Comprehensive Study Notes: VCE Psychology Unit 1 - Brain Function, Plasticity, and Disorders
Foundations of Neuroplasticity and Neuronal Communication
The human brain is a remarkably complex and adaptable organ. While every human brain shares a similar appearance, no two brains are identical. Development is directed by genetic information, while individual life experiences actively shape the structure and organization of the brain. The fundamental building blocks of the brain and the entire nervous system are neurons. From the onset of development through the end of life, these neurons and the connections between them remain in a state of flux, changing dynamically in response to experience. Despite this adaptability, it is important to note that the brain cannot repair or recover from every form of damage.
To understand the mechanisms of neuroplasticity, it is essential to first understand the role of the neuron. Specific components of the neuron work in tandem to transmit information throughout the body. Dendrites are specialized to receive neuronal messages from other cells. The myelin sheath acts as an insulating layer that prevents electrical disturbances from neighboring neurons and increases the efficiency of message transmission. At the end of the neuron, axon terminals are responsible for sending neuronal messages to the subsequent cell. Communication between these neurons occurs at the synapse, which is defined as the region encompassing the axon terminals of the pre-synaptic neuron, the synaptic gap (the space between the neurons), and the dendrites of the post-synaptic neuron.
Developmental Plasticity: The Maturing Brain
Neuroplasticity is defined as the ability of the brain to change in response to experience or environmental stimulation. This phenomenon is categorized into two primary types: developmental plasticity and adaptive plasticity. Developmental plasticity refers to the changes in the brain that occur in response to ageing and maturation. This involves three distinct processes: synaptogenesis, synaptic pruning, and myelination.
Synaptogenesis is the formation of synapses between neurons as axon terminals and dendrites grow. When an individual learns new information, neurons form connections with nearby cells, facilitating most of the brain’s growth in size. Conversely, synaptic pruning involves the elimination of underused synapses to free up space and strengthen more frequently used connections. This "fine-tuning" occurs throughout the lifespan, with the most intense periods occurring between ages and and during adolescence. Myelination is the process of developing white, fatty myelin around the axons to facilitate more efficient communication. While myelination begins before birth, it continues through childhood, adolescence, and into early adulthood. Neuroscientists have identified infancy and adolescence as the two most significant periods of developmental plasticity, where synaptic density is at its peak in late infancy and then refined through pruning during the teenage years.
Adaptive Plasticity and the Impact of Brain Trauma
Adaptive plasticity refers to the brain's capacity to restore adequate neural functioning over time after sustaining injury or in response to the need to adapt. This recovery generally occurs through two neuronal processes. The first is sprouting, which is the ability of a neuron to develop new branches on its dendrites or axons, expanding its reach to form new connections where activity was previously depleted. The second is rerouting, where a neuron abandons a connection with a damaged neuron to form a new connection with an undamaged one, allowing cognitive functioning to be re-developed.
Brain trauma is defined as damage to the brain caused by an external force, such as falls, head assaults, vehicle accidents, or sporting injuries. When trauma occurs, the biological impact can be severe. It can cause the death of neurons and the destruction of existing connections. Furthermore, trauma can lead to the overstimulation of neurons due to an excessive accumulation of neurotransmitters in the tissue, which in turn causes further neuronal death. Damage to specific groups of neurons can result in the loss of mass function, such as the loss of hand movement if the neurons responsible for those motor signals are destroyed.
Maintaining and Maximizing Brain Function
There are several evidence-based methods for maintaining brain health and maximizing functional capacity. Mental stimulation is crucial, as activities like crosswords, learning a new instrument, or meditating activate neuronal connections and build resistance to future cell loss. Physical activity is another vital factor; it is recommended that children and young people engage in moderate to vigorous activity for at least per day. This increases blood supply to the brain and promotes the growth of new neurons in the hippocampus, an area critical for learning and memory. Social support, involving interaction with groups or friends, reduces loneliness and decreases the risk of cognitive decline.
Dietary choices also play a significant role. A balanced diet should include leafy greens like kale and spinach, which are rich in vitamin K and help slow cognitive decline. Fatty fish are sources of omega- fatty acids, which are linked to lower blood levels of beta-amyloid, a protein that contributes to Alzheimer’s disease. Daily recommendations include to serves of vegetables and legumes, pieces of fruit, and to serves of meat or alternatives to support long-term brain health.
Acquired Brain Injury (ABI): Impacts on Functioning
Acquired brain injury (ABI) is an umbrella term for all types of brain injuries occurring after birth, including traumatic brain injuries (caused by external forces) and non-traumatic brain injuries. The impact of an ABI is directly related to the specific area of damage. Injury to the frontal lobe may cause trouble deciding what to wear or mood swings. Temporal lobe damage can affect the ability to recognize music or hear alarms. Parietal lobe injury might impair the ability to guess distances or tie shoelaces, while occipital lobe damage affects sight and color recognition. Damage to the cerebellum or brain stem can impact balance, heart rate, and breathing.
ABI impacts functioning across three domains. Biologically, patients may suffer from seizures due to electrical disturbances, movement impairments (paralysis), or smell impairments (temporary or permanent). Psychologically, individuals may experience memory loss, amnesia, personality changes, and an increased risk of disorders such as anxiety or depression. Socially, an ABI can lead to job productivity loss, increased unemployment, social isolation, and occasionally aggressive or antisocial behavior as interpersonal skills and self-esteem decline. Recovery from ABI is often complex because the effects vary based on the severity of the injury, the timing of intervention, and access to treatment.
Case Studies and Contemporary Research in Neurology
History provides key insights through case studies. Phineas Gage, a -year-old railway worker, survived an iron rod piercing his frontal lobes. While his physical abilities seemed intact, his personality shifted from friendly and quiet to aggressive, irresponsible, and crude. Another case is Cameron Mott, who at age had a hemispherectomy—the removal of the entire right side of her brain—to treat Rasmussen's syndrome. Despite the removal of half her brain, she made a full recovery because of her young age and the brain's plasticity, allowing the remaining side to take over the functions of the removed half. Dr. George Jallo noted that children's brains are particularly adept at "rewiring" themselves.
Neurological disorders, such as Parkinson's Disease and Epilepsy, are now better understood through contemporary research. Parkinson's is a progressive neurodegenerative disease characterized by the loss of dopamine-producing neurons in the substantia nigra. Lack of dopamine leads to motor tremors and coordination issues. Epilepsy is marked by recurrent seizures due to abnormal electrical activity. Emerging research areas like machine learning use statistics and algorithms to predict disorder outcomes and improve diagnosis. Additionally, the gut-brain axis is a major focus; research suggests that imbalanced gut microbiota can influence the progression of CNS diseases. For example, some studies suggest Parkinson's may actually begin in the gut, illustrated by constipation symptoms. Treatments like the ketogenic diet (high fat/protein, low carbohydrate) are used to induce ketosis and decrease seizure frequency in children with epilepsy.
Chronic Traumatic Encephalopathy (CTE)
Chronic traumatic encephalopathy (CTE) is a progressive and fatal neurodegenerative disease associated with repeated head injuries and concussions. Concussions are mild traumatic brain injuries that temporarily disrupt function; while they often arise from contact sports or combat, CTE can also result from a single severe trauma in some cases. Symptoms of CTE typically appear to years after the initial repetitive injuries and include depression, memory loss, anxiety, paranoia, aggression, and impairments in executive functions like reasoning and decision-making.
A conclusive diagnosis of CTE can currently only be made through post-mortem examination. Pathological markers include the widespread accumulation of a protein called p-tau, which forms neurofibrillary tangles that disrupt neuronal functioning and lead to cell death. These abnormalities are often concentrated in the brainstem, hippocampus, cerebral cortex, and particularly the frontal and temporal lobes. While there is no cure for CTE, research has significantly influenced sporting regulations, leading to stricter concussion protocols and the use of helmets to protect athletes from the long-term, fatal effects of the disease.
Questions & Discussion
The following section details interactions and questions regarding the material:
Case Study: Jodie / Cameron Mott Question: Which of Jodie’s cerebral hemispheres was likely removed during the surgery? Justify your response. Answer: Following the surgery, Jodie/Cameron experienced motor impairments on the left side of her body; therefore, the right hemisphere was removed because the brain controls the contralateral (opposite) side of the body.
Question: What does the case reveal about the human brain? Answer: It demonstrates the incredible capacity for neuroplasticity, particularly in children, where one hemisphere can adapt to perform the functions of both.
Question: Why is it better she had surgery at age rather than in adolescence? Answer: Brain plasticity is significantly higher in early childhood due to the rapid growth and higher synaptic density associated with developmental plasticity, making recovery and functional transfer easier than in the adolescent brain.
Case Study: The Man Who Mistook His Wife for a Hat (Oliver Sacks) Question: Why could the patient identify the rose by smell but not by sight? Answer: He had damage to an association area in the occipital lobe. While he could see basic features (edges, colors), he could not integrate that information with memory to identify the object until he invoked his olfactory (smell) sense, which utilized a different, undamaged neural pathway.
Research Inquiry: Why is contemporary research important for neurological disorders? Answer: It allows for the discovery of less invasive, more effective treatments. It helps scientists understand the bidirectional relationship of the gut-brain axis and utilize machine learning for more accurate predictions of disease progression.