Temporal lobe

It occupies the middle cranial fossa below the lateral sulcus, bounded behind by a conventional line to the occipital lobe; the temporal pole points forward. Its gyri are the superior, middle and inferior temporal gyri, the fusiform and parahippocampal gyri on the inferior and medial surfaces.

The primary auditory cortex (Brodmann areas 41 and 42) lies on the transverse temporal gyri of Heschl within the lateral sulcus. Wernicke area (area 22, posterior superior temporal gyrus, dominant hemisphere) supports comprehension. The inferior temporal cortex processes object and face recognition; medially lie the hippocampal formation, parahippocampal gyrus and amygdala. The arcuate fasciculus links Wernicke and Broca areas.

The middle cerebral artery supplies the lateral surface and the superior temporal gyrus; the posterior cerebral artery supplies the inferior and medial surfaces including the hippocampus; the anterior choroidal artery supplies parts of the uncus, amygdala and hippocampal tail. Anterior temporal pole branches arise from the MCA.

Afferents: auditory input from the medial geniculate nucleus via the auditory radiation, and olfactory, visual and association inputs. Efferents: via the arcuate fasciculus to the frontal lobe, the fornix to the hypothalamus and mammillary bodies, and the amygdala to the hypothalamus and brainstem.

It analyses sound, comprehends spoken and written language in the dominant hemisphere, recognises objects and faces, forms new declarative memories through the hippocampus, and assigns emotional significance to stimuli through the amygdala.

Dominant superior temporal lesions cause Wernicke (fluent, receptive) aphasia with impaired comprehension. Fibres of Meyer loop pass through the temporal lobe, so lesions give a contralateral superior homonymous quadrantanopia. Temporal lobe epilepsy produces auras (déjà vu, epigastric rising, olfactory), automatisms and impaired awareness; mesial temporal sclerosis is a common cause. Herpes simplex encephalitis characteristically involves the temporal lobes, and bilateral hippocampal damage causes amnesia.

• Primary auditory cortex (areas 41 and 42) lies on Heschl gyri; Wernicke area is area 22 in the dominant hemisphere.
• Wernicke aphasia: fluent, meaningless speech with poor comprehension and repetition; Broca aphasia is non-fluent.
• Meyer loop lesion gives a superior homonymous quadrantanopia (pie in the sky).
• Temporal lobe seizures: aura, automatisms, impaired awareness; look for mesial temporal sclerosis.
• Herpes simplex encephalitis and bilateral hippocampal lesions: temporal involvement and amnesia.

1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
2. Kandel ER, Koester JD, Mack SH, Siegelbaum SA. Principles of Neural Science. McGraw-Hill, 6th edition (2021) — Tier 3 (textbook)
3. Haines DE, Mihailoff GA. Fundamental Neuroscience for Basic and Clinical Applications. Elsevier, 5th edition (2018) — Tier 3 (textbook)

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