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Sam Krimmel

@samkrimmelneuro

Neuroscientist post-doc working with Nico Dosenbach at Washington University in St. Louis

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14.02.2025
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Latest posts by Sam Krimmel @samkrimmelneuro

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Stimulant medications affect arousal and reward, not attention networks Stimulant medications (e.g., methylphenidate) were thought to improve attention by acting on the brain's attention networks. Functional connectivity data now reveal that stimulants are associated with...

as well as research articles on how stimulant medications affect arousal and reward rather than attention networks
www.cell.com/cell/fulltex...

24.12.2025 17:43 πŸ‘ 8 πŸ” 5 πŸ’¬ 1 πŸ“Œ 0
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It’s time to rethink Parkinson’s disease. Our work reframes PD as a disorder of the somato-cognitive action network (SCAN), and shows that normalizing SCAN connectivity represents a shared mechanism across diverse effective therapies.
rdcu.be/e2n4t
@ndosenbach.bsky.social @gordonneuro.bsky.social

05.02.2026 00:35 πŸ‘ 32 πŸ” 19 πŸ’¬ 2 πŸ“Œ 1
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Parkinson’s disease as a somato-cognitive action network disorder - Nature The substantia nigra and all Parkinson’s disease deep-brain stimulation targets are selectively connected to the somato-cognitive action network rather than to effector-specific motor regions.

A recently discovered brain network that links cognition (thinking) and actions may have an important role in Parkinson’s disease and could improve its treatment, according to a study published in Nature: spklr.io/63320DMwOi

#Neuroscience #Neuroskyence #Parkinsons 🧠 πŸ§ͺ

04.02.2026 20:11 πŸ‘ 31 πŸ” 16 πŸ’¬ 0 πŸ“Œ 0
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Scientists discover brain network that may cause Parkinson’s disease An β€œextraordinary” brain network discovery shows that Parkinson’s disease may not be a movement disorder after all

An β€œextraordinary” brain network discovery shows that Parkinson’s disease may not be a movement disorder after all

04.02.2026 16:20 πŸ‘ 393 πŸ” 114 πŸ’¬ 9 πŸ“Œ 7

Non-invasive brain surface stimulation targeting personalized SCAN alleviated symptoms in patients with Parkinson’s disease. See the videos below.(www.nature.com/articles/s41...)

05.02.2026 02:08 πŸ‘ 16 πŸ” 17 πŸ’¬ 2 πŸ“Œ 0
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Happy to share a short but super cool video that gives a quick overview of our Nature paper on the somato-cognitive action of netwokr in Parkinson's disease
www.nature.com/articles/s41...

05.02.2026 13:22 πŸ‘ 21 πŸ” 14 πŸ’¬ 0 πŸ“Œ 3
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I’m very excited about this new work describing the specific cortical-striatal circuits that are altered in Parkinson’s Disease and that should be targeted for optimal PD treatment.

www.nature.com/articles/s41...

05.02.2026 19:24 πŸ‘ 48 πŸ” 25 πŸ’¬ 1 πŸ“Œ 2

incredible and exciting work

06.02.2026 18:58 πŸ‘ 0 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0
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My med school textbook says stimulants like Ritalin treat hyperactivity by β€œstimulating” the brain’s attention and cognitive control systems. We studied children taking stimulants in the ABCD Study, and the largest differences were actually in arousal and reward networks! Check out our preprint!

22.05.2025 21:33 πŸ‘ 145 πŸ” 55 πŸ’¬ 11 πŸ“Œ 10

Had a great time speaking with Sydney about our most recent paper out now in @natcomms.nature.com @macwoodburn.bsky.social . Paper link here: rdcu.be/ehbOy

16.05.2025 19:45 πŸ‘ 19 πŸ” 7 πŸ’¬ 0 πŸ“Œ 0

SCAN is the coolest!

10.04.2025 17:00 πŸ‘ 3 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

@washuneurology.bsky.social

10.04.2025 15:47 πŸ‘ 2 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

The advancements in brainstem imaging will make it possible to examine a host of clinically relevent structures like the eriaqueductal gray and substantia nigra in humans, something that has been very hard to do well previously

10.04.2025 15:45 πŸ‘ 9 πŸ” 3 πŸ’¬ 1 πŸ“Œ 0

This work was supported by a lot of people including @drdamienfair.bsky.social @ndosenbach.bsky.social @roselynechauvin.bsky.social @gordonneuro.bsky.social @jarodroland.bsky.social @forrestwhiting.bsky.social @nasiametoki.bsky.social

10.04.2025 15:45 πŸ‘ 4 πŸ” 0 πŸ’¬ 2 πŸ“Œ 0
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We have a lot of supplemental information, including tests against partial volume effects that I really encourage people to check out. Functional imaging now allows for single voxel level high quality results, something that I thought was impossible when I started my post-doc.

10.04.2025 15:45 πŸ‘ 4 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

We speculate that the human red nucleus is well positioned to implement goal-directed behavior by integrating behavioral valence (through salience network) with action plans (through action-mode network) instead of serving a pure motor-effector function.

10.04.2025 15:45 πŸ‘ 5 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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Additionally, networks, a well-recognized dominant model of cortical organization, also appear to be an organizing principle as far down as the brainstem. This nicely highlights that networks aren’t really β€˜cortical’ they are a system of whole brain organization.

10.04.2025 15:45 πŸ‘ 5 πŸ” 0 πŸ’¬ 1 πŸ“Œ 1
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Frontiers | Unique Features of the Human Brainstem and Cerebellum The cerebral cortex is greatly expanded in the human brain. There is a parallel expansion of the cerebellum, which is interconnected with the cerebral cortex...

Big takeaway: the brainstem is nowhere near as evolutionarily conserved as many believe. This contradicts a lot of neuroscience training (certainly mine). In fact, the brainstem has undergone very active selection over evolution. For more reading please see Joan Baizer tinyurl.com/mry5tvac

10.04.2025 15:45 πŸ‘ 7 πŸ” 1 πŸ’¬ 1 πŸ“Œ 0
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We next assumed that averaging over the red nucleus must have obscured motor-effector regions within the structure, so we tested if any voxels had primary connectivity to any of the 3 motor-effector networks. Shockingly, basically no voxels are preferentially motor-effector connected (triangles).

10.04.2025 15:45 πŸ‘ 4 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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So where is the red nucleus functional connectivity within the precentral gyrus, something that you would predict from tract tracing? It is specific to @gordonneuro.bsky.social recently discovered somato-cognitive action network (SCAN) and not motor-effector regions.

10.04.2025 15:45 πŸ‘ 4 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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Looking at task data from the HCP, we found that cues to indicate upcoming movement had a large effect in the red nucleus, larger than actual movement. Motor cues also greatly activate the action-mode network. Additionally, task analysis shows the red nucleus responds to rewarding stimuli.

10.04.2025 15:45 πŸ‘ 2 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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Shockingly, red nucleus connectivity was virtually absent with motor effector networks (le-SMN, ue-SMN, and f-SMN). Instead, connectivity was largest to the salience network (involved in motivated behavior) and the action-mode network (a.k.a. cingulo-opercular network; involved in action).

10.04.2025 15:45 πŸ‘ 5 πŸ” 0 πŸ’¬ 1 πŸ“Œ 1
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If the red nucleus is a motor structure, it should 1) be connected to motor-effector networks (somatomotor hand/foot/mouth) and 2) respond to movement. To test this, we used high SNR data with multi-echo ICA (tinyurl.com/55vr747p; example noise component below) and group-averaged task/rest datasets

10.04.2025 15:45 πŸ‘ 4 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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a cartoon of spongebob with a long pink tongue ALT: a cartoon of spongebob with a long pink tongue

However, perspective pieces and a lot of literature still seemed to assume the red nucleus had to do something related to the control of muscles (either directly or indirectly) in the service of movement, making it a motor nucleus.

10.04.2025 15:45 πŸ‘ 4 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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As walking changed from quadrupedal to bipedal, so has the red nucleus. The magnocellular red nucleus (projects to the spinal cord; shaded) has shrunken! But another division, the parvocellular red nucleus (shown white) expands tinyurl.com/2ctttmmw

10.04.2025 15:45 πŸ‘ 4 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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the beatles are walking across a zebra crossing in a black and white photo . ALT: the beatles are walking across a zebra crossing in a black and white photo .

Based on offhand commends during my graduate training, I remembered that the red nucleus was supposed to be involved in walking, because its emergence in evolution coincided with the use of limbs for walking (and also navigating shallow waters).

10.04.2025 15:45 πŸ‘ 5 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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The red nucleus is a slightly pinkish structure (hence the name β€˜red’) in the midbrain of the brainstem. Fortunately, it is easily visible on standard structural MRI images, especially T2 weighted.

10.04.2025 15:45 πŸ‘ 5 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
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It's shocking how little is known about the brainstem red nucleus. In our new paper β€œThe human brainstem’s red nucleus was upgraded to support goal-directed action” out now in @naturecomms.bsky.social we show that current thinking on the red nucleus is in need of a serious upgrade. rdcu.be/ehbOy

10.04.2025 15:45 πŸ‘ 68 πŸ” 32 πŸ’¬ 1 πŸ“Œ 5