Table 1 Studies on improvement of cognitive function in healthy people after transcranial photobiomodulation

Chang et al. (2012) [68]

20–21 years old

830 nm;

7 mW per diode, 20 J/cm², 10 min, PW at 10 Hz with DC of 50%

Remote tissue irradiation;

1 site, left palm

Laser stimulation at 10 Hz can increase the power of

alpha rhythms and theta activities, EEG can be interfered

Barrett and Gonzalez-Lima (2013) [69]

18–35 years old

1064 nm;

250 mW/cm², 60 J/cm², 4 min, one irradiation session, CW

Transcranially;

2 sites, unilateral (right frontal pole on 4 cm medial and lateral)

After 2 weeks of irradiation, subjects have positive emotional states, significant improvement of both attention and memory

Gonzalez-Lima et al. (2015) [70]

Mean age: 20.4 years

1064 nm;

250 mW/cm², 60 J/cm², 8 min, one irradiation session, CW

Transcranially;

2 sites, (lower and upper portion of right lateral forehead at EEG map sites: FP2, F4

Improved executive function

Gonzalez-Lima et al. (2016) [71]

17–35 years old

1064 nm;

250 mW/cm², 60 J/cm², 8 min, one irradiation session, CW

Transcranially;

2 sites, lower and upper portion of right lateral forehead at EEG map sites: FP2, F4, and F8 site

Improved prefrontal rule-based learning, and increased learning related cognitive function

Salimi et al. (2018) [29]

Males:19–25 years

Females:18–25 years

850 nm;

285 mW/cm²,60 J/cm², 2.5 min, 1.4 cm², CW

Transcranially;

On the right prefrontal cortex, especially Fp2 region

After photobiomodulation, attention and alertness are improved, cognitive function is enhanced, and delta power is decreased simultaneously

Chan et al. (2019) [37]

Mean age: 66.2 years

870 nm;

44.4 mW/cm², 7.5 min, 22.48 cm² and 999 mW totally

Transcranially;

3 sites; Left frontopolar at FP1 and right frontopolar at FP2 and Pz

The older adults who received photobiomodulation exhibited significant improvements in the frontal brain functions, such as action selection, inhibition ability, and mental flexibility