Neurology

Liquid Fear Antagonist

Alcohol reduces the connection between the amygdala and the prefrontal cortex, so the fear and smart centres don’t communicate as much.

Research people did an experiment, as they often claim to do. It was a suspiciously small sample of participants, as it often is. The difference here was the humanoid laboratory rats being drunk on almost half a litre of alcohol. In fMRI, there was reduced amygdala to prefrontal cortex activity during alcohol intoxication. This suggests reduced connectivity.

Specifically, the decreased amygdala to orbitofrontal cortex interaction messes up the processing and behavioural inhibition around emotional stimuli.

References

  1. Gorka, S. M., Fitzgerald, D. A., King, A. C., & Phan, K. L. (2013). Alcohol attenuates amygdala-frontal connectivity during processing social signals in heavy social drinkers: a preliminary pharmaco-fMRI study. Psychopharmacology, 229(1), 141–154. https://doi.org/10.1007/s00213-013-3090-0
  2. Rolls, E. T., Cheng, W., & Feng, J. (2020). The orbitofrontal cortex: reward, emotion and depression. Brain communications, 2(2), fcaa196. https://doi.org/10.1093/braincomms/fcaa196

Xerox In Biology

Circular definitions are a trap. It’s good to avoid traps.

Hence, in simple terms, here are some useful explanations.

Genes are the computer coding for people, because we all know people are actually robots. (Click. Whirr. This is a joke.)

A genotype is the total computer code print-out for a person. It’s relevant to inheritable diseases. A disease is a state of poor health, by the way. It has to be significantly abnormal enough for it to be classed as diagnosable, given these things are based on artificial cut-offs. They can be somewhat arbitrary, but generally there’s a reasonable basis underneath them.

A phenotype is the outside casing of the computer product, which is distinct from its wiring inside. It represents how matters surface in the material world.

A phenocopy is a materialised appearance of things that doesn’t actually have the relevant genotype. That is, it looks like that computer coding output, but the computer coding is different from what it’s expected to be. It resembles a syndrome but without the genetic basis for it.

The phenocopy situation can occur in Huntington’s disease, where the autosomal dominant CAG-repeater mutation isn’t apparent but similar clinical manifestations arise.

References

  1. Moore RC, Xiang F, Monaghan J, Han D, Zhang Z, Edström L, Anvret M, Prusiner SB. Huntington disease phenocopy is a familial prion disease. Am J Hum Genet. 2001 Dec;69(6):1385-8. doi: 10.1086/324414. Epub 2001 Oct 9. PMID: 11593450; PMCID: PMC1235549.

Luria’s Test

Fist, slap, slice! Or fist, cut, slap! Fist, cut, slice?!

It can be tricky to recall the order of Luria’s 3-step test for frontal lobe function.

Here’s a business-minded way to remember it.

GIVE MONEY NOW!

Give

Make a fist.

This represents the aggression of forcing someone to give you something.

Money

Make the slicing motion.

This emulates the handshake of a business deal.

Now!

Slap the hand with the palm facing down.

This is like being a demanding gangster and banging on a table to intimidate your enemy.

References

  1. PsychDB (2021). Luria Sequence (Luria’s Test). [online] PsychDB. Available at: https://www.psychdb.com/neurology/neuro-exam/luria.

Sometimes Neurology Is Symmetrical

Huntington disease is a problem of too many CAG repeats. The mutated HTT gene codes for the huntingtin protein. It’s located on chromosome 4.

To remember this, note that H is a rather symmetrical letter. It can be divided into quadrants.

The next time you cut a cake, consider doing it in 4 equal pieces and think of this unfortunate neurological condition.

Bibliography

  1. MedlinePlus Genetics. 2020. HTT gene. [online] Available at: <https://medlineplus.gov/genetics/gene/htt/> [Accessed 1 September 2021].

Broca And Wernicke Memory Aids

Facebook and Twitter! Two important procrastination tools of our time! Many a student has suffered gloriously from these distractions. Finally, they help us to learn medicine, just like you’ve always wanted.

Broca’s Area

Location

  • In the frontal lobe of the brain
  • Facebook
    • Frontal Broca
    • FB

Lesion

  • Broca’s aphasia is expressive aphasia
    • Patient understands things but cannot talk well

Wernicke’s Area

Location

  • In the temporal lobe of the brain
  • Twitter
    • Temporal Wernicke
    • TW

Lesion

  • Wernicke’s aphasia is receptive aphasia
    • Affectionately known as “word salad”
    • Patient says fluent gibberish but does not understand things

Unity

  • Both are usually on the left side
  • Connected by the arcuate fasciculus nerve fibres

References

  1. THE BRAIN FROM TOP TO BOTTOM. (n.d.). BROCA’S AREA , WERNICKE’S AREA, AND OTHER LANGUAGE-PROCESSING AREAS IN THE BRAIN. [online] Available at: http://thebrain.mcgill.ca/flash/d/d_10/d_10_cr/d_10_cr_lan/d_10_cr_lan.html [Accessed 26 Aug. 2018].

Contraindications To Lumbar Puncture

A lumbar puncture is a procedure that involving drawing out cerebrospinal fluid, fondly known as CSF. For example, it can be used to check CSF for immune cells and glucose levels in suspected meningitis.

Lumbar puncture is considered an invasive procedure. But even with that aside, it’s not appropriate for everyone. That is, it does not suit all patients.

Contraindications to lumbar puncture are:

  • Skin infection at the lumbar puncture site
  • Uncorrected coagulopathy
  • Increased intracranial pressure
  • Trauma to the spinal cord

References

  1. Queen’s University School of Medicine. (n.d.). Contraindications. [online] Available at: https://meds.queensu.ca/central/assets/modules/lumbar_puncture/contraindications.html [Accessed 2 Feb. 2018].