Phillips & Singer (P&S) extend ideas derived from the observation eight years ago that the coherence (synchronization) of cortical oscillations can be modulated by the structure of visual stimuli. As described in the target article, a large part of the continued interest in this finding is related to independent theoretical work suggesting that synchronized cell firing could help solve the problem of binding together within cortex neuronal activity associated with different attributes of visual stimuli. The authors present an abstract “proof (...) of concept” model describing how their cortical processing scheme could work, but our biologically realistic models of cortical relationships suggest that the proposal is biologically implausible. Our realistic models lead to a very different interpretation of the significance of cortical oscillations. (shrink)

The primary assumption made in this series of target articles is that the cerebellum is directly involved in motor control. However, in my opinion, there is ample and growing experimental evidence to question this classical view, whether or not learning is involved. I propose, instead, that the cerebellum is involved in the control of data acquisition for many different sensory systems, [CRÉPEL et al., HOUK et al., SMITH, THACH].

Braitenberg et al.'s proposal, like most previous theories of cerebellar function (see Bower 1997, for review), is fundamentally based on the striking geometric relationship between parallel fibers and Purkinje cells. As in previous models, the current theory assumes that the activation of granule cells results in a of activated Purkinje cells, although it adds the new requirement that the granule cell layer itself have a particular spatial/temporal pattern of activation. I believe there is clear evidence that parallel fibers do not (...) have the type of excitatory effects on Purkinje cells required by this theory. (shrink)