🧠 Neuroanatomy — Gross Brain

The cerebral cortex is the most superficial layer of the cerebrum. It and the underlying white matter accounts for the largest part of the human brain. — Radiopaedia

🎯 Core Concept

The brain has 4 cerebral lobes, each responsible for different functions. The surface is folded into gyri (ridges) and sulci (grooves) to maximize surface area within the skull.

🖼️ Approved Images

Fig 1. Lobes of the Cerebrum

> Source: TeachMeAnatomy — Neuroanatomy: Structures > Alt: “Illustration of the lobes of the cerebral cortex, highlighting their anatomical regions.”

Fig 2. Basal Ganglia Components

> Source: TeachMeAnatomy — Neuroanatomy: Structures > Alt: “Illustration of the components of the basal ganglia and their anatomical relations.”

🧠 The 4 Cerebral Lobes

🔑 Key Sulci That Define Lobe Boundaries

🧩 Deep Gray Nuclei (Deep Brain Structures)

These are collections of neurons deep within the cerebrum, not in the cortex.

The Basal Ganglia Circuit

Cortex → Striatum (Caudate + Putamen) → GPi/SNr → Thalamus → Cortex
              ↑                              ↓
              ←←←←←←←← (Direct/Indirect pathways) ←←←←←←←←

Other Deep Gray Nuclei

🧬 Cerebral Cortex — Microscopic Structure

Neocortex (6 Layers) vs Allocortex (3 Layers)

• Neocortex: ~90% of human cortex — 6 layers (I–VI), responsible for higher functions
• Allocortex: ~10% — 3 layers (hippocampus, olfactory cortex)

The 6 Layers of Neocortex

Board Pearl: Layer IV = thalamic input layer — prominent in primary sensory cortices. Layer V = corticofugal output — prominent in primary motor cortex (Betz cells).

💡 Gyri — Key Functional Landmarks

🔬 Surface Area — Why Folding Matters

• The cerebral cortex contains ~16 billion neurons
• Two-thirds of the cortex lies within sulci (hidden in the grooves)
• One-third is exposed on gyri (visible on the surface)
• This folding allows ~2,200 cm² of cortical surface to fit inside the skull

📋 Clinical Pearls

🎯 Brodmann Areas — High Yield

🗺️ Functional Organization

ANTERIOR (Frontal)          →          →          →    POSTERIOR (Occipital)
                                                                     
Prefrontal    Motor        Sensory       Parietal      Visual
Cortex        Cortex       Cortex        Association   Cortex
(Executive)    (M1)         (S1)          Cortex        (V1)

📚 Sources

• Alberstone et al. — Anatomic Basis of Neurologic Diagnosis (2nd ed, 2023)
• Bradley — Neurology in Clinical Practice (8th ed)
• Adams & Victor — Principles of Neurology (12th ed, 2023)
• Radiopaedia — Cerebral cortex
• TeachMeAnatomy — Neuroanatomy: Structures

🔗 Related Topics

• [[wiki/foundation/NEUROANATOMY_BLOOD_SUPPLY|Blood Supply — Cerebral Circulation]]
• [[wiki/foundation/NEUROANATOMY_LIMBIC|Limbic System — Memory & Emotion]]
• [[wiki/foundation/NEUROANATOMY_BASAL_GANGLIA|Basal Ganglia — Motor Circuits]]
• [[wiki/foundation/CRANIAL_NERVES|Cranial Nerves Overview]]

🃏 Anki Prompts

Last updated: 2026-04-24 | Phase 1 — Foundation | Status: 🔄 In Progress