A role for the insula in color-induced nasal thermal sensations

Uncovering Interoceptive Human Insular Lobe Function through Intraoperative Cortical Stimulation-A Review

The insular cortex, a critical hub in the brain's sensory, cognitive, and emotional networks, remains an intriguing subject of study. In this article, we discuss its intricate functional neuroanatomy, emphasizing its pivotal role in processing olfactory information. Through concise exploration, we delve into the insula's diverse connectivity and its involvement in sensory integration, particularly in olfaction. Stimulation studies in humans reveal compelling insights into the insula's contribution to the perception of smell, hinting at its broader implications for cognitive processing. Additionally, we explore an avenue of research in which studying olfactory processing via insular stimulation could unravel higher-level cognitive processes. This innovative approach could help give a fresh perspective on the interplay between sensory and cognitive domains, offering valuable insights into the neural mechanisms underlying cognition and emotion. In conclusion, future research efforts should emphasize a multidisciplinary approach, combining advanced imaging and surgical techniques to explore the intricate functions of the human insula. Moreover, awake craniotomies could offer a unique opportunity for real-time observation, shedding light on its neural circuitry and contributions to higher-order brain functions. Furthermore, olfaction's direct cortical projection enables precise exploration of insular function, promising insights into cognitive and emotional processes. This multifaceted approach will deepen our understanding of the insular cortex and its significance in human cognition and emotion.

Interhemispheric balance sets nostril differences in color-induced nasal thermal judgments

Sniffing out of sight always the same colorless and odorless solution containing no thermal agents while viewing a bottle with colored water increases sensitivity of the left nostril/right hemisphere (RH) for warming sensations and sensitivity of the right nostril/left hemisphere (LH) for cooling sensations. It is likely that engagement in a temperature judgment task and the development of specific expectancies due to the presence of color cues alter and enhance processing in brain areas involved in thermosensory processing. The lateralized patterns thus intimate hemispheric specialization for thermosensory processing probably originating in reciprocal inhibition that confers balance between the hemispheres. If the inhibition-balance hypothesis were correct then the more the left nostril proves sensitive to warming the more the right nostril would prove sensitive to cooling. One hundred and ninety one healthy volunteers were tested here. The left nostril dominance for warming and the right dominance for cooling were replicated once more. The dominance of the left nostril for warming (left minus right nostril) correlated highly with the dominance of the left nostril to cooling (right minus left nostril) and the individual patterns of results were distributed along an axis starting from the expected left nostril/warming - right nostril/cooling pattern and ending at the opposite left nostril/cooling - right nostril/warming pattern. Furthermore, the point where the left nostril dominance for warming responses dropped and inverted perfectly coincided with the point where the right nostril dominance for cooling responses inverted too. Such a good continuum between the expected and the opposite patterns supports the inhibition-balance hypothesis. Finally, 66% of subjects exhibited the expected left-warming/right-cooling pattern suggesting, therefore, that, despite this continuum, there is a dominant lateral specialization for temperature processing.

Transnasal cooling: a Pandora's box of transnasal patho-physiology

The innovative concept of transnasal evaporative cooling for therapeutic hypothermia in cardio-pulmonary-cerebro-resuscitation has therapeutic implications with evidence of rapid and selective brain cooling; however, this author wants to elicit that this concept may hold answers for many physiological phenomena which have not been explored or completely understood up till now. To affirm the physiological role of transnasal cooling, the innovative non-invasive brain temperature monitoring can help the investigators to explore and understand the following transnasal pathophysiological phenomena: (1) understanding correlation of brain temperature and sinus headache secondary to nasal blockade, (2) exploring the therapeutic role of nasal oxygen for prevention of delirium in intubated patients, (3) realizing the impact of controlled enclosed environments on the mood and affect of the inhabitants, (4) understanding the etio-pathogenesis of claustrophobia after excluding the confounding factors of morbid obesity, severe cardiopulmonary disease and incapacitating musculoskeletal diseases, (5) exploring the anthropological role of male pattern of moustache, beard and hair loss, and (6) possible development of a coolant moustache as proposed by the author. In summary, transnasal pathophysiology offers many promising lines of fruitful research to explore the non-olfactory physiological functions of nose in human beings.