A longstanding hypothesis on the role of piriform cortex has been that

it functions to reconstruct patterns selleck kinase inhibitor of stored activity in the face of degraded or noisy stimuli (Haberly and Bower, 1989). This view has received some support recently from detailed studies of local cortical circuitry (Franks et al., 2011) and odor-evoked activity (Chapuis and Wilson, 2012). The feedback of a completed or reconstructed pattern of activity to the olfactory bulb may provide a useful signal for plasticity in the bulb. Indeed cortical inputs to granule cells are one of the few places in which synaptic plasticity has been observed in the olfactory bulb (Gao and Strowbridge, 2009; Nissant et al., 2009). However, such a mechanism would seem to require that the feedback be provided specifically

to those bulbar neurons that were initially activated by the current or stored odor. This provides motivation for future studies that analyze the topography of the cortical feedback projections to the bulb. In addition, any analysis of the role of feedback also must consider that the bulb-cortex interactions will be dynamic. If cortical feedback changes activity in the bulb, this will in turn change activity in the cortex which will alter activity in the bulb etc. Previous work indicating that beta oscillations in the bulb depend on cortical feedback (Neville and Haberly, 2003) are consistent with this view in which the echoes of cortical activity reverberate throughout early stages of olfactory processing. “
“Human observers explore their visual environment using rapid gaze shifts

called saccades. While saccades facilitate the efficient Screening Library sampling of information across the visual field, they also impose a heavy computational cost on the brain. Many early visual neurons encode spatial information using eye-centered receptive fields whose positions are fixed relative to the retina. As a result, the information they convey depends on where the eyes are looking. Every change in eye position alters mafosfamide the retinal location of objects that remain fixed relative to the external world. This makes spatial localization following an eye movement challenging. One obvious solution is to discard information each time the eyes move, wait until the movement is complete, and then reacquire target locations based on (slow) visual feedback. However, we can localize a target in complete darkness even when an eye movement intervenes between the presentation of the target and its capture by a saccade, indicating that the brain does not exclusively rely on current visual information (Hallett and Lightstone, 1976). Instead, an internal signal representing eye position or eye displacement must be used in combination with retinal information to compensate for the eye movement. Various mechanisms have been proposed for how the brain performs this important computation. In the current issue of Neuron, Xu et al.