Discuss two effects of the environment on physiological processes.
SAQ First Sentence – One effect of the environment on physiological processes is the effect of navigational experience on
neuroplasticity as demonstrated by Maguire at al. (2001).
LAQ Thesis – This paper will discuss two effects of the environment on physiological process as demonstrated in studies by Maguire et
al. (2000), Rosenzweig et al. (1972), and Avery et al. (2001).
Maguire et al. (2000) – Navigation-related structural change in the hippocampi of taxi drivers
Hippocampus is a structure found inside each hemisphere of the brain that is thought to play a role in spatial memory and navigation.
Aim: To investigate whether the healthy human brain can undergo structural changes in response to extensive navigation experience, and
the role of the human hippocampus in navigation.
Research Method: Naturalistic experiment.
Procedure
 16 licensed London taxi drivers with a minimum of 18 months job experience and non-taxi drivers (50 participants for VBM
template, 16 for pixel counting).
o Taxi drivers were all right-handed, male, aged from 32 to 62, with average job experience of 14.3 years. Non-taxi drivers
were matched for health, handedness, sex, average age, and age range to remain consistent
 MRI scans were taken for all participants
 Voxel-based morphometry used to normalize brain scans to a template which eliminates the size of participant brains as a variable
and compared the taxi drivers’ brains with the 50 non-taxi drivers
 Volume of anterior, body and posterior cross-sections of the taxi drivers’ hippocampi were compared with those of 16 matched nontaxi drivers’ through pixel counting.
Results
 VBM analysis showed no significant differences in the brain between the two groups but taxi drivers had significantly increased
grey matter volume in the left and right posterior hippocampus compared to the non-taxi drivers

Pixel counting revealed no significant difference in overall hippocampus volume but confirmed results from VBM analysis
 Significant positive correlation was found between time as a taxi driver and right posterior hippocampal volume and a negative
correlation for the right anterior section
 Human spatial representations and navigational experience are likely stored in posterior hippocampus.
Strengths
 Control of variables led to strong correlation data
 Demonstrated that brain structure can be altered by environment stimulation, contrary to prior belief
 Methods of measurement were objective and well-controlled
Limitations
 The study does not explain the mechanisms behind the structural changes.
 Findings are over-simplified and study is reductionist
Rosenzweig et al. (1972)
Cerebral Cortex – Outer layer of neural tissue in brain. Plays a key role in functions such as memory, attention, perceptual awareness,
thought, language, and consciousness.
Aim - investigate whether environmental factors such as a rich or impoverished environment affect development of neurons in the
cerebral cortex
Research Method - Laboratory experiment
Max Chen and Walid Herzallah
Discuss two effects of the environment on physiological processes.
Procedure
 Rats place in two conditions – enriched environment condition and impoverished condition
 Enriched condition – 10-12 rats in a cage provided with different stimulus objects to play with, also received maze training
 Impoverished condition – each rat isolated in individual cage with no stimulation
 Rats spent 30-60 days in these environments before being killed so their brain anatomy could be studied
Results
 Brain anatomy was different for rats in each condition
 Enriched condition rats had increased thickness and higher weight of the cortex
 Also developed acetylcholine receptors in cerebral cortex (neurotransmitter important to learning and memory)
Strengths
 Strong control of variables leads to cause/effect relationship being established
 Implies human brain will also be affected by environmental factors such as intellectual and social stimulation.
 Challenged earlier belief that brain weight cannot change
 Results showed that just 2 hours a day in enriched condition had same results as rats who were constantly there. This shows that
brain can adapt and change to new situations.
Limitations
 Study was done on rats so results may not be generalized to humans.
 Ethical considerations – rats were sacrificed, however justified due to better understanding of brain plasticity as result of findings
Avery et al. 2001
Based on previous study from Rosenthal
Rosenthal’s study suggested that higher levels of melatonin cause a mild form of depression called seasonal affective disorder (SAD).
Symptoms of SAD include lethargy and craving for carbohydrates. Reduced levels of sunlight in autumn and winter are thought to be
responsible for increased melatonin levels and SAD due to disruption in the circadian rhythm.
Aim: To determine the effect of various light treatments on Seasonal Affective Disorder (SAD) patients.
Research Method - Laboratory experiment
Procedure:
 95 patients diagnosed with SAD were allocated to one of three conditions:
o dawn simulation where a light would come on in the person’s bedroom beginning at 4:30am and peaking at brightness at 6am
replicating conditions in months when there is more sunshine
o
bright light therapy where participants were exposed to a bright light for 30 minutes from 6:00am to 6:30am which is a
traditional therapy for SAD patients
o
red light therapy where participants are exposed to a dim red light from 4:30am to 6:00am (placebo group)
 interviews used to determine effect of different conditions on SAD
Results
 Dawn simulation group experienced greatest improvement and less side effects than other two groups.
 Both dawn simulation and bright light therapy realigned sleep patterns to some extent
 Participants in red light therapy group suffered the most side effects, including insomnia
Strengths
 Results showed dawn simulation is effective in treatment of SAD.
 Control of variables allows cause/effect relationship to be made between SAD treatments and effectiveness,
 Easily replicable procedure.
Limitations
 Patients suffered physical side effects (nausea and headaches in bright light therapy condition).
 Melatolin levels were not actually measured and effectiveness of treatment was determined solely by interviews
Max Chen and Walid Herzallah