Brain networks: symptoms rarely have an address in the brain.
They have a rhythm.
Seven networks, explained in plain language: where they sit, what they do, how it shows when one runs too loud or too quiet, and how we assess it. For anyone who wants to know what “a network out of rhythm” means.
A symptom is rarely a broken area
Rumination, sensory overload, a head that no longer plans, a body on alert: what you experience rarely arises at a single point in the brain. It arises in the interplay of regions that fire together as a network. In health these networks take turns. The resting network steps back as soon as the executive network takes over, and the salience network decides when. Complaints often show exactly where this switch no longer works: one network runs too loud, another too quiet, or both at the wrong time.
This page walks through the networks one by one, always in the same grid: where it sits, what it does, how over- and underactivity show, which conditions it is typically involved in, and how we assess and influence it. The symptom lists describe what is common, not a diagnosis. A network finding does not replace a diagnosis; it explains what the diagnosis leaves open: why two people with the same word in their referral letter should be treated differently.
Seven networks, one grid
The graph shows six of the seven networks, the way they appear in the brain network self-assessment and in the brain map. The visual network is added on this page because it asks the first question of any qEEG. Jump straight to the network you are interested in.
- 01Default Mode Network (DMN)inner focus, memory, rumination
- 02Salience Networkdecides what matters right now
- 03Central Executive Network (CEN)planning, working memory, control
- 04Attention Networks (DAN and VAN)dorsal holds, ventral interrupts
- 05Limbic Networkemotion, stress, memory
- 06Sensorimotor Networkmovement, body sense, pain
- 07Visual Networkvision and stimulus processing
- A to ZGlossarythe terms on this page, briefly explained
Six networks · schematic · the visual network is not shown in the graph
Default Mode Network (DMN)
The default mode network is the network that switches on when you do nothing. In rumination, it does too much of that.
What it normally does
As soon as no task arrives from outside, this network takes over. It retrieves memories, runs through next week, thinks about you and about other people, and holds your life story together as a whole. That is no idle activity: learning from experience, putting yourself in someone else’s place, forming a plan for tomorrow, all of it needs exactly this inward view.
What matters is the switch. When a task arrives, the DMN steps back and the executive network takes over; specialists call this anticorrelation. A healthy DMN is one that can be switched off the moment the world wants something from you.
Typical symptoms when overactive / upregulated
- Rumination and looping thoughts that cannot be stopped, especially in the evening and at night
- Constant self-reference: what did I do wrong, what do the others think
- Hard to get out of your head and into the task; reading without taking anything in
- Inner restlessness despite exhaustion; the network does not step back during tasks
Typical symptoms when underactive / downregulated
- Little access to memories and to your own story, “standing beside yourself”
- Difficulty planning the future or putting yourself in someone else’s place
- Emptiness instead of an inner life, flat drive
- In cognitive decline: the posterior and anterior nodes lose their connection
Conditions in which it is typically involved
A DMN that is too loud, or that does not step back during tasks, is seen in connection with:
- Depressionrumination, negative self-reference
- Treatment-resistant depressionoften together with a quiet executive network
- Anxietyworry chains that feed themselves
- PTSD and traumaaltered connection to the hippocampus
- Long COVID and brain fogaltered DMN connectivity in imaging studies, evidence still young
- Tinnitustogether with the salience network
- Insomnia and sleepnight-time rumination
- MCI and cognitive declinehere rather underactivity: the posterior nodes decouple
How we assess and influence it
Every network starts with a structured assessment: history, existing findings, questionnaires, clinical examination. For the DMN we ask specifically about rumination, about the evening and about the night. Whether a qEEG is added is decided after that. In the qEEG, a DMN that does not settle often shows as a rhythm over the midline and posterior leads that looks the same with eyes closed as with eyes open. Imaging is added when a structural cause has to be ruled out, for instance in early cognitive decline.
The DMN can rarely be influenced directly; it sits too deep in the midline. The route runs through its counterparts. rTMS over the dorsolateral prefrontal cortex strengthens the executive network and, through it, the ability to switch the DMN off; for depression this route is described in clinical guidelines. Neurofeedback trains the switch between inner and outer focus with real-time feedback. Alongside that, the concept includes whatever keeps the DMN running. Sleep deprivation lowers control over this network, so sleep sits in the same plan. After infections, inflammatory messengers hold the brain in a state where the inward view dominates, so lab work belongs in it. And what you have lived through changes the wiring measurably, so psychological support is part of the same plan.
Salience Network
The salience network decides what is important right now. When it treats everything as important, the world feels too loud.
What it normally does
Every second, stimuli from outside and signals from the body arrive: heartbeat, breath, gut, muscle tension, plus sounds, faces, news. The salience network sorts which of these deserve attention and then switches: inner view off, action on, or the other way round. The anterior insula reads the body (interoception); the dACC evaluates and mobilises.
That is why this network sits at the interface of brain and body. What the vagus nerve reports from gut and heart lands here first.
Typical symptoms when overactive / upregulated
- Sensory overload: sounds, light and crowds quickly become too much
- Alarm readiness, palpitations, sweating with no obvious trigger
- Body sensations are read as threats (heart, breath, gut)
- Hard to come back down from alarm; sleep stays shallow
Typical symptoms when underactive / downregulated
- Apathy, little reaction to what matters
- Switching fails; you stay stuck in rumination or in a task
- Body signals are noticed late or not at all
- Flat emotional response, little drive
Conditions in which it is typically involved
An overactive salience network often shows in anxiety, trauma and chronic pain; a sluggish one rather in apathy. It is seen in connection with:
- Anxietybody signals become threats
- PTSD and traumahyperarousal, startle
- Chronic painpain stays permanently “important”
- Fibromyalgiastimulus and pain sensitivity
- Tinnitusthe sound never loses salience
- ME/CFSstimulus sensitivity, autonomic dysregulation
- Long COVIDracing heart, sensory overload
- OCDerror signals that do not fade
- Depressionhere rather the sluggish side: anhedonia
How we assess and influence it
In the assessment we ask about stimulus sensitivity, palpitations, sleep and the gut, and we measure heart rate variability (HRV) as a window into autonomic regulation; HRV and qEEG show two sides of the same state. A qEEG is added when the question is whether the brain stays on alert even at rest. That often shows as an excess of fast rhythms over the frontal and central leads.
The most direct route to the salience network runs through the vagus nerve. taVNS stimulates its branch at the ear and reaches the insula and cingulate via the brainstem; the evidence is growing, though younger than for rTMS. Neurofeedback and HRV biofeedback train you to recognise your own alarm response and turn it down. Then there is whatever makes the doorman nervous. A gut that keeps reporting produces a salience network that keeps listening: gut barrier and gut flora talk to the insula directly via the vagus and via inflammatory signals, so gut diagnostics and nutrition belong in the same plan. A chronic infection keeps the immune system running and lowers the alarm threshold; stimulating only the network means working against a motor that keeps going.
Central Executive Network (CEN)
The executive network is the part of you that makes a plan and sticks to it. When it goes quiet, everything becomes hard work.
What it normally does
Working memory, planning, deciding, braking impulses, holding attention on purpose and putting feelings in perspective: this is the network for the tax return, the difficult conversation and tomorrow’s list. It works “top down” and keeps the DMN and the amygdala in check while it does.
It is also the most energy-hungry network in the brain and the first to fade when sleep or energy runs short. A quiet executive network is therefore very often a symptom of something else.
Typical symptoms when overactive / upregulated
- Over-control and perfectionism; solutions are sought but never closed
- Tension, a “full head”, planning that does not stop in the evening
- Cognitive exhaustion after a short time, because the network runs non-stop
- Falling asleep is hard because thinking does not step back
Typical symptoms when underactive / downregulated
- Planning, starting and finishing become difficult
- Working memory has gaps: threads get lost, sentences stay half finished
- Decisions are postponed, impulses are braked less well
- Feelings flood in because the brake is missing; brain fog, thinking through cotton wool
Conditions in which it is typically involved
An executive network that has “gone quiet”, especially on the left, is seen in connection with:
- Depressionleft DLPFC, the rTMS target in the guidelines
- Treatment-resistant depressionwhen medication has not reached the network
- Adult ADHDworking memory, impulse control
- Long COVID and brain fogthe cotton wool in the head
- ME/CFScognitive exhaustion after exertion
- Burnoutnon-stop, then collapse
- Stress and exhaustionthe overactive side
- MCI and cognitive declineplanning and multitasking
- Traumatic brain injurythe frontal lobe is exposed on impact
How we assess and influence it
Here the assessment includes short cognitive tests (working memory, verbal fluency, attention) and lab work that checks the energy supply: thyroid, iron, vitamin B12, inflammation markers, cortisol where needed. If the thyroid is underactive, the quiet prefrontal cortex is a thyroid matter first and a stimulation target second. Nerve cells are the most energy-hungry cells in the body; when energy production stalls after an infection or under chronic stress, this network loses performance before any image shows it. A qEEG is added when the question of network activity itself is open; a quiet executive network often shows there as an excess of slow rhythms over the forehead or as an imbalance between left and right.
For stimulation, this network is the best-studied site in the brain. rTMS over the left DLPFC is backed in depression by randomised trials, meta-analyses and guidelines; accelerated TMS condenses the same stimulation into a few days. tDCS targets the same site with a weak direct current, with growing evidence. Neurofeedback trains you to turn the slow rhythms down yourself. No one is an average: where we start is decided by your findings, and whether the plan is working shows in the course.
Attention Networks (DAN and VAN)
Attention is two networks: one keeps your eyes on the target, the other interrupts when something important happens. Concentration problems are often a dispute between the two.
What it normally does
Dorsal attention network (DAN)
It points attention at a target on purpose and keeps it there: the line in the text, the face in the conversation, the junction while driving. It steers gaze and attention through space.
Ventral attention network (VAN)
It interrupts when something unexpected and relevant appears: the shout, the movement at the edge, the smell of smoke. It sits mostly in the right hemisphere. In health the two balance each other: one holds, the other may interrupt, and the salience network decides when.
Typical symptoms when overactive / upregulated
- DAN: tunnel vision, hyperfocus, being unable to leave a task
- VAN: every little thing pulls attention away, startle
- Sensory overload in rooms with a lot of movement and noise
- Exhaustion after concentrating, because holding runs against constant interruption
Typical symptoms when underactive / downregulated
- DAN: focus cannot be held on purpose, thoughts drift off
- Reading without taking anything in; tasks take twice as long
- VAN: important things are missed, reactions come late
- After a right-sided stroke: one side of space is neglected
Conditions in which it is typically involved
Attention networks that hold too little or interrupt too often are seen in connection with:
- Adult ADHDthe qEEG complements, it does not diagnose
- Long COVID and brain fogconcentration breaks off early
- ME/CFSattention as an exhaustible resource
- Depressionconcentration as a core symptom
- Insomnia and sleepfocus is the first thing to go
- Stroke rehabilitationneglect after right-sided stroke
- Traumatic brain injurydistractibility, slowing
- Multiple sclerosiscognitive fatigue
How we assess and influence it
With concentration problems the assessment starts with the history, for ADHD back into childhood, with validated questionnaires and a screen-based attention test that measures holding and interrupting separately. And with sleep: an attention network that gets too little every night is a sleep matter first, occasionally a sleep apnoea matter. The qEEG can give pointers, such as an excess of slow rhythms over the forehead; it does not make an ADHD diagnosis, which remains clinical. After a stroke, neurological examination of the visual field and of spatial awareness is part of it.
Neurofeedback is the longest-used method here: it trains holding attention against your own rhythm, with moderate evidence in ADHD. tDCS and rTMS over prefrontal and parietal nodes are under investigation; the evidence is younger, and we use them when the findings support it. After a stroke, neuro-physiotherapy works with the ventral network to bring the neglected side back. In long COVID, immune system and energy metabolism belong in the same plan, because a network that lacks energy does not have a training problem.
Limbic Network
The limbic network decides how much something hurts before you have thought about it.
What it normally does
This network evaluates: danger or reward, near or far, relevant to me or not. The amygdala learns fear and has to be able to unlearn it. The hippocampus files new memories and knows the context: here and now is safe. The OFC weighs value against consequence; the ACC connects feeling with action. Through the hypothalamus the network sets the stress hormone axis, that is cortisol and adrenaline.
It is faster than thought. That is useful in the forest and a problem in daily life when it no longer tells then from now.
Typical symptoms when overactive / upregulated
- Anxiety, panic, startle; situations are read as danger when they are not
- Feelings flood in, irritability, thin skin
- Stress hormones permanently high: light sleep, waking around three, muscle tension
- Memories intrude (flashbacks); yesterday feels like today
Typical symptoms when underactive / downregulated
- Lack of drive and anhedonia: nothing rewards any more
- Emotional numbness, distance from people who matter to you
- Memory for new things has gaps when the hippocampus is under constant stress
- Motivation is missing despite wanting
Conditions in which it is typically involved
A limbic network that sounds the alarm too fast, or no longer rewards anything, is seen in connection with:
- Anxietyan amygdala that does not unlearn
- PTSD and traumathe hippocampus loses the context “over”
- Depressionanhedonia, cortisol
- Bipolar disordermood as a control loop
- OCDOFC and ACC, the loop
- Chronic painpain is evaluated emotionally here
- Burnoutthe stress axis after running non-stop
- Insomnia and sleepcortisol at the wrong time
- Alzheimer’s and dementiathe hippocampus is affected early
How we assess and influence it
Here the assessment includes a conversation that takes its time: what happened, what is happening, what triggers it. Questionnaires on anxiety, mood and strain; lab work with a cortisol day profile, thyroid, sex hormones and inflammation markers, because hormones set the baseline tension of the nervous system. The amygdala itself cannot be measured directly in a surface EEG; a qEEG shows the consequences at the surface, such as an imbalance between the left and right forehead or an excess of fast rhythms. With memory gaps, imaging is added to see the hippocampus itself.
Neuromodulation reaches this network through its brakes. rTMS over prefrontal regions that regulate the amygdala is being studied in anxiety and PTSD with growing evidence; in depression the same route is established. taVNS dampens the stress axis via the vagus nerve; the data are young. HRV biofeedback and neurofeedback give the body a message it has not had for a long time: that the danger is over. What you have lived through changes the wiring measurably, so neuromodulation and psychological support work on the same network from two sides.
Sensorimotor Network
The sensorimotor network is the map of your body in the brain. In chronic pain, the map is often distorted.
What it normally does
It plans and executes movement, senses the body (touch, position, temperature, the location of a pain) and fine-tunes both with the cerebellum. Every body part has its place on this strip, hands and face an especially large one.
At rest this strip has a rhythm of its own, the sensorimotor rhythm (SMR, 12 to 15 Hz). It stands for the state “awake but physically calm” and is easy to see in the EEG.
Typical symptoms when overactive / upregulated
- Constant muscle tension, tightness, teeth grinding
- Oversensitivity to touch, pressure or temperature
- Motor restlessness, tics, the feeling of never being able to sit still
- Pain that remains after the tissue has healed: the map has learned the pain
Typical symptoms when underactive / downregulated
- Clumsiness, slowed movement, fine motor skills decline
- The body feels foreign or numb without any nerve damage
- Balance and coordination become unsteady
- After a stroke: loss of strength or paralysis on one side
Conditions in which it is typically involved
A sensorimotor network that does not settle, or has lost its access, is seen in connection with:
- Chronic painthe distorted body map
- Fibromyalgiastimulus processing and pain threshold
- Migrainetouch sensitivity during an attack
- Parkinson’sbasal ganglia as the network’s partner
- Stroke rehabilitationregaining strength and fine motor control
- Traumatic brain injurycoordination, balance
- Multiple sclerosisspasticity, fine motor control
- Cerebral palsyspasticity, movement planning
- Tinnitusforms that can be modulated somatosensorily
How we assess and influence it
Here the clinical neurological examination is the core of the assessment: strength, reflexes, sensation, coordination, gait. Plus pain questionnaires and, where a structural cause is possible, an MRI. In the qEEG, a sensorimotor strip that does not settle often shows as an absent or weak SMR over the central leads. Sleep deprivation lowers the pain threshold measurably, and chronic inflammation keeps pain pathways sensitive; we ask about both before we talk about stimulation.
rTMS over the motor cortex has been studied in neuropathic pain for years and is rated effective in European expert recommendations; in fibromyalgia and after stroke the evidence is moderate and growing. tDCS targets the same site. SMR neurofeedback trains the strip’s resting state. And because a map is only redrawn by being used, neuro-physiotherapy belongs in the plan: stimulation opens a window, movement uses it.
Visual Network
The visual network is the brain’s largest stimulus-processing system. When it is overstimulated, even light becomes a burden.
What it normally does
It turns light into contrast, colour, motion, faces and letters and passes the result on to the parietal and temporal lobes, where seeing becomes acting and recognising. Almost a third of the cortex is busy with it.
When you close your eyes, this network should drop into the alpha rhythm (8 to 12 Hz), the most stable rhythm in the EEG. Whether it does is one of the first questions asked of any qEEG.
Typical symptoms when overactive / upregulated
- Light sensitivity, glare, sunglasses even indoors
- Flicker, aura, visual snow: the network fires without a matching stimulus
- Overload in supermarkets, in front of screens, with patterns and motion
- In the qEEG: the network builds no alpha rhythm with eyes closed
Typical symptoms when underactive / downregulated
- Recognising and reading become slow and tire quickly
- Visual field defects after stroke or traumatic brain injury
- Orientation and motion vision become unreliable
- Blurred processing despite healthy eyes
Conditions in which it is typically involved
A visual network that fires too easily, or has lost its input, is seen in connection with:
- Migrainehyperexcitable visual cortex, aura
- Long COVIDlight and screen sensitivity
- ME/CFSstimulus sensitivity as part of the exhaustion
- Stroke rehabilitationvisual field, neglect
- Traumatic brain injuryvisual processing after impact
- Multiple sclerosisoptic nerve and processing
How we assess and influence it
Before any network question come the eyes and the optic nerve: ophthalmological work-up, neurological examination with visual fields, imaging where needed. Only then is the qEEG worthwhile, and there alpha reactivity is the core question: does the network build its resting rhythm with eyes closed, and does it break off cleanly on opening? A network that does not settle is often an overstimulated network.
Direct stimulation of the visual cortex with rTMS or tDCS is being studied in migraine; the evidence is limited, and we use it only as an adjunct after thorough informed consent. More often the route runs through whatever overstimulates the visual cortex: sleep and light hygiene, in migraine the hormone cycle, in long COVID the immune system that lowers the stimulus threshold. After a stroke, visual field training and neuro-physiotherapy are part of it, because the network only regains its input by being used.
From network to plan
None of these networks works alone. A quiet executive network and a loud DMN are often the same picture from two sides, and a salience network on alert pulls the limbic network with it. So we treat the pattern the assessment shows, and whatever drives it: sleep, immune system, hormones, gut, lived experience. Our aim is to restore functional balance, as far as possible without drugs; how far that carries in your case shows in the course, which is why we measure before and after.
A first impression of which networks look strained in your case comes from the brain network self-assessment in ten minutes. How an assessment turns into a program is described on the method page. Shorter treatments of this topic: The six brain networks, simply explained and The default mode network.
The terms on this page
- Network (functional)
- Regions that become active together even when they lie far apart. Visible in functional imaging and in the qEEG as regions whose rhythms swing in step.
- Node (hub)
- A region that bundles an especially large number of connections within a network. The PCC is the central node of the DMN.
- Connectivity
- How strongly two regions exchange with each other. “Hyperconnectivity” means coupled too tightly, “hypoconnectivity” too loosely.
- Anticorrelation
- Two networks that take turns: when one becomes active, the other steps back. DMN and executive network are the best-known pair; in rumination and brain fog this switch is often disturbed.
- Over- and underactivity
- A network works more or less than the situation calls for. Both can cause complaints; the direction decides the approach.
- Up- and downregulation
- The shift of a network’s baseline activity upwards or downwards, for instance through chronic stress, sleep deprivation or inflammation.
- Salience
- How much a stimulus draws attention to itself. The salience network assigns this weighting.
- Interoception
- The perception of your own body interior: heartbeat, breath, gut. Seated mainly in the insula.
- Prefrontal cortex
- The front part of the frontal lobe. Dorsolateral (DLPFC) steers, medial (mPFC) relates to the self, orbitofrontal (OFC) evaluates.
- Cingulate (ACC / PCC)
- A belt around the corpus callosum. At the front (ACC) it connects feeling with action; at the back (PCC) it is the core of the inward view.
- qEEG
- Quantitative EEG: brain rhythms are recorded with many electrodes and compared with a normative database. A diagnostic method, not a treatment.
- Alpha, theta, beta, SMR
- Frequency bands of the EEG: alpha (8 to 12 Hz) rest with eyes closed, theta (4 to 8 Hz) drowsiness and inward focus, beta (13 to 30 Hz) active thinking or alarm, SMR (12 to 15 Hz) a calm body.
- Neuromodulation
- Methods that change the activity of nerve cells in a targeted way without surgery: rTMS, tDCS, taVNS, neurofeedback. With us, one building block within the overall concept.
- HRV
- Heart rate variability: the fine fluctuations of the heartbeat, a measure of regulation by the vagus nerve. Shows the same state as the qEEG, seen from the body.
Which network is out of rhythm in your case?
In a free consultation, 15 to 20 minutes with our medical team, we clarify whether an assessment is worthwhile in your case and which measurements belong to it. You leave with a clear appraisal.