Neurodynamics
The Neurodynamics group investigates the functional roles of neuronal dynamics.
Selective neuronal synchronization for selective attention
Neuronal dynamics like neuronal rhythms and their synchronization likely subserve important cognitive functions (1, 2). One central cognitive function is selective attention. Selective attention is important when one stimulus needs to be selected out of multiple simultaneously present stimuli. Those different stimuli induce separate rhythms in early visual cortex, and only the rhythm induced by the attended stimulus entrains higher visual areas and synchronizes with them (3-5). This synchronization leads to an alignment of the higher areas' rhythmic susceptibility specifically to the rhythmic input that conveys the attended stimulus. Thereby, the attended stimulus is selectively and efficiently transmitted, while unattended stimuli are not. Essentially, only the attended stimulus is represented in higher areas and affects conscious perception and behavior (6).
Communication through coherence (CTC)
This selective communication by means of selective neuronal synchronization has been named „Communication through Coherence“ or CTC (1, 7). A core aspect of CTC is that neuronal synchronization renders a subset of all structural anatomical neuronal projections effective, and another subset ineffective. More generally, CTC configures the full set of all structural anatomical projections, and dynamically and flexibly determines the momentary subset of effective projections.
Frequency bands for feedforward versus feedback communication
Projections between cortical areas can be classified as feedforward or feedback, depending on whether they project from lower to higher areas or vice versa. Intriguingly, the communication in the two directions is subserved by CTC in different frequency bands (8-10). The gamma band, between 40 and 90 Hz, primarily serves feedforward communication, whereas the beta band, between 15 and 30 Hz, primarily serves feedback communication. Feedforward communication is associated with signaling new information that could not be predicted, whereas feedback communication is associated with predictions based on the integration of previous information (11). In the absence of new information, feedback communication is likely associated with maintaining a state (12).
Rhythms for moving or maintaining posture
These CTC principles apply beyond visual areas and visual attention, e.g. to movement control by motor cortex. Motor cortex synchronizes with the spinal cord and the corresponding muscles both in the gamma and beta band (13). Beta synchronization is strong when a motor state is maintained, which in the motor system corresponds to a posture. By contrast, when a posture is given up to engage in a new movement, beta synchronization drops and is replaced by gamma synchronization. The relative strength of gamma versus beta synchronization before a go cue predicts the speed with which the response to the cue is issued.
From basic research to medical applications
In the Neurodynamics group, we investigate the transfer of those insights to further cognitive and emotional operations. One central operation of interest decides between approach versus avoidance behavior, a decision of great relevance for seeking reward. We hypothesize that this operation is also linked to rhythmic synchronization in different frequency bands. This might open a door towards therapeutic applications, because approach versus avoidance processes are central to depression and anxiety.
References
1. Fries P. Rhythms for Cognition: Communication through Coherence. Neuron 88: 220-235, 2015.
2. Fries P. Rhythmic attentional scanning. Neuron 111: 954-970, 2023.
3. Bosman CA, Schoffelen JM, Brunet N, Oostenveld R, Bastos AM, Womelsdorf T, Rubehn B, Stieglitz T, De Weerd P, and Fries P. Attentional stimulus selection through selective synchronization between monkey visual areas. Neuron 75: 875-888, 2012.
4. Womelsdorf T, Fries P, Mitra PP, and Desimone R. Gamma-band synchronization in visual cortex predicts speed of change detection. Nature 439: 733-736, 2006.
5. Fries P, Reynolds JH, Rorie AE, and Desimone R. Modulation of oscillatory neuronal synchronization by selective visual attention. Science 291: 1560-1563, 2001.
6. Rohenkohl G, Bosman CA, and Fries P. Gamma Synchronization between V1 and V4 Improves Behavioral Performance. Neuron 100: 953-963 e953, 2018.
7. Fries P. A mechanism for cognitive dynamics: neuronal communication through neuronal coherence. Trends in cognitive sciences 9: 474-480, 2005.
8. Bastos AM, Vezoli J, Bosman CA, Schoffelen JM, Oostenveld R, Dowdall JR, De Weerd P, Kennedy H, and Fries P. Visual areas exert feedforward and feedback influences through distinct frequency channels. Neuron 85: 390-401, 2015.
9. Michalareas G, Vezoli J, van Pelt S, Schoffelen JM, Kennedy H, and Fries P. Alpha-Beta and Gamma Rhythms Subserve Feedback and Feedforward Influences among Human Visual Cortical Areas. Neuron 89: 384-397, 2016.
10. Vezoli J, Vinck M, Bosman CA, Bastos AM, Lewis CM, Kennedy H, and Fries P. Brain rhythms define distinct interaction networks with differential dependence on anatomy. Neuron 109: 3862-3878 e3865, 2021.
11. Bastos AM, Usrey WM, Adams RA, Mangun GR, Fries P, and Friston KJ. Canonical microcircuits for predictive coding. Neuron 76: 695-711, 2012.
12. Engel AK, and Fries P. Beta-band oscillations--signalling the status quo? Current opinion in neurobiology 20: 156-165, 2010.
13. Schoffelen JM, Oostenveld R, and Fries P. Neuronal coherence as a mechanism of effective corticospinal interaction. Science 308: 111-113, 2005.