Imagine waking up after a severe brain injury.

You can breathe. Your heart is beating. Your eyes may even open.

But can you see?

Can you hear?

Can you recognise the person standing beside your bed?

Most importantly, are you consciously experiencing any of it?

For clinicians caring for patients with disorders of consciousness, these are not philosophical questions. They are among the most difficult clinical questions in medicine.

And now, an unusual imaging technology is giving neuroscientists a new way to investigate them.

It is called transcranial focused ultrasound neuromodulation.

It does not produce an ultrasound image.

Instead, it uses precisely focused acoustic energy to temporarily alter neural activity deep within the brain—potentially allowing researchers to ask what happens to perception, attention and consciousness when a specific brain region is deliberately perturbed.

That distinction is important.

For decades, neuroscience has been exceptionally good at observing the brain.

Focused ultrasound may help us experimentally interfere with it.

And that could change how we study consciousness.

The problem with simply looking at the brain

Modern neuroimaging has taught us an extraordinary amount about consciousness.

Functional MRI can demonstrate changes in brain activity associated with perception, attention and awareness. PET can reveal changes in cerebral metabolism. EEG can track electrical activity over milliseconds.

But there is a fundamental limitation.

When an fMRI study shows that a particular region becomes active when a person sees an object, we know that the region is associated with the experience.

We do not necessarily know whether it is causing the experience.

This is the difference between correlation and causation.

If a light bulb switches on whenever you press a particular button, you can reasonably suspect a relationship. But to establish causality, you need to manipulate the system.

That is considerably more difficult in the human brain.

Historically, some of the strongest evidence came from neurosurgery.

The Penfield experiment

In the middle of the 20th century, neurosurgeon Wilder Penfield electrically stimulated exposed areas of the brains of awake patients during surgery.

The results were remarkable.

Stimulation of different regions could evoke sensations, movements, memories and perceptual experiences.

Penfield was effectively asking:

“What happens when I activate this part of the brain?”

But there was an unavoidable problem.

The brain is not a collection of isolated boxes.

Neural structures are connected by enormous networks. Stimulating one location can influence activity elsewhere.

Consequently, finding that stimulation of a particular region produces an experience does not necessarily mean that the region itself generates consciousness.

The deeper question remained unresolved.

The cortex may not be the whole story

For much of modern neuroscience, the cerebral cortex has occupied centre stage in discussions of consciousness.

That is understandable.

The cortex supports sophisticated functions including language, abstraction, planning, complex perception and self-reflection.

But consciousness may not be synonymous with cognition.

A growing body of research has focused on structures beneath the cortex, particularly the thalamus.

The thalamus is often introduced to medical students as a relay station.

That description is useful—but incomplete.

The thalamus participates in extensive reciprocal connections with cortical and subcortical networks and has long been implicated in arousal, attention and conscious processing.

A 2025 systematic review of thalamic involvement in consciousness concluded that conscious states depend on interactions between cortical and subcortical structures rather than on an isolated anatomical location.

This creates an intriguing possibility.

Perhaps consciousness is not produced by one anatomical “consciousness centre” at all.

Perhaps it emerges from a network.

And perhaps some of the most important nodes in that network lie deep within the brain.

Enter focused ultrasound

This is where radiology becomes directly relevant.

Low-intensity transcranial focused ultrasound can deliver acoustic energy through the skull and focus it on a relatively small target within the brain.

The technology is fundamentally different from diagnostic ultrasound.

Diagnostic ultrasound asks:

“What is inside the body?”

Focused ultrasound neuromodulation asks:

“What happens if I influence this specific region?”

The target is usually defined using the patient's own neuroanatomical imaging.

MRI provides detailed anatomical localisation and can be used to identify the intended target.

CT can be particularly valuable because the skull is not acoustically transparent. Its thickness, density and geometry influence the propagation of the ultrasound beam.

The imaging therefore becomes part of the treatment—or experimental—planning process.

The sequence is conceptually elegant:

MRI/CT → identify target → calculate acoustic pathway → focus ultrasound → alter neural activity → measure behavioural or physiological response.

Radiology is no longer merely showing the brain.

It is helping determine where an intervention should occur.

Can ultrasound actually change perception?

This question has now moved from theory toward experiment.

In a 2025 Nature Communications study, researchers used low-intensity focused ultrasound to modulate different thalamic regions in healthy participants performing a near-threshold visual perception task.

The researchers reported that stimulation of the ventroanterior thalamus could enhance object-recognition sensitivity, while other stimulation conditions disrupted object-categorisation performance. The effects were examined in relation to the functional connectivity and cellular organisation of the targeted thalamic regions.

That is an important distinction.

The study did not “find the location of consciousness.”

It demonstrated something more scientifically useful:

Changing activity in a specific deep-brain region can alter conscious visual processing.

That is causal evidence.

And it suggests that the thalamus is not merely passively relaying information between the cortex and the rest of the brain.

The thalamus is becoming an experimental target

The story became even more interesting in 2026.

A July 2026 study examined focused ultrasound stimulation of the bilateral centromedian thalamic nuclei in 16 healthy adults. The investigators found that a brief 25-Hz stimulation protocol improved performance on a directed-attention task compared with sham stimulation, with effects persisting for at least 40 minutes. EEG changes were also associated with the behavioural effects, and pre- and post-procedure MRI showed no structural changes attributable to stimulation in the study.

This is not evidence that ultrasound can “switch consciousness on.”

It is evidence that carefully targeted neuromodulation can influence components of arousal and attention.

That distinction matters.

Consciousness is not the same thing as attention.

But the two are intimately related, and experimentally separating them may help researchers understand how conscious states are constructed.

What about patients who cannot respond?

The potential clinical implications are even more intriguing in disorders of consciousness.

Patients in minimally conscious or other prolonged disorders of consciousness may have preserved neural activity that cannot easily be expressed through conventional behavioural responses.

This creates a difficult clinical problem.

A patient who cannot reliably follow commands may still possess some degree of awareness.

Could deep-brain neuromodulation reveal or even enhance that capacity?

A 2026 preprint reported a single-arm study of 16 adults with chronic disorders of consciousness who underwent thalamic transcranial focused ultrasound. After stimulation, behavioural scores on the Coma Recovery Scale-Revised increased, alongside changes in EEG measures and cerebral metabolic findings. The authors interpreted the convergent findings as evidence consistent with modulation of thalamocortical networks, while emphasising the need for larger sham-controlled trials.

This is promising.

But it is not yet clinical proof.

The study was single-arm and open-label, and therefore cannot exclude important placebo, measurement or regression-to-the-mean effects.

That distinction is exactly where responsible medical journalism should separate interesting evidence from established treatment.

Why the skull matters

Focused ultrasound sounds deceptively simple.

“Point ultrasound at the brain.”

In reality, the skull is one of the biggest technical obstacles.

Bone strongly affects acoustic transmission.

The ultrasound beam can be distorted, attenuated and phase-shifted as it passes through the skull.

Therefore, targeting deep structures requires careful modelling and patient-specific planning.

This is one reason imaging is so important.

The patient's anatomy can be incorporated into the targeting process, while CT information can help characterise the skull and improve acoustic modelling.

MRI then provides the anatomical framework for identifying structures such as the thalamus.

The future system may therefore look less like a conventional ultrasound examination and more like an integrated image-guided neuromodulation platform.

Imaging plus intervention

Radiology has traditionally been divided into two broad ideas:

diagnostic imaging

and

image-guided intervention.

Focused ultrasound neuromodulation occupies an interesting space between them.

The imaging identifies the target.

The imaging helps plan the pathway.

The intervention changes neural activity.

Other modalities then measure what happened.

MRI can assess anatomy and functional connectivity.

PET can evaluate metabolism.

EEG can measure electrical activity.

Behavioural testing can determine whether perception or responsiveness changed.

The result is a multimodal experiment:

Anatomy + ultrasound + physiology + behaviour.

That is a very different paradigm from simply performing an MRI and observing which areas “light up.”

We may eventually map the brain by perturbing it

This may be the most important conceptual shift.

For decades, neuroscience has largely relied on observation:

What happens in the brain when a person experiences something?

Focused ultrasound allows a complementary question:

What happens to the experience when we change a specific part of the brain?

That is a much more powerful experimental framework.

Imagine systematically targeting different thalamic nuclei while measuring perception, attention, memory and awareness.

Then combine those experiments with functional connectivity maps.

The result could be something approaching a causal map of human consciousness—not a single location, but a network of structures whose interactions are necessary for particular aspects of experience.

But there are substantial limitations

The technology is still experimental.

Focused ultrasound does not provide millimetre-perfect control over neural circuits in every situation. Acoustic propagation through the skull varies between individuals. The biological mechanism of low-intensity ultrasound neuromodulation is still being investigated. Effects can depend on acoustic parameters, target anatomy and stimulation protocol.

Recent work has also shown that ultrasound can produce changes in large-scale functional brain networks after stimulation, reinforcing the idea that the biological effects may extend beyond the immediately targeted region.

That is both an opportunity and a challenge.

A stimulation site may not equal the biological site of action.

The brain is a network.

And networks rarely respect the boundaries drawn on an anatomical atlas.

So, have we found the seat of consciousness?

No.

And that is precisely what makes the research interesting.

The evidence increasingly suggests that conscious experience depends on interactions between cortical and subcortical systems.

Focused ultrasound is beginning to provide a way to perturb those systems noninvasively and measure the consequences.

The goal is therefore not to discover a tiny anatomical box labelled “CONSCIOUSNESS.”

The more realistic goal is to determine:

Which structures are necessary?

Which connections are necessary?

Which patterns of activity are sufficient?

And how does the brain transform neural activity into subjective experience?

Those questions remain unanswered.

But for the first time, we are acquiring tools capable of asking them with increasing experimental precision.

A new role for radiology

For radiologists, this story represents something larger than another application of ultrasound.

It illustrates how medical imaging is evolving.

Imaging began as a way of seeing anatomy.

Then it became a way of characterising physiology.

Then it became a way of guiding procedures.

Now, in technologies such as focused ultrasound neuromodulation, imaging can become part of a closed experimental or therapeutic loop:

See → target → stimulate → measure → adjust.

That is a profound change.

The radiologist of the future may not simply interpret what the brain looks like.

They may increasingly participate in systems designed to understand—and potentially modify—how the brain functions.

And perhaps that brings us back to the mouse.

If a brain can navigate a maze, learn from experience and respond intelligently, does it necessarily experience anything?

We still do not know.

But with MRI, CT, EEG, PET and focused ultrasound working together, neuroscience is beginning to ask the question in a way that is no longer purely philosophical.

The mystery of consciousness remains.

But now, for perhaps the first time, we have a tool that allows us to perturb the machinery of experience—and see what happens next.