Brain structure
Note: This article is mostly motivated by Saul Mcleod, PhD, BSc (Hons) Psychology, MRes, PhD, University of Manchester and his work in "https://www.simplypsychology.org"
The brain is a complex organ that controls thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger and every process that regulates our body. The functions of the brain as part of the Central Nervous System (CNS) is to regulate the majority of our body and mind purpose. This includes vital functions like breathing or heart rate, to basic functions like sleeping, eating, or sexual instinct, and even superior functions like thinking, remembering, reasoning, or talking. In order to carry-out any seemingly simple task, our brain has to perform thousands of processes to ensure that we properly complete the task. In this article, I presented anatomy of brain related to our cognitive activities. In addition, I presented how brain works and explained about myelin.
Brain parts
Brain has three main parts
Left and right parts
Cerebrum of the brain divided to two parts called hemisphere, which connected by a thick band of neural fibers known as the corpus callosum, consisting of about 200 million axons.
Left and Right brain functions
Both hemispheres of cerebrum contains areas with different functionalities. The left hemisphere controls the right-hand side of the body and receives information from the right visual field, controlling speech, language, and recognition of words, letters, and numbers. The right hemisphere controls the left-hand side of the body and receives information from the left visual field, controlling creativity, context, and recognition of faces, places, and objects.
Lobes of brain
Each hemisphere divided to four lobes.
Frontal lobe
Main functions of frontal lobes are associated with higher cognitive functions, including problem-solving, decision-making, attention, intelligence, and voluntary behaviors. Motor cortex (and premotor cortex) responsible for planning and coordinating movements. Prefrontal cortex, which is responsible for initiating higher-lever cognitive functioning and Broca’s Area, which is essential for language production.
Temporal Lobe
These lobes include understanding, language, memory acquisition, face recognition, object recognition, perception and auditory information processing. The left temporal lobe is associated with language, learning, memorizing, forming words, and remembering verbal information. The left lobe also contains a vital language center known as Wernicke’s area, which is essential for language development. The right temporal lobe is usually associated with learning and memorizing non-verbal information and determining facial expressions.
Parietal Lobe
These lobes allow us to perceive our bodies through somatosensory information (e.g., through touch, pressure, and temperature). It can also help with visuospatial processing, reading, and number representations (mathematics). The parietal lobes also contain the somatosensory cortex, which receives and processes sensory information, integrating this into a representational map of the body. This means it can pinpoint the exact area of the body where a sensation is felt, as well as perceive the weight of objects, shape, and texture.
Occipital Lobe
The occipital lobes receive sensory information from the eyes’ retinas, which then encoded into different visual data. Some of the functions of the occipital lobes include being able to assess the size, depth, and distance, determine color information, object and facial recognition, and mapping the visual world. The occipital lobes also contain the primary visual cortex, which receives sensory information from the retinas, transmitting this information relating to location, spatial data, motion, and the colors of objects in the field of vision.
Limbic system
The limbic system is a complex set of brain structures which is located within the cerebrum of the brain, immediately below the temporal lobes, and buried under the cerebral cortex (the cortex is the outermost part of the brain)
Functionalities of limbic system involved in emotion (especially those tied to survival instincts), motivation, memory, and behavior regulation. Key components include the amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus.
Hippocampus
There are two hippocampi located in each hemisphere of the brain.
Episodic memory is a type of long-term, declarative memory that involves the recollection of personal experiences or events, including the time and place they occurred. It allows you to travel back in time to relive past experiences, like remembering your first day at school. Episodic memories are formed in the hippocampus and then filed away into long-term storage throughout other parts of the cerebral cortex. The hippocampus plays a role in spatial navigation and has also been associated with learning and emotions. This area also has widespread connections to brain regions involved in cognition and movement control.
Amygdala
An almond-shaped structure located right next to the hippocampus.
The main function of the amygdala is in emotional responses, including feelings of happiness, fear, anger, and anxiety. This area is also key for the formation of new memories. The amygdala interacts with the hippocampus by attaching emotional content to memories. It has a role in how memorable memories can be – memories with strong emotional components tend to stick rather than those with little emotional content. ‘Fear learning’ is also an element of the amygdala. Fearful memories can be formed after only a few repetitions, which can result in avoidance of certain fearful stimuli.
Cingulate Gyrus
An arch-shaped convolution situated just above the corpus callosum. The frontal portion is termed the anterior cingulate gyrus
Functionalities of cingulate gyrus involved in autonomic and endocrine responses to emotion, and memory storage. It is recruited when we make predictions about the outcome of behavior, and helps to execute said behavior through cingulo-spinal projections. It is thought to be involved in processing information around reward-based decision making and cognitive activity associated with intentional motor control. Involved in processes of internally directed cognition such as memory retrieval, planning, and processing spatial information. It is also hypothesized to be involved in self-monitoring and assessment of events for self-relevance. It is involved in orientating one’s body in a visual space. has been implicated in spatial navigation, autobiographical memory retrieval and imagination.
Thalamus and Hypothalamus
It is a paramedian symmetrical structure of two halves (left and right), within the vertebrate brain, situated between the cerebral cortex and the midbrain.
This region controls most autonomic functions, such as hunger, thirst, body temperature, blood pressure, heart rate, and sexual activity. The hypothalamus also serves as an interface between the nervous system and the endocrine system and in the regulation of sexual motivation and behavior. The hypothalamus also has a role in controlling the body’s response to stress. To control these many functions, the hypothalamus integrates information from other parts of the brain and is responsive to a variety of stimuli, such as light, odor, stress, and arousal.
Basal Gangila
Located deep beneath the cerebral cortex (the highly convoluted outer layer of the brain)
Its main functions are to regulate voluntary movements, including eye movements, and help with balance as well as posture. There is a limbic region of the basal ganglia, which has multiple components (nucleus accumbens, ventral tegmental area, and ventral pallidum). These areas are involved in cognitive and emotional behaviors and have a role in rewards and reinforcements. Because of this, it can be linked with addictive behaviors and the formation of habits.
Cerebellum
Cerebellum located under the cerebrum and above brainstem.
Cerebellum monitors and regulates motor behaviors, especially automatic movements. This structure is also important for regulating posture and balance and being involved in learning and attention. Although the cerebellum only accounts for roughly 10% of the brain’s total weight, this area is thought to contain more neurons (nerve cells) than the rest of the brain combined.
Brainstem
Brainstem located at the base of the brain. This area connects the cerebrum and the cerebellum to the spinal cord, acting as a relay station for these areas.
The brainstem regulates automatic functions such as sleep cycles, breathing, and body temperature, digestion, coughing, and sneezing.
Neuron
Neurons are the nerve cells of the central nervous system that transmit information through electrochemical signals throughout the body. Neurons contain a soma, a cell body from which the axon extends. Axons are nerve fibers that are the longest part of the neuron, which conduct electrical impulses away from the soma. There are different types of neurons.
There are three types of neurons
Sensory Neuron
Sensory neurons (sometimes referred to as afferent neurons) are nerve cells that carry nerve impulses from sensory receptors toward the central nervous system and brain. When these nerve impulses reach the brain, they are translated into ‘sensations’, such as vision, hearing, taste, and touch. This sensory information can be either physical – through sound, heat, touch, and light, or it can be chemical – through taste or smell. Once this happens, the sensory neurons will send signals to the central nervous system about the information they have received. Most sensory neurons are characterized as being pseudounipolar. This means that they have one axon, which is split into two branches.
Motor Neuron
Motor neurons (also referred to as efferent neurons) are the nerve cells responsible for carrying signals away from the central nervous system towards muscles to cause movement. They release neurotransmitters to trigger responses leading to muscle movement. Motor neurons are located in the brainstem or spinal cord (parts of the central nervous system) and connect to muscles, glands, and organs throughout the body. These neurons transmit signals from the spinal cord and brainstem to skeletal and smooth muscle to control muscle movements directly or indirectly. There are two types of motor neurons:
?
Lower motor neurons – these are neurons that travel from the spinal cord to the muscles of the body.
Upper motor neurons – these are neurons that travel between the brain and the spinal cord.
Motor neurons are characterized as being multipolar. This means they have one axon and several dendrites projecting from the cell body.
Interneuron
An interneuron neuron (also known as a relay) allows sensory and motor neurons to communicate with each other. These connect various neurons within the brain and spinal cord and are easy to recognize due to their short axons. Alike to motor neurons, interneurons are multipolar. This means they have one axon and several dendrites. As well as acting as a connection between neurons, interneurons can also communicate with each other by forming circuits of differing complexities. The communication between interneurons assists the brain in completing complex functions such as learning and decision-making, as well as playing a vital role in reflexes and neurogenesis – which means the regeneration of new neurons.
Types of memory
Depending on durability and effectiveness there are four types of memories
Sensory memory: Sensory memory is a very brief (about three seconds) recall of a sensory experience, such as what we just saw or heard. Some compare sensory memory to a quick snapshot of what you just experienced that quickly disappears.?
Short-term memory: Short-term memory is that brief period of time where you can recall information you were just exposed to.?Short-term?often encompasses anywhere from 30 seconds to a few days, depending on who is using the term.
Working memory: Some researchers use the term working memory and distinguish it from short-term memory, though the two overlap.1 Working memory can be defined as the ability of our brains to keep a limited amount of information available long enough to use it. Working memory helps process thoughts and plans, as well as carries out ideas.
You can think of working memory as your short-term memory combining strategies and knowledge from your long-term memory bank to assist in making a decision or calculation.
Long-term memory: Long-term memory encompasses memories that range from a few days to decades. In order for successful learning to take place, information has to move from the sensory or the short-term memory to the long-term memory.
How memory works
There are three main processes that characterize how memory works. These processes are encoding, storage, and retrieval (or recall).
Encoding: Encoding refers to the process through which information is learned. That is, how information is taken in, understood, and altered to better support storage. Information is usually encoded through one (or more) of four methods: (1) Visual encoding (how something looks); (2) acoustic encoding (how something sounds); (3) semantic encoding (what something means); and (4) tactile encoding (how something feels).
Storage: Storage refers to how, where, how much, and how long encoded information is retained within the memory system. The modal model of memory (storage) highlights the existence of two types of memory: short-term and long-term memory. Encoded information is first stored in short-term memory and then, if need be, is stored in long-term memory. Short-term memory only lasts between 15 and 30 seconds and only stores between five and nine items (any piece of information) of information, with seven items being the average number. Long-term memory, however, has immense storage capacity (can be stored there indefinitely).
Retrival: retrieval is the process through which individuals access stored information. Due to their differences, information stored in STM and LTM are retrieved differently. While STM is retrieved in the order in which it is stored, LTM is retrieved through association.
Myelin
Myelin is a protein material which insulate axons and increase the rate at which electrical impulse pass along axon.
Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's electrical wires) to insulate them and increase the rate at which electrical impulses (called action potentials) pass along the axon. Information is passed around 100 times faster along a myelinated axon than a non-myelinated one. The process of generating myelin is called myelination or myelinogenesis. In humans, myelination begins early in the 3rd trimester, although only little myelin is present at the time of birth. During infancy, myelination progresses rapidly, with increasing numbers of axons acquiring myelin sheaths. This corresponds with the development of cognitive and motor skills, including language comprehension, speech acquisition, crawling and walking. Myelination continues through adolescence and early adulthood and although largely complete at this time, myelin sheaths can be added in grey matter regions such as the cerebral cortex, throughout life.
Reefernces