Modulation of functional connectivity in parietal cortex rhythms Alexandros Gelastopoulos Nancy Kopell's lab Boston University Cognitive Rhythms Collaborative Retreat April 2017

Gamma/beta2 to beta1 (15 Hz) Switches Roopun et al 2006, 2008 In vitro (S2, rodent) With kainate: gamma superficially, beta2 in deep layers Lower kainate: beta1 in both deep and superficial layers Separating layers destroys the beta1 rhythm everywhere Switch to beta1 only seen in parietal cortex superficial deep

Switch to beta1: Mechanism Kramer, Kopell, Roopun, Whittington… 2008 Model reproduces behavior for both beta2+gamma and beta1 Gamma and beta2 periods concatenate to produce beta1 Concatenation created by inhibitory rebound Experiments validate model Plasticity allows synchronization of IB cells and control of superficial interneurons

Kopell, Whittington, Kramer 2011 Implication: Network Memory, Cell Assembly Beta 1 rhythm continues without (much) continuing input; Added input to cells in network displaying beta1 creates gamma cell assembly within beta 1 rhythm Beta 1 activity remains. New input doesn't get rid of old input Kopell, Whittington, Kramer 2011

Questions Bottom-up input comes in the form of gamma oscillations into the superficial layers (through the middle layers). Can the beta1 remain in the presence of gamma input? Can gamma assemblies form without erasing remembered input? What are the functional implications?

How Does S2 Beta 1 React to Gamma Inputs ? Simplified version of the network producing beta1 Behavior in the absence of inputs RS FS LTS IB

Beta1 continues even if superficial layers are driven by gamma RS cells are entrained to gamma Beta1 continues RS cells and IB cells fire out of phase LTS and IB periods concatenate to get beta1 LTS cells participate in two rhythms

Silencing LTS cells makes deep layers synchronize with input RS and IB cells fire in phase VIP cell activation can switch off LTS cells VIP cells active when hyper-vigilant

Cell assemblies can form with gamma input Gamma cell assemblies can form in response to phasic input Old input is remembered

Conclusions Previous work suggests that beta1 can support memory and cell assemblies on top of it. - Special to parietal cortex Beta1 persists in the presence of superficial gamma input. Old input can remain with new input and be kept separate. Turning on/off LTS cells allows switching between listening/not listening state. Inputs to deep layers from higher-order regimes can bias output to predicted signals, not disturbed by current input. Removal of LTS cells can allow current input to dictate output. Current work: Implement this in multiple columns