Inferior temporal gyrus

At a glance

English

Inferior temporal gyrus

Latin (TA2)

Gyrus temporalis inferior

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the inferior temporal gyrus

The inferior temporal gyrus runs from near the temporal pole back towards the occipital lobe along the lower edge of the lateral surface of the temporal lobe. Above, the inferior temporal sulcus separates it from the middle temporal gyrus. Its lower border is not the edge of the brain: the gyrus rolls round the inferolateral margin of the hemisphere onto the basal surface, where the occipitotemporal sulcus divides it from the fusiform (lateral occipitotemporal) gyrus. Behind, the inferior occipital gyrus continues it. It rests on the floor of the middle cranial fossa, and much of it is Brodmann area 20.

Together with the fusiform gyrus and parts of the middle temporal gyrus it forms the inferior temporal cortex, the last stage of the ventral visual stream, often called the 'what' pathway. Visual signals from the retina pass through the lateral geniculate body to the primary visual cortex and then forward through areas V2 and V4 into this region. Its neurons respond only to vision, have large receptive fields that include central vision and often both halves of the field, and prefer complex shapes over simple spots or bars. Some are tuned to particular objects, hands or faces, and the strength of their response depends on shape more than on size or colour.

The region is the place where what is seen is matched against stored knowledge of objects. It has strong links with the hippocampus, amygdala and prefrontal cortex, and its cells can hold short- and long-term memories of visual stimuli. Neighbouring specialised patches deal with faces, bodies, scenes and shapes. Imaging has also linked it with recognising colours and written numbers.

Damage to the inferior temporal region produces visual agnosias: the patient sees normally but cannot recognise what is seen. Lesions on the right side, often reaching the fusiform gyrus, can cause prosopagnosia, in which familiar faces are not recognised although the person may identify people by their voice, gait or hair. Lesions of the ventral occipitotemporal area can also cause loss of colour perception (cerebral achromatopsia). In semantic dementia, atrophy of the inferior and middle temporal gyri, often worse on the left, leads to a gradual loss of word meaning and knowledge about objects.

Function and supply

Function

Final stage of the ventral visual stream: recognises objects, faces and shapes by comparing what is seen with visual memory; also linked with colour and number recognition.

Blood supply

Temporal branches of the middle cerebral artery on the lateral surface; inferior temporal branches of the posterior cerebral artery on the basal surface.