Holmes, C.D., Papadimitriou, C., Snyder, L.H.(2018) Dissociation of LFP Power and Tuning in the Frontal Cortex during Memory Journal of Neuroscience
Nice paper. Well done. But with a caveat. The authors show that absolute power is dissociated from neural tuning in spiking activity. From this, they conclude that “oscillatory activity by itself is likely not a substrate of memory” and “may be an epiphenomenon of a rate code in the circuit, rather than a direct substrate”.
Not quite. No one is claiming that absolute power alone carries specific information. Rather, it is *patterns of coherence* that carry information (e.g., Buschman et al., 2012; Salazar et al 2012; Antzoulatos and Miller, 2014). If so, there is no reason to think that information would be carried by absolute power. For example, two different patterns of coherence for two different items could have equal global power because it is the pattern, not the global power, that matters. In fact, we and others have shown that coherence and power can be dissociated (Buschman et al., 2012). Using absolute power as a proxy to argue against a functional role for oscillations is a “straw man” argument. It tests a hypothesis that does not reflect the state-of-the-art of thinking on this matter.
Antzoulatos, E.G. and Miller, E.K. (2014) Increases in functional connectivity between the prefrontal cortex and striatum during category learning. Neuron, 83:216-225. View PDF »
Buschman, T.J., Denovellis, E.L., Diogo, C., Bullock, D. and Miller, E.K. (2012) Synchronous oscillatory neural ensembles for rules in the prefrontal cortex. Neuron. 76: 838-846. View PDF »
Salazar, R.F., Dotson, N.M., Bressler, S.L., and Gray, C.M. (2012). Content-Specific Fronto-Parietal Synchronization During Visual Working Memory. Science 1224000
Another point: The reason they see “tuning” for contra vs ipsilateral targets in power is not because of stimulus tuning per se, it is because the right vs left visual hemifields are somewhat independent. See:
Buschman,T.J., Siegel, M., Roy, J.E. and Miller, E.K. (2011) Neural substrates of cognitive capacity limitations. Proceedings of the National Academy of Sciences. 108(27):11252-5. View PDF »
Kornblith, S., Buschman, T.J., and Miller, E.K. (2015) Stimulus load and oscillatory activity in higher cortex. Cerebral Cortex. Published online August 18, 2015 doi: 10.1093/cercor/bhv182. View PDF »
About the Author
The Miller Lab uses experimental and theoretical approaches to study the neural basis of the high-level cognitive functions that underlie complex goal-directed behavior. ekmillerlab.mit.edu