recent research has identified a third class of C-fibre afferents that code for the pleasurable properties of touch - c-tactile afferents or CTs.</p>
</blockquote>
<p>To keep answers to this question reasonably short, let's ask just how is tactile pleasure distinguished from (tactile) pain in the brain.</p>
<h2>References</h2>
<p>Lloyd, D. M., McGlone, F. P., &amp; Yosipovitch, G. (2015). Somatosensory pleasure circuit: from skin to brain and back. <em>Experimental dermatology</em>, 24(5), 321-324. doi: <a href="https://doi.org/10.1111/exd.12639" rel="nofollow noreferrer">10.1111/exd.12639</a><br>Free Full Text: <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/exd.12639" rel="nofollow noreferrer">https://onlinelibrary.wiley.com/doi/full/10.1111/exd.12639</a><br>Free PDF: <a href="https://onlinelibrary.wiley.com/doi/epdf/10.1111/exd.12639" rel="nofollow noreferrer">https://onlinelibrary.wiley.com/doi/epdf/10.1111/exd.12639</a></p>

CC BY-SA 4.0
2018-09-21T16:26:29.917Z
Actually, it looks like we'd have to involve more than the somatosensory cortex in an answer just about discrimination. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4879201/
got trolled too much this week
<neuroscience><perception><neurophysiology><brain><sensory-perception>
How are tactile pleasure and pain differentiated in the somatosensory cortex?
got trolled too much this week
# How are tactile pleasure and pain differentiated in the somatosensory cortex?

(Asked by: username_0 on 2018-09-21)

A [recent question](https://psychology.stackexchange.com/questions/20736/is-there-a-region-of-the-brain-that-mediates-pain-a-la-mesolimbic-pathway) here asked about (mostly) how pain and pleasure are differentiated in pathways involving reward/aversion cues. But there was some confusion as to what the question really wanted to ask as it also mentioned "somatosensory mapping".

A reasonably different but also good question is how are pleasure and pain decoded before it gets to any feedback/reinforcement pathways, i.e. how are pain and pleasure distinguished in the somatosensory cortex. This discussion probably involves considering the way such stimuli are transmitted/encoded from the peripheral nervous system, (e.g. [Lloyd, et al. 2015](https://onlinelibrary.wiley.com/doi/full/10.1111/exd.12639))

> The skin senses serve a discriminative function, allowing us to manipulate objects and detect touch and temperature, and an affective/emotional function, manifested as itch or pain when the skin is damaged. Two different classes of nerve fibre mediate these dissociable aspects of cutaneous somatosensation: (i) myelinated A-beta and A-delta afferents that provide rapid information about the location and physical characteristics of skin contact; and (ii) unmyelinated, slow-conducting C-fibre afferents that are typically associated with coding the emotional properties of pain and itch. However, recent research has identified a third class of C-fibre afferents that code for the pleasurable properties of touch - c-tactile afferents or CTs.

To keep answers to this question reasonably short, let's ask just how is tactile pleasure distinguished from (tactile) pain in the brain.

## References

Lloyd, D. M., McGlone, F. P., & Yosipovitch, G. (2015). Somatosensory pleasure circuit: from skin to brain and back. *Experimental dermatology*, 24(5), 321-324. doi: [10.1111/exd.12639](https://doi.org/10.1111/exd.12639)  
Free Full Text: <https://onlinelibrary.wiley.com/doi/full/10.1111/exd.12639>  
Free PDF: <https://onlinelibrary.wiley.com/doi/epdf/10.1111/exd.12639>

**Tags:** neuroscience, perception, neurophysiology, brain, sensory-perception

> **Comments:**
> **username_0**: Actually, it looks like we'd have to involve more than the somatosensory cortex in an answer just about discrimination. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4879201/  

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## 1 answers

### Answer by username_1 on 2020-12-17. Score: 2

Obviously, pain and touch receptors are represented by entirely different receptors in the skin, *i.e.* [nociceptors](https://en.wikipedia.org/wiki/Nociceptor#:) and [mechanoreceptors](https://en.wikipedia.org/wiki/Cutaneous_receptor), respectively. Each has physically different afferents that carry the signal to the brain. Pleasant touch is mediated by C-tactile afferents to the brain, represented by low-threshold non-myelinated C-fibers [(Nees *et al*., 2019](https://www.sciencedirect.com/science/article/pii/S2452073X18300229). Pain is mainly mediated via Aδ and C fibers [(Beissner *et al*., 2010)](https://www.sciencedirect.com/topics/immunology-and-microbiology/pain-receptor#:%7E:text=Pain%20receptors%2C%20also%20called%20nociceptors,and%20most%20of%20visceral%20organs.). Hence, different afferent pathways to the S1 exist from the periphery to the brain.

Once in the brain, there is no such thing as a single localized 'pain center', as proposed by Descartes in the early days ([Ha, 2000)](https://www.nlc-bnc.ca/obj/s4/f2/dsk1/tape2/PQDD_0033/MQ64365.pdf). In fact, SI cannot be called the 'pain center', as ablation of this cortical region leads to an altered perception of pain, rather than its disappearance [(Backonja, 1996)](https://www.sciencedirect.com/science/article/abs/pii/S1082317496800262#:%7E:text=Pages%20174%2D180-,Primary%20somatosensory%20cortex%20and%20pain%20perception%3A%20Yes%20sir%2C%20your%20pain,in%20your%20head%20(Part%20I)&text=This%20Focus%20article%20proposes%20that,as%20any%20other%20novel%20stimulus.). Pain perception involves many more brain centers, including S2, and those involved in higher cognitive and emotional-motivational processes, such as the orbitofrontal cortex (OFC), the anterior cingulate cortex (ACC), the ventral striatum (VS), and the insular cortex [(Nees *et al*., 2019](https://www.sciencedirect.com/science/article/pii/S2452073X18300229).

In the brain, pleasant touch seems mediated by a set of brain regions overlapping with that of pain, involving the insula, considered to be the primary somatovisceral cortex and connections to the striatum [(Migliorini *et al*., 2013)](https://www.sciencedirect.com/science/article/pii/S0376871613003311?casa_token=W1HFjAvr2N4AAAAA:Yx98lsVnynJ93xSuSixyR6nAoCJAAketVI-hwoe7xf97bYujMdMnG5jmyF-oopd0RQkfDtmfsFI) and ACC. Interestingly, however, pleasant touch was also shown to activate the nucleus accumbens [(Kreuder *et al*., 2017)](https://onlinelibrary.wiley.com/doi/full/10.1002/hbm.23679).

In all, to me it seems the pathways largely overlap centrally, barred the activation of the nucleus accumbens for pleasurable tactile stimuli, which is consistent with it being a [pleasure center](https://en.wikipedia.org/wiki/Nucleus_accumbens). I think there must be specific connections that are separated very early in the very periphery through a different set of skin receptors that signal to different neurons in brain regions that largely overlap between the two modalities.

**References**  
**-** [Backonja, *Pain Forum* (1996); **5**(3): 174-80](https://www.sciencedirect.com/science/article/abs/pii/S1082317496800262#:%7E:text=Pages%20174%2D180-,Primary%20somatosensory%20cortex%20and%20pain%20perception%3A%20Yes%20sir%2C%20your%20pain,in%20your%20head%20(Part%20I)&text=This%20Focus%20article%20proposes%20that,as%20any%20other%20novel%20stimulus.)  
**-** [Beissner *et al*., *Encyclopedia of the Neurological Sciences* 2nd ed., 2014](https://www.sciencedirect.com/topics/immunology-and-microbiology/pain-receptor#:%7E:text=Pain%20receptors%2C%20also%20called%20nociceptors,and%20most%20of%20visceral%20organs.)  
**-** [Ha, MSc thesis, McGill University, Montreal, 2000](https://www.nlc-bnc.ca/obj/s4/f2/dsk1/tape2/PQDD_0033/MQ64365.pdf)  
**-** [Kreuder *et al*., *Human Brain Mapping* (2017); **38**(9): 4525-34](https://onlinelibrary.wiley.com/doi/full/10.1002/hbm.23679)  
**-** [Migliorini *et al*., *Drug and Alcohol Dependence* (2013); **133**(2): 661-8](https://www.sciencedirect.com/science/article/pii/S0376871613003311?casa_token=W1HFjAvr2N4AAAAA:Yx98lsVnynJ93xSuSixyR6nAoCJAAketVI-hwoe7xf97bYujMdMnG5jmyF-oopd0RQkfDtmfsFI)  
**-** [Nees *et al*., *Neurobiology of Pain* (2019); **5**: 100025](https://www.sciencedirect.com/science/article/pii/S2452073X18300229)


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