The Insular Lobe

The recessed position of the insular cortex is ontogenetically determined, as during fetal development, the other, more well-known lobes of the cerebral cortex continue to grow, whereas the insula ceases its development earlier and remains roughly the size of a two-euro coin. Nevertheless, many anatomists regard it as the fifth lobe of the cerebrum.

Phylogenetically spoken, meaning in terms of its evolutionary age, the insula is ancient. Like many old neural structures, it must perform multiple functions. The insular cortex is regarded as the primary gustatory cortex, from which information is relayed to secondary olfactory regions in the orbitofrontal cortex. This demonstrates that the brain’s processing of two senses, namely smells and taste, are closely interconnected.

The insular lobe also covers a surprising range on its own: Not only is taste processed and perceived, but its evaluation also takes place immediately. For example, a massive rejection manifests itself as a feeling of disgust, and this also becomes conscious in the insula. The extreme rejection would probably be pathological preference and it is known, at least from heavy smokers, that a stroke in the insular cortex can free them from their addiction. However, its removal is not recommended as a therapy, since this brain structure also makes us aware of our hunger and thirst.

However, much more happens in the insular cortex, which is considered a multisensory cortex and is involved in the emotional evaluation of pain. As an important projection site of the viscerosensory pathway – i.e. the sensations of the internal organs – it receives a lot of other information in addition to hunger, including information about shortness of breath, nausea and a feeling of fullness. In addition, this brain structure is involved in monitoring the filling status of the urinary bladder. In addition, the insula is reciprocally connected to the thalamus and the amygdala in order to directly – and indirectly – influence homeostasis as well as emotions and emotional sensations. Furthermore, there is evidence that bilateral destruction of the insular cortex can lead to complete auditory agnosia. Last but not least, the insular cortex is one of several vestibular centers in the brain and is therefore concerned with balance.

The insula is also involved in speech production, at least in automated speech. During simple word repetitions, the insular cortex becomes active shortly after the perception of spoken words. Moreover, it has been shown that lesions in the posterior insula can impair speech motor functions, thereby leading to a disruption in speech.

The insular cortex is even involved in "compassion," one of the most human abilities, such as when we empathize with the pain of others. As social neuroscience studies employing imaging techniques have revealed, activity in the anterior insula is not only observed during personal pain but also when witnessing pain in others.

In addition to empathy, the insular cortex appears to be involved in the sense of fairness, maternal love, orgasms, sudden insights and decision-making. Its activity in relation to attention is particularly noteworthy, especially regarding self-awareness and one's current state. This introspective quality may be one reason why the insula is disproportionately larger in humans as compared to their closest relatives.

Individuals diagnosed with frontotemporal dementia (FTD) frequently exhibit symptoms that include a loss of empathy, repetitive and compulsive behaviors, impaired judgment, language impairments and inappropriate social behavior. The observed alterations are associated with degeneration or atrophy of the insular cortex.

Damage to the insular cortex can result in a wide range of sensory perception impairments. Individuals with such an insular dysfunction may still perceive sensory inputs but might no longer respond to them appropriately.

First published on September 22, 2011
Last updated on July 8, 2025