1. Exercise and neurobiology
James Robertson and Yufeng Zhang

2. Introduction Lifestyle need aerobic capacity
aerobic physical activity (APA)
generates and protects new neurons,
increases the volume of brain
improves cognition and reduce anxiety
positive correlation between aerobic capacity and brain size across a wide range of mammals

3. Introduction Three times larger than expected for our body size.
Major increase in brain size and brain size
occurred during the early evolution of the genus Homo (Figure 1)

4. APA and brain
brain size changes in human evolution are often interpreted in
the context of cognition
social complexity
enhanced ecological demands on cognition
at the same time as brain size began to increase, aerobic activity levels
long-distance trekking

5. APA and brain Hypothesis: APA leads to neurogenesis
human locomotor endurance had a measurable effect on the evolution of human brain structure and cognition
APA leads to neurogenesis
dentate gyrus of the hippocampus
Gliogenesis frontal cortex

6. APA and growth factors
Voluntary and forced running induce upregulation of BDNF
Physical activity increase
Insulin-like growth factor I
Vascular endothelial growth factor (VEGF)
BDNF, IGF-1 and VEGF all have important effects on metabolic pathways
Growth factors in the periphery triggering neurogenic action

7. APA and growth factors
two hypotheses for activity-induced adult neurogenesis:
Neurotrophins and growth factors increased from endurance activity with ancillary effects on the brain
links between activity and neurogenesis may create a neurogenic to enhance cognitive engagement during locomotor bouts

8. Physical activity and the evolution of brain growth

9. Correlation Intraspecific correlation Interspecific correlation
BDNF
IGF-1
VEGF
Interspecific correlation
MMR and brain size across mammals is likely to be related to differences in VEGF expression
Do not clearly demonstrate evolutionary mechanisms

11. Figure 2. Relationships between body size, brain size and exercise capacity.
Raichlen DA, Gordon AD (2011) Relationship between Exercise Capacity and Brain Size in Mammals. PLoS ONE 6(6): e doi: /journal.pone

12. Artificial selection experiments
Selected for high and low MMR in rats
high levels of aerobic capacity both VEGF and IGF-1
Selective breeding for endurance running capacity affects cognitive but not motor learning in rats
Selectively bred for high amounts of voluntary wheel-running
higher BDNF levels
larger mid-brain and dentate gyrus volumes

13. Human evolution
Long hind-limbs

14. larger canal dimensions strongly associated with animals locomotor behaviours

16. Conclusion
(i) intraspecific data linking aerobic capacity, brain size, neurotrophins and growth factors;
(ii) interspecific data showing a relationship between aerobic capacity and brain size
(iii) evolution experiments detailing how selection for aerobic performance alone can affect neurobiology

17. Raichlen 2012 – The Runners High
Aerobic capacity linked to brain size, growth factors
Problem: What happens if you don’t “need” to run?
Goal-oriented behaviors with high energy costs
Motivated by neurological rewards
Conditions fitness enhancement
Is there a reward-response from running?

18. Raichlen 2012 – The Runners High
Endocannabinoids
Released in activity-dependent manner
Mesolimbic dopamine system
eCBs relieve influence of inhibitory, GABAergic CB1 receptors
eCBs activate dopamine (DA) neurons
Sparling (2003) showed exercise AEA
eCBs may not immediately impact anxiety system
But, rewarding the exercise effort could select for beneficial traits
Shown in other cursorial mammals

19. Raichlen 2012 – The Runners High
10 recreationally fit humans
Could run for 30 min
8 mixed breed dogs
Local mongrels
8 stupid ugly ferrets
Minimal training (30 min running)
Compared plasma AEA pre-post walk/run
Stupid ferrets couldn’t walk on the treadmill
Compared with stationary AEA

20. Raichlen 2012 – The Runners High
Humans and Dogs
Running increases plasma AEA
Encourage aerobic exercise
High intensity necessary
Ferrets
Jeez ferret, get off the couch sometime!
Don’t you want to feel good?!?!
Cursorial mammals rule!!!

21. Raichlen 2012 – The Runners High
Running increases positive affect in humans

22. Heyman 2012 – eCBs, BDNF
Does exercise influence anxiety via effects on neurogenesis?
BDNF – neurotrophic factor critical for plasticity and neurogenesis
Likely link between exercise and anti-depressive effect
Previous studies in humans and animals are problematic
Running wheel = novel environmental stimulation
Human exercise not standardized for subjects

23. Heyman 2012 – eCBs, BDNF
Study subjects: Homogenous group of male cyclists (n=11)
Underwent exercise test to find standardized intensity – maximal power output (Wmax)
60 min at 55% Wmax
30 min at 75% Wmax (equivalent output condensed into time trial for intensity)
Blood taken: 1- at rest; 2 – 60 min; 3 – immediately post-exercise; 4 – recovery
Tested for:
AEA, 2-AG
AEA congeners OEA, PEA
BDNF
Beta endorphins
cortisol

24. Heyman 2012 AEA and congeners increased during exercise and recovery
2-AG did not

25. Heyman 2012 Serum cortisol increased during exercise and recovery
Positively correlated with AEA
BDNF increased during exercise, fell during recovery
Positively correlated with AEA at end of time trial, recovery
Beta-endorphins only increased significantly during intense exercise

26. Heyman 2012
Rates of perceived exertion were not correlated with eCB levels
RPE only correlated with Beta-endorphin during intense exercise

27. Heyman 2012 – eCBs, BDNF
AEA and congeners definitely affect mood post-exercise
Anti-depressant effect?
What about the Beta-endorphins, could that be the runners high?
Is it fair to point to BDNF as the method of influencing long term anxiety?

28. LETS GO OUTSIDE!!!!