How the Brain works... a very brief introduction!
Updated: Jan 30
The brain is arguably our most complex organ, and governs activities as basic as movement, breathing and heart rate and those as elegant as communication, thought and our sense of who we are. Here, I outline the fundamentals of brain structure and function as they relate to cognition and memory.
The brain weighs on average between one to one and a half kilos, yet contains billions of nerve cells and innumerable connections between them. These form a vast circuit through which messages are conveyed both in an electrical and chemical form. It is generally divided into two hemispheres - left and right - and in each hemisphere there are four lobes. These include the frontal lobe, parietal lobe, temporal lobe and occipital lobe. The hemispheres are connected by a think bundle of nerves called the corpus callosum.
Each lobe has different functions, though there is a degree of overlap:
The temporal lobe is critical for memory formation, and damage to a particular part, the hippocampus, is the hallmark early feature of Alzheimer's disease. This is the most common cause of dementia.
The parietal lobe is important for our visuospatial skills (knowing where we are in relation to other objects in our environment), maths and purposeful movement (praxis)
The frontal lobe oversees many of the other functions of the brain and is its executive centre. It has an important role in working memory, is relevant to our language abilities and is considered by many to be the seat of our personality. It allows us to follow usual social rules, inhibit unhelpful impulses, and plan and organise ourselves.
The occipital lobe is critical in processing visual messages sent to our brain from the outside world - so we can make sense of what we see.
The lobes together make up the cortex of the brain. This is the wrinkly outer layer that we are all familiar with. Deeper within the brain, there are a number of other structures, collectively known as subcortical structures. These include the cerebellum, the brainstem, the basal ganglia and the limbic system. They serve a number of other functions including regulation of emotion, housing of emotional and procedural (auto-pilot) memories like driving a car, and balance. Parts of the subcortex are also responsible for basic physiological functions like control of body temperature, breathing and heart rate.
Damage to different parts of the brain causes different symptoms, with dementia the potential end-point.
Basic Cognitive Functions
Cognitive functions are those related to our thinking. Memory is perhaps the one that first comes to mind, This can be further divided into sensory memory (a very brief memory of something we have seen, heard or otherwise experienced), short-term memory and long term memory. Though there is some controversy about the division of memory, short-term memory is often used interchangeably with working memory, and relates to our ability to hold pieces of information in mind so that we can manipulate or use them. Recalling a phone number have just been been told about is one example. Long term memory is that memory stored in our brain so that we can later retrieve it. Different parts of the brain are responsible for registering, encoding, storing and retrieving these memories.
Other cognitive functions include attention and concentration, language abilities, visuospatial skills, praxis (our ability to move ourselves in a way that helps us e.g. using cutlery), gnosis (our ability to recognise familiar objects), calculation and executive skills. These latter skills are those that allow us to perform more complex cognitive tasks that involve planning, sequencing and organisation. Again, different parts of the brain allow us to have these skills.