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After a biological clock, which controls our time experience in a second or minute range, brain researchers have been searching for a long time. New insights show, that our physical feeling plays a central role: Self-Perception and time experience are inseparably connected to each other.

This is the second part of this article series. If you have missed the first part, don't forget to catch up on it:

• Perception of Time: How does our feeling for time emerge - Part 1

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How does our feeling for time emerge - Part 2

Experiences in the floating tank put us on the right path

The mentioned feelings in the isolation tank from Part 1 let us suggest an answer: It is the body perception which is underlying perception of time. You can't hear, see or smell anything in the container. Gravity is strongly reduced. Nevertheless, time is felt immediately, because body perception can't be turned off. Neuroscientific studies help to understand the experience of Floating, according to which, a specific region of the brain - the insular lobe, Latin: Insula - is active while perceiving time duration in a second range. Between 2004 and 2009 Martin Paulus and Alan Simmons from the University of California in San Diego did some research on how exactly subjects experience time, with plotting their brain activity using Magnetic Resonance Tomography (MRT).

The participants were presented with sounds that lasted a few seconds long and after having listened they had to reproduce the duration of the tone in the most possible exact way, by pressing a button. Only one area of the two brain hemispheres was reacting noticeably stronger at presentation as well as reproduction, namely the insular lobe. The neuronal activity was increasing in both iterations til the end of the interval, whereas later, activity was strongly decreasing. Apparently the reaction of the Insula describes external stimulus - in our case the tone - within a given time interval. Longer time duration means bigger activity.

The insular lobe qualifies as primary interoceptive cortex, for initial processing of signals which come from the brain parts that are responsible for body perception. In the same way as there are areas responsible for vision in the occipital lobe and for hearing in the temporal lobe, the Insula is the primary area for incorporation of body feelings like temperature, pain, itching, hunger, muscle tension, haptics and signals from the guts. They also represent the basis for complex feelings, according to Antonio Damasio from the University of Southern California in Los Angeles and are important for intuition and decision making, as one could imaging when thinking about the term "gut feeling".

Lobes of the brain

The so called vegetative nerve system is responsible for interoception. It connects body and brain and regulates autonomous organ functions. Thereby body signals travel through specific nerve cores of the Thalamus to the insular lobe. As a consequence we can perceive them consciously. This relationships were researched by the neuroanatomist A. D. (Bud) Craig from the Barrow Neurological Institute in Phoenix, Arizona. Craig developed the theoretical principles for the understanding of how body signals let us experience time. The experience of a "Body-I" is based on the ongoing incorporation and processing of signals coming from the body over time. Above this structure of body representation a feeling for passage of time emerges as continuously changing "Body-I". As our example with the isolation tank shows, subjective time is not created by perception of outer sensoric stimuli, but rather by oneself. Every single person with his body feeling, is his own biological clock.

Images: scienceinseconds

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Perception of Time: How does our feeling for time emerge - Part 3