University Studies 15A:

Consciousness I

Brains

Brains: More than we can hope to learn

Brain Details: What and Why?

“Why” will lead us to ‘What”

We want to know about consciousness as the quality of first-person experience of the world.

We want to know about the “I think,” “I see,” “I feel.”

“What” we want to know about in the brain is what is important for the creation of this first-person quality.

Some aspects of the brain will not matter that much:

The actual biochemistry of neuronal firing

The actual biology of “long-term potentiation”

We will need to know some of the basics of brain structure (i.e. neuroanatomy)

We will need to know some of the basics of functional organization (covered in greater detail in later lectures)

Today we start with the basics of brain structure

A Final Point about Actual Neurons:

Note the myelin sheath surrounding the axon.

These glial cells are basically fat. They serve to insulate the axon and make its electrical transmission more efficient.

Neurons that have acquired the myelin sheath form the “white matter” of the brain.

Although as “species-ists,” we are most interested in the human brain, some perspective is useful.

Brain Stem:

Much nervous system housekeeping (breathing, heart beat)Connects the spinal cord to the brain

Cerebellum:Muscle control

Olfactory bulb & Optic Lobe:Brain hardware devoted to handling smell and sight

Brain Parts: the Early Version

For Humans, same basics + expanded cortex:

Let’s follow Baar’s and Gage’s approach and build from the brainstem up.

The Brainstem, Pons, and Thalami:

thalamusPons

The Brainstem, Pons, Thalami, Hippocampi, and Amygdalas:

hippocampusamygdala

Brainstem, Pons, Thalami, Hippocampi, Amygdalas,and Everything Else:

Basal ganglia

Cerebellum

The basic human brain

Cortex

White Matter

Another Drawing of the Same Structures + Reticular Formation

In humans, the cortex grows somewhat slowly:

More crucial for us are two other aspects of maturation: Dendritic Arborization: the creation of new dendrites Myelination: the covering of the axons with myelin

The Neocortex is a made of six layers of cells which grows in an “inside-out” pattern.

The Neocortex is a made of six layers of cells which grows in an “inside-out” pattern starting with Layer 6.

Layer 1: Not many actual cells Mainly dendrites from cells in other layers to allow dense horizontal connectionsLayers 2 - 3: Horizontal connections (like Layer 1) Axons leading to cells in Layers 4-6Layer 4: Most input (axons from White Matter) end here Mainly dendrites from cells in other layersLayers 5-6: Output neurons to other areas of brain

Terms you might as well learn:Dorsal: UpVentral: Down

The Cortex

The Four Lobes:Occipital LobeParietal LobeTemporal LobeFrontal Lobe

Two Major Lines:Central SulcusSylvian (Lateral) Fissure

Sylvian (Lateral) Fissure

Central Sulcus

Lateral: On the side Medial: In the middle

Functional Organization of the Cortex

Primary Visual Cortex

Visual Association Areas

Auditory Cortex

Primary Somatosensory Cortex

Somatosensory Association Areas

Motor Cortex

Premotor Cortex

Prefrontal Cortex

On the Two Sides of the Central Sulcus

In front of the central sulcus, the motor cortex

Behind the central sulcus, the primary somatosensory cortex

“White Matter” Fiber Pathways(Back of the Brain to the Left)

One Last Neuroanatomical Slide: The Medial Temporal Lobe Structures

Limbic Cortex (Paleocortex) goes with Limbic System

One Last Neuroanatomical Slide (Really): The Medial Temporal Lobe Structures

Anterior Cingulate cortex

Parahippocampal cortex