Read the internal capsule through its grey-matter neighbours, compare its limbs and genu, and keep reconstructed pathways separate from individual localisation.
Goals
Orient the posterior limb between thalamus and lentiform nucleus.
Compare all five capsular parts through their displayed projection relationships.
Describe insular layers, somatotopy and mapping evidence without turning group anatomy into an individual threshold.
The internal capsule is first a relationship, not a segmented mesh. At the posterior-limb level, the thalamus is medial and the lentiform nucleus, made of putamen and globus pallidus, is lateral. The scene places the CST in that deep interval as a spatial cue, but its construction cannot establish exact capsule occupancy or a measurable interval.
Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.
Targets
Thalamus, gross
Putamen
Globus pallidus
CST, corticospinal tract
Compare
Set the hemisphere to left if needed. Use the anterior camera with deep structures on, then compare the CST with thalamus, putamen and globus pallidus. Name the medial and lateral references, then state what the line cannot prove about the hidden capsule.
Read the neighbours
The lentiform nucleus is the lateral grey reference for the posterior-limb neighbourhood.
The thalamus is a gross mesh here, so it supplies position rather than relay-nucleus detail.
The CST is reconstructed white matter, while the capsule itself is not separately segmented in this scene.
The visible interval is a spatial guide. It does not show perforators, ventricular boundaries or every fibre population that may occupy the internal capsule.
Explain before revealing
A left deep lesion overlaps the CST interval between thalamus and lentiform nucleus. What can you call the leading capsular relationship, and what must you refuse to infer from this display?
Explanation
The thalamus is medial, the lentiform nucleus is lateral and the displayed CST occupies the same deep interval in this population reference. The combination supports a posterior-limb neighbourhood hypothesis. It does not segment the capsule, establish exact occupancy or define a measurable interval.
In a surgical discussion
For a resident, a useful deep description identifies the grey references, the inferred capsular level and the displayed pathway as separate observations. The scene supports that relationship, not exact occupancy of the capsule by one reconstructed family.
Putamen, globus pallidus, caudate and thalamus at the coarsest scale of a group subcortical parcellation. Anterior and posterior thalamus are merged into one mesh; no nucleus is individually named or targetable here.
The installed Melbourne scale-1 thalamus is gross anatomy. It does not segment lateral geniculate, VMpo or other relay nuclei; no named nucleus can be inferred from the outline.
A group-average cortical surface with a population parcellation, a population-averaged bundle atlas, and gross subcortical meshes. No patient image, no registration, no functional map, no brainstem or thalamic nuclei.
Ask the learner to answer before opening the explanation. Compare the answer with the named structures and the cited method. Teaching point: The thalamus is medial, the lentiform nucleus is lateral and the displayed CST occupies the same deep interval in this population reference. The combination supports a posterior-limb neighbourhood hypothesis. It does not segment the capsule, establish exact occupancy or define a measurable interval.
This relationship draws on 6 cited sources.
Relationship 2 of 7 · atlas
Name all five capsular parts
Orient
Use five positional parts around the deep grey landmarks: anterior limb, genu, posterior limb, retrolenticular part and sublenticular part. The anterior limb lies between the head of the caudate medially and the lentiform nucleus laterally. The genu is the bend, and the posterior limb lies between the thalamus medially and lentiform nucleus laterally. The retrolenticular part lies behind the lentiform nucleus, while the sublenticular part lies below it and is associated with the anterior optic radiation, including Meyer’s loop, and auditory radiations.
Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.
Targets
Caudate nucleus
Putamen
Thalamus, gross
OR, optic radiation
Compare
Compare TR_A with CPT_F, CBT with CST, and OR with TR_P. Keep caudate, thalamus, putamen and globus pallidus visible. Treat OR as a visual-radiation reference, not as a layer-specific label for either retrolenticular or sublenticular fibres.
Read the neighbours
The anterior limb, genu, posterior limb, retrolenticular part and sublenticular part are distinct positional descriptions.
The anterior limb is the caudate-head to lentiform interval; the genu is the bend; the posterior limb is the thalamus to lentiform interval.
The retrolenticular part is behind the lentiform nucleus, while the sublenticular part is below it and is the temporal relationship for anterior optic and auditory radiations.
These selected tract-family relationships are not mutually exclusive histological compartments. OR is a visual thalamocortical system, and the separate TR_P atlas label does not make every posterior-radiation description an independent biological system.
Explain before revealing
A visual deficit is being assigned to the retrolenticular part because OR is highlighted. What positional distinction should you check, and what can the displayed OR not decide?
Explanation
Check whether the proposed relationship is behind or below the lentiform nucleus, distinguishing retrolenticular from sublenticular. The five-part vocabulary also keeps the anterior limb at the caudate-head to lentiform interval and the posterior limb at the thalamus to lentiform interval. OR is a displayed optic-radiation family, not a layer-specific label that can decide the capsular part alone.
In a surgical discussion
When presenting a deep lesion, name the capsular part, the grey neighbours and the pathway reference separately. The five-part vocabulary prevents a temporal sublenticular relationship from being collapsed into the retrolenticular label used for a different level.
Putamen, globus pallidus, caudate and thalamus at the coarsest scale of a group subcortical parcellation. Anterior and posterior thalamus are merged into one mesh; no nucleus is individually named or targetable here.
The installed Melbourne scale-1 thalamus is gross anatomy. It does not segment lateral geniculate, VMpo or other relay nuclei; no named nucleus can be inferred from the outline.
A group-average cortical surface with a population parcellation, a population-averaged bundle atlas, and gross subcortical meshes. No patient image, no registration, no functional map, no brainstem or thalamic nuclei.
Ask the learner to answer before opening the explanation. Compare the answer with the named structures and the cited method. Teaching point: Check whether the proposed relationship is behind or below the lentiform nucleus, distinguishing retrolenticular from sublenticular. The five-part vocabulary also keeps the anterior limb at the caudate-head to lentiform interval and the posterior limb at the thalamus to lentiform interval. OR is a displayed optic-radiation family, not a layer-specific label that can decide the capsular part alone.
This relationship draws on 7 cited sources.
Relationship 3 of 7 · atlas
Read the genu as a bend with a corticobulbar marker
Orient
The genu is the bend between the anterior and posterior limbs. Corticobulbar fibres are conventionally used to orient this bend, while corticospinal fibres continue through the posterior limb. A face-related clinical pattern therefore calls for level and side, not a claim that a single rendered line is the whole face representation.
Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.
Targets
Area 4, precentral
CBT, corticobulbar tract
CST, corticospinal tract
Putamen
Compare
Compare CBT with CST in the anterior view and keep area 4 as a cortical reference. Ask where the genu is inferred from the neighbouring limbs, because it is not a separate mesh or a separately labelled facial subfield.
Read the neighbours
The cited dissection and tractographic literature supports a genu and corticobulbar relationship.
CBT is a corticobulbar comparison, without assigning all its fibres to the genu; level and method can change the apparent distribution.
Area 4 is a population cortical parcel and does not divide the displayed cortex into hand, arm, leg or face territories.
A face finding can be a useful clue to the capsular level, but it is not a label for a hidden facial nucleus or a complete cortical map.
Explain before revealing
A resident calls a facial sign proof of an isolated genu lesion because CBT is visible. What would you say back?
Explanation
CBT is a conventional marker for the corticobulbar relationship at the bend between the limbs. It does not identify a face-only tract or an individualized face subfield. The scene leaves the exact distribution of corticobulbar fibres and any facial nucleus unresolved.
In a surgical discussion
A resident should describe a facial finding alongside limb strength, sensation, side and lesion level. The compact genu relationship is clinically relevant to the hypothesis, but the image cannot establish the exact distribution of corticobulbar fibres in one person.
Putamen, globus pallidus, caudate and thalamus at the coarsest scale of a group subcortical parcellation. Anterior and posterior thalamus are merged into one mesh; no nucleus is individually named or targetable here.
The installed Melbourne scale-1 thalamus is gross anatomy. It does not segment lateral geniculate, VMpo or other relay nuclei; no named nucleus can be inferred from the outline.
A group-average cortical surface with a population parcellation, a population-averaged bundle atlas, and gross subcortical meshes. No patient image, no registration, no functional map, no brainstem or thalamic nuclei.
Ask the learner to answer before opening the explanation. Compare the answer with the named structures and the cited method. Teaching point: CBT is a conventional marker for the corticobulbar relationship at the bend between the limbs. It does not identify a face-only tract or an individualized face subfield. The scene leaves the exact distribution of corticobulbar fibres and any facial nucleus unresolved.
This relationship draws on 6 cited sources.
Relationship 4 of 7 · reconstruction
Why this CST sample cannot identify body-part fibres
Orient
A CST display can support a discussion of capsular motor-fibre organisation, but this step is an evidence exercise rather than a fixed somatotopic map. The cited dissection and tractography literature describes relative organisation at selected levels and with selected methods; it does not give this population sample a universal hand, arm, leg or face ordering.
Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.
Targets
CST, corticospinal tract
Area 4, precentral
Thalamus, gross
Globus pallidus
Compare
Keep CST bright and CBT and TR_S ghosted. Rotate around the anterior view, then separate the installed D2 geometry from a study result: the scene has no effector labels, study level, method or region-of-interest selection.
Read the neighbours
A study may report a relative arrangement at a specified level, but the level, dissection or diffusion method and region-of-interest choices qualify that result.
The installed CST is a population-averaged reconstruction for spatial reference, not an individual capsule or a body-part-labelled map.
The display has no effector labels, and line count is not axon count or a functional map.
The general population-atlas idea is useful for comparing reference geometry, but it cannot transfer a group ordering to an individual capsule.
Explain before revealing
Why can this CST sample not identify hand, arm or leg fibres, even if a study reports an ordering?
Explanation
The sample has no effector labels and does not expose the study’s level, method or region-of-interest recipe. A reported ordering belongs to that evidence context, while the installed geometry is only a population reference. It therefore cannot assign body-part fibres in an individual capsule.
In a surgical discussion
In a case discussion, record the level and evidence method when using capsular motor-fibre organisation. Use the atlas to orient the relationship, then keep an individual deficit or functional territory as a separate observation.
Putamen, globus pallidus, caudate and thalamus at the coarsest scale of a group subcortical parcellation. Anterior and posterior thalamus are merged into one mesh; no nucleus is individually named or targetable here.
The installed Melbourne scale-1 thalamus is gross anatomy. It does not segment lateral geniculate, VMpo or other relay nuclei; no named nucleus can be inferred from the outline.
A group-average cortical surface with a population parcellation, a population-averaged bundle atlas, and gross subcortical meshes. No patient image, no registration, no functional map, no brainstem or thalamic nuclei.
Ask the learner to answer before opening the explanation. Compare the answer with the named structures and the cited method. Teaching point: The sample has no effector labels and does not expose the study’s level, method or region-of-interest recipe. A reported ordering belongs to that evidence context, while the installed geometry is only a population reference. It therefore cannot assign body-part fibres in an individual capsule.
This relationship draws on 7 cited sources.
Relationship 5 of 7 · experimental anatomy
Frame the transsylvian corridor around missing layers
Orient
The putamen’s lateral edge is a layered boundary: the external capsule is lateral to putamen, the claustrum is lateral to the external capsule, the extreme capsule is lateral to the claustrum, and insular cortex is lateral and superficial to the extreme capsule. Ig, PoI2 and AVI point to the insular surface. A transsylvian description must add the Sylvian fissure, opercula, inferior limiting insular sulcus, temporal stem and vessels, none of which is a separate atlas mesh.
Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.
Targets
Ig, granular insular
PoI2, posterior insular
AVI, anterior ventral insula
Putamen
Compare
Lower the surface opacity and use the left lateral view. Compare AVI, Ig and PoI2 with putamen and globus pallidus, then identify which corridor boundaries are brought from anatomy rather than shown. Do not treat a parcel highlight as a dissection.
Read the neighbours
The external capsule and extreme capsule are distinct layers, with the claustrum between them; none is separately rendered here.
Ig, PoI2 and AVI are HCP parcel references, not complete insular gyri or individualized functional borders.
The transsylvian corridor includes the insular surface, opercular boundaries and vascular context, while MCA branches and perforators are not rendered.
The inferior limiting insular sulcus and temporal stem add boundaries to the lateral relationship, but they are not separate scene objects.
Explain before revealing
What must be added to a parcel and deep-structure comparison before it can be called a transsylvian anatomical description?
Explanation
It must add the unrendered external and extreme capsules, claustrum, Sylvian fissure, opercular and sulcal boundaries, temporal stem and vascular context. Ig, PoI2 and AVI are only cortical pointers, while putamen and globus pallidus are gross deep references. The atlas orients those relationships without reproducing a corridor.
In a surgical discussion
For a resident, a transsylvian anatomical account should separate cortical pointers, interposed layers, lentiform relationships, sulcal boundaries and vascular context. The atlas can highlight the surface and gross core, but it cannot turn those highlights into an exposed corridor or a layer-by-layer image.
Putamen, globus pallidus, caudate and thalamus at the coarsest scale of a group subcortical parcellation. Anterior and posterior thalamus are merged into one mesh; no nucleus is individually named or targetable here.
A group-average cortical surface with a population parcellation, a population-averaged bundle atlas, and gross subcortical meshes. No patient image, no registration, no functional map, no brainstem or thalamic nuclei.
Ask the learner to answer before opening the explanation. Compare the answer with the named structures and the cited method. Teaching point: It must add the unrendered external and extreme capsules, claustrum, Sylvian fissure, opercular and sulcal boundaries, temporal stem and vascular context. Ig, PoI2 and AVI are only cortical pointers, while putamen and globus pallidus are gross deep references. The atlas orients those relationships without reproducing a corridor.
This relationship draws on 6 cited sources.
Relationship 6 of 7 · association
Interpret subcortical mapping beside the CST
Orient
Subcortical motor mapping is best read here as a relationship among stimulation-current threshold, motor evoked potential change and observed outcome. Q6 reports that relationship in a clinical study near reconstructed motor tracts. This atlas supplies a population CST and gross deep landmarks but no stimulation site, current, MEP trace or individual outcome, so it cannot translate the report into a threshold to act on.
Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.
Targets
CST, corticospinal tract
Thalamus, gross
Putamen
Globus pallidus
Compare
Show CST with thalamus, putamen and globus pallidus in the anterior view. State which facts are visible in the scene and which would have to come from an individual mapping and monitoring record.
Read the neighbours
The cited study relates subcortical stimulation-current threshold, motor evoked potential change and outcome in its clinical setting.
The descending sample in this viewer is population averaged and has no stimulation site, current display, individual lesion, MEP trace or outcome.
Threshold, MEP change and outcome are separate observations, not interchangeable measures or a universal rule.
The atlas contributes gross spatial context for the CST and its neighbours; it cannot establish the study conditions or reproduce an individual mapping result.
Explain before revealing
What can this scene contribute to a report of a subcortical stimulation-current threshold, MEP change and outcome?
Explanation
It contributes a population CST reference and its gross thalamic and lentiform neighbourhood. It cannot provide the stimulation site or current, the MEP change, the individual lesion or the observed outcome. Those facts remain study-specific evidence and cannot be converted into an atlas-based action threshold.
In a surgical discussion
When reviewing mapping evidence, keep the stimulation-current threshold, tract definition, monitoring change and outcome as separate facts. A reported relationship can inform an anatomical hypothesis, but it is not a universal cut-off for an individual decision.
Putamen, globus pallidus, caudate and thalamus at the coarsest scale of a group subcortical parcellation. Anterior and posterior thalamus are merged into one mesh; no nucleus is individually named or targetable here.
The installed Melbourne scale-1 thalamus is gross anatomy. It does not segment lateral geniculate, VMpo or other relay nuclei; no named nucleus can be inferred from the outline.
A group-average cortical surface with a population parcellation, a population-averaged bundle atlas, and gross subcortical meshes. No patient image, no registration, no functional map, no brainstem or thalamic nuclei.
Ask the learner to answer before opening the explanation. Compare the answer with the named structures and the cited method. Teaching point: It contributes a population CST reference and its gross thalamic and lentiform neighbourhood. It cannot provide the stimulation site or current, the MEP change, the individual lesion or the observed outcome. Those facts remain study-specific evidence and cannot be converted into an atlas-based action threshold.
This relationship draws on 5 cited sources.
Relationship 7 of 7 · schematic
Predict the capsular part from the deficit pattern
Orient
Teaching vignette: a left deep lesion is followed by right face, arm and leg weakness with hemisensory loss, while no formal visual-field finding is reported. Use the deficit pattern to choose the leading capsular hypothesis, but keep retrolenticular and sublenticular relationships open because an unreported complaint is not a negative test.
Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.
Targets
TR_A, anterior thalamic radiation
CST, corticospinal tract
OR, optic radiation
Thalamus, gross
Compare
Compare the full set of limb references, with TR_A and CPT_F at the caudate-head to lentiform interval, CST and TR_S at the thalamus to lentiform interval, OR and TR_P behind the lentiform complex, and CBT as a corticobulbar comparison, without assigning all its fibres to the genu. Keep caudate, thalamus, putamen and globus pallidus visible while answering.
Read the neighbours
Anterior-limb relationships are relevant to frontothalamic and frontopontine systems.
Posterior-limb relationships are relevant to CST and superior thalamic radiation, with the genu providing an adjacent corticobulbar context.
Retrolenticular and sublenticular relationships are relevant to visual radiation, so a formal visual finding would add evidence about the leading hypothesis.
A deficit pattern is clinical evidence to localise, not a direct segmentation of the rendered capsule. The side of the deficit also matters because the lesson scene defaults to the left hemisphere.
Explain before revealing
Which capsular part should lead the hypothesis for right face, arm and leg weakness with hemisensory loss after a left deep lesion, and how should the missing visual report be treated?
Explanation
The posterior limb should lead because it is the key relationship for the CST and superior thalamic radiation. The sensorimotor pattern prioritizes a posterior-limb hypothesis; visual-field involvement remains unassessed unless examination is specified. The facial component can also raise a nearby genu question, but this is a structured localisation hypothesis, not proof of the exact injured fibres.
In a surgical discussion
Present the side and pattern first, then the capsular level and candidate pathways. A resident should preserve alternative explanations and ask how the individual lesion, examination and imaging compare with this population reference.
Putamen, globus pallidus, caudate and thalamus at the coarsest scale of a group subcortical parcellation. Anterior and posterior thalamus are merged into one mesh; no nucleus is individually named or targetable here.
The installed Melbourne scale-1 thalamus is gross anatomy. It does not segment lateral geniculate, VMpo or other relay nuclei; no named nucleus can be inferred from the outline.
A group-average cortical surface with a population parcellation, a population-averaged bundle atlas, and gross subcortical meshes. No patient image, no registration, no functional map, no brainstem or thalamic nuclei.
Ask the learner to answer before opening the explanation. Compare the answer with the named structures and the cited method. Teaching point: The posterior limb should lead because it is the key relationship for the CST and superior thalamic radiation. The sensorimotor pattern prioritizes a posterior-limb hypothesis; visual-field involvement remains unassessed unless examination is specified. The facial component can also raise a nearby genu question, but this is a structured localisation hypothesis, not proof of the exact injured fibres.
This relationship draws on 7 cited sources.
Recap
A left deep lesion is followed by right face, arm and leg weakness with hemisensory loss, while visual-field involvement is unassessed. Which capsular part leads, and what evidence remains missing?
Place the posterior limb between thalamus and the lentiform nucleus.
Compare anterior, posterior and retrolenticular relationships by their displayed pathways.
Use the deficit pattern to form a capsular hypothesis while preserving evidence limits.
Review the final explanation
The posterior limb should lead because it is the key relationship for the CST and superior thalamic radiation. The sensorimotor pattern prioritizes a posterior-limb hypothesis; visual-field involvement remains unassessed unless examination is specified. The facial component can also raise a nearby genu question, but this is a structured localisation hypothesis, not proof of the exact injured fibres.
Stepwise human dissections of the insula, capsules, basal ganglia and thalamus. Gross atlas meshes illustrate only part of these layered relationships.
A stepwise Klingler dissection guide to the anterior limb, genu, posterior limb, retrolenticular and sublenticular relationships. It supports a teaching description of relative organisation while leaving method and level limits explicit.
Provenance for the HCP1065 population-averaged bundles rendered here. Every displayed line is an average-space reconstruction sampled for display; it is not a patient’s pathway and carries no direction of conduction.
Provenance for the Melbourne Subcortex Atlas scale-1 meshes rendered here. Scale 1 is the coarsest level: anterior and posterior thalamus are merged and no brainstem nucleus is included.
Provenance for the S1200 group-average surface rendered here. A group-average midthickness surface is a population object; individual gyral and sulcal anatomy differs from it.
Probabilistic diffusion tractography relating thalamic territory to cortical target. A connectivity-defined territory is a model output, not a nuclear boundary, and this viewer ships no thalamic nuclei.
Population averaged structural connectome atlas supporting general population level discussion of callosal and cingulum topography. It is background for atlas methods, not the provenance of the installed HCP1065 bundle geometry.
Human cadaveric anatomy of the insular gyri, external and extreme capsules, claustrum and lentiform relationships. It anchors the layered transsylvian description without supplying a patient-specific corridor.
Human microsurgical anatomy of the inferior limiting insular sulcus and temporal stem. It supports the anatomical boundaries of transsylvian and transcortical descriptions without making a universal distance claim.
A clinical study relating subcortical stimulation-current threshold, motor evoked potential change and observed outcome. The reported relationship is evidence from that setting, not a universal threshold to act on.