Session 16: Environment and physiological processes

Today's learning outcome Discuss two effects of environment on physiological processes: Environmental effects on brain plasticity Environmental stressors and physiological processes

Questions for the session What are the methodological and ethical strengths and limitations of the following studies? What are the general strengths and limitations of research? E.g. possible applications, generalisability, methodological problems, other possible factors that may have influenced results What conclusion can be drawn from the research? To what extent is the brain affected by environment? How much do we know about these processes?

1. Environmental effects on brain plasticity Brain plasticity is a term that refers to the brain's ability to change as a result of experience. These changes can occur as a result of learning new things or because of damage to the brain. Gopnick et al. (1999) describe neurons as growing telephone wires that communicate with each other. Experiences are processed in the brain’s nervous system, and stimulating environments will result in increased numbers of synapses (brain plasticity). Environmental stimulation refers to the way the environment provides stimulation in the form of social interaction and learning opportunities for animals and humans. An enriched environment is characterized by multiple opportunities to learn new things. Researchers have used animal models to study synaptic changes in the brain because it is not possible to use humans in deprivation experiments.

1. Rozenweig and Bennett (1972) Performed experiment with rats Wanted to study role of environmental factors on brain plasticity Rats spent up to 60 days in their respective environments before being killed Group 1 Group 2 Enriched environment- lots of toys Deprived environment- no toys Unit 2: Biological LOA

Rosenzweig & Bennett (1972) Findings: Post mortem studies of the rats´ brains showed that those that had been in a stimulating environment had an increased thickness in the cortex.

Evaluation of Rosenzweig & Bennett (1972) The experiment was a rigorously controlled laboratory experiment so it was possible to establish a cause-effect relationship. The research challenged the belief that brain weight cannot change. This was an important finding. There are ethical issues in the use of animals in research like this- Since the results contributed to a much better understanding of the role of environmental factors in brain plasticity it can be argued that the research was justified in spite of the ethical issues. Kolb (1999) replicated the study and also found that rats raised raised in enriched environments showed a large increase of the length of dendrites in cortical neurons Can we really generalise results from animal studies to humans?

Studying deprivation in humans Researchers use case studies of children who have grown up in total neglect, i.e. with little or no experience of language, touch and interaction with other humans. The brains of neglected children are often smaller and there is scientific evidence of altered brain function (e.g. in intelligence and emotions)

Perry (1997) Brain scans of three year olds who had a normal upbringing and those who were severely neglected Found differences in brain size and development

Case study: Genie Curtis (1977) A case study on a girl (Genie) who was socially isolated (strapped to a potty chair in an isolated room) until the age of 11. She had virtually no language ability. Although tests showed that she was highly intelligent, her language abilities never progressed beyond those of a third grader. Genie spent a lot of time alone so the period in which she should acquire the language and the abilities to interact with other people passed; as a result, when she tried to learn to speak, she only learnt words but she was not able to make complete sentences

Watch the documentary on Genie and take notes

Evaluation of Genie Case Study Allows us to study sensory deprivation in humans which could have practical applications for treating other cases One woman sample not representative; personal brain structure & no control on variables. Later studies show critical periods favourable to behaviour but plasticity throughout life (Gage 2002). Ethical issues???

2. Environmental Stressors and Physiological Processes What do we mean by ‘Environmental Stressors’? An environmental stressor is any stimulus from the environment that affects the condition of someone and may cause an abnormality in their physiological responses.    Examples of environmental stressors include toxins, viruses, drugs, noise, temperature, traumas, abuse, workplace stress and life events such as relationships, jobs and school. 

Environmental Stressors and hippocampal damage in PTSD patients EVERYONE SUFFERS TRAUMA AT SOME TIME. It can be the death of a loved one; it can be war; an attack, robbery, rape; it can be the loss of a job. Usually the person recovers after some time, and the trauma fades to a memory – painful but not destructive. Trauma, however, is not the same as the mental disorder PTSD – Post Traumatic Stress Disorder.

Environmental Stressors and hippocampal damage in PTSD patients What is Post Traumatic Stress Disorder? If the trauma is prolonged, extreme or repetitive, it can actually physically injure the brain. The best analogy is that the amygdala (area of brain associated with fear) stays in the alert state so long that it gets “stuck” there. The after effects can last for years, physical damage can occur, and one suffers the debilitating effects of PTSD. In about 5% of the population this may lead to PTSD (post-traumatic stress disorder) with effects that can last for a brief period or a lifetime.

Post Traumatic Stress Disorder Six criteria for a diagnosis of PTSD. The person goes through or sees something that involves actual or threatened death or serious injury. The person responds to this with intense fear, helplessness or horror. The person then relives this traumatic event through dreams, or recollections. He or she can behave as if the trauma is actually happening right then, and can react strongly to events that even resemble the original trauma. The person tries desperately to avoid this, and to avoid anything associated with the trauma, in fact, may not even remember the trauma yet still react strongly to certain stimuli. The person often has difficulty sleeping and concentrating. All this lasts longer than a month causes significant distress in daily life.

Watch the video on Post Traumatic Stress Disorder and take notes

Environmental Stressors and hippocampal damage in PTSD patients Combat veterans and survivors of childhood sexual abuse who suffer from PTSD tend to have a number of stress related problems such as forgetfulness and difficulty learning. In such patients stress–related physiological changes have been observed in the brain, especially in the hippocampus, which play an important role in integrating different aspects of a memory at the time of recollection.

Bremner et al. (2003) Stress, PTSD and memory problems related to reduction of hippocampal volume. Task: Read through the article and make notes about how stress can affect the brain.

Bremner et al (2003) Stress & PTSD 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. Procedure: MRI scans were made of the brains of the participants and participants completed memory tests (e.g. remembering a story or a list of words). The participants were veterans and female adults who had experienced early childhood sexual abuse. Some had developed PTSD, but not all. Results: The researchers found that there were deficits in short- term memory and then performed MRI scans of the participants’ brains. They found that the hippocampus was smaller in PTSD patients than in a control group. The veterans with most memory problems also had the smallest hippocampus. The findings showed a clear correlation between number of years of abuse as measured by a trauma test, memory problems and hippocampal volume.

Evaluation of Bremner et al (2003) The sample was very small so it is difficult to say anything definite about the relationship between trauma and hippocampal volume. There could be alternative explanations to differences in hippocampal volume (e.g. that people who suffer from PTSD often suffer from depression as well). Depression is also associated with reduction of the hippocampus. However, the findings of a large reduction of hippocampal volume in combat-related PTSD has been replicated many times. Knowing how PTSD affects the brain (and vice versa), however, is very important to study. Understanding which parts of the brain may impact PTSD can lead to the development of better, more effective medications for the treatment of PTSD.

Environmental Stress and the immune system Cortisol is a hormone produced by the adrenal cortex that is produced in response to stress and restore homeostasis. Chronic stress may result in prolonged cortisol secretion. This leads to a damaged immune system and impairment of memory and learning. Both result from atrophy of hippocampus (Sapolsky, 1996)

Kiecolt-Galser et al (1984) – Exam Stress Aim: Investigate the stress from examinations and its effect on the immune system. Procedure: Participants were 75 first year medical students (49 males, 26 females). Blood samples were taken before and during their exams. Immune functioning was assessed by measuring the T-cell activity in the blood sample. Students were given survey for self assessment on other psychological variables e.g. Loneliness Results Samples taken during exams had a weaker immune system Students that claimed that they felt lonely in the survey had a more vulnerable immune system. Conclusion: Exam tress decreases the functionality of our immune system. Immune functioning is also affected by psychological variables. These long term stressors may make individuals more vulnerable to the effect of short term stressors such as exams.

Evaluation of Kiecolt-Galser et al (1984) Confounding variable: No control over other factors that might have affected the immune system e.g. Caffeine, drugs, diet, sleep, stress of having injection for study etc. Correlational study: cannot identify cause and effect relationship. Did stress cause sickness? Or did sickness cause stress? The study uses measurable, quantitative evidence (t cell blood count). The study uses an unrepresentative sample (medical students) and so the results cannot be generalised to other groups. The study uses data that is open to interpretation (questionnaire)

Structuring the Question in the exam... Discuss two effects of environment on physiological processes

Reminder Final edit of essay due on Wednesday!

Journal Entry: Ethics of the Genie case study The studies and testing for Genie were funded by the National Institute of Mental Health, and David Rigler, a scientist on Genie’s case, agreed to care for Genie, acting as a scientist, therapist, and foster parent to Genie for four years. Rigler found it difficult to juggle his many roles and did not accurately document the research project. After several warnings from the NIMH, funding was stopped for the Genie project, citing a failure to collect data in a scientifically meaningful way. In the year following the loss of the research grant, the Riglers ended their care for Genie. She currently lives in an adult foster care home in southern, California. It’s at least the sixth home she has lived in since the research project ended. This leaves us with several questions: Did the team go as far as it could go in treating Genie, or did the research get in the way? Was this case treated ethically? What could or should have been done differently? What can it teach us about the rewards and risks of conducting “a forbidden experiment?”