Neuroanatomy: Temporal Lobe

Structure and Function

• Localizationism: Concept that certain brain parts have specific functions. However, functions are more accurately defined by connections.
• Understanding structure, connections, and functions is necessary to see the complete picture.
• Brodmann's Areas & Human Connectome Project (HCP):
  • Initially 47 areas defined, now 180 parcellations identified.
  • Traditional divisions include superior, middle, inferior gyrus, etc.
• Major Association Fiber Tracts:
  1. Uncinate fasciculus (UF)
  2. Inferior longitudinal fasciculus (ILF)
  3. Inferior fronto-occipital fasciculus (IFOF)
  4. Middle longitudinal fasciculus (MdLF)
  5. Arcuate fasciculus (AF) and cingulum
  6. Commissural fibers - corpus callosum and anterior commissure (AC)

Cognitive Domains and Temporal Lobe

• Identified cognitive domains:
  1. Speech perception, production, hearing - posterior superior temporal gyrus
  2. Episodic memory - medial structures
  3. Phonological - dorsal and posterior structures
  4. Semantic - ventral temporal lobe
  5. Social - two areas in the temporal lobe
  6. Visual - temporo-occipital junction

Functional Connectivity (HCP Scheme)

• Lateral: Semantic processing
• Polar: Emotional processing
• Inferior: Visual processing
• Medial: Memory and visuospatial processing

Lateral Temporal System

• Superior temporal sulcus (STS): Motion, speech, facial processing, language comprehension, audiovisual integration.
• Temporal Area 1 (TE1): Visual information processing, working memory.
• Area PHT: Semantic information retrieval.
• STGa: Acoustic sound processing.

Polar Temporal System

• TG Areas: Language, social cues, emotion processing, facial recognition.

Inferior Temporal System

• TE2a and TE2p: Vision processing.
• Area TF: Working memory, object recognition, reading.
• Area PeEC: Declarative memories, semantic knowledge.

Medial Temporal System

• Medial Temporal Areas: Involved in spatial information processing and memory consolidation.
• Area PreS, EC, PHA: Episodic memory, spatial processing.

Hippocampus

• Resembles a seahorse; involved in declarative memory (episodic and semantic).
• Structure: Divided into dentate gyrus, CA1, CA3.
• Function: Memory creation and consolidation.

Amygdala

• Almond-shaped; involved in emotional responses, fear, anxiety, reward processing.
• Structure: Basolateral, cortical, and centromedial groups.
• Function: Emotion, cognition, psychiatric implications.

Embryology

• Development linked to cerebral cortex.
• Neural plate forms neural tube, brain regions develop and differentiate over gestation.

Clinical Significance

• Temporal Lobe Lesions: Unilateral volume loss, bilateral pathology, space-occupying lesions.
• Symptoms: Mental disturbances, personality changes, seizures, speech disorders.
• Wernicke Aphasia: Impaired language function common post-stroke.
• Other Conditions: PTSD, Alzheimer’s, temporal lobe epilepsy.