How the environment affects the brain

Not only can the brain determine and change behaviour, but behaviour and

environment can change the brain

Brain PlasticityBefore 1960s, the brain was thought to

be unchangeable

• After, the view has changed through many studies on humans and animals.

• Brain plasticity: the brain’s ability to change due to learning or experience

Brain Plasticity

• Environmental input can modify the brain, especially the cerebral cortex, which is the area of higher

cognitive functioning

• The brain adapts to the New challenges• High levels of stimulation and numerous

learning opportunities at the appropriate times lead to an increase in the density of neural connections

Dendritic Branching

• The dendrites of the neurons grow in numbers and connect with other neurons, because…

Every time we learn something new, the neurons connect to create a new trace in the brain.

Example: if you spend a lot of time studying, compared to someone who doesn’t, you should have a thicker area in the cortex related to that knowledge.

Example of someone who did not get a lot of stimulation: Genie

The outcomes of neglect• According to Bruce Perry, institutionalized and

neglected children tend to show low IQs, developmental delays and small head size.

• This developmental trend is reversed when children are placed in good foster homes or adopted, younger children making better progress than older ones.

• Perry’s investigation of head size leads him to conclude that neglect results in impaired brain development and he supports this conclusion by referring to evidence from brain scans.

• “Childhood Experience and the Expression of Genetic Potential: What Childhood Neglect Tells Us About Nature and Nurture”.

Evaluation?

Evaluation

• All we have is a correlation between neglect and poor development.

• We don’t know if the neglect caused the poor

development, or if it did, which elements of the neglect caused what developmental deficits.

Rosenzweig and Bennet (1972)

• Study on rats (animal experiments)• Enriched (toys) and deprived environment (no

toys)• 30 or 60 days• Post-mortem studies• Results: one group had increased thickness in

the cortex, frontal lobe (the thickest if they also had company (other rats))

Evaluation

• Can these findings be generalized to humans?

Videos

• The Plastic Brain (full animation) • http://

www.youtube.com/watch?v=8Vo-rcVMgbI

• The Learning Brain • http://

www.youtube.com/watch?v=cgLYkV689s4 (can you spot the TOK link?)

AN EXAMPLE OF THE BRAIN’S PLASTICITY

Video about split brain patients:

http://www.youtube.com/watch?v=8Vo-rcVMgbI (animation)Ramachandran’s videohttp://www.youtube.com/watch?v=Chr3rQ6Vpcwhttp://www.youtube.com/watch?v=sq6u4XVrr58&list=PLD5C09769BDFCC933Split brainhttp://www.youtube.com/watch?v=MZnyQewsB_Y&feature=relatedHalf brain gone:http://www.youtube.com/watch?v=TSu9HGnlMV0

Effect 2

• Melatonin production due to the environment• (darker days – more production, could lead to

SAD)• You can use the same knowledge here as for

the learning outcome for hormones (same study).

Effect 3: Environmental stressors and hippocampal damage in PTSD patients

• PTSD: post traumatic stress disorder

• A stressor could be any event that threatens to disrupt the body’s normal balance

• Example: being attacked, having an accident, worrying too much (abuse, war, rape)

• The fight or flight response activates• Cortisol is being released over a long period of

time

PTSD

• War veterans and survivors of childhood sexual abuse are likely to suffer from PTSD

• Tend to have problems such as forgetfulness and difficulty of learning

• Physiological changes has been observed in such patients, especially in the hippocampus (important role in memory) due to cortisol

PTSD: Study

• Bremner et al. 2003 studied stress, PTSD and memory problems related to reduction of hippocampal volume

• Aim: to measure the volume of the hippocampus based on the theory that prolonged stress may reduce the volume of the hippocampus due to increased cortisol levels

Bremner et al. 2003

• Procedure: participants (veterans and female adults who had experienced sexual abuse as young, some had PTSD, some did not)

They completed memory tests while being put through MRI scans

Bremner et al. 2003

• Results: They found that the hippocampus was smaller in PTSD patients

• The veterans with most memory problems had the smallest hippocampus

• Clear correlation between number of years of abuse, memory problems and hippocampal volume

• Evaluation:?

• Another study’s result: MRI and PET Study of Deficits in Hippocampal Structure and Function in Women With Childhood Sexual Abuse and Posttraumatic Stress Disorder by Bremner et al. 2003