Ch. 6, cerebral oxygenation and blood flow

explain how NIRS works

• Looks at light just outside the range of human perception (760 nanometers)

• deoxygenated blood absorbs this light whereas oxygenated blood does not

  • with this, we can see how much blood travels through tissue, measuring cerebral oxygenation

• if there is more deoxygenated blood, there has been more activity in that specific part of the brain

  measures the balance between the oxygen availability and oxygen used

downside of NIRS

also includes a measure of skin blood flow, which also increases during exercise

what relationship exists between exercise intensity and effect on cerebral oxygenation?

quadratic relationship. this just means it is ever changing

• at moderate/hard levels there is an increase in cerebral oxygenation

• for very hard exercise there is a drop off for cerebral oxygenation

  *this occurs at 60% vo2 max

what brain areas are measured for cerebral oxygenation?

• prefrontal

• premotor

• motor cortex

all in the primary cx

recall: flanker test measures?

executive function, response inhibition and suppress the interference from other stimuli

Ando et al. (2011): effects of o2 during exercise

• found an increase in cerebral oxygenation during the task compared to rest

  • this shows that doing a cognitive task engages the frontal lobes

• increase in cerebral oxygenation at 40% and 60% VO2 max

• drop off at 80% vo2max

exercise does impact brain oxygenation!

• reaction times get faster specifically at vo2max

  • this is associated with overall trials, not only congruent or incongruent

no change in performance though

the procedure of endo et al: effects of o2 after exercise

ppl performed the test, exercised at different intensities, had a 5 min rest, then did a second test

findings of endo et al effects of exercise on o2

• change in prefrontal oxygenation response during exercise

  • this is correlated to intensity of exercise

• during the stroop task, there is a change in prefrontal oxygenation

  • no exercise = no change between test 1 & 2

  • 40% vo2max = increased frontal oxygenation response

  • 60% vo2 max = blunted response / counter effect

    it diminished the availability of oxygen

endo et al, relation with performance on the stroop task after exercise

• after exercise: prefrontal oxygenation reflects preforntal neuron activation during performance

  • with exercise at 40% vo2 max, you get much faster at the stroop task

what did Lucas et al. (2012) find in regards to blood flow and cognitive performance

• at rest, the better the blood flow, the better the performance

• as exercise intensity increases, the relationship disappears

Ogoh et al (2014) findings on blood flow and cognition

controlled the amount of blood flow through hypercapnic gas (contains co2), which triggers vasodialation (makes the arteries wider) and increases blood flow

• found an improvement in reaction time 20 minutes later, but no change in accuracy

conclusion: the changes in blood flow is not associated with changes in oxygenation

the improvement in cognitive function is unlikely to be directly related to the blood flow

define hypoxia

a state in which oxygen is not available in sufficient amounts at the tissue level to maintain adequate homeostasis

2 conditions that can bring about hypoxia

low blood supply

low oxygen content in the blood (hypoxemia)

results of hypoxia

• mpaired brain function

  therefore, we assume it can also impair cognitive performance

climbers, who get hypoxia at high altitude, report an impairment of cognitive function and decreases in oxygen getting to the brain

Ando et al. (2013): findings regarding hypoxia

they found that creating hypoxic conditions lowered brain o2 levels

but the amount of oxygen available had NO IMPACT on cognitive function

but exercise did have an impact on cognitive function

overall takeaway from this chapter

takeaway: exercise improves oxygenation, but this is not what improves cognitive function