The Brain

First brain experiments:

Brain lesioning: involves disrupting or damaging the normal structure or function of part of the brain. Brain lesioning studies involved creating and/or studying the effects of existing damage to an area of the brain, but not removing tissue. 

Brain ablation: Brain ablation involves the destruction and surgical removal of a region of brain tissue.

REGIONS OF THE BRAIN:

Hindbrain:

Structures:

• Cerebellum

The cerebellum is responsible for coordinating voluntary movements. Also plays a key role in balance, posture, and motor learning.

• Medulla

The medulla controls heart rate, breathing, blood pressure, and swallowing. Damage to this area can be life-threatening.

• Pons

The pons acts as a communication bridge between different regions of the brain. It helps regulate sleep, dreaming, and arousal, and assists in coordinating movement between the left and right sides of the body.

Midbrain: 

Structures:

• Reticular Formation

The reticular formation helps regulate levels of alertness and consciousness. It filters incoming sensory information to prevent overload and plays a role in attention and arousal.

• Substantia Nigra

The substantia nigra is involved in the control of voluntary movement and the production of 

dopamine. Degeneration of neurons in this area is associated with Parkinson’s disease.

Forebrain: 

Structures:

• Hypothalamus

The hypothalamus maintains the body's internal balance (homeostasis) by regulating temperature, hunger, thirst, sleep cycles, and hormone release through its connection to the pituitary gland.

• Thalamus

The thalamus acts as a relay station for most sensory information (except smell), directing it to the appropriate areas of the cerebral cortex for processing.

• Cerebrum

The cerebrum is the largest part of the brain and is responsible for higher-order cognitive processes such as decision-making, problem-solving, planning, thinking, and voluntary movement.

LOBES OF THE BRAIN:

Frontal lobe

• Primary motor cortex
  

  • Controls motor movements

  • The body parts that make more complex or ‘fine’ movements are assigned more cortical space

  • The body is represented upside down on the motor cortex

  • The left side of the body is  controlled by the right primary motor cortex, and vice versa (contralateral)

• Prefrontal cortex

  • Reasoning, problem solving,  personality

• Broca’s area (LEFT hemisphere)

  • Production of fluent speech

  • coordinates the muscle movements required to produce fluent speech, such as tongue, lip, jaw, and vocal cord movements.

PARIETAL LOBE

Primary Somatosensory Cortex

• Receives and processes sensory information from the skin and body parts.
  
  

• The more sensitive the body part (e.g., lips, fingertips), the more cortical space it receives.
  
  

• Also organised contralaterally and upside down.
  
  

Functions

• Spatial awareness
  
  

• Perception of touch, pressure, temperature, and pain
  
  

OCCIPITAL LOBE

Primary Visual Cortex

• Processes visual information received from the eyes.
  
  

• Left visual field is processed in the right hemisphere and vice versa.
  
  

Functions

• Interpretation of visual stimuli like shapes, colours, and motion
  
  

TEMPORAL LOBE

Primary Auditory Cortex

• Processes sounds from both ears
  
  

• Interprets pitch, volume, and rhythm
  
  

Wernicke’s Area (LEFT hemisphere)

• Comprehension of spoken and written language
  
  

• Involved in formulating meaningful, coherent speech
  
  

General Functions

• Memory (especially auditory)
  
  

• Understanding language
  
  

• Recognising faces and objects
  
  

HEMISPHERIC SPECIALISATION

Left Hemisphere

• Language (Broca’s and Wernicke’s areas)
  
  

• Logical thinking
  
  

• Maths and science
  
  

• Controls the right side of the body
  
  

Right Hemisphere

• Spatial and visual thinking
  
  

• Creativity and imagination
  
  

• Facial recognition
  
  

• Controls the left side of the body
  
  

CONSEQUENCES OF INJURY TO THE BRAIN

Frontal Lobe

• Personality changes
  
  

• Difficulty with planning or decision-making
  
  

• Impaired movement (if motor cortex is affected)
  
  

Parietal Lobe

• Loss of sensation
  
  

• Spatial neglect (especially left neglect from damage to the right hemisphere)
  
  

Occipital Lobe

• Vision problems or blindness
  
  

Temporal Lobe

• Memory loss
  
  

• Inability to understand speech (Wernicke’s aphasia)
  
  

BRAIN PLASTICITY

Developmental Plasticity (normal brain development)

• Myelination: Coating axons with myelin for faster transmission
  
  

• Synaptogenesis: Creation of new synapses
  
  

• Synaptic Pruning: Removal of unused or weak synaptic connections
  
  

Adaptive Plasticity (brain adapting after injury)

• Sprouting: New dendrites grow to form new connections
  
  

• Rerouting: Neurons find new pathways to restore function
  
  

NEUROIMAGING TECHNIQUES

CT (Computed Tomography)

Type: Structural
Description: Uses X-ray technology to create cross-sectional images of the brain.

Pros:

• Fast and widely accessible
  
  

• Useful for detecting strokes, tumors, and bleeding
  
  

Cons:

• Involves radiation exposure
  
  

• Lower image resolution compared to MRI
  
  

MRI (Magnetic Resonance Imaging)

Type: Structural
Description: Uses magnetic fields and radio waves to produce highly detailed images of the brain.

Pros:

• High-resolution imaging of brain structures
  
  

• No radiation involved
  
  

Cons:

• More expensive and time-consuming than CT
  
  

• Not safe for patients with metal implants or pacemakers
  
  

fMRI (Functional Magnetic Resonance Imaging)

Type: Functional
Description: Measures brain activity by detecting changes in blood oxygen levels (BOLD response).

Pros:

• Shows both brain structure and function
  
  

• High spatial resolution to pinpoint active brain regions
  
  

Cons:

• Poor temporal resolution (slight delay in activity detection)
  
  

• Sensitive to head movement and costly
  
  

PET (Positron Emission Tomography)

Type: Functional
Description: Uses a radioactive glucose tracer to map brain activity based on metabolic activity.

Pros:

• Detects functional changes before structural changes appear
  
  

• Useful for identifying disorders like Alzheimer's and epilepsy
  
  

Cons:

• Involves radiation exposure
  
  

• Lower resolution than fMRI and more invasive
  
  
  

BRAIN FUNCTION & LIFESTYLE

Ways to Maximise Brain Function

• Mental stimulation: e.g., puzzles, strategy games
  
  

• Physical activity: e.g., running, HIIT – boosts oxygen and blood flow
  
  

• Healthy diet: e.g., Omega-3 (salmon, chia seeds), kietic diet
  
  

• Social support: e.g., calling friends/family, engaging in community
  
  

PARKINSON’S DISEASE

Cause

• Degeneration of neurons in the substantia nigra
  
  

• Results in reduced dopamine production
  
  

Symptoms

• Tremors
  
  

• Muscle rigidity
  
  

• Slowed movement (bradykinesia)
  
  

• Postural instability
  
  

Treatment

• Levodopa: Converts to dopamine in the brain
  
  

• DBS (Deep Brain Stimulation): Electrode implants stimulate motor areas
  
  

• Gut-brain axis treatments: e.g., pre/probiotics
  
  

EPILEPSY

Symptoms

• Focal seizures: Specific area of the brain (e.g., vision, speech, movement)
  
  

• Generalised seizures: Affect the whole brain
  
  

Treatments

• Anticonvulsant medication
  
  

• Vagus nerve stimulation
  
  

• Ketogenic diet
  
  

CHRONIC TRAUMATIC ENCEPHALOPATHY (CTE)

Cause

• Repeated head trauma (common in contact sports)
  
  

Symptoms

• Memory loss
  
  

• Mood swings
  
  

• Depression
  
  

• Aggression
  
  

Diagnosis

• Confirmed post-mortem by examining brain tissue
  
  

NEURONS & SYNAPTIC TRANSMISSION

Structure of a Neuron

• Dendrites: Receive messages
  
  

• Soma (cell body): Processes info
  
  

• Axon: Transmits message
  
  

• Myelin sheath: Insulates axon, speeds up transmission
  
  

• Axon terminals: Pass message to next neuron
  
  

Steps of Communication

1. Action potential travels down the axon
   
   

2. Neurotransmitters are released into the synapse
   
   

3. Bind to receptors on the postsynaptic neuron