Figure 1.

Proposed time course of feedforward and feedback events during early visual processing. Top row: Feedforward-dominant latencies, which are well-documented in the literature (e.g., Nowak and Bullier, 1997). Light pink shading refers to earliest reported latencies, likely corresponding to the depicted areas' first spikes, while darker pink shading corresponds ongoing feedforward responses. Bottom row: Areas are shaded orange when they are known to be receiving recurrent feedback. Most reports of recurrent feedback to V1 center around an absolute latency of 100 ms after stimulus presentation, with some reports being slightly faster. Common methods used to detect feedback (coarse application of TMS, MEG, EEG) do not have the spatial resolution to distinguish between feedback to V1 and extrastriate areas, but the view taken here is that feedback originates in immediately adjacent areas, and thus those areas that fire earliest during the feedforward dominant phase will also be the first to receive feedback.