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Robotic Brain Universe

The limbic system, cingulate and insula

How the brain's inner rim and the hidden insula sense the body, shape feelings, register pain and conflict, and how stimulators and decoders now target mood.

Intermediate · about 10 min · updated 2026-10-02 · awaiting clinical review

See it in 3D:

Illustrative simulation excitatory inhibitory

Broca's limbic lobe, the Papez circuit and MacLean's limbic system; the four-region cingulate, the insula and the amygdala; interoception and interoceptive inference; pain affect and conflict monitoring; fear learning and associability; amygdala and insula lesions; deep brain stimulation for depression and its trials; mood decoding and closed-loop stimulation.

Contents
  1. Feeling from the inside
  2. What the limbic regions are
  3. Why we need them
  4. How feelings may be built
  5. When: moments, days and months
  6. When they fail
  7. Models of learning, conflict and feeling
  8. Technology: stimulators and mood decoders
  9. Milestones
  10. Frontiers
  11. Check yourself

Feeling from the inside

Researchers exposed a patient known as SM, whose amygdalae are damaged on both sides, to live snakes and spiders, a haunted house and frightening films. SM never showed fear and never reported more than minimal fear, yet could experience other basic emotions.[1]

Smokers with brain damage involving the insula were more likely than other brain-damaged smokers to stop smoking easily and immediately, without relapse and without the urge to smoke.[2]

This reading explores the brain's inner rim, the region once called the limbic lobe (from the Latin limbus, border), together with the insula folded inside the lateral sulcus: how they sense the body, colour experience with feeling, register pain and conflict, and what happens when they fail. It also looks at the stimulators and decoders now being aimed at mood.[3,4]

What the limbic regions are

The limbic lobe. In 1878 Broca called the curved rim of cortex including the cingulate and parahippocampal gyri, the great limbic lobe. A white matter bundle, the cingulum, runs within this rim, joining the cingulate and parahippocampal gyri.[3]

A circuit for emotion. In 1937 Papez proposed that 'the hypothalamus, the anterior thalamic nucleus, the cingulate gyrus, the hippocampus and their interconnections' form a mechanism for emotion; in 1952 MacLean coined the term limbic system for Broca's lobe and related subcortical nuclei.[3,5,6]

The cingulate cortex. Brodmann divided the cingulate gyrus in two, but cytoarchitectural studies support a model of four regions, each with subregions, defined by connections and function. In the atlas the Desikan–Killiany labels split it into rostral anterior, caudal anterior, posterior and isthmus parts.[7,8]

The insula. The insula lies hidden beneath the frontal, parietal and temporal opercula, bounded by the circular sulcus and divided by the central insular sulcus into short anterior and long posterior gyri. It is supplied by insular branches of the middle cerebral artery.[4,9]

The amygdala. The amygdala, an almond-shaped group of nuclei deep in the temporal lobe, is an important part of the system for acquiring, storing and expressing fear memory.[3,10]

Key numbers

Regions in the modern cytoarchitectural model of the cingulate gyrus (Brodmann had two)
4[7]
Months of real-life experience sampling in which patient SM reported little fear
3[1]
Patients in the first subgenual cingulate stimulation study who went into remission
4 of 6[11]
Insular glioma operations followed in one surgical series (104 patients)
115[12]

Why we need them

Sensing the body. An afferent system carries signals about every aspect of the body's physiological condition, a representation of 'the material me' that may underlie feelings, emotion and self-awareness. The anterior insula re-represents these interoceptive signals; it is engaged in conditions as varied as bowel distension, cigarette craving and sudden insight, and may be part of the basis of awareness itself.[13,14]

The unpleasantness of pain. When hypnotic suggestion changed how unpleasant a painful stimulus felt, without changing how intense it felt, activity changed in the anterior cingulate cortex but not in primary somatosensory cortex.[15]

Noticing conflict. The conflict-monitoring theory proposes that the anterior cingulate detects conflicts in information processing and so signals when more cognitive control is needed. Negative affect, pain and cognitive control all activate an overlapping region, the anterior midcingulate cortex, which links information about rewards and punishments with motor centres for action.[16,17]

Learning what to fear. In a reversal-learning task, activity in the human amygdala tracked a cue's associability (how surprising its outcomes have been), while the striatum carried the reinforcement prediction error.[18]

How feelings may be built

Interoceptive inference. One influential account treats the brain as a prediction machine: emotions arise from actively inferred models of the causes of signals from inside the body. This generalises appraisal theories, in which emotions emerge from evaluations of bodily changes.[19]

Measuring interoception. Interoception has at least three distinct, dissociable dimensions: accuracy (performance on objective heartbeat-detection tests), sensibility (self-report) and awareness (how well confidence tracks accuracy). In 80 people, accuracy was only partly predicted by the other two.[20]

From the body to a feeling (simplified)Body stateheartbeat, gut and other bodilysignalsInteroceptive pathwaysafferent signals about thebody's conditionAnterior insulare-represents interoceptivesignalsPredictions meet signalspredicted and actual bodysignals comparedFeeling and awarenesssubjective feeling statesCingulate: control andactionanterior midcingulate linksaffect to goal-directed action
From the body to a feeling (simplified). A simplified picture that combines interoception research with the predictive account of emotion; how these steps map onto anatomy is still debated.[13,14,17,19]
Text version of the diagram
  1. Body state: heartbeat, gut and other bodily signals. Leads to Interoceptive pathways.
  2. Interoceptive pathways: afferent signals about the body's condition. Leads to Anterior insula.
  3. Anterior insula: re-represents interoceptive signals. Leads to Predictions meet signals; Cingulate: control and action.
  4. Predictions meet signals: predicted and actual body signals compared. Leads to Feeling and awareness.
  5. Feeling and awareness: subjective feeling states. Leads to Cingulate: control and action.
  6. Cingulate: control and action: anterior midcingulate links affect to goal-directed action.

When: moments, days and months

Moments. In the reversal-learning study, associability rose when a cue's outcomes became surprising and gated how quickly its value was relearned, trial by trial.[18]

Days. In seven people with epilepsy who reported their mood intermittently over several days, models of intracranial brain activity decoded how their mood changed over time, mostly from limbic regions, and estimated the timescales of those mood changes.[21]

Months. In the randomised trial of subcallosal cingulate stimulation, both the active and sham groups improved over the six-month blinded phase, with no significant difference between them.[22]

When they fail

Amygdala. A rare patient with damage restricted to both amygdalae could no longer recognise fear in facial expressions, nor several emotions blended in one face, but still recognised who the faces belonged to. Patient SM, with focal damage to both amygdalae, showed an overall impoverished experience of fear despite a life history full of traumatic events.[1,23]

Insula. Damage involving the insula disrupted addiction to cigarette smoking, suggesting that the insula is a critical substrate of that addiction. Surgery for insular tumours is difficult because of the surrounding arteries and functional structures; in one series (115 operations in 104 patients), new permanent deficits followed in 6 patients (6%).[2,12]

Cingulate and depression. Mayberg's group had observed that the subgenual cingulate (Brodmann area 25) is metabolically overactive in treatment-resistant depression. Chronic stimulation of the adjacent white matter was followed by sustained remission in four of six patients, but a later multisite, sham-controlled trial of 90 participants found response in 20% with active stimulation against 17% with sham, not a significant difference.[11,22]

Models of learning, conflict and feeling

Simple equations capture how the amygdala might gate learning, how the cingulate might detect conflict and how the brain might infer the body's state.[16,18,19]

Learning gated by associability[18]
δt=rt−Vt,Vt+1=Vt+κ αt δt,αt+1=η ∣δt∣+(1−η) αt\delta_t = r_t - V_t, \qquad V_{t+1} = V_t + \kappa\,\alpha_t\,\delta_t, \qquad \alpha_{t+1} = \eta\,|\delta_t| + (1-\eta)\,\alpha_t

A hybrid of the Rescorla–Wagner and Pearce–Hall models. The prediction error δ updates the value V, but the size of the update is scaled by the associability α, which tracks recent surprise: learning speeds up for cues that have predicted badly and slows when predictions become reliable. In humans, amygdala activity tracked α and striatal activity tracked δ.

Symbols in Learning gated by associability
SymbolMeaningUnit
rtr_toutcome on trial t (for example, a shock or no shock)—
VtV_tpredicted value of the cue—
δt\delta_tprediction error—
αt\alpha_tassociability: the cue's recent surprise—
κ,η\kappa, \etalearning-rate and associability-update parameters—
Conflict as energy[16]
E=−∑i∑jwij ai ajE = -\sum_{i}\sum_{j} w_{ij}\, a_i\, a_j

In conflict-monitoring models, conflict is measured as the energy of the response layer: it is high when mutually inhibitory responses (negative weights w) are active at the same time. The theory proposes that the anterior cingulate signals this quantity so that control can be increased.

Symbols in Conflict as energy
SymbolMeaningUnit
aia_iactivity of response unit i—
wijw_{ij}connection weight between units i and j (negative for competing responses)—
EEconflict (energy)—
A precision-weighted prediction[19]
μ^=μprior+πsπs+πp (s−μprior)\hat{\mu} = \mu_{\text{prior}} + \frac{\pi_s}{\pi_s + \pi_p}\,\left(s - \mu_{\text{prior}}\right)

A simple illustration of the predictive idea for Gaussian beliefs: the brain's estimate of a bodily state moves from its prediction towards the incoming signal by an amount that depends on how reliable (precise) the signal is relative to the prediction. Interoceptive inference applies this kind of reasoning to the causes of signals from inside the body.

Symbols in A precision-weighted prediction
SymbolMeaningUnit
μprior\mu_{\text{prior}}predicted bodily state—
ssincoming interoceptive signal—
πs,πp\pi_s, \pi_pprecisions (inverse variances) of the signal and the prediction—
μ^\hat{\mu}updated estimate—

Technology: stimulators and mood decoders

Deep brain stimulation. Stimulating white matter next to the subgenual cingulate reduced the region's elevated blood flow and changed activity in connected limbic and cortical areas, alongside clinical remission in four of six patients. The larger randomised trial confirmed that the approach was safe and feasible but did not show efficacy over six months; 28 patients had 40 serious adverse events, 8 of which were judged related to the device or surgery.[11,22]

Decoding mood with machine learning. Dynamic models fitted to multi-site intracranial recordings decoded mood variations over days in each of seven people, drawing largely on signals from limbic regions whose spectral and spatial features were tuned to mood.[21]

Intracranial channelsSpectral featuresLatent brain stateMood estimate
A mood decoder (schematic). A schematic of the decoding approach: power in different frequency bands across many recording sites is summarised by a dynamic model of a few hidden states, from which the person's mood is estimated.[21]

Closing the loop. Scangos and colleagues used several days of intracranial recording and stimulation to find one person's symptom-specific brain biomarker and a site where stimulation helped, then implanted a device that stimulated only when the biomarker signalled high symptom severity. Depression improved rapidly and lastingly; whether the approach generalises is not yet known.[24]

Limbic and paralimbic regions at a glance[1,2,10,11,14,15,16,17,23]
RegionRoles discussed hereKey evidence
AmygdalaFear learning, triggering fear, fear in facesFear conditioning; patient SM; bilateral lesions
Anterior insulaInteroception, feelings, awareness, cravingInteroception reviews; smokers with insula damage
Anterior cingulatePain unpleasantness, conflict monitoringHypnosis and PET; computational models
Anterior midcingulateHub for negative affect, pain and controlImaging and anatomical review
Subgenual cingulate (area 25)Overactive in treatment-resistant depressionDeep brain stimulation studies

Milestones

From the limbic lobe to closed-loop stimulation

  1. 1878Broca names the great limbic lobe.[3]
  2. 1937Papez proposes a mechanism of emotion.[3,5]
  3. 1952MacLean coins the term 'limbic system'.[3,6]
  4. 1955Penfield and Faulk report further observations on the insula.[25]
  5. 1994Bilateral amygdala damage impairs recognition of fear in faces.[23]
  6. 1997Pain unpleasantness is linked to the anterior cingulate.[15]
  7. 2001The conflict-monitoring theory of the anterior cingulate.[16]
  8. 2002Interoception is described as the sense of the body's physiological condition.[13]
  9. 2005Subgenual cingulate stimulation for depression; a four-region cingulate model.[7,11]
  10. 2007Insula damage disrupts addiction to smoking.[2]
  11. 2011Patient SM and fear; the amygdala tracks associability; the midcingulate hub.[1,17,18]
  12. 2017A sham-controlled trial of cingulate stimulation finds no significant benefit.[22]
  13. 2018Mood variations are decoded from intracranial recordings.[21]
  14. 2021Closed-loop stimulation in one person with depression.[24]

Frontiers

Personalised, responsive stimulation. Rather than stimulating constantly at a standard site, closed-loop therapy finds each person's biomarker and stimulates only when symptoms are severe. This report concerns a single individual, and the authors stress that broader studies are needed.[24]

From decoding to treatment. Decoding mood from brain activity is a step towards closed-loop systems that could adjust treatment to a person's state; in the study it was shown in seven people with electrodes implanted for epilepsy.[21,24]

Check yourself

Check yourself

  1. Where does the word 'limbic' come from, and what did Broca apply it to?
    Show answer

    From the Latin limbus, border; Broca applied it to the curved rim of cortex, including the cingulate and parahippocampal gyri.

  2. Which structures did Papez name in his 1937 mechanism of emotion?
    Show answer

    The hypothalamus, the anterior thalamic nucleus, the cingulate gyrus, the hippocampus and their interconnections.

  3. What did patient SM show in the haunted house and with snakes and spiders?
    Show answer

    No fear, and no more than minimal reported fear, after bilateral amygdala damage.

  4. What happened to smokers whose brain damage involved the insula?
    Show answer

    They were more likely to quit easily and immediately, without relapse or persistent urges.

  5. Which region changed with the unpleasantness, but not the intensity, of pain?
    Show answer

    The anterior cingulate cortex (primary somatosensory cortex did not change).

  6. In the hybrid learning model, what does associability do?
    Show answer

    It scales the learning rate, speeding learning for cues that have recently been surprising.

  7. What did the sham-controlled trial of subcallosal cingulate stimulation find?
    Show answer

    Response in 20% with active and 17% with sham stimulation, not a significant difference.

  8. Name the three dimensions of interoception.
    Show answer

    Accuracy, sensibility and awareness.

Glossary[3,4,5,6,11,13,16,18,24]

Limbic lobe
Broca's name for the curved rim of cortex that includes the cingulate and parahippocampal gyri.
Limbic system
MacLean's term for the limbic lobe and related subcortical nuclei, a functional concept.
Papez circuit
The loop of hypothalamus, anterior thalamus, cingulate gyrus and hippocampus proposed in 1937 as a mechanism of emotion.
Cingulum
The white matter bundle running within the cingulate and parahippocampal gyri.
Insula
The cortex hidden beneath the opercula inside the lateral sulcus.
Interoception
The sense of the physiological condition of the body.
Associability
How much a cue's outcomes have recently surprised the learner, which sets how fast it is learned about.
Conflict monitoring
Detecting simultaneous, competing responses as a signal to increase control.
Subgenual cingulate
The part of the cingulate below the front of the corpus callosum (Brodmann area 25).
Closed-loop stimulation
Stimulation triggered by a measured brain signal rather than delivered continuously.

References

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  2. Naqvi NH, Rudrauf D, Damasio H, Bechara A. Damage to the insula disrupts addiction to cigarette smoking. Science 2007;315(5811):531-534. doi:10.1126/science.1135926
  3. RajMohan V, Mohandas E. The limbic system. Indian Journal of Psychiatry 2007;49(2):132-139. doi:10.4103/0019-5545.33264
  4. Türe U, Yaşargil DCH, Al-Mefty O, Yaşargil MG. Topographic anatomy of the insular region. Journal of Neurosurgery 1999;90(4):720-733. doi:10.3171/jns.1999.90.4.0720
  5. Papez JW. A proposed mechanism of emotion. Archives of Neurology and Psychiatry 1937;38(4):725-743. doi:10.1001/archneurpsyc.1937.02260220069003
  6. MacLean PD. Some psychiatric implications of physiological studies on frontotemporal portion of limbic system (visceral brain). Electroencephalography and Clinical Neurophysiology 1952;4(4):407-418. doi:10.1016/0013-4694(52)90073-4
  7. Vogt BA. Pain and emotion interactions in subregions of the cingulate gyrus. Nature Reviews Neuroscience 2005;6(7):533-544. doi:10.1038/nrn1704
  8. Desikan RS, Ségonne F, Fischl B, Quinn BT, Dickerson BC, Blacker D, et al.. An automated labeling system for subdividing the human cerebral cortex on MRI scans into gyral based regions of interest. NeuroImage 2006;31(3):968-980. doi:10.1016/j.neuroimage.2006.01.021
  9. Türe U, Yaşargil MG, Al-Mefty O, Yaşargil DCH. Arteries of the insula. Journal of Neurosurgery 2000;92(4):676-687. doi:10.3171/jns.2000.92.4.0676
  10. LeDoux JE. Emotion circuits in the brain. Annual Review of Neuroscience 2000;23:155-184. doi:10.1146/annurev.neuro.23.1.155
  11. Mayberg HS, Lozano AM, Voon V, McNeely HE, Seminowicz D, Hamani C, et al.. Deep brain stimulation for treatment-resistant depression. Neuron 2005;45(5):651-660. doi:10.1016/j.neuron.2005.02.014
  12. Sanai N, Polley MY, Berger MS. Insular glioma resection: assessment of patient morbidity, survival, and tumor progression. Journal of Neurosurgery 2010;112(1):1-9. doi:10.3171/2009.6.JNS0952
  13. Craig AD. How do you feel? Interoception: the sense of the physiological condition of the body. Nature Reviews Neuroscience 2002;3(8):655-666. doi:10.1038/nrn894
  14. (Bud) Craig AD. How do you feel — now? The anterior insula and human awareness. Nature Reviews Neuroscience 2009;10(1):59-70. doi:10.1038/nrn2555
  15. Rainville P, Duncan GH, Price DD, Carrier B, Bushnell MC. Pain affect encoded in human anterior cingulate but not somatosensory cortex. Science 1997;277(5328):968-971. doi:10.1126/science.277.5328.968
  16. Botvinick MM, Braver TS, Barch DM, Carter CS, Cohen JD. Conflict monitoring and cognitive control. Psychological Review 2001;108(3):624-652. doi:10.1037/0033-295X.108.3.624
  17. Shackman AJ, Salomons TV, Slagter HA, Fox AS, Winter JJ, Davidson RJ. The integration of negative affect, pain and cognitive control in the cingulate cortex. Nature Reviews Neuroscience 2011;12(3):154-167. doi:10.1038/nrn2994
  18. Li J, Schiller D, Schoenbaum G, Phelps EA, Daw ND. Differential roles of human striatum and amygdala in associative learning. Nature Neuroscience 2011;14(10):1250-1252. doi:10.1038/nn.2904
  19. Seth AK. Interoceptive inference, emotion, and the embodied self. Trends in Cognitive Sciences 2013;17(11):565-573. doi:10.1016/j.tics.2013.09.007
  20. Garfinkel SN, Seth AK, Barrett AB, Suzuki K, Critchley HD. Knowing your own heart: distinguishing interoceptive accuracy from interoceptive awareness. Biological Psychology 2015;104:65-74. doi:10.1016/j.biopsycho.2014.11.004
  21. Sani OG, Yang Y, Lee MB, Dawes HE, Chang EF, Shanechi MM. Mood variations decoded from multi-site intracranial human brain activity. Nature Biotechnology 2018;36(10):954-961. doi:10.1038/nbt.4200
  22. Holtzheimer PE, Husain MM, Lisanby SH, Taylor SF, Whitworth LA, McClintock S, et al.. Subcallosal cingulate deep brain stimulation for treatment-resistant depression: a multisite, randomised, sham-controlled trial. The Lancet Psychiatry 2017;4(11):839-849. doi:10.1016/S2215-0366(17)30371-1
  23. Adolphs R, Tranel D, Damasio H, Damasio A. Impaired recognition of emotion in facial expressions following bilateral damage to the human amygdala. Nature 1994;372(6507):669-672. doi:10.1038/372669a0
  24. Scangos KW, Khambhati AN, Daly PM, Makhoul GS, Sugrue LP, Zamanian H, et al.. Closed-loop neuromodulation in an individual with treatment-resistant depression. Nature Medicine 2021;27(10):1696-1700. doi:10.1038/s41591-021-01480-w
  25. Penfield W, Faulk ME. The insula. Brain 1955;78(4):445-470. doi:10.1093/brain/78.4.445

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Template anatomy for education. Not patient-specific. Not for clinical decision-making.