Are you a morning person or a night owl? Is it just a personal preference or is there something to it? It's a complex puzzle with a lot of variables to consider. Literature concerning variation of sensory function according to the circadian cycle is lacking and chronobiological studies have focused on circadian fluctuation in performing simple motor tasks, fine skilled movement, and anaerobic exercise.
To try and determine when people at their optimal, researchers observed and compared the circadian fluctuations in tactile sense, joint reposition sense and two-point discrimination in 21 healthy adult subjects, at approximately 9:00, 13:00 and 18:00 during the day.
Sensation is generally categorized by superficial sense - pain, temperature, touch - deep sense, such as awareness of movement and combined cortical sense - two-point discrimination, tactile localization, even things like graphesthesia, which is the ability to recognize writing on the skin using touch. They are perceived as a combination of multimodal sensory modules.
Variation of three different sensory modules according to time of day. Credit and link:
Information is transferred from each sensory receptor to multiple brain structures via the anteriolateral spinothalamic tract or the dorsal column-leminscal pathway and understanding of the sensory processing mechanism has been e keen interest for neuroscience. Recruitment of the 21 subjects occurred through and used only those with no history of neurological impairment medication use or psychiatriic issues were used.
Participants sat in a chair with a back rest in a quiet room. Measurements of sensory ability using three different types of sensory modules were repeated so that they all had the three different experimental schedules according to time sequence. Tactile sensory stimulation was generated using a Biopac STM100C stimulator module with a STMISOC isolation unit . The STMISOC unit modulated the current voltage output from the electrodes, with constant square pulse.
They found that the distribution of ranking for perceptual ability was significantly different among the three different time points in each individual, with highest perceptual ability in the evening compared with noon and morning, in terms of tactile sense and two-point discrimination.
Interestingly, they found a link with body temperature, which may be support for claims that motor tempo and these physiological changes of diurnal pattern are linked - an association of body temperature with muscle performance and cognitive abilities.