Localization of function in the brain

Week 3 Sep. 17th

What was Phrenology and what was he right and wrong about?

(Franz Gall, 1819)

Different bumps on the skull reveal our mental abilities and character traits

Wrong about:

• Bumps

• traits

Right about:

• LOCALIZATION (that’s why we still talk about him)

What was the popular pseudoscience of the 19th century?

Phrenology

• Skull measures 

• This data was used as a scientific basis for racism and colonialism 

What is brain localization?

• Brain location and functioning is oversimplification 

• Note that it’s *useful* oversimplification 

  • as is most of science, really 

• Most of the processing that’s now thought to occur in certain areas really does occur there, in normal cases 

  • just not all of it, and not in al cases 

Modern “Phrenology”

• A combination of ideas!

• The brain as a whole is active during any task, but there are areas of peak activity which suggests a single region involves in a particular task 

Brain Organization

Frontal lobe…. in the front

Parietal lobe… in the top-back

Temporal lobe… in the sides

Occipital lobe… in the back

Embryological development

The vertebrate nervous stem forms out of a simple tube with three lumps

• The midbrain and hindbrain become the brainstem

• The forebrain becomes the cerebral cortex and other higher structures

Brain Organization

Top: Luxuries

Bottom: Necessities

1. Voluntary action, complex judgment symbolic thought

2. Emotion, motivation, simple judgement

3. Sensory information

4. Basic motor programs

5. Basic life functions (breathing, heartbeat)

What actions happen in the cerebral cortex?

• Voluntary action

• Complex judgement 

• Symbolic thought  

What actions happen in the limbic system? 

• Emotion 

• Motivation 

• Simple judgement 

What information is processed in the thalaums?

Sensory information, sensory relay station!!!

What type of basic motor program occurs in the cerebellum?

Repetitive movement, etc.

(the cerebellum is the butt of the brain, think twerking… repetitive movement in the butt of the brain) 

What basic life functions happens in the brain stem?

Breathing, heartbeat

Brainstem equals?

Survival

Cerebellum equals?

Movement

Cerebellum

• Integrates visual, auditory, somatosensory information 

• Modifies the motor outflow

  • exerting a coordinating and smoothing effect on the movement 

• Cerebellar damage results in jerky, poorly coordinated, exaggerated movements 

  • extensive cerebellar damage makes it impossible even to stand 

Forebrain

• Thalamus

  • located above the hypothalamus 

  • receives information from the cerebral cortex 

  • projects information to specific regions of it 

• Sensory hub 

Limbic system - Emotions

• Hypothalamus 

  • regulates emotional and motivated behavior 

• Amygdala 

  • an almond-shaped structure crucial for emotional processing 

  • deep inside the temporal lobes 

• Hippocampus 

  • vital for memory processing 

Forebrain

• Cerebral cortex

  • the outer covering of the forebrain

  • it’s composed of gray matter

    • the cell bodies of the cortical neurons

• Interior of the forebrain is composed of white matter or axons of cortical neurons

  • is it white because of its myelin coating

Left vs Right Brain 

Left side:

• Control of the right side of the body 

• Written and spoken language 

• Mathematical calculations 

• Logical decision making 

• Reasoning 

Right side:

• Control left side of the body

• Understanding language

• Non-literal thinking

• Spatial awareness

• Imagination

• Facial Recognition

Contralateral Organization 

• Most of the sensory and motor information that travels to and from the brain goes to the opposite side of the body 

• Motor crossover 

  • right hemisphere controls left side

  • left hemisphere controls right side

Visual Crossover 

• Left visual field to right hemisphere 

• Right visual field to left hemisphere 

Cerebral cortex regions

Frontal lobe, parietal lobe, occipital lobe, and temporal lobe

What is the central sulcus?

Central Sulcus 

• Prominent, deep groove that runs roughly in the middle of the lateral surface of the cerebral hemisphere

Lateral Sulcus

• Deep fissure (also called the Sylvian fissure) that separates the temporal lobe from the frontal and parietal lobes

• Lobe Division:

  Separates the frontal lobe from the parietal lobe, while the lateral sulcus (also known as the Sylvian fissure) separates the frontal and parietal lobes from the temporal lobe below

What part of the brain for the four lobes live in?

Forebrain

The Corpus Callosum

• Large bundle of neural fibers (axons specifically) connecting the two brain hemispheres 

• The main pathway that links and send communication between the two hemispheres 

Experience and the Brain 

• The two halves of the brain 

  • work with individuals who haev the “split-brain” operation (severing the corpus callosum) to control seizures provides evidence that the two hemispheres are highly specialized 

The two halves of the brain…

• The right hemisphere communicates with the left in order to name the objects in its visual field 

• the left hemisphere works with the right to synthesize details into a whole picture (e.g. combining the parts of a face into a whole recognizable image) 

How does the cerebral cortex communicate with the body?

The spinal cord!!! 

• reflex and voluntary responses

Lets talk spinal cord…

• A reflex is a rapid, automatic response to a stimulus 

  • usually originate in the spinal cord 

• Voluntary responses originate in the brain and travel via the spinal cord to the muscles to carry out movements 

Reflex in the spinal cord

1. Stimulant triggers MUSCLE CONTRACTION and withdraws parts being stimulated

2. Dendrite of AFFERENT NEURONS receives stimuli then transports electrical signals (stimuli becomes electrical signals) down toward its cell body then to axon 

3. The electrical signals travel along the axon to the CNS, reaches the synapse and triggers release of neurotransmitters

4. Passed to cell body of efferent neuron, down its axon to, inhibiting or exciting postsynaptic neuron