Discuss two effects of the environment on physiological processes.


1. The effect of light on melatonin and vitamin D levels

Melatonin: A hormone secreted by the pineal gland. Regulates sleep and the circadian rhythm. The production of melatonin by the pineal gland is stimulated by darkness and inhibited by light. (the reverse is true for serotonin)

Circadian rhythm: Our biological clock that is based on a 24-hour day/night cycle. The circadian rhythm is regulated by melatonin.

Seasonal affective disorder (SAD): A type of depression in which the patient experiences depressive symptoms in the autumn and winter. Is believed to depend on reduced levels of sunlight in autumn and winter. (Other animals hibernate in the winter, e.g. bears. It is suggested that pets also can suffer from SAD)

Vitamin D: The “sunshine vitamin”, is synthesized in our skin when we are exposed to direct sunlight. Vitamin D is thought to activate and deactivate enzymes in the brain and cerebrospinal fluid that are involved in neurotransmitter synthesis and nerve growth. Studies suggest that Vitamin D protects neurons and reduces inflammations.

Supporting studies

Kent (2009): A correlational study on 14,474 American participants. The findings showed that participants with low exposure to sunlight was associated with a significantly higher cognitive impairment.

Llewellyn (2009): A correlational study on 1,700 British participants. The findings showed that the lower the participants vitamin D levels, the lower their performance on mental tests.

University of Manchester (2009): A correlational study on vitamin D levels and cognitive performance 3,100 men aged 40 to 79 in eight European countries. The findings showed that people with lower vitamin D levels had slower information-processing speed.

Golden (2009): A meta-analysis on eight studies on 228 patients who had been treated for SAD with light therapy. The findings showed very weak evidence that light therapy is effective for SAD. There was a large acute effect of light therapy on symptoms of SAD the first week of treatment, but this effect disappeared quickly thereafter.

2. The effect of deprivation and stimulation on neuroplasticity



NEUROPLASTICITY - The changing of neurons, the organization of their networks, and their function via new experiences.



Rosenzweig & Bennett (1972)

Aim: To investigate the effect of enrichment or deprivation on the development of neurons in the cerebral cortex in rat

Research method: Experiment

Procedure: Rats were placed in either a stimulating environment (toys) or a deprived environment (no toys). The rats spent 30 or 60 days in their environment and then they were dissected

Findings: Post modern studies of the rats´ brains showed that those that had been in a stimulating environment had an increased thickness in the cortex

Kolb (1999)

Aim: To investigate if stimulating environments affects the growth of neurons in rats

Research method: Experiment

Procedure: Rats were placed in enriched environments beginning at weaning or as young adults. Control group were placed in standard cages

Findings: Both age groups raised in enriched environments showed a large increase of the length of dendrites in cortical neurons.

Kolb et. al. (2004): Pregnant rat mothers were housed in enriched environments. Their babies had increases in synaptic space on cortical neurons as adults.

Pascal-Leone (2002): Participants were instructed to learn to practice a five-finger piano exercise for five days, two hours every day. During the session, the participants’ motor cortex was investigated by the use of a transcranial-magnetic-stimulation test (TMS). The findings showed that practice altered the structure of the area devoted for the finger movements. For a group of participants who also had been instructed to imagine they were playing five-finger piano tone outside of practice, the area for finger movements in the motor cortex expanded even more. The results suggest that training and imagination can alter brain physiology.




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