![]() These periodic bursts of spikes focus stimulus information into gamma-rhythmic packages ( Womelsdorf et al., 2012). For presynaptic populations, it coordinates their spiking output into periodic bursts, increasing their postsynaptic impact ( Steinmetz et al., 2000 Fries et al., 2001 Azouz and Gray, 2003 Taylor et al., 2005 Zandvakili and Kohn, 2015). In this scheme, gamma-rhythmic activity serves multiple functions. One influential idea proposes interareal synchronization of oscillatory neural activity in the gamma-band (40–100 Hz) to enact dynamic modulation of effective connectivity between presynaptic and postsynaptic populations ( Fries, 2005, 2015 Kreiter, 2006, 2020). Hence, selective responses in downstream areas cannot result exclusively from upstream rate modulations, suggesting that selective attention relies on a different mechanism to dynamically change effective connectivity depending on task demands. However, there is only a small attention-dependent modulation of firing rates of the V1/V2 populations providing the input signals from the two visual stimuli to V4 ( Moran and Desimone, 1985 Motter, 1993 Luck et al., 1997 McAdams and Maunsell, 1999 Mehta et al., 2000 Salinas and Sejnowski, 2000). Selective processing is already observed at the single neuron level: when presented with two stimuli inside their receptive fields (RFs) of which one is attended, V4 neurons respond primarily as if only this stimulus was present ( Moran and Desimone, 1985 Reynolds et al., 1999 Grothe et al., 2018). Selective attention helps to reduce this computational complexity by focusing on signals which are behaviorally relevant at the expense of other, irrelevant signals ( Lavie, 1995). Visual information processing is computationally demanding, requiring the brain to handle a continuous, high-dimensional stream of sensory input signals. Our investigations provide direct evidence that selective attention relies on rhythmic temporal coordination between visual areas, and establish novel methods for pinpointing pulsed transmission schemes in neural data. ![]() What are the neural mechanisms which allow such selective processing in the visual system? We analyzed data from area V4 and found that the amount of visual signal information content is tightly linked to the phase of local gamma-rhythmic activity, with maximal signal content occurring near peaks of neural excitability. SIGNIFICANCE STATEMENT The ability to focus on the behaviorally relevant signals is essential for the brain to cope with the continuous, high-dimensional stream of sensory information it receives. For the attended stimulus, we find highest stimulus information content near excitability peaks, an effect that increases with oscillation amplitude, establishing a functional link between selective processing and gamma-activity. To test this prediction, we quantified gamma-phase-dependent stimulus content within neural activity from area V4 of two male macaques performing a visual attention task. Therefore, visual signals should be transferred through gamma-rhythmic bursts of information, resulting in a modulation of the stimulus content within the receiving population's activity by its gamma phase and amplitude. Conversely, non-attended signals arrive unaligned to the receiver's oscillation, reducing signal transfer. As a possible mechanism, routing-by-synchronization was proposed: neural populations receiving attended signals align their gamma-rhythmic activity to that of the sending populations, such that incoming spikes arrive at excitability peaks of receiving populations, enhancing signal transfer. Selective visual attention allows the brain to focus on behaviorally relevant information while ignoring irrelevant signals.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |