PSYC 304 - 2.25

Neuroplasticity

What does Neuroplasticity look like?

• Change in likelihood of AP

• Changes in shape

• Changes in amount of branches

• Change in intensity of firing

Mechanisms of Neuroplasticity

1. Functional Plasticity

2. Structural Plasticity

3. Neurogenesis 

Functional Plasticity

• Changes in neurotransmission 

• LTP can affect number of receptors + NT → increases activity of synapse + increase likelihood of AP

Structural Plasticity

• Changes in brain structure

• Dendritic spines made/lost

Neurogenesis

• Birth of new neurons!

• Go through process to become a neuron → mostly occurs during development 

• Evidence for neurogenesis in adult human brain remains controversial

Neuroplastic Critical Periods

Time intervals where NS has high degree of plasticity 

• Determines irreversible nervous system changes 

• Childhood experiences are formative to how we end up as an adult! Children's NS is capable of immense change as children

• Essentials like vision + touch come first  (can get vision problems later if not properly stimulated as a child) → higher cognition occurs during childhood 

• Tapers off as we age

Sensitive periods

• Also characterized by un usually strong neuroplasticity, not as potent as critical periods 

  • Reversible! 

  • Ex. higher cognition, if you didn't learn math as a kid you can still learn it; just might be harder

The Visual System 

• Wired contralaterally  

• Left visual field sends info to right primary visual cortex and vice versa

Ocular Plasticity

• Visual systems neuron have critical period where they are sensitive to input (or lack thereof) 

• In order for our visual system to develop properly, we need stimulation 

• In early months of life, ocular dominance is shaped by experience! 

• Monocular deprivation (one eye not stimulated while other is, ex. Baby wears eyepatch its whole life) during critical period can shift ocular dominance to the ipsilateral eye (same eye to same side of brain)

  • Didnt get input from one eye so brain gives other eye more responsibility

Amblyopia

Brain favors one eye over the other

• Some children have vision obstruction in one eye (ex. Cataracts, misalignment, etc)

• Deprives visual cortex of typical stimulation from that eye 

• Since it is a neuroplastic critical period, brain reorganizes to favor unimpaired eye 

• Even if impaired eye is surgically corrected, vision will be poor in that eye as the brian as been rewired!

  • Must eyepatch the good eye (unobstructed)

  • Force child to use the fixed (previously bad eye), and hope neuroplasticity can make this eye better 

• Cannot get amblyopia in adults! Neuroplastic critical period closes during development 

• Wearing an eyepatch as an adult isn't gonna mess up your eye 

• If you catch amblyopia before critical period closes, can correct with an eye-patch 

Sensory deprivation tank

• deprive someone of every kind of sensory input 

• Lower input = high excitability 

• Depriving neurons of stimulations can increase their excitability and make them spontaneously fire (people hear + see things that aren't there; feel psychedelic) 

  • Ex. when it's especially quiet, you hear things you wouldn't normally hear 

  • Tinnitus can also be caused by lack of auditory input due to damaged hearing cells → constant ringing in ears that does not actually exist

harles Bonnet Syndrome (CBS)

• visual cortex neurons fire on their own in absence of environmentally-relevant sensory input 

• Ex. patient reported that he would see cattle in his living room 

• Elderly people + visual hallucinations 

• No treatment for CBS. brain is sensitive + shows things that may not be there 

• Something you have to deal with. More stress thinking about getting treatment than the pain of going through condition

Drug-Induced Plasticity

• iPlasticity = i[nduced juvenile-like] plasticity 

• Psychedelics can induce iplasticity 

• Drugs can reopen neuroplastic

• Plasticity from drugs is activity dependent! Environment/experience must trigger neuroplasticity

Improve Neuroplasticity

• Exercise

• Existing in an enriched environment 

• Engage in cognitive exercise + medication 

• antidepressants /psychedelics