Social Psychology: Final Take Home Answers, Essay Example

Describe the stages of brain development.

The stages of brain development include neurogenesis, cell migration, cell differentiation, synaptogenesis, and myelination. Neurogenesis is the developmental stage in which the neurons develop. This occurs during the first trimester of pregnancy to give rise to all of the neurons a person will ever have. During cell migration, neurons move to their functional location in the brain (Hood, 2008) this movement begins towards basic brain structures and then continues to the advanced. This stage of development is completed seven months after conception. Cell differentiation begins once the neurons are in their proper positions and includes the maturation of cells and growth of dendrites and axons. During synaptogenesis, axons connect with the dendrites of other neurons to form synapses; this allows the connection of neuronal networks. Synapse formation occurs primarily during the first three years of human life. During myelination, a white fatty substance known as myelin coats the axon; this protects the axon and helps increase the speed of chemical message transmission via neurons. This step of brain development begins during the third trimester of pregnancy and continues until adulthood; myelin unlike neurons themselves can be continuously generated in an adult human. Neurons involved in basic processes are coated by the myelin first (during fetal development) while neurons involved in more complex processes and located in the frontal lobe of the cortex aren’t myelinated until adulthood.

Contrast the different ways in which rods and cones contribute to our visual experiences (i.e. color perception and specificity). Describe the visual pathways from the retina to the brain.

Rods and cones are sensory neurons that are responsible for detecting light energy (transduction) and converting these energy into neuronal signals. The process by which light energy is converted to neuronal signals is the same in both rods and cones; however the two types of receptors detect different visual pigments. Rods detect very low levels of light at all wavelengths of the visible spectrum by generating a signal. Therefore they are useful in situation where we experience conditions with dim lighting and discriminating colors is not completely necessary. Thus, our rods assist with our ability to see at night. The cones pick up signals that are more wavelength specific than the rods which assists our ability to see color. Cones are less sensitive than rods, and require higher levels of light to generate signals; they help us see during the daytime. The visual pathway from the retina to the brain begins with the photoreceptors in the retina. In the form of chemical information, the “vision message” leaves the eye by means of the optic nerve, where there is a partial crossing of axons called the optic chiasm. The axons then become the optic tract which are wrapped around the lateral geniculate nucleus where the axons synapse. These LGN axons then spread out through the white matter of the brain as optic radiations which connect to the primary visual cortex at the back of the brain.

How is location of objects in the environment coded in the eye and the brain?

The retina helps detect the stimuli in the environment which are then transduced and stored in the brain. Feature detectors are groups of neurons that enable us to quickly detect significant stimuli. The sensory pathway grows more complex as the pathway continues, allowing us to detect more and more complex environmental stimuli. This feature detection helps us differentiate things in the environment including distance and depth.

What is a biological clock and how is it related to both body functions and the environment? Describe evidence for the neural basis of a biological clock.

The biological clock is a phenomenon that is also known as Circadian rhythm. This cycle is about 24 hours long and corresponds with one Earth day. While we are born with this internal programing, our biological clocks can be adjusted based on external stimuli such as awareness of night and day. Our biological clock affects our sleep patterns and is a contributing factor to why most people attain the best night’s sleep during certain periods (such as midnight to 8 am when it is darkest). Different parts of our day correspond with different biological factors such as varying melatonin secretion, core body temperature, and plasma level of cortisol. The system that is responsible for the generation and regulation of circadian rhythms is called the circadian timing system. This neural system consists of a biological clock located in the paired suprachiasmatic nuclei (SCN) of the anterior hypothalamus, of an input pathway from the retina, and output pathways from SCN. Our biological clock is regulated by our exposure to light (daytime) and a lack thereof (nighttime). Therefore the amount of light detected by our retina stimulates this reaction. When people were placed in dark rooms during an experimental procedure, researchers found that the 24 hour cycle we prefer was disrupted. We thus need to be able to detect light using our rods and cones; this signal will eventually be sent to the primary visual cortex.

How does experience with the environment change the structure of the brain? What specific evidence do we have that experience changes the structure of brain?

Neuroplasticity is the term used to describe the effects that the environment has on the structure of the brain. This results due to cellular changes from learning and occasionally from injury. Studies have shown that the brain has the ability to remain plastic even into adulthood. The most substantial changes occur in the lowest neocortical processing areas, and that these changes can change the pattern of neuronal activation in response to experience. A major example of neuroplasticity can be seen in adult people who become blind later in their lives. Since the neurons that allow for vision are no longer necessary, the brain rewires itself over time to sharpen the affected person’s remaining senses such as hearing, touch, and smell. In 1923, Karl Lashley conducted an experiment using rhesus monkeys to show physical changes in neuronal pathways, which he concluded to be evidence of plasticity. He showed that there is no single biological locus of memory, which supports the theory of brain plasticity.

References

Hood, BM. (2008). How brains develop. Nature 453, 157. doi:10.1038/453157a.