Stroke and Recovery

brain represents % of body’s mass but consumes _% of body energy

brain represents % of body’s mass but consumes _% of body energy

2, 20

where do neurons spend energy?

maintaining resting membrane potential, neurotransmitter uptake to end synaptic transmission, filling vesicles with neurotransmitters, turnover of proteins

what entropy do neurons have?

negative; system becomes less disordered or more ordered

what do neurons require a continuous supply?

oxygen

what protein do blood cells contain?

hemoglobin

hemoglobin

protein that binds oxygen and carbon dioxide

blood cells function

move to lung, take up oxygen in lungs by binding it, deliver oxygen to different tissues of the body or releases oxygen into the brain

carbon dioxide

waste product; blood cells bind this and take it away to be filtered in kidneys

functional hyperemia

activity-dependent regulation of blood flow

blood oxygenation level dependent (BOLD) imaging

technique used to generate images in fMRI studies, oxygenated and deoxygenated hemoglobin have different paramagnetic properties, fMRI detects relative changes in cerebral blood flow, fMRI assess directly the brain regions with heightened activity

function of blood in cooling and nourishing brain

brain consumes lots of energy, which produces heat; some neuronal processes are sensitive to heat; blood provides oxygen and nutrients to brain and removes carbon dioxide and excess heat

ischemic stroke

a blood clot blocks the blood flow to part of the brain (80% of strokes)

hemorrhagic stroke

bursting of a blood vessel (20% of strokes)

cellular processes triggered by a stroke

lack of oxygen and nutrients > energy failure > ion gradient imbalance > neuronal depolarization > glutamate release > intracellular calcium increase > cell injury and death

intracellular calcium increase > glutamate release > neuronal depolarization (positive feedback loop leads to massive cell injury and death)

ischemic-reperfusion injury

paradoxical exacerbation of cellular dysfunction and death, following restoration of blood flow to previously ischemic tissues

signs of a stroke

sudden trouble walking, dizziness, loss of balance or coordination; sudden trouble seeing in one or both eyes; sudden weakness of face; sudden weakness of arm or leg, most often on one side of the body; sudden confusion, trouble speaking, or understanding speech; sudden severe headache with no known cause; BEFAST

thrombolytes

help reestablish blood flow to the brain by breaking up blood clots (clot busters) (aka tPA - tissue plasminogen activator)

what is the critical period of time for treatment following a stroke?

3 hours

controllable risk factors of a stroke

high blood pressure, atrial fibrillation, high cholesterol, diabetes, atherosclerosis, obesity, circulation problems, tobacco use and smoking, alcohol use, physical inactivity

uncontrollable risk factors of a stroke

age, gender, race, family history, having previously had a stroke

what is the goal of stroke rehabilitation?

independence and quality of life

what methods are used to treat stroke patients?

• repetitive practice of movements related to specific skills

• new ways of moving to compensate for lost functions

• passive movements, if stroke is severe

• transcutaneous nerve stimulation to promote brain reorganization

Dr. Edward Taub

• deafferentation (cutting of sensory nerves) in monkeys

• credited with one of the top ten translational neuroscience accomplishments of the 20th century: constraint-induced therapy

How did Dr. Edward Taub’s experiment change neuroscience?

• previously thought that all movements were based off a series of spinal reflexes (reflexological theory of movement)

• showed that restraining the good arm of a deafferented monkey made the monkey use its affected arm

  • finding indicated that brain--not just spinal reflexes--were commanding motor behavior

What implications did Dr. Edward Taub’s experiment have for other fields?

reflexological theory indicates that every action is a reaction; his experiments demonstrate an argument for free will

goal of Taub’s constraint-induced therapy

induce plasticity of brain connections controlling affected function

principles of Taub’s constraint-induced therapy

• isolation of affected part of body

• repetitive practice of individual tasks

• massed practice (many repetitions in a short time)

• connects to Hebbian principles of “use it or lose it” or “use it to improve it”

rat experiment description and findings

• following a “stroke,” animal has a good limb and an affected limb

• using good limb impedes recovery of bad limb

• preventing the use of good limb aids recovery of bad limb; no impact on good limb

conditions required to be considered for CI therapy

• lift an item (e.g. a washcloth)

• drop item with affected arm

• no significant muscular deficiencies

Broca’s aphasia

damage of Broca’s area involved in speech production

Wernicke’s aphasia

damage of Wernicke’s area involved in speech recognition

goals after a stroke (use Hebbian principles)

• promote beneficial plasticity (use it to improve it)

• avoid detrimental plasticity (avoid use it or lose it)