PSYCH 454 Lecture Notes - Lecture 26: Transcranial Magnetic Stimulation, Synaptic Plasticity, Dsm-5
24 May 2018
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Lecture 26: When things go wrong/Parkinsons part 1
What goes wrong in brain disorders?
●Brain Disorder: Changes in information processing and transmission
○ Leading to changes in thoughts, behavior and feelings
●Changes can occur at multiple levels
○Molecular, cellular, cell ensemble, network/systems
●Too much or too little of transmitter is generally too simplistic
○Transmitters are located at synapses; and each synapse is part of a circuit
○ Different synapses and circuits contribute to information processing in different
ways
○ Broadly increasing or reducing transmitter levels across brain lacks the
necessary specificity
●Specific brain circuits and networks are changing
○Need to target treatment to these altered circuits and networks
●“The key concept: If mental disorders are brain circuit disorders, then successful
treatments need to tune circuits with precision. Chemicals may be less precise than
electrical or cognitive interventions that target specific circuits.”
○To be clear:
Many medicinal drugs are vital for the treatment of brain disorders;
That said, we are aiming for more specific treatments that may or may not
include drugs
Types of Brain Disorders
●DSM-5: diagnostic and statistical
manual of Mental Disorders
●Mental disorders (DSM-5) and
Neurological disorders (Merck)
○Don’t need to memorize list!
●For many of these disorders, we don’t
have effective treatments
●Specific circuits that underlie the
disorder→ ** target circuits specific to
disorder**
Target Manipulation of Neural Activity in Brain Networks/Circuits to treat disorders
●Non-invasive measures:
○Cognitive interventions: sensing thinking and acting activate specific circuits
■Counseling→ facilitate certain thinking that can activate specific brain
circuits
●Introduce synaptic plasticity by manipulating activity
■Increase circuitry of healthy circuits
■How to target circuit during counseling: give you a cue to activate
neurons that represent “spider”
○Transcranial magnetic stimulation: use magnetic fields to affect scalp from coil
on scalp
■Influence neural activity, increase activity or reduce activity of cells
■Targeting many many cells, some specificity, but not to level of thinking
of neurons wiring together to form circuit
■only effective 40%
○Transcranial current stimulation: use electric currents (from electrodes on head)
to affect cells
■Normalize or disturb circuits of brain
○Advantage of non invasive: no penetrating treatment;
●Invasive measures:
○Cell transplantation: replace damaged cells using embryonic or stem cells
■Replaced damaged cells with stem cells in hope they make normal
connections
○Deep brain stimulation: electrical stimulation can perturb or enhance activity in
brain area
○Pharmacogenetics: targeted delivery of specific genes, to re-program cells
■Ex: Introduce genes to synthesize something new
○Optogenetics: use viruses to introduce light sensitive-ion-channels into cells
■Basic idea:
●cell membrane with ion channel that’s light sensitive is introduced
with a virus
●Cell will eventually express this ion channel
●Once introduced, all you need to do is shine light to let channel
open and get transmitter flow!
■Light: can use optic fiber, shine light source down optic fiber to brain area
of interest to ion channel light
■** targets specific cell types **
Optogenetics
●Light sensitive proteins from algae
○This protein = ion channel that responds to blue
light
●Take the gene for this protein…
Document Summary
Lecture 26: when things go wrong/parkinsons part 1. Brain disorder: changes in information processing and transmission. Leading to changes in thoughts, behavior and feelings. Too much or too little of transmitter is generally too simplistic. Transmitters are located at synapses; and each synapse is part of a circuit. Different synapses and circuits contribute to information processing in different ways. Broadly increasing or reducing transmitter levels across brain lacks the necessary specificity. Specific brain circuits and networks are changing. Need to target treatment to these altered circuits and networks. The key concept: if mental disorders are brain circuit disorders, then successful treatments need to tune circuits with precision. Chemicals may be less precise than electrical or cognitive interventions that target specific circuits. To be clear: many medicinal drugs are vital for the treatment of brain disorders; That said, we are aiming for more specific treatments that may or may not include drugs. Dsm-5: diagnostic and statistical manual of mental disorders.
