Real-world events unfold at different time scales and, therefore, cognitive and neuronal processes must likewise occur at different time scales. We present a novel procedure that identifies brain regions responsive to sensory information accumulated over different time scales. We measured functional magnetic resonance imaging activity while observers viewed silent films presented forward, backward, or piecewise-scrambled in time. Early visual areas (e.g., primary visual cortex and the motion-sensitive area MT+) exhibited high response reliability regardless of disruptions in temporal structure. In contrast, the reliability of responses in several higher brain areas, including the superior temporal sulcus (STS), precuneus, posterior lateral sulcus (LS), temporal parietal junction (TPJ), and frontal eye field (FEF), was affected by information accumulated over longer time scales. These regions showed highly reproducible responses for repeated forward, but not for backward or piecewise-scrambled presentations. Moreover, these regions exhibited marked differences in temporal characteristics, with LS, TPJ, and FEF responses depending on information accumulated over longer durations (~36 s) than STS and precuneus (~12 s). We conclude that, similar to the known cortical hierarchy of spatial receptive fields, there is a hierarchy of progressively longer temporal receptive windows in the human brain.
Figure- Maps are shown on inflated (top) and unfolded (bottom) left and right hemispheres. White outlines mark the main regions in which responses were not time reversible. Anatomical abbreviations: ITS, inferior temporal sulcus; LS, lateral sulcus; STS, superior temporal sulcus; TPJ, temporal parietal junction; CS, central sulcus; IPS, intraparietal sulcus. Several higher-order visual areas were functionally defined based on their responses to faces (red outlines), objects (blue outlines), and houses (green outlines). Functionally and anatomically defined cortical areas: V1, primary visual cortex; MT+, MT complex responsive to visual motion; PPA, parahippocampal place area; FFA, fusiform face area; LO, lateral occipital complex responsive to pictures of objects; STS-face, area in superior temporal sulcus responsive to faces.
Thursday, March 27, 2008
A hierarchy of temporal receptive windows in our brains
Here is the abstract from a fascinating study by Hasson et al. on how our visual system assembles time narratives - as during watching a movie - followed by part of one of the figures from the paper: