Neuroanatomy and Functional Organization of the Brain

Neuroanatomical Orientation and Brain Slices

Directional Terms and Brain Slices

Understanding the orientation of the brain and its anatomical terminology is essential for studying neuroanatomy and brain function in psychology.

• Lateral: Side

• Medial: Middle/inside

• Anterior/Rostral: Front

• Posterior/Caudal: Back

• Superior/Dorsal: Top

• Inferior/Ventral: Bottom

Common brain slice orientations:

• Horizontal/Transversal: Parallel to the ground, dividing the brain into upper and lower parts.

• Coronal: Perpendicular to the ground, dividing the brain into front and back parts.

• Sagittal: Divides the brain into left and right halves.

Types of Brain Matter

White Matter, Gray Matter, and Ventricles

The brain is composed of different types of tissue, each with distinct functions:

• Gray Matter: Contains neuron cell bodies; involved in processing and cognition.

• White Matter: Made up of myelinated axons; responsible for communication between different brain regions.

• Ventricles: Cavities filled with cerebrospinal fluid (CSF), which cushions the brain and removes waste.

Major Divisions of the Brain

Forebrain

The forebrain is the largest and most complex part of the brain, responsible for higher-order functions.

• Consists of:

  • Cerebrum (neocortex)

  • Thalamus

  • Hypothalamus

• Functions:

  • Sensory processing (seeing, hearing)

  • Higher-order cognition (thinking, problem solving)

Midbrain

The midbrain sits atop the brainstem and is involved in sensory and motor functions.

• Contains structures such as the colliculi (bumps) and nuclei (cores).

• Functions:

  • Motor control

  • Sleep

  • Arousal and temperature regulation

  • Visual and auditory processing

Hindbrain

The hindbrain includes the cerebellum and is crucial for basic life functions.

• Functions:

  • Body-brain connection

  • Motor control and movement

  • Arousal and sleep

Cerebral Cortex and Its Lobes

Overview of Cortex Lobes

The cerebral cortex is divided into four main lobes, each with specialized functions.

• Frontal Lobe:

  • Involved in complex and integrative work

  • Motor control (furthest back part)

  • Executive functions: attention, working memory, inhibition

  • Damage can result in personality changes (e.g., Phineas Gage)

• Parietal Lobe:

  • Contains the sensory cortex (processes information from touch sensors)

  • Involved in recognizing and forming objects

  • Important for attention mechanisms; damage can cause neglect

• Temporal Lobe:

  • Functions include hearing, speech, language, emotion, memory, and complex aspects of vision (faces, places, words)

  • Damage to Wernicke's area (towards the back) can cause aphasia (inability to understand speech)

• Occipital Lobe:

  • Mainly responsible for visual processing

  • Damage results in blindness, except for rare cases of blindsight

Macrostructure of the Brain

Gyri and Sulci

The surface of the brain is characterized by ridges and grooves, which increase surface area and cognitive capacity.

• Gyrus (plural: gyri): Ridge between two grooves

• Sulcus (plural: sulci): Groove or furrow

Subcortical Structures and Their Functions

Hippocampus

The hippocampus is a critical structure for memory formation and spatial navigation.

• Involved in encoding and retrieving memories

• Damage can cause memory loss (e.g., anterograde amnesia as in patient H.M.)

• Size can increase with years of experience or study

Amygdala

The amygdala is involved in emotional processing, especially fear and threat evaluation.

• Links memories to emotional responses

• Damage can result in loss of fear response

Basal Ganglia

The basal ganglia are a group of interconnected structures involved in movement and reward-based learning.

• Crucial for voluntary movement

• Involved in behavioral learning related to reward

• Disorders include Parkinson's disease

Brain Connectivity

Commissures and Projections

Brain hemispheres and regions are connected by bundles of nerve fibers.

• Commissures: Connect the two hemispheres (e.g., corpus callosum)

• Projections: Connect the brain to the outside world (e.g., sensory and motor pathways)

• Damage to projection fibers (e.g., internal capsule) can have widespread effects on sensory processing

Imaging Techniques

Modern imaging techniques help visualize brain pathways and structures.

• Diffusion Tensor Imaging (DTI): A form of MRI that visualizes white matter tracts in the brain

Summary Table: Major Brain Lobes and Their Functions

Lobe	Main Functions	Consequences of Damage
Frontal	Executive function, motor control, personality	Personality changes, impaired executive function
Parietal	Sensory processing, attention, object recognition	Neglect, sensory deficits
Temporal	Hearing, language, memory, complex vision	Aphasia, memory loss
Occipital	Visual processing	Blindness, blindsight

Key Terms and Definitions

• Gyri: Ridges on the cerebral cortex

• Sulci: Grooves on the cerebral cortex

• Corpus Callosum: Major commissure connecting the two hemispheres

• Wernicke's Area: Region in the temporal lobe involved in language comprehension

• Blindsight: Ability to respond to visual stimuli without conscious visual perception

• Aphasia: Impairment of language, often due to brain damage