Hodos NETWORKS & TRACTS

Lesson text is an educational draft awaiting anatomical review.

Network lectures · 6 relationships · 18 minutes · Neurosurgical residents

Attention networks · orienting, reorienting & neglect

Follow dorsal and ventral frontoparietal systems, compare their white matter, and build a network account of a spatial deficit.

Goals

Start this lesson in the atlas

Relationships

Relationship 1 of 6 · atlas

Start with the dorsal frontoparietal system

Orient

Preparing to look for a target at a chosen location recruits a distributed dorsal attention system. Frontal eye-field and intraparietal regions are useful anatomical anchors on its anterior and posterior sides.

Rotate the atlas until you can name what lies in front, behind and beneath the displayed structures.

Compare

Inspect the green dorsal-attention wash from lateral and superior views. Find its separated frontal and parietal territories before selecting individual parcels in later steps.

Read the neighbours

  • The Yeo-7 wash describes population functional coupling across cortex. Its separated patches belong to a network estimate, not one continuous gyrus.
  • The dorsal system has bilateral representation. The hemisphere control changes which reference surface you inspect.

Explain before revealing

Why is a posterior parietal lesion insufficiently described as damage to an isolated “attention centre”?

Explanation

The region participates in a frontal–parietal system. A useful account identifies the affected territory, its connections and the observed spatial behaviour. Local tissue injury and remote network dysfunction are different possibilities to examine.

In a surgical discussion

For a superior frontal or parietal lesion, include spatial selection and orienting in the anatomical discussion alongside strength and sensation. The relevant question extends to the connections between separated cortical territories.

Sources & anatomy notes

Evidence class: atlas

Network map, parcel and functional observation

The Yeo-7 wash is a group resting-state partition. HCP parcels are anatomical pointers, not transferred activation clusters or stimulation sites. Salience and language studies use definitions that do not correspond to dedicated Yeo-7 labels.

Evidence class: atlas · N1 · M1 · N11 · N7

Teaching notes

Ask for a spatial explanation before a network name. Then compare the proposed mechanism with the observed task. Discussion answer: The region participates in a frontal–parietal system. A useful account identifies the affected territory, its connections and the observed spatial behaviour. Local tissue injury and remote network dysfunction are different possibilities to examine.

This relationship draws on 6 cited sources.

Relationship 2 of 6 · atlas

Distinguish preparing attention from redirecting it

Orient

A cue can prepare attention before a target appears. An unexpected relevant target can require reorienting. These are different experimental questions, even when the same person performs both in one trial.

Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.

Targets

  • TPOJ1 · temporoparietal
  • 45 · inferior frontal

Compare

Compare the right TPOJ1 and inferior frontal 45 references. The magenta ventral-attention wash supplies broad context; the outlined parcel is an anatomical pointer, not a measurement of task activation.

Read the neighbours

  • TPOJ1 orients the temporoparietal junction near the posterior Sylvian region. Parcel 45 orients an inferior frontal reference.
  • Corbetta’s task study separated intraparietal preparatory responses from right temporoparietal target-detection responses. HCP parcels and those task regions have different definitions.

Explain before revealing

In a cued task, what distinguishes a deficit in using the cue from a deficit when a target appears at the uncued location?

Explanation

The first concerns preparation or allocation of attention; the second raises a reorienting question. Compare performance across conditions before proposing a dorsal or ventral network explanation. The task dissociation is more informative than the label “attention impaired.”

In a surgical discussion

A right perisylvian lesion can motivate a question about detecting or reorienting toward behaviourally relevant events. Name the tested behaviour rather than treating every difficulty as sustained inattention.

Sources & anatomy notes

Evidence class: atlas

Network map, parcel and functional observation

The Yeo-7 wash is a group resting-state partition. HCP parcels are anatomical pointers, not transferred activation clusters or stimulation sites. Salience and language studies use definitions that do not correspond to dedicated Yeo-7 labels.

Evidence class: atlas · N1 · M1 · N11 · N7

Teaching notes

Ask for a spatial explanation before a network name. Then compare the proposed mechanism with the observed task. Discussion answer: The first concerns preparation or allocation of attention; the second raises a reorienting question. Compare performance across conditions before proposing a dorsal or ventral network explanation. The task dissociation is more informative than the label “attention impaired.”

This relationship draws on 5 cited sources.

Relationship 3 of 6 · reconstruction

Add the parietal–frontal white matter

Orient

The superior longitudinal fasciculus family provides several parietal–frontal courses. Inspect the separate branches before using the phrase “frontoparietal disconnection.”

Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.

Targets

  • SLF I
  • SLF II
  • SLF III
  • FEF · frontal eye field
  • LIPd · intraparietal

Compare

Follow SLF I, II and III individually on the right. Compare their superior/inferior courses with the frontal eye-field and intraparietal references; restore the scene between selections.

Read the neighbours

  • The atlas contains separate SLF1, SLF2 and SLF3 samples. Their displayed endpoints do not assign every line to the selected cortical parcels.
  • The cited lateralization study related frontoparietal anatomy to visuospatial performance. Rightward anatomical asymmetry is a population observation, not an exclusive right-hemisphere function.

Explain before revealing

How can a frontal white-matter lesion contribute to a parietal-type spatial deficit while the parietal cortex appears structurally preserved?

Explanation

It can affect a pathway participating in frontal–parietal communication. That is a disconnection hypothesis: it requires the lesion’s actual location, a compatible behavioural finding and supporting individual anatomy. A normal-looking distant cortex does not settle network function.

In a surgical discussion

A subcortical extension can interrupt communication while leaving a distant cortical node structurally intact. Describe which branch and anatomical level are implicated by the individual lesion, rather than naming the entire SLF family.

Sources & anatomy notes

Evidence class: reconstruction

Network map, parcel and functional observation

The Yeo-7 wash is a group resting-state partition. HCP parcels are anatomical pointers, not transferred activation clusters or stimulation sites. Salience and language studies use definitions that do not correspond to dedicated Yeo-7 labels.

Evidence class: atlas · N1 · M1 · N11 · N7

Teaching notes

Ask for a spatial explanation before a network name. Then compare the proposed mechanism with the observed task. Discussion answer: It can affect a pathway participating in frontal–parietal communication. That is a disconnection hypothesis: it requires the lesion’s actual location, a compatible behavioural finding and supporting individual anatomy. A normal-looking distant cortex does not settle network function.

This relationship draws on 7 cited sources.

Relationship 4 of 6 · atlas

Separate spatial attention from maintaining a task

Orient

Selecting a location, changing a rule and maintaining a task set are related demands, but they are not the same operation. A difficult attention test may recruit more than one control system.

Rotate the atlas until you can name what lies in front, behind and beneath the displayed structures.

Compare

Inspect the orange frontoparietal-control wash. Compare lateral frontal and parietal territories with the dorsal-attention pattern remembered from step 1.

Read the neighbours

  • Dosenbach’s analysis distinguished adaptive frontoparietal control from more sustained cingulo-opercular task-set activity.
  • A seven-network partition and a task-defined control model divide cortex at different scales; similar names do not imply identical borders.

Explain before revealing

A patient searches both sides accurately until the task rule changes. Does that alone demonstrate a lateralized spatial-attention deficit?

Explanation

No. First characterize the failure to adapt to the rule and whether a left–right bias is present. A task-control difficulty and a spatial bias can coexist, but one should not be inferred solely from the other.

In a surgical discussion

When performance worsens during a prolonged or changing task, distinguish a spatial bias from loss of rule maintenance, reduced alertness or other task demands. Each account leads to a different question about the lesion.

Sources & anatomy notes

Evidence class: atlas

Network map, parcel and functional observation

The Yeo-7 wash is a group resting-state partition. HCP parcels are anatomical pointers, not transferred activation clusters or stimulation sites. Salience and language studies use definitions that do not correspond to dedicated Yeo-7 labels.

Evidence class: atlas · N1 · M1 · N11 · N7

Teaching notes

Ask for a spatial explanation before a network name. Then compare the proposed mechanism with the observed task. Discussion answer: No. First characterize the failure to adapt to the rule and whether a left–right bias is present. A task-control difficulty and a spatial bias can coexist, but one should not be inferred solely from the other.

This relationship draws on 5 cited sources.

Relationship 5 of 6 · functional measurement

Read a spatial bias as a measured behaviour

Orient

A rightward error on line bisection is an observation about spatial judgement. Its direction and task conditions matter more than calling the result simply abnormal.

Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.

Targets

  • PF · supramarginal
  • PFm · parietal transition
  • TPOJ1 · temporoparietal
  • SLF II

Compare

Compare right PF/PFm and TPOJ1 around the supramarginal and temporoparietal region, then follow the parietal–frontal samples. These are orientation pointers, not registered stimulation sites.

Read the neighbours

  • The cited study reported shifts with right inferior-parietal and caudal superior-temporal stimulation, with larger shifts at a subcortical site. These anatomical territories are broader than the selected HCP parcels.
  • The paper’s historical tract terminology is not used to certify any one modern atlas SLF branch as the stimulated pathway.

Explain before revealing

What must accompany the statement “stimulation disturbed spatial awareness” for another surgeon to interpret it?

Explanation

The task, direction and reproducibility of the error, stimulation conditions and localized site. A rightward bisection shift is more informative than “the test failed”; it still does not by itself establish the complete syndrome or a universal tract boundary.

In a surgical discussion

Task-specific spatial observations can contribute to a mapping discussion. Distinguish them from a visual-field defect or an isolated motor limitation; the atlas does not supply the individual examination or a mapping protocol.

Sources & anatomy notes

Evidence class: functional measurement

Network map, parcel and functional observation

The Yeo-7 wash is a group resting-state partition. HCP parcels are anatomical pointers, not transferred activation clusters or stimulation sites. Salience and language studies use definitions that do not correspond to dedicated Yeo-7 labels.

Evidence class: atlas · N1 · M1 · N11 · N7

Teaching notes

Ask for a spatial explanation before a network name. Then compare the proposed mechanism with the observed task. Discussion answer: The task, direction and reproducibility of the error, stimulation conditions and localized site. A rightward bisection shift is more informative than “the test failed”; it still does not by itself establish the complete syndrome or a universal tract boundary.

This relationship draws on 6 cited sources.

Relationship 6 of 6 · schematic

Present a right frontoparietal case as a network problem

Orient

Teaching vignette: after a right frontoparietal procedure, a person repeatedly omits items on the left during visual search despite useful strength in the left hand. Build the account from the behaviour outward.

Select each structure to light it on the atlas, then rotate until you can name what lies in front, behind and beneath it.

Targets

  • LIPd · intraparietal
  • FEF · frontal eye field
  • SLF II

Compare

Relate the intraparietal and frontal eye-field references to SLF II. Then identify what individual evidence would distinguish a local cortical lesion from a disconnection or wider network disturbance.

Read the neighbours

  • Useful hand strength does not describe spatial selection or awareness.
  • Stroke connectivity observations show that dysfunction can extend beyond the structural lesion; their outcomes cannot be transferred directly to a tumour resection.

Explain before revealing

Left-sided omissions persist despite useful hand strength after a right parietal procedure. Which findings could change an attention-network interpretation?

Explanation

Characterize the search bias alongside visual fields, sensation, movement and the time course. A field deficit or inconsistent task performance could change the interpretation of the omissions. Relate reproducible findings to the actual lesion and postoperative imaging before distinguishing cortical involvement from a disconnection or wider network disturbance; preserved strength alone does not settle that distinction.

In a surgical discussion

A resident presentation should specify the spatial bias, relevant sensory/motor findings, time course and lesion anatomy. Network reasoning adds a mechanism to investigate without replacing those observations.

Sources & anatomy notes

Evidence class: schematic

Network map, parcel and functional observation

The Yeo-7 wash is a group resting-state partition. HCP parcels are anatomical pointers, not transferred activation clusters or stimulation sites. Salience and language studies use definitions that do not correspond to dedicated Yeo-7 labels.

Evidence class: atlas · N1 · M1 · N11 · N7

Teaching notes

Ask for a spatial explanation before a network name. Then compare the proposed mechanism with the observed task. Discussion answer: Characterize the search bias alongside visual fields, sensation, movement and the time course. A field deficit or inconsistent task performance could change the interpretation of the omissions. Relate reproducible findings to the actual lesion and postoperative imaging before distinguishing cortical involvement from a disconnection or wider network disturbance; preserved strength alone does not settle that distinction.

This relationship draws on 6 cited sources.

Recap

A person omits items on the left during search despite useful hand strength. How would you localize the question?

  1. Distinguish preparatory orienting from reorienting toward a relevant event.
  2. Compare the separate superior-longitudinal courses in a frontoparietal account.
  3. Connect the observed spatial bias to a cortical or disconnection hypothesis and individual evidence.
Review the final explanation

Characterize the search bias alongside visual fields, sensation, movement and the time course. A field deficit or inconsistent task performance could change the interpretation of the omissions. Relate reproducible findings to the actual lesion and postoperative imaging before distinguishing cortical involvement from a disconnection or wider network disturbance; preserved strength alone does not settle that distinction.

Full source list

  1. N1 · Yeo et al., 2011 · intrinsic cortical network organization

    Resting-state fMRI in 1,000 adults. Source of the installed seven-network cortical partition; no individual task activation or subcortical network map is supplied.

    Evidence class: atlas

  2. N2 · Corbetta et al., 2000 · voluntary orienting and target detection

    Event-related fMRI distinguished preparatory intraparietal activity from right temporoparietal target responses. Functional task regions are not identical to HCP parcel boundaries.

    Evidence class: functional measurement

  3. N4 · He et al., 2007 · network disconnection in spatial neglect

    Stroke cohort linking spatial deficits to frontoparietal connectivity disruption. A lesion-network association is not a glioma resection-risk model.

    Evidence class: association

  4. M1 · Glasser et al., 2016 · multi-modal parcellation of human cerebral cortex

    HCP population reference built from converging cortical features. A parcel boundary here is a group boundary; it does not locate one person’s functional border and it has not been registered to any individual in this viewer.

    Evidence class: atlas

  5. N11 · Seeley et al., 2007 · salience and executive-control networks

    Task-free connectivity separated a frontoinsular/dorsal-cingulate network from a lateral frontoparietal control network. This is a different definition from the coarse Yeo-7 ventral-attention partition.

    Evidence class: association

  6. N7 · Fedorenko et al., 2011 · individually localized language-selective regions

    Individual-subject fMRI localizers distinguished high-level language responses from several nonlinguistic task responses. This atlas has no equivalent individual language localizer.

    Evidence class: functional measurement

  7. N3 · Thiebaut de Schotten et al., 2011 · lateralized visuospatial attention network

    Human tractography and visuospatial task associations. Hemispheric asymmetry in that sample does not make attention exclusively right-sided or identify an individual surgical boundary.

    Evidence class: association

  8. D2 · Yeh, 2022 · population-based tract-to-region connectome of the human brain

    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.

    Evidence class: atlas

  9. N13 · Dosenbach et al., 2007 · adaptive and stable task control

    Task-response patterns and resting-state connectivity motivated distinct frontoparietal and cingulo-opercular control systems. Network definitions and proposed timescales belong to that analysis.

    Evidence class: functional measurement

  10. N14 · Thiebaut de Schotten et al., 2005 · stimulation and spatial awareness

    Intraoperative stimulation produced rightward line-bisection shifts. The paper used historical fascicle terminology; this lesson does not relabel its stimulation sites as a particular installed SLF branch.

    Evidence class: functional measurement