CorpusHuman Anatomy
NervousBrain region

Temporal lobe

Lobus temporalis

The lobe below the lateral sulcus, housing the primary auditory cortex, Wernicke's area for language comprehension, the ventral visual "what" stream, and medial structures (hippocampus, amygdala) for memory and emotion.

Show on body map Brain — Lateral View

Overview

Primary auditory cortexBrodmann 41, 42
Wernicke's areaPosterior Brodmann 22
Field defect from anterior temporal lesionContralateral superior quadrantanopia

The temporal lobe lies in the middle cranial fossa below the lateral sulcus and in front of the occipital lobe. Its lateral surface carries the superior, middle and inferior temporal gyri. The upper surface of the superior gyrus, hidden in the lateral sulcus, bears the transverse temporal (Heschl) gyri, the primary auditory cortex (areas 41, 42). The auditory cortex is tonotopic and receives input from both ears via the medial geniculate body, so a unilateral lesion does not cause deafness. The planum temporale behind it is usually larger on the left and forms part of Wernicke's area (posterior area 22), where heard speech is decoded into meaning.

The inferior surface carries the fusiform (occipitotemporal) gyrus and the inferior temporal gyrus. These form the end of the ventral "what" visual stream for recognising objects, words and faces; the fusiform face area is usually right-sided. The anterior temporal lobes store semantic knowledge. Medially the lobe contains the hippocampal formation and parahippocampal gyrus (episodic memory), the amygdala (emotion, fear) and the uncus.

The lower loop of the optic radiation (Meyer's loop) sweeps forward around the temporal horn of the lateral ventricle. A temporal lesion therefore causes a contralateral superior quadrantanopia ("pie in the sky").

Location

Middle cranial fossa, deep to the temporal bone; below the lateral sulcus, anterior to the occipital lobe.

Parts & subdivisions

  1. Primary auditory cortex (areas 41, 42)
    Transverse temporal (Heschl) gyri on the superior temporal plane; tonotopic (low frequencies anterolateral, high posteromedial); bilateral input.
  2. Wernicke's area (posterior area 22)
    Posterior superior temporal gyrus and planum temporale of the dominant hemisphere; comprehension of spoken and written language.
  3. Middle and inferior temporal gyri
    Semantic memory, word meaning, visual object recognition (ventral stream).
  4. Fusiform gyrus
    Face (fusiform face area) and visual word-form recognition.
  5. Hippocampal formation
    Declarative memory consolidation and spatial memory.
  6. Amygdala
    Threat detection, fear learning, emotional memory.
  7. Parahippocampal gyrus and entorhinal cortex
    Gateway between the neocortex and hippocampus.
  8. Meyer's loop
    Inferior fibres of the optic radiation (upper contralateral visual field) passing through the temporal lobe.

Anatomy

Arterial supply

Middle cerebral artery (inferior division): lateral surface including Wernicke's area and Heschl's gyri. Posterior cerebral artery (temporal branches): inferior and medial surfaces including much of the hippocampus. Anterior choroidal artery: uncus, amygdala, anterior hippocampus.

Function

  • Hearing and sound localisation
  • Comprehension of language (dominant hemisphere)
  • Recognition of objects, faces and words
  • Formation of new declarative memories
  • Emotional processing and fear (amygdala)
  • Olfactory processing (uncus and adjacent piriform/entorhinal cortex)

Clinical significance

Wernicke's (receptive) aphasia

Speech is fluent but empty, with phonemic and semantic paraphasias and neologisms ("word salad"). Comprehension and repetition are poor and the patient is often unaware of the deficit. It is caused by an infarct of the inferior division of the left MCA and usually occurs without hemiparesis. A lesion of the arcuate fasciculus gives conduction aphasia, in which comprehension and fluency are preserved but repetition is disproportionately impaired.

Temporal lobe epilepsy

The commonest focal epilepsy in adults, often due to mesial temporal (hippocampal) sclerosis. Auras include a rising epigastric sensation, déjà vu or jamais vu, fear, and olfactory or gustatory hallucinations ("uncinate fits"). These are followed by impaired awareness with staring, lip-smacking and fumbling automatisms. Refractory cases may be cured by anterior temporal lobectomy.

Herpes simplex encephalitis

HSV-1 has a predilection for the medial temporal and orbitofrontal lobes, causing fever, confusion, personality change, seizures and aphasia. It produces haemorrhagic necrosis on MRI. Untreated mortality is high, so IV aciclovir is started on suspicion. Bilateral damage can leave dense amnesia and Klüver–Bucy features.

Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.