I have chosen „40Hz“ as the name of this website since it happens to be the nickname for one of the experimental phenomena my group is interested in, namely, fast neuronal oscillations in the so-called gamma-frequency range. Although gamma oscillations can be observed across a broad range of frequencies between 30 and 150Hz, many early studies of gamma activity described them as occurring prominently around 40-50Hz – hence the label „40Hz“.
Gamma oscillations have first been observed by microelectrode recordings in animal studies. These studies have provided evidence for synchronized gamma activity in many neural circuits and across a wide range of species. Gamma oscillations have been observed in all sensory systems, in the motor system and in memory and association structures. The species include primates, carnivores, lagomorphs, rodents, birds, reptiles, amphibia and insects.
What the available studies demonstrate is the occurrence of gamma activity under a wide variety of tasks and paradigms including processing of coherent stimuli, perceptual discrimination, focussed attention, short-term memory, sensorimotor integration, and language processing. Typically, the observed amount of gamma is positively correlated with increased „processing load“ and, thus, with the level of attention, as well as with the difficulty or integrative nature of the processing. Generally, the human data are in good agreement with the animal studies suggesting a role of gamma synchronization in the binding and selection of distributed information. More recently, it has been suggested that gamma-band oscillations may be particularly relevant for communicating novel information in a „bottom-up“ manner to other brain regions.
- Engel AK, Fries P, Singer W (2001) Dynamic predictions: oscillations and synchrony in top-down processing. Nat Rev Neurosci 2: 704-716 (pdf)
- Herrmann CS, Munk MHJ, Engel AK (2004) Cognitive functions of gamma-band activity: memory match and utilization. Trends Cogn Sci 8: 347-355 (pdf)
- Fries P (2005) A mechanism for cognitive dynamics: neuronal communication through neuronal coherence. Trends Cogn Sci 9: 474-480 (Pubmed)
- Fries P (2009) Neuronal gamma-band synchronization as a fundamental process in cortical computation. Annu Rev Neurosci 32: 209-224 (Pubmed)
- Engel AK, Fries P (2010) Beta-band oscillations - signalling the status quo? Current Opinion in Neurobiology 20: 156-165 (pdf)
The banner image displays connections mapped in the human brain by diffusion-spectrum imaging. The data have been recorded by the Human Connectome Project. The image is used with permission from Macmillan Publishers Ltd, Nature (483, p.394), copyright (2012).