Abstract

The concept of “caves” in the human brain appears in two distinct scientific traditions: (1) radiology, which uses the term to describe small cerebrospinal-fluid–filled anatomical variants such as the cavum septi pellucidi and Meckel’s caves; and (2) functional neuroscience, where “caves” serve as metaphors for deep integrative processing hubs within the brain’s large-scale networks. This article offers the first integrated synthesis of these two frameworks, clarifying their differences, overlaps, and combined relevance for neuroanatomy, cognition, and clinical neuroscience.

Introduction

The human brain contains both literal anatomical cavities and functional “interior processing hubs.” Radiologists use the “five caves” mnemonic to identify benign neurodevelopmental variants on MRI: the Cavum Septi Pellucidi (CSP), Cavum Vergae (CV), Cavum Veli Interpositi (CVI), and the bilateral Meckel’s caves. At the same time, cognitive neuroscience identifies deep macro-domains of integration—large hubs that unify perception, memory, regulation, and executive function.

Although both traditions use the word “cave,” they refer to vastly different phenomena. This article unifies these perspectives into one coherent scientific interpretation.

Part I — Radiological Caves: The Five Anatomical CSF-Containing Spaces

In everyday neuroimaging, radiologists and neurologists frequently encounter five fluid-filled or potential spaces that have historically been called “cava” (Latin = caves). Although only some communicate with the true ventricular system, they share a common radiological appearance (CSF-isointense on all sequences) and can be confused with pathological cysts. The mnemonic of the “five caves” is a longstanding teaching tool in radiology residency programs worldwide.

1. Cavum Septi Pellucidi (CSP) — The “Fifth Ventricle”

• Anatomy: Thin, midline, slit-like space (usually 1–4 mm wide) between the two laminae of the septum pellucidum, located anterior to the foramen of Monro and superior to the fornix.
• Embryology: Present in nearly 100 % of fetuses; physiological closure occurs by 3–6 months postnatally in ~85 % of infants.
• Adult prevalence: 10–20 % on thin-slice MRI (higher in premature infants, boxers, and professional athletes).
• Radiological key points:
  • Fluid signal identical to CSF on all sequences
  • No communication with ventricles after infancy (closed cavity)
  • Anteroposterior length < 10 mm = normal variant; > 10 mm = “cyst of the septum pellucidum”
  • Sagittal T2/FLAIR best shows separation of the two septal leaflets
• Clinical relevance: Usually asymptomatic. Large/symptomatic cysts may obstruct foramina of Monro → hydrocephalus. Statistically associated (not necessarily causal) with schizophrenia, fetal alcohol spectrum disorder, and chronic traumatic encephalopathy.

2. Cavum Vergae (CV) — The “Sixth Ventricle”

• Anatomy: Direct posterior extension of the CSP beyond the columns of the fornix and anterior to the splenium of the corpus callosum. Triangular on sagittal images.
• Key rule: CV never exists in isolation — a CSP must always be present (termed cavum septi pellucidi et vergae, CSPV).
• Prevalence: 2–5 % in adults; much higher in neonates.
• Radiological key points:
  • Located posterior to the fornix (use sagittal images to differentiate from CVI)
  • Communicates anteriorly with CSP; no direct ventricular communication
  • When very large, may mimic interhemispheric cyst or dilated third ventricle roof
• Clinical relevance: Almost always benign. Rare symptomatic CSPV cysts treated by endoscopic fenestration.

3. Cavum Veli Interpositi (CVI) — Cistern of the Velum Interpositum

• Anatomy: Potential space created by separation of the two layers of tela choroidea in the roof of the third ventricle. Extends from foramina of Monro anteriorly to the pineal recess/habenula posteriorly.
• Location mnemonic: Lies superior to the pineal gland and internal cerebral veins, inferior to the fornices.
• Prevalence: A small CVI is seen in > 80 % of normal adult MRIs; prominent dilatation in up to 20–30 %.
• Radiological key points:
  • Classic “winged” or “boomerang” appearance on sagittal T2
  • Internal cerebral veins and medial posterior choroidal arteries course through it
  • Communicates with quadrigeminal cistern → true CSF cistern (unlike CSP/CV)
  • Most common mimic of pineal region cyst, arachnoid cyst, or vein of Galen malformation
• Clinical relevance: Virtually always normal. Extreme dilatation (rare) may compress tectal plate → Parinaud syndrome or hydrocephalus.

4. & 5. Meckel’s Caves (Left & Right) — Cavum Meckelii / Cavum Trigeminale

• Anatomy: Paired dural recesses in the posteromedial middle cranial fossa, at the petrous apex. Each contains the trigeminal (Gasserian) ganglion, root, and proximal divisions (V1, V2, V3) surrounded by a sleeve of CSF.
• Embryology: Remnant of the embryonic meninx primitiva; present bilaterally in 100 % of individuals.
• Radiological key points:
  • Best seen on high-resolution 3D T2 sequences (CISS, FIESTA, DRIVE)
  • Appear as symmetric CSF-filled pouches with “feathered” nerve roots inside
  • Communicate with prepontine cistern posteriorly
  • Enlargement, asymmetric filling defects, or enhancement = pathology
• Pathology involving Meckel’s cave:
  • Trigeminal schwannoma (most common benign tumor)
  • Meningioma, metastasis, perineural spread (especially adenoid cystic or squamous cell carcinoma)
  • Inflammatory: Tolosa–Hunt syndrome, IgG4 disease, sarcoidosis
  • Infectious: Gradenigo syndrome (petrous apicitis)
  • Traumatic/CSF leak: Meckel’s cave diverticulum

Summary Table — The Five Radiological Caves

Radiological Take-Home Points

• CSP, CV, and small CVI are normal variants — report as incidental unless > 10 mm or symptomatic.
• Always specify location relative to the fornix on sagittal images to distinguish CV (posterior/inferior) from CVI (superior).
• Meckel’s caves are normal anatomy but become clinically relevant when asymmetric, enlarged, or enhancing.
• These five “caves” have no direct role in cognition, emotion, or behavior — they are purely structural/radiological entities.
• Understanding these five caves prevents unnecessary alarm and guides accurate differential diagnosis in daily neuroimaging practice.

Part II — Functional Caves: The Five Neurocognitive Macro-Domains of the Human Brain

While the anatomical “caves” (cava) discussed in Part I are fluid-filled spaces, the brain can also be conceptualized through five great functional caves — vast, interconnected macro-domains that operate as the principal computational engines of human cognition, emotion, and behavior. This framework, increasingly used in systems neuroscience and clinical neuropsychiatry, integrates resting-state fMRI, lesion-mapping, and large-scale connectomics to define five core large-scale networks that dominate information processing.

Cave I — Medial Integrative Cave (mPFC–ACC Domain)

Core regions: medial prefrontal cortex (mPFC), anterior cingulate cortex (ACC), ventromedial PFC, subgenual cingulate (Brodmann areas 10, 11, 24, 25, 32), posterior cingulate/precuneus (BA 23, 31).

Primary functions:

• Autobiographical memory and self-referential processing
• Value-based decision making and reward prediction error
• Internal modeling of the world and mental simulation (“theory of mind”)
• Long-range maintenance of internal states across time (default-mode network core)
• Integration of emotional salience with cognitive context

Clinical signature when dysfunctional: depression, anhedonia, rumination, obsessive-compulsive disorder, apathy syndromes, and disorders of self (depersonalization/derealization).

Cave II — Posterior Perceptual Cave (Parietal–Occipital Domain)

Core regions: superior & inferior parietal lobules (BA 7, 39, 40), lateral occipital complex, cuneus, lingual gyrus, intraparietal sulcus, temporo-parietal junction (TPJ).

Primary functions:

• Construction of coherent perceptual scenes (Gestalt binding)
• Multisensory integration (visual-auditory-somatosensory)
• Spatial attention, coordinate transformations, and egocentric/allocentric mapping
• Tool use, body schema, and visuomotor transformation

Clinical signature: Balint’s syndrome, simultanagnosia, visuospatial neglect, apraxia, topographical disorientation, and posterior cortical atrophy.

Cave III — Dorsal Executive Cave (Dorsolateral Frontoparietal Domain)

Core regions: dorsolateral prefrontal cortex (dlPFC, BA 9/46), posterior parietal cortex (especially superior parietal lobule and intraparietal sulcus), frontal eye fields (BA 8), pre-SMA/supplementary motor area.

Primary functions:

• Working memory maintenance and manipulation
• Cognitive control, task-set switching, and rule-based behavior
• Goal-directed attention and inhibitory control
• Logical reasoning, planning, and fluid intelligence

Clinical signature: dysexecutive syndrome, ADHD (adult), frontal lobe lesions, abulia without apathy, utilization behavior, and impaired set-shifting in schizophrenia and OCD.

Cave IV — Subcortical Regulatory Cave (Thalamic–Basal Ganglia Domain)

Core regions: entire thalamus (all nuclei), basal ganglia (striatum, globus pallidus, subthalamic nucleus, substantia nigra), extended amygdala, brainstem arousal nuclei (locus coeruleus, raphe, ventral tegmental area).

Primary functions:

• Global arousal and vigilance regulation
• Sensory gating and salience filtering
• Motor and cognitive action selection via direct/indirect pathways
• Broadcast synchronization/desynchronization of cortical oscillations</
• Homeostatic control (sleep–wake, hunger, thermoregulation)

Clinical signature: disorders of consciousness, akinetic mutism, Parkinson’s and Huntington’s diseases, Tourette syndrome, catatonia, and thalamic stroke syndromes.

Cave V — Limbic-Contextual Cave (Hippocampal–Amygdalar Domain)

Core regions: hippocampus (CA fields, dentate gyrus, subiculum), entorhinal cortex, parahippocampal gyrus, amygdala (all subnuclei), fornix, mammillary bodies, anterior thalamic nuclei.

Primary functions:

• Episodic and contextual memory encoding/retrieval
• Spatial navigation and cognitive map formation
• Emotional tagging and fear/anxiety conditioning
• Assignment of personal significance and meaning
• Scene construction and future simulation (together with Cave I)

Clinical signature: Alzheimer’s disease (earliest involvement), transient global amnesia, medial temporal lobe epilepsy, Korsakoff syndrome, PTSD, and anxiety disorders.

Summary Table of the Five Functional Caves

Integrated Summary

These five functional caves do not work in isolation; they continuously interact via long-range white-matter highways (superior longitudinal fasciculus, cingulum, uncinate, fornix, medial forebrain bundle). Cognition and consciousness emerge from their orchestrated dialogue. Modern neuropsychiatry increasingly localizes disorders not to single Brodmann areas, but to disruption within or between these macro-domains — offering a powerful, clinically actionable framework for diagnosis, prognosis, and targeted interventions (TMS, DBS, psychedelics, cognitive training).

Part III — Integrating Both Frameworks

Although both systems use the word “cave,” they differ in scale, purpose, physiology, and meaning. The anatomical caves of radiology are fluid-filled structural spaces, while the functional caves are neural network domains responsible for higher-order cognition.

Combined Comparison Table

Together, the two frameworks offer a full-spectrum picture of the “cavernous” features of the brain: from microstructural CSF pockets to macro-functional processing domains.

Clinical Implications

Understanding both cave frameworks deepens interpretation of:

• MRI anomalies that distort nearby functional hubs
• Neurosurgical approaches involving the trigeminal system
• Network-level disorders (depression, schizophrenia, PTSD)
• Correlations between structural variants and cognitive profiles

This synergy may eventually help clinicians predict how structural anomalies influence functional network behavior.

Conclusion

The “caves” of the human brain exist on two levels: as structural recesses visible on MRI and as deep computational hubs shaping human cognition. By integrating radiological anatomy with functional neuroarchitecture, we gain a more complete picture of how the brain’s inner spaces—both literal and metaphorical—organize perception, thought, emotion, and behavior.