Parts of the Brain Overview

Defining Parts of the Brain in Directional Terms

Anterior – toward the front

Posterior – toward the back

Medial – toward the middle

Lateral – toward the outside

Rostral – toward the mouth (beak)

Caudal – toward the feet

Dorsal – toward the back surface

Ventral – toward the belly or undersurface

Cell layers

There are six cells layers of the cerebral cortex. Here is a brief summary of what each layer seems to do.

Layers 1, 2, 3 – cortical projections from primary cortex originate here

Layer 4 – sensory, receives projections from other areas of cortex and brain, higher in sensory cortex, ascending projections terminate here

Layers 5, 6 – zone of output, send axons to other brain areas, high in motor cortex

Posterior Cerebral Cortex

Sensory – receives, processes, and stores information.

Anterior Cerebral Cortex

The Motor Unit (formulates intentions, and organizes them into programs of actions, and executes the actions/programs) Both the anterior and posterior cortex has primary, secondary, and tertiary zones.

Primary Sensory Zone – sensory input enters the primary sensory zones.

Secondary Sensory Zone – elaborates sensory information.

Tertiary Sensory Zone – integration sensory information.

Primary Motor Zone – execution is initiated.

Secondary Motor Zone – information from tertiary motor zone is elaborated upon and processed.

Tertiary Motor Zone – information received from the sensory cortex.

Dominant Hemisphere Characteristics (usually the left side of the brain)

• More grey matter
• Extends farther posteriorly
• Longer Sylvian Fissure
• Larger insular cortex
• More dense
• Doubling of cingulate gyrus
• Larger inferior parietal lobe
• Increased lateral posterior thalamic nucleus
• Wider occipital lobe
• Larger total area of inferior frontal operculum
• Speech center
• Perception of words
• Process language related sounds
• Sequential analysis
• Increased blood flow during speech perception
• Process details, individual units
• Letters and words
• Language related sounds
• Complex voluntary movements
• Verbal memory
• Speech
• Reading
• Writing
• Arithmetic

Non-dominant Hemisphere Characteristics (usually the right side of the brain)

• Larger and heavier
• Extends farther anteriorly
• Longer internal skull size
• Doubling of Heschel’s gyrus
• Wider frontal area
• Larger medial geniculate thalamic nucleus
• Larger convexity of frontal operculum
• Facial recognition
• Perception of melodies
• Pitch/prosody
• Social cues
• Reading facial expression
• Increased blood flow during tonal memory
• Read Braille better with left hand
• Process spatial information (parietal)
• Recognition of objects by touch
• Slightly more blood flow to right side
• Integrate information (gestalt or big picture)
• Complex geometric patterns
• Faces
• Music
• Nonlanguage environmental sounds
• Movements in spatial patterns
• Nonverbal memory
• Geometry
• Sense of direction
• Mental rotation of shapes