neuroplasticity

what does the systematic study of neuroanatomy make the interconnections between various structures?

rigid, exact, and genetically predetermined

why is that systematic study of neuroanatomy bad?

it simplifies neuroanatomy

what is nature?

genetics, provides the layout of the nervous system

what is nurture?

environment and experiences, various connections are adjusted to meet demands of environment

what is another word for various connections that are adjusted to meet demands of environment?

neuroplasticity

when is neuroplasticity most prominent?

during the critical periods of development

what happens to critical periods

it reduces (not abolished as scientists once believed)

what are critical periods?

early development

what are ongoing adjustments?

learning and memory; constraint-induced movement therapy; etc.

what is neuroplasticity defined as?

the ability of the brain to change its own structure and function through activity and thought

what do neurons and their connections adjust to match the nervous system to?

the body and the environment

what is neurogenesis?

creating new neurons

what was once believed about neurons?

that all neurons were produced during embryonic/fetal development

what disproved the belief that all neurons were produced during fetal development?

the existence of neural stem cells

what can neural stem cells do?

they can produce new CNS neurons or glial cells

where has stem cells been found?

walls of the ventricles, hippocampus, subventricular zone of lateral ventricles

what do the stem cells do in the walls of the ventricles?

remain latent

what do the stem cells do in the hippocampus?

they produce newborn neurons

what do the stem cells do in the subventricular zone of lateral ventricles?

they migrate to the olfactory bulb and produce newborn neurons

what is re-wiring?

creating new neural pathways

what is unmasking?

uncovering existing, but rarely used neuronal pathways

what is cortical re-organization?

reassigning cortical “real estate” to new functions

what does changes in the synaptic efficiency mean?

strengthening or weakening the connections between neurons

how are neuronal pathways created?

by signals passing from one neuron to the next at the synapse

what are the signals called?

neurotransmitters

what is a synapse?

the space between neurons

how can we strengthen or weaken the connection between neurons?

by the things we do or think

what is potentiation?

an increase in synaptic efficency

how do we cause potentiation?

with the more we do or think something, the more efficient the synapses become and the easier it is to do or remember something

what is Hebb’s principle about potentiation?

“neurons that fire together wire together”

what is depression?

a decrease in synaptic efficiency

how do we cause depression?

the less we do or think something, the less efficient the synapses become and the harder it is to do or remember something

what is Hebb’s principle about depression?

“neurons that fire apart, wire apart”

what is short-term potentiation (STP) or depression (STD)?

it lasts a few minutes and a general consequence of activity

what is an example of a STP?

patient able to do one-handed shoe tying after a bit of practice in the clinic, but can’t replicate it at home after therapy

what is long-term potentiation (LTP) or depression (LTD)?

it produces lasting changes (hours to years) and is the basis of learning and memory and what we hope to affect in neurorehab

what is an example of long-term potentiation?

patient is able to do one-handed shoe-tying anytime - in therapy, at home, in the store, etc.

what facilitates neuroplasticity?

novelty, physical exercise, intensity/redundancy, complex problem-solving, enhanced environments, saliency, active, and goal-driven tasks

what did the mice and early human studies show?

novelty and physical exercise increase number of stem ceslls in their hippocampi and prolong the life of the cells

what does intensity/redundancy mean?

the more you do something, the more likely your brain will change

during prenatal and early postnatal development, what is produced in excess?

neurons and the connections

how do infants get rid of the excess neurons?

through the matching process

what is the matching process?

the dying off of surplus neurons and retracting inappropriate connections

what is neuronal competition?

when neurons compete for eurotrophic factors during development

what is a critical period?

where plasticity is maximal and synapses made during critical periods are more or less permanent

how long does critical periods last?

they vary in length for different parts of the brain and different skills

what is an example for critical period?

young children learn language more easily than adults

do synaptic connections adjust throughout life?

yes, on a smaller scale, based on synaptic efficiency (potentiation/depression)

what are the two main types of long-term memory?

declarative (explicit) and non declarative (implicit) memory

what is declarative (explicit) memory?

memory of facts, events, concepts, and places

what is nondeclarative (implicit) memory?

procedural memory, how-to memory

what is an example of implicit memory?

riding a bike

what are the 3 stages of declarative (explicit) memory?

1.) immediate memory

2.) working memory

3.) long-term memory

what is immediate memory?

a snapshot of sensory input

how long does immediate memory last?

lasts up to 3 seconds

where is immediate memory processed?

by primary sensory and sensory association areas of the brain and is encoded for the next stage

what is working memory?

short-term memory which is effortfully processed

how long does working memory lasts?

lasts 3-30 seconds

what is an example of working memory?

remember in phone numbers

what is long term memory?

relatively permanent storage of information that has been processed in working memory

what are the two versions of long-term memory?

recent memory and remote memory

what is recent memory?

memories formed hours to weeks ago

what is remote memory?

memories in more distant past

what is consolidation?

the conversion of working memory to long-term memory

what is the primary structure associated with declarative memory (consolidation)?

the hippocampus

what is the hippocampus?

a curved area of cortex that lies in the limbic lobe

who is HM?

a patient who had bilateral removal of his medial temporal lobes

why was HM’s medial temporal lobes removed?

to try to stop his frequent severe epileptic seizures

what happened to HM?

HM had retrograde amnesia and anterograde amnesia

what is retrograde amnesia?

loss of memories from a period prior to the brain injury

what is anterograde amnesia?

deficit in forming new memories

what are the three general types of nondeclarative memory?

1.) skills and habits

2.) emotional associations

3.) conditioned reflexes

what are the areas associated with skills and habits?

basal ganglia, cerebellum, and neocortex

what are the areas associated with emotional associations?

amygdala

what are the areas associated with conditioned reflexes?

cerebellum

what are the three stages involved in motor learning?

1.) cognitive

2.) associative

3.) autonomous

what is the cognitive part of motor learning?

verbally guide motor task; requires much attention

what is the associative part of motor learning?

movement is refined and made more efficient

what is the autonomous part of motor learning?

movements are practically automatic; requires very little conscious attention

what are the areas commonly affected in a cerebral contusions/TBI?

anteromedial temporal lobes and basal orbitofrontal cortex

what memory is affected in a cerebral contusions/TBIs?

anterograde memory

what does “shrinks forward” mean for cerebral contusions/TBIs?

more remote memories come back first, with recent memories of events just prior to injury coming back last or not at all

can strokes and anoxia affect memory?

yes

what structure is especially vulnerable with a stroke and anoxia?

the hippocampus, because of its poor blood supply

Korsakoff’s psychosis is often seen in who?

people with alcoholism and people with vitamin B12 deficiency

what does Korsakoff’s psychosis affect?

mammillary bodies

what are the characteristics of Korsakoff’s psychosis?

anterograde amnesia and lack of awareness of deficits

what can lack of awareness of deficits lead to?

confabulation

what is confabulation?

filling in memory gaps by fabrication

how does Alzheimer’s disease affect memory?

early stages tend to affect memory loss of recent events

what structures of the brain does Alzheimer’s disease effect?

bilateral hippocampal, temporal, and basal forebrain structures

what are symptoms psychogenic amnesia?

dissociation, repression, functional neurological disorder, and malingering

how is psychogenic amnesia related to memory?

linked to memory loss of an emotional event or loss of autobiographical info

what is normal memory loss?

• infantile amnesia

• benign senescent forgetfulness (normal aging)

• during or shortly after awakening from sleep

• passage of time (forgetting)

can PNS nerve fibers re-grow after injury?

yes

what is the rate of regrowth of PNS nerve fibers?

1 mm/day or 1 inch/month

why do crush injuries regenerate so well?

because the “pipes are laid” to guide axons where to grow

do CNS neurons regenerate?

do not typically regenerate

what does glial cells do?

they impede growth by laying down scar tissue