Brain Structure

Have you ever heard that we only use 10% of our brain? In fact, each part of our brain has an important function; some store our most cherished memories, some help us decide what coffee we want to order, and others are responsible for moving our muscles to get to the coffee shop.

Our brain is the reason we can interact with the world around us, receive information through our senses and act through our muscles.

Moreover, it is incredibly complex, and we're still working to understand all its secrets. To help us unpack how the brain works and communicate about it, we divide it into distinct structures. In this article, we will take a look inside our brain and what each part of this puzzle does, exploring the brain structure and function.

• We will introduce the topic of brain structure and function by identifying the parts that make up a brain.
• Next, we'll use a brain structure diagram to visualise where these structures are located.

• Then, we'll explore where different functions are localised and look at the brain structure involved in memory.

• We'll move on to the concept of lateralisation and examine how is the left brain different to the right brain.

• Finally, we will discuss the subcortical structures of the brain that lay under the cortex, including the brain stem structure.

Fig. 1 - To help us unpack how the brain works and communicate about it, we divide it into distinct structures.

Brain Structure and Function in Psychology

Throughout the years, psychologists have attempted to understand how the structures and sub-structures are connected and how these structures and connections cause our brain to operate the way it does.

Brain Structure and Function

The brain can be divided into four main structures: cerebrum, cerebellum, diencephalon, and brain stem. Out of all these structures, the cerebrum is the largest; it includes the entire cerebral cortex (the outer layer of the brain), as well as a few structures beneath it like the hippocampus, basal ganglia and the olfactory bulb.

The brain's cerebral cortex is also divided into smaller parts called lobes. Lobes are visibly separated from each other by folds and furrows of the brain. They are also distinct in terms of their functions.

• The frontal lobe is placed in the front of our brain. It is responsible for decision-making, problem-solving, controlling our attention, helping us regulate emotional responses and storing short-term memories. The motor cortex, responsible for voluntary muscle control, resides in the back of the frontal lobe.

• The parietal lobe is placed right behind the frontal lobe. Here lies the somatosensory cortex, which is responsible for sensing the position of our body and the perception of touch. The parietal lobe is also important for visuospatial perception and a key region for helping us recognise how we can act on different objects. We recognise the faces of our friends using the parietal lobe, for instance.

• On the sides of our brain, there are temporal lobes. The temporal lobe is the hearing part of the brain, allowing us to understand auditory information we hear, for example, speech. It includes the primary auditory cortex, which function is to process sound.

Brain Structure Diagram

The diagram shows how the lobes are separated from each other and placed in relation to each other.

Fig 2: The brain can be divided into a number of smaller structures.

Subcortical Structures of the Brain

Subcortical brain structures are located deeper in the brain, below the cerebral cortex.

One subcortical structure is the diencephalon, which contains structures like the thalamus, responsible for transmitting sensory information to the cerebral cortex and the hypothalamus, which controls the autonomic nervous system. Under the hypothalamus, there is also the pituitary gland, responsible for excreting important hormones that regulate the stress response, growth, and metabolism.

The hypothalamus and thalamus are also a part of the limbic system, which additionally includes the amygdala, hippocampus, and cingulate gyrus. This system of structures is associated with memory and emotions.

Basal ganglia is a structure composed of a group of nuclei that together are responsible for motor control, they allow desired movements and inhibit undesired movements.

At the base of the brain lies the brain stem, which connects the cerebrum to our spinal cord. The brain stem controls biological functions like heartbeat, digestion, breathing and regulates sleep.

The brain stem is also connected to the cerebellum, a structure responsible for maintaining balance, movement coordination and learning sequences for motor movements, e.g., when learning to play an instrument.

Brain Stem Structure

The brain stem can be further divided into the midbrain, the pons, and the medulla. Because of its position, the brain stem is responsible for communicating sensory and motor information to and from the spinal cord. The midbrain controls our reflexes and the pons and the medulla are responsible for the control of the autonomic nervous system, sleep, and wakefulness processes.

Fig. 3 - The brain stem can be further divided into the midbrain, the pons, and the medulla.

Localisation of Function in the Brain

Localisation of function in the brain refers to specific regions of the brain being responsible for specific functions. The following table covers the function of the brain and the associated areas responsible for said function.

Penfield's Study of the Interpretive Cortex

Wilder Penfield was a brain surgeon who performed open brain surgery to treat patients with epilepsy. Before the surgery, he would electrically stimulate different areas of the brain to test what they are responsible for and avoid removing areas that are critical to functioning.

Penfield wrote about his findings in 1959; he stressed that when stimulated both left and right temporal lobes can produce a spontaneous recall of previous experiences and concluded that these areas must be where the brain stores our memories.

He also found that some patients had interpretive experiences, where they would interpret what they were seeing or hearing at that moment in an unusual way.

Brain Structures Involved in Memory

As the findings of Penfield's research suggest, the temporal lobes play a crucial role in storing memories. Currently, we also know that the hippocampus, a structure in the temporal lobe, is especially important for storing episodic and autobiographical memories.

Another region, the medial temporal lobe is where semantic memory is stored, whiles the amygdala, a structure placed in the medial temporal lobe, is associated with the memory of emotional experiences. The prefrontal cortex is also important for memory, especially short-term memory.

Damasio et al. (1994)

Phineas Gage became one of the most famous case studies in psychology and neuroscience after he survived an accident during which a metal rod went right through his head. The accident occurred in 1848, at the time Phineas was working on the construction of a railroad. Phineas remained fully conscious after the accident and went to see a doctor, that couldn't believe what he was seeing.

After recovering from the surgery he received, Gage appeared to be regaining his ability to function, despite losing a portion of his brain, there wasn't a dramatic change in his memory and intelligence.

However, people that knew Gage reported that his personality has changed; he became aggressive and was drinking heavily, and his social skills also appeared to change, as he became more socially disinhibited and was acting inappropriately. The changes in his character were the reason he was fired from his previous job.

In 1994, 134 years after the death of Phineas Gage, Hanna Damasio and colleagues used modern neuroimaging techniques to learn more about Gage's injuries. Using x-rays of Phineas's skull, they reconstructed his injuries on a cadaver and concluded that the damage Gage experienced damage affected his prefrontal lobe and reached both of his hemispheres.

Fig. 4 - Visualisation of Phineas Gage's injury, wikimedia.commons.

Lateralisation Sperry (1968)

You might have heard about our right hemisphere being more creative and the left being more analytical. The idea that one hemisphere is more specialised for a particular function is called lateralisation. To investigate whether the functioning of the two hemispheres is actually different, Sperry conducted a series of experiments on split-brain patients.

Different functions of our brain are considered contralateral, meaning that information from the right side of the body (e.g. the right hand) is processed by the left hemisphere and vice versa. Sperry found that although the two hemispheres can both perform different functions, some functions are more lateralised. He found that language abilities are left-lateralised, while the right hemisphere is more specialised for spatial processing.