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Clinical Trial
. 2017 Jul;32(5):1153-1162.
doi: 10.1007/s10103-017-2221-y. Epub 2017 May 2.

Beneficial Neurocognitive Effects of Transcranial Laser in Older Adults

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Free PMC article
Clinical Trial

Beneficial Neurocognitive Effects of Transcranial Laser in Older Adults

Enrique Vargas et al. Lasers Med Sci. .
Free PMC article

Abstract

Transcranial infrared laser stimulation (TILS) at 1064 nm, 250 mW/cm2 has been proven safe and effective for increasing neurocognitive functions in young adults in controlled studies using photobiomodulation of the right prefrontal cortex. The objective of this pilot study was to determine whether there is any effect from TILS on neurocognitive function in older adults with subjective memory complaint at risk for cognitive decline (e.g., increased carotid artery intima-media thickness or mild traumatic brain injury). We investigated the cognitive effects of TILS in older adults (ages 49-90, n = 12) using prefrontal cortex measures of attention (psychomotor vigilance task (PVT)) and memory (delayed match to sample (DMS)), carotid artery intima-media thickness (measured by ultrasound), and evaluated the potential neural mechanisms mediating the cognitive effects of TILS using exploratory brain studies of electroencephalography (EEG, n = 6) and functional magnetic resonance imaging (fMRI, n = 6). Cognitive performance, age, and carotid artery intima-media thickness were highly correlated, but all participants improved in all cognitive measures after TILS treatments. Baseline vs. chronic (five weekly sessions, 8 min each) comparisons of mean cognitive scores all showed improvements, significant for PVT reaction time (p < 0.001), PVT lapses (p < 0.001), and DMS correct responses (p < 0.05). The neural studies also showed for the first time that TILS increases resting-state EEG alpha, beta, and gamma power and promotes more efficient prefrontal blood-oxygen-level-dependent (BOLD)-fMRI response. Importantly, no adverse effects were found. These preliminary findings support the use of TILS for larger randomized clinical trials with this non-invasive approach to augment neurocognitive function in older people to combat aging-related and vascular disease-related cognitive decline.

Keywords: Attention; Brain photobiomodulation; EEG; Infrared laser; Memory; fMRI.

Conflict of interest statement

Conflict of interest The authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
a The FDA-cleared Class 4 laser apparatus (HD Laser, Cell Gen Therapeutics, Dallas, TX) consisted of a control unit (16” × 14” × 13”) with a black hand piece (45-mm diameter laser aperture) connected via a fiber-optic cable. b The laser was aimed at the forehead using an internal red diode aiming light. Since the 1064 nm laser is invisible, the beam area provided visual confirmation to facilitate precise tissue targeting. During laser operation, participants were instructed to keep their eyes closed, and the experimenters and participants both wore dark safety glasses that block the specific infrared wavelength from reaching the eyes
Fig. 2
Fig. 2
Normalized mean performance (n=12) on the psychomotor vigilance test (a: PVT) and delayed match-to-sample test (b: DMS) across five weeks of treatment. Reaction time and number of correct trials are expressed as the percentage change from performance at baseline. Subjects showed progressively faster responding in the PVT, and progressively more accurate responses in the DMS, over weeks of laser treatment. The apparently weaker mean effects for week 5 were due to 3 subjects approaching ceiling performance and missing the last session
Fig. 3
Fig. 3
Cognitive effects of 1064-nm laser treatment on attention and memory in older adults with subjective memory complaint (n=12). The psychomotor vigilance test (PVT) and delayed match-to-sample test (DMS) were conducted immediately before the first laser treatment (Baseline: week 1), immediately after the first laser treatment (Acute: week 1), and on subsequent weeks after additional laser treatments (Chronic: average of weeks 2, 3, 4, 5). a Reaction time (in msec) and b number of lapses (trials in which the subject failed to respond within 500 msec of the stimulus) were recorded for the PVT; c number of correct responses were recorded for the DMS. Bars show group means plus standard errors
Fig. 4
Fig. 4
Effects of TILS on EEG power spectral density (PSD) normalized by the power within the bandwidth of 0–50 Hz before (pre, blue curve), during (laser, green) and after (post, red) stimulation. The integral of PSD in each bandwidth is the relative power of the signal within that bandwidth. This power times epoch duration time gives the energy of the signal within that bandwidth (10 epochs of 1-min each for pre, laser and post recording periods). There were clear bilateral enhancements of alpha power in the occipital recordings (peaks around 10 Hz for alpha). The alpha power increased progressively from frontal, to parietal, to occipital recordings during laser and post-laser relative to pre-laser. No alpha effects were found in temporal recordings, which instead showed increased gamma power (32+ Hz) and beta power around 20 Hz
Fig. 5
Fig. 5
Right prefrontal cortex region with lower BOLD-fMRI responses to a 2-back vs. 0-back cognitive task compared between pre- and post-treatment with TILS to the right forehead (delineated area in a). The bar graphs b show the corresponding values of brain intensity signal (t-score) from this region, averaged between 3 treated subjects (pre- and post-treatment) and 3 untreated subjects (control). Bars show means plus standard errors

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