It is much more difficult to attribute higher-order activation as being specifically related to multisensory processing, as these regions did not show superadditivity, perhaps due to ceiling effects from these robust stimuli (Stevenson et al. 2007).
Simultaneous action potentials fired by lower order neurons [3] [5] provide an effective drive on higher order neurons, the activations of which enable object discrimination and perception.
Although simple motor acts elicited motor and premotor activity, higher order actions elicited more anterior activations within Broca's area, with transitions between chunks favoring BA 44, and termination of superordinate chunks activating BA 45.
The results are consistent with previous studies, showing activation in higher order brain centers that are involved in emotional coding of taste experience.
Accordingly, for the poststimulus interval, there is a growing consensus that early neural activity related to the stimulus representation in sensory regions (i.e., not driven by recurrent activation from higher order areas) alone does not determine whether a stimulus will become reportable, but only when it is embedded in a network (Lamme 2006).
The Default Mode Network (DMN) is a higher order functional neural network that displays activation during passive rest and deactivation during many types of cognitive tasks.
Further analysis using known ligands for D. melanogaster olfactory receptors and mutation data would help us to understand which model is functional and also to uncover whether olfactory receptor OR83b/OR22a complex is functional or a higher order oligomer is required for receptor activation.
Considering the fact that TLR9 activation was restricted to phosphorothioate (PS) CpG-motif DNA [12], [13], [14], our findings suggest that its activation is not associated with CpG DNA induced formation of dimer or higher order oligomers, and additional prerequisites might be necessary for its activation.
The formation of higher order oligomers possibly representing a conserved mechanism of activation has been demonstrated as a signaling prerequisite for a number of TLRs [23], [24].
The initial, stereotyped activation constitutes a pre-identification, higher order temporal TD error response, or possibly response generalisation to rewarding stimuli or contexts.
