How does neurological damage affect behaviour? Having a healthy and well-functioning brain is essential for overall well-being in humans. Suffering from brain damage can have tremendous repercussions on someone's life. Some individuals who have damaged their brains may not be able to recognise visual objects and can have difficulties with their communication skills. After brain damage, individuals experience many challenges in their lives, and full recovery is complex and dependent on the person.
Historically, psychologists have learned a lot about The Brain after individuals have damaged it. Let's take a look at how neurological damage impacts behaviour.
- In this explanation, we will start by reviewing neurological damage on behaviour, providing a neurological damage definition.
- We will explore neurological damage on behaviour effects.
- We will look into what neurological damage is and discuss neurological damage in behaviour research.
- And lastly, we will examine studies showing the effect neurological damage has on behaviour.
Fig. 1 - Neurological damage can have different effects on behaviour.
Neurological Damage Definition
Neurological damage is the injury or impairment of any part of the Nervous System (the CNS and the PNS). Neurological damage can occur due to brain injury or as a consequence of brain surgery.
The Nervous System has two components which interact: the central Nervous System (CNS) and the peripheral Nervous System (PNS). The CNS consists of The Brain and the spinal cord. For a response (e.g. move your hand away from a hot surface) to be activated, the PNS is needed.
In some cases, neurological damage is specific to a given brain region (e.g., the amygdala is impaired), but sometimes neurological damage can happen in larger brain areas (e.g., the frontal lobe is impaired). Neurological damage can evoke substantial impairments in behaviour. Even more, healing a damaged brain can be a complex process.
An example of neurological damage is presenting speech impairments after a stroke.
A stroke takes place when the blood supply of a given brain region is blocked for some time. The lack of oxygenation in a brain region can lead to different impairments.
Speech impairment can happen for a few reasons. Broca's Area, which is responsible for speech production, or Wernicke's Area, which is responsible for speech comprehension, can be damaged.
Alternatively, the facial nerve may be damaged. The facial nerve allows us to speak and move our facial muscles, which can result in facial paralysis when damaged.
Other behavioural difficulties present when the motor cortex is damaged are impairments in fine motor skills. Fine motor skills involve hand and arm coordination, such as buttoning clothes, closing a zipper or dialling the phone.
Neurological Damage on Behaviour Effects
The consequences of neurological damage on behaviour can vary. Much research has been devoted to establishing how brain injury can impact behaviour. In this section, you will find evidence of how neurological damage can affect personality, impulse control, and self-awareness.
Neurological Damage on Behaviour Research: Phineas Gage
One of the most researched and well-known examples of the effects of brain injury on behaviour is the case of Phineas Gage (PG). In 1848 when he was 25 years old, he had an accident at work. An explosion caused an iron rod - around 1m long and 3cm in diameter - to make a hole from PG's cheek to the skull.
Fig. 2 - Phineas Gage had an accident where a rod pierced his skull and damaged his brain.
Although PG survived the accident, his personality changed. Before the accident, PG was calm and responsible, but he became impolite and impulsive. PG died 12 years after the accident took place after having epileptic seizures. His brain, however, was donated to Harvard University, where Damasio and her colleagues have further studied this case.
In 1994, Damasio and her research group studied which specific brain areas had been damaged in PG's accident. The study aimed to understand the full extent of the damage PG suffered and how this affected his behaviour. They created 3D representations of PG's skull after the iron cod had been inserted to investigate this.
- By comparing the 3D representations to the actual skull, they could estimate the actual trajectory of the cod. Once the representation was as accurate as possible, researchers could map the brain regions affected by the accident.
Damasio and her colleagues established that the frontal lobe wasn't the only brain area affected during the accident. Both the left and right prefrontal cortices had been impaired. White matter within the frontal lobe had been damaged, which impaired the connection between the frontal lobe and other brain regions.
White matter is tissue containing axons of neurones in the brain.
The ventromedial area of the frontal lobe, the deeper and lower area of the frontal lobe, had been more damaged than the dorsolateral area, the less deep and more superficial area of the frontal lobe.
Fig. 2 - The ventromedial area of the brain was damaged in the case of Phineas Gage, amongst other areas.
Based on these results, Damasio and her colleagues reached certain conclusions. Considering the evidence of PG and 12 other patients, they established that the ventromedial frontal lobe is associated with decision-making and impulsive behaviour.
Impaired decision-making and impulse control were associated with damage to the ventromedial frontal lobe.
Evaluation of Damasio et al.'s (1994) Study
Damasio et al. (1994) provided more detailed evidence of what happened to Phineas Gage. Still, we need to consider the strengths and weaknesses of the study to identify if we can trust this evidence.
Strengths | Weaknesses |
- Damasio and colleagues used 3D imaging, which showed precisely which areas were affected by the accident.
| - Although Damasio considered evidence from other patients, these may not represent the whole population. The study lacks generalizability as a result.
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- The study allows researchers to estimate behavioural changes if someone has damaged their frontal lobe.
| - Researchers had never met PG and instead worked with the existing written records. However, these may not have been accurate and reduces the reliability.
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Psychological Effects of Brain Damage
One of the neurological diseases that individuals can suffer from is epilepsy. Individuals diagnosed with the disease often experience seizures. These are unusual bursts of electrical activity that change the brain's usual functionality for the time they last.
Epilepsy has no single identifiable cause, and in the past, individuals diagnosed with epilepsy underwent an invasive surgical procedure to lower the number and intensity of their seizures. This procedure involved cutting the corpus callosum, the connector between the left and right hemispheres.
Brains are contralateral, which means that the information that comes through the senses on the left side of the body is processed by the right brain hemisphere and vice versa.
Thus, their brain hemispheres could no longer communicate after surgery, and their behaviour and ability to process information and perceive the world were drastically affected.
Today the surgical procedure of removing the corpus callosum of individuals with epilepsy is only used in severe cases due to its adverse side effects.
Sperry (1986) wanted to study the implications of undergoing the neurological surgery described above. He tried to understand how the different hemispheres process information and test whether there were any differences between healthy individuals and those who had had their corpus callosum severed.
- Sperry recruited 11 participants who had already undergone surgery.
- The study was a quasi-experiment with independent measures design under laboratory conditions.
- The independent variable of the study was whether or not participants had a split brain, and the dependent variable was participants' performance in two tasks: a visual and a tactile task.
In another experimental condition, visual stimuli would be presented on either the screen's left or right side. At the same time, an object would be put on either the participant's left or right hand. Participants' task was to say whether what they saw on the screen matched what they could feel in their hands.
These results suggest that in the sample that Sperry used, there was a lack of information sharing between the left and the right hemisphere. The main conclusion that Sperry drew from this study was that each brain hemisphere could function independently of the other. However, in individuals with a severed corpus callosum, each hemisphere has a separate Memory system independent of the other hemisphere. This is different in healthy individuals.
Furthermore, Sperry's (1968) study showed that each brain hemisphere has different specialisations. While the left hemisphere specialises primarily in language abilities, the right hemisphere specialises in visuospatial abilities.
Evaluation of Sperry's (1968) Study
Let's examine the strengths and weaknesses of Sperry's study.
Strengths | Weaknesses |
- The experimental conditions in the laboratory setting were controlled, which facilitated the replication of the study, making it reliable.
| - The study's small sample does not allow the results to be generalised to the broader population.
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- The study implied reducing the number of neurological interventions performed in individuals with epilepsy due to the severe implications of the intervention.
| - The study did not include a control group to compare the results with.
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Personality Changes due to Brain Damage
As you learned earlier in this explanation, patient PG's personality changed after his accident. The calm and responsible young man became impulsive and had bad manners.
Personality changes have widely been reported in patients suffering from brain damage. Some of the most common personality changes include:
- Lower patience and show anger or frustration faster.
- Difficulty regulating emotions, which is referred to individuals' ability to control one's own emotional state. This is manifested by laughing or crying at inappropriate times, for example.
- Showing aggressive behaviour can be challenging for the patient's social circle to manage and accept.
- Becoming obsessive and unable to act flexibly. This can be manifested as showing a stubborn personality.
All these symptoms make people with brain damage show poor impulse control. Neuropsychologists can support brain-damaged patients in learning coping skills and techniques to reduce symptoms and increase recovery rates.
Neurological Damage on Behaviour - Key takeaways
- The central nervous system (CNS) is composed of the brain and the spinal cord and sends and receives information from the peripheral nervous system (PNS).
- Neurological damage is the impairment of the central and/or peripheral nervous system. Strokes are an example of how neurological damage can occur, resulting in impairments, paralysis (muscle control issues) and personality changes.
- Phineas Gage's case study shows how neurological damage to the frontal lobe leads to personality and impulse control changes.
- Neurological damage, such as the severing of the corpus callosum in case studies, shows how neurological damage affects behaviour and perception of the world.
- Sperry's (1968) study proved that the two hemispheres have different functionalities and Memory systems.
References
- Fig. 1: Phineas Gage injury picture. Polygon data is generated by Database Center for Life Science(DBCLS)[3]., CC BY-SA 2.1 JP , via Wikimedia Commons
- Fig. 2: Ventromedial area of frontal lobe diagram. Ventromedial_prefrontal_cortex.png: *derivative work: finereach (talk)Brain_human_sagittal_section.svg: Patrick J. Lynch, medical illustratorBrain_human_cranial_nerves.svg Patrick J. Lynch, medical illustratorderivative work: Mabhobs, CC BY 3.0 , via Wikimedia Commons
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