Is there a mindfulness meditation technique that tends to produce gamma rhythms in the brain (and not just the alpha frequencies that are typical)? This is a follow up to a paper (^) that was cited in a response to one of my past questions here. It was found that experienced Buddhist monks generate a substantial increase in gamma waves on demand during their meditation, while novices don't.  

This website cites a study (*) that found that mindfulness meditation causes an increase in alpha waves in subjects.  

I'm therefore wondering if there is something that the Buddhist monks are doing differently. Is there a mindfulness meditation technique that tends to produce gamma rhythms in the brain (and not just the alpha frequencies that are typical during mindfulness practice)?  

Perhaps gamma waves (in the orbitofrontal cortex and areas of the prefrontal cortex) are generated from simply a deeper focus. However, if that's the case, it's still not clear to me how one can attain this. What kind of techniques are likely to lead to this phenomenon? Is it more likely that a more open/wide focus (example cue: "pay attention to all thoughts/feelings/sensations that appear in your mind and, if you get distracted, just come back to the meditation") or narrow/sharp focus (example cue: "pretend to receive a huge reward for focusing on your breath with high clarity and minimal distractions") leads to gamma activity? Are there any other dimensions of mindfulness meditation that are relevant here?

(^) The Brain of Buddha - Christof Koch
(*) Mindfulness starts with the body: somatosensory attention and top-down modulation of cortical alpha rhythms in mindfulness meditation
It looks like increased gamma activity is pronounced simply for long-term meditation practitioners. 


  Long-term Vipassana meditators sat in meditation vs. a control rest
  (mind-wandering) state for 21 min in a counterbalanced design with
  spontaneous EEG recorded. Meditation state dynamics were measured with
  spectral decomposition of the last 6 min of the eyes-closed silent
  meditation compared to control state. Meditation was associated with a
  decrease in frontal delta (1–4 Hz) power, especially pronounced in
  those participants not reporting drowsiness during meditation.
  Relative increase in frontal theta (4–8 Hz) power was observed during
  meditation, as well as significantly increased parieto-occipital gamma
  (35–45 Hz) power, but no other state effects were found for the theta
  (4–8 Hz), alpha (8–12 Hz), or beta (12–25 Hz) bands. Alpha power was
  sensitive to condition order, and more experienced meditators
  exhibited no tendency toward enhanced alpha during meditation relative
  to the control task. All participants tended to exhibit decreased
  alpha in association with reported drowsiness. Cross-experimental
  session occipital gamma power was the greatest in meditators with a
  daily practice of 10+ years, and the meditation-related gamma power
  increase was similarly the strongest in such advanced practitioners.
  The findings suggest that long-term Vipassana meditation contributes
  to increased occipital gamma power related to long-term meditational
  expertise and enhanced sensory awareness.  


Also, 


  Early studies of meditators implicated alpha (8–12 Hz) power increases
  as both a state and trait effect of Yogic, Zen, and Transcendental
  Meditation practice. Later studies have failed to replicate the early
  findings of increased alpha in advanced practitioners but have
  reported increased alpha coherence, especially in assays of TM
  practitioners (Gaylord et al. 1989; Travis 1991; Travis and Pearson
  1999; Travis et al. 2002), theta (4–8 Hz) power, especially in the
  assays of concentrative/focused attention practitioners (Aftanas and
  Golocheikine 2001; Baijal and Srinivasan 2009; Hebert and Lehmann
  1977; Pan et al. 1994), or gamma effects (Lehmann et al. 2001; Lutz et
  al. 2004). 


Cahn, B. Rael, Arnaud Delorme, and John Polich. "Occipital gamma activation during Vipassana meditation." Cognitive processing 11.1 (2010): 39-56. doi: 10.1007/s10339-009-0352-1

Whether one can accelerate the gamma power with a particular meditation training technique is another question, however.  

Activities likely to trigger gamma power

Even if particular subtypes of mindfuless meditation techniques promoting gamma power in novices may not be known yet, we can conjecture the characteristics thereof based on other activities that trigger gamma activity in the prefrontal cortex. From the comments, Angela Richardson writes  


  Noise, flashing lights, movement and high-contrast or striped patterns
  can all increase gamma activity. In some people the resulting increase
  in gamma activity is so large that it causes seizures or migraines. If
  you want a meditation exercise to increase your gamma power then
  imagine loud music, strobe lights and brightly coloured rapidly moving
  shapes and patterns.  


However, the corresponding gamma waves are primarily observed in the visual cortex. See  

Adjamian, Peyman, et al. "Induced visual illusions and gamma oscillations in human primary visual cortex." European Journal of Neuroscience 20.2 (2004): 587-592. https://doi.org/10.1111/j.1460-9568.2004.03495.x

Azizi et al. note that gamma waves also get activated during an n-back exercise, which requires active focus and working memory utilization:  


  during cross-modal sensory processing (perception that combines 2
  different senses such as sound and sight). Also, it is shown during
  short-term memory matching of recognized objects, sounds, or tactile
  sensations


Roohi-Azizi, Mahtab, et al. "Changes of the brain’s bioelectrical activity in cognition, consciousness, and some mental disorders." Medical journal of the Islamic Republic of Iran 31 (2017): 53. https://doi.org/10.14196/mjiri.31.53 

A common theme in the gamma activity literature seems to be a mental state that is awake and alert, with a deep and selective focus/attention. It has also been observed in the phenomenon of "getting it right" and feature extraction, as Phillip Gilley demonstrates in this beautiful visualization:  

https://www.youtube.com/watch?v=OCpYdSN_kts

A mental state that sufficiently mirrors these characteristics during meditation may possibly lead to the desired gamma activity.