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.