Averagely, humans blink their eyes about 15,000 times per day, approximately 15 to 20
times per minute in a relaxed mode (van de Post, de Waal, de Kam, Cohen, & van Gerven,
2004). It is called as spontaneous eye blinking, which refers to the movement of both
upper eyelids occur unconsciously and transient in a highly symmetrical and coordinated
manner without the presence of a stimulus (Cruz, Garcia, Pinto, & Cechetti, 2010).
Interestingly, it is evident that spontaneous blink rates correlate with dopamine levels in
the brain, whereby the functioning of the dopaminergic system reflected in spontaneous
eye blinks rate (Taylor et al., 1999). Hence, a wide range of researchers indicated that the
rate of spontaneous eye blink serves as a functional marker of central dopaminergic
activity to determine vast diseases (Blin, Masson, Azulay, Fondarai, & Serratrice, 1990;
Karson, 1983; Kleven & Koek, 1996; Sax & Strakowski, 1998; Taylor et al., 1999).
Having said that, the emergence of abnormal eye blink rates can determine the
dopaminergic transmission, either excessive or deficiency in dopamine.
However, this concept has been challenged by van de Post, de Waal, de Kam, Cohen and
van Gerven (2004) that there was no evidence of the usefulness of eye blinking as a
functional marker for central dopaminergic activity. Thus, this has raised a question that
does the dopamine function really affect spontaneous blink rates so that spontaneous blink
rates be served as the functional marker of central dopaminergic activity? The objective of
this essay is to discuss whether the activity levels of the dopamine system are associated
with the rates of the spontaneous eye blink.
In controlling eye blinking, it is mediated by both autonomic and voluntary neural control.
To trigger the contraction of the orbicularis oculi and levator palpebrae muscles, motor
nerves in the upper and lower eyelids are innervated by the VII and III cranial nerves. This
eyelid movement is important for maintaining the stability of tear film for vision clarity
and the disturbance at the ocular surface (Cruz, Garcia, Pinto, & Cechetti, 2010).
In the early study, Karson (1988) suggested that spontaneous eye blinking is regulated by
the caudate nucleus. Further to that, it was supported by a study of Taylor et al. (1999),
which found that the spontaneous blink rates were correlated positively with the
concentration of dopamine in the rostral portion of the body of the ventromedial head of
the caudate nucleus. Moreover, Taylor et al. (1999) also suggested that the oculomotor
