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

Discuss two effects of the environment on

physiological processes

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

•Effect 1: stimulation•Physiological process: brain plasticity (your brain will change due to stimulation)

HUMANS as participants

• Case studies on children who have grown up in total neglected environment

• Prolonged, severe or unpredictable stress (including abuse and neglect) during a child’s early years

• could have a negative impact on physical, cognitive, emotional and social growth.

• Abuse = physical, sexual and emotional• Neglect = lack of stimulation• Few cases e g “Genie”, and “Czech Twin case study”,

Koluchova (1976)

The Romanian Orphans

• In 1989 Nicolae Ceaușescu regime was overthrown in Romania.

• the world became aware of thousands of children who were warehoused in Romanian orphanages.

• http://www.youtube.com/watch?v=3ISSgupUtpU

• between 100,000 and 300,000 children lived in these baby homes or orphanages

• Most children experienced severe emotional and physical deprivation.

• Many of the children was apathetic

• They could not walk, speak and used diapers, almost like they had mental disabilities.

• This showed that the lack of care made them “sick”.

• Case studies on the children

• When Westerners saw television documentaries of the appalling conditions, many were eager to adopt and rushed to take action.

• thousands of adoptive parents from the United States, Canada and other countries ultimately succeeded in adopting children.

• The simultaneous adoptions of so many Romanian orphans provided researchers with a unique opportunity to view the impact of adoption on primarily institutionalized babies and young children.

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”.

Neglect in early childhood

• Perry and Pollard 1997 examined various aspects of neurodevelopment in neglected children.

• Global neglect: a history of relative sensory deprivation in more than one domain (e.g. minimal exposure to language, touch and social interactions).

• Chaotic neglect: more common and with a history of consistent physical, emotional or cognitive neglect.

• History was obtained from multiple sources (e.g. investigating CPS (child protective service) workers, family and police)

Procedure

• The neglected children (n=122) were divided into four groups:

1. Global neglect (GN; n=40)2. Global neglect with Prenatal Drug

Exposure(GN+PND; n= 18)3. Chaotic neglect (CN; n= 36)4. Chaotic neglect with Prenatal Drug Exposure

(CN+PND; n = 28)

Procedure

• Measures of growth were compared across group and compared to standard norms developed and used in all major pediatric setting.

• FOC (the frontal-occipital circumference) is a measure of head size

Results• Globally neglected children had lower FOC

values indicating abnormal brain growth. The group mean was below the 5th percentile.

• Chaotically neglected children did not demonstrate this marked difference.

• In cases where MRI and CT scans were available, 11 out of 17 (64,7%) scans were abnormal in GN group compared to only 3 of 26 scans from the CN group (11,5%).

• Enlarged ventricles or cortical atrophy (see next slide)

Deprivation has a measurable effect on brain growth

Linking back to the effect:• These findings strongly suggest that when early life

neglect is characterized by decreased sensory input (e.g., relative poverty of words, touch and social interactions) it will have a similar effect on humans as it does in other mammalian species. Sensory deprivation has been demonstrated to alter the physical growth and organization of the brain in animals.

• The present studies suggest that the same is true for children globally neglected in the first three years of life.

• It is important to emphasize the timing of the neglect. The brain is undergoing explosive growth in the first years of life, and, thereby, is relatively more vulnerable to lack of organizing experiences during these periods.

• These unfortunate globally neglected children (some literally were raised in cages in dark rooms for the first years of their lives) appear to have altered brain growth.

• There are likely many factors contributing to this observation. Nutrition is one key aspect. Based upon the relative impact on the brain as opposed to other growth, a total nutritional explanation is inadequate. It is likely that the actual lack of experiences (sound, smell, touch) associated with global neglect in these children plays a major role.

Evaluation?

Evaluation

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

• We don’t know which elements of the neglect caused what developmental deficits.

• But the research has high ecological validity• On humans and not on animals (supporting)• Ethics: children

Impoverished environment

Enriched environment

Rosenzweig and Bennet (1972)The effect of stimulation on p. 46

• Study on rats (animal experiments)Aim:

animals raised in highly stimulating environments will demonstrate differences in the brain growth and chemistry when compared with animals reared in dull circumstance

• IV: Enriched (toys) and deprived environment (no toys)

• Spent 30 or 60 days in their environment• Then sacrificed: Post-mortem studies• Results: one group had increased thickness in

the cortex, frontal lobe (associated with thinking, planning, decision making)

• similar studies have shown that it will increase even more if they also had company (other rats))

• Company + toys = the best condition for a developing cerebral cotex

Evaluation

• Can these findings be generalized to humans?• What the strenghts and limitations?

• Strengths: (of a lab experiment)• Can be replicated easily• The duration of the experiment• Replicated studies had supporting results• Limitations: (of a lab experiment)• Ethics• Can the Rats’ behaviours be generalised to

humans?

For: • The results could not be obtained by any other method.• If humans were used in this study, long term

psychological and physical harm could have occurred.• The treatment of the rats, until they were sacrificed,

was to an acceptable standard.Against: • Unethical to sacrificed rats to obtain a result that may

not even be applicable to humans.• The rats in the deprived cage endured unfair treatment,

lacked social contact and lived in small cages.

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?)

Effect 3: (amount of light/darkness)physiological process: melatonin production

and changes that could lead to SAD

• 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).• But then you also need to evaluate the study:• Method, gender, culture, ethics

Effect 4: 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