Neuroscience: Brain Regions Overview

The Brain

• Ventral Tegmental Area (VTA) and Substantia Nigra (SN) produce dopamine
• VTA is associated with reward and addiction, SN is critical for movement. Damage to SN is associated with Parkinson's disease.

Brain Regions

• Hindbrain:

  • Medulla: controls bodily functions (breathing, heart rate)
  • Pons: controls sleep, waking, dreaming, and movement
  • Cerebellum: responsible for balance, coordination, fine motor movements, some memory function, and higher cognitive tasks. Damage can lead to clumsiness, uncoordination, and difficulty walking.

• Midbrain:

  • Reticular Formation: spans hindbrain, midbrain, and forebrain. The reticular activating system (RAS) controls sleep/wake, arousal, alertness, and motor activity.
  • Ventral Tegmental Area (VTA)
  • Substantia Nigra (SN)

• Forebrain:

  • Thalamus: "Traffic officer" of the brain, relays sensory information (except olfaction) to higher order cortical regions.
  • Hypothalamus: lies below the thalamus and directs maintenance activities such as eating, drinking, and body temperature. It governs the endocrine system via the pituitary gland and plays a role in emotions.

The Limbic System

• Includes the hippocampus, amygdala, and hypothalamus. Associated with emotions such as fear, aggression, drives for food and sex, and MEMORY.

Cerebral Cortex

• The surface of the brain.
• Gyri: folds or bumps.
• Sulci: grooves.
• Longitudinal fissure: deep groove that separates the brain into two hemispheres.

Organization of the Cerebral Cortex

• Primary Cortical Areas: first to receive sensory information or initiate motor movement (motor cortex). They project information to association areas.
• Association Cortical Areas: process and integrate information sent from primary cortices.

Lobes of the Cerebral Cortex

• Frontal lobe: front of the brain. Contains primary and association motor cortices that plan, sequence, and execute motor movements.

  • Broca's area: usually located in the left frontal lobe. Responsible for the production of language. Damage can lead to Broca's aphasia.
  • Involved in social judgement, rational decision-making, ability to set goals, make plans, and carry through plans.
  • Involved in the inhibition of behavior.

• Parietal lobe: top to the rear of the head.

  • Somatosensory cortex: receives input about pressure, temperature, pain, and touch from the body.
  • Posterior parietal cortex: involved in directing movement in space (e.g., visually guided movement).

• Temporal lobe: side of the head.

  • Primary auditory cortex: responsible for hearing.
  • Amygdala: involved in emotions.
  • Hippocampus: involved in memory.
  • Visual association cortices: involved in face and object recognition.
  • Wernicke's area: responsible for language comprehension. Damage can lead to receptive aphasia.

• Occipital lobe: back of the head.

  • Primary and association visual cortices.
  • Processes qualities of color, motion, shape, and spatial location.
  • Damage can lead to inability to perceive color, motion, or recognize objects (visual agnosia).

Hemispheres and Language

• Right-handed people typically have language processes in the left hemisphere and spatial processing in the right hemisphere.
• Left-handed people:
  • 40% have language dominance in the left hemisphere.
  • 40% have language dominance in the right hemisphere.
  • 20% have mixed language dominance.

Broca's and Wernicke's Areas

• Broca's area: responsible for the production of language. Damage can lead to Broca's aphasia where speech production is impaired, but comprehension remains intact.
• Wernicke's area: responsible for language comprehension. Damage can lead to Wernicke's aphasia, where comprehension is impaired but speech production remains fluent, although often nonsensical.

Corpus Callosum

• Connects the two hemispheres of the brain so they can communicate.

Neuroplasticity

• The brain's capacity for modification.
• The brain is constantly changing and adapting through learning and memory, forming new synapses.
• Children's brains are more plastic than adult brains.
• Important for rewiring the brain after brain injury, developmental incidents, and amputation.

Brain Imaging Techniques

• Clinical observations: provide insights into brain disorders.

• Computerized Tomography (CT scan):

  • Uses x-rays to create images of the brain.
  • Provides high-resolution images.
  • Good for obtaining structural information.

• Positron Emission Tomography (PET scan):

  • Produces visual displays of brain activity.
  • Detects radioactive glucose while the brain performs a task.

Spinal Cord

• Connects the brain to the outside world.
• Organized in 30 segments corresponding to the vertebrae.
• Sensory nerves bring messages in.
• Motor nerves send messages out to muscles and organs.
• Some reflexes are controlled solely by the spinal cord and don't need to communicate with the brain.