Crossmodal propagation of sensory-evoked and spontaneous activity in the rat neocortex.
In the cortex, neural responses to crossmodal stimulation are seen both in higher association areas and in primary sensory areas, and are thought to play a role in integration of crossmodal sensations. We used voltage-sensitive dye imaging (VSDI) to study the spatiotemporal characteristics of such crossmodal neural activity. We imaged three cortical regions in rat: primary visual cortex (V1), barrel field of primary somatosensory cortex (S1bf) and parietal association area (PA, flanked by V1 and S1bf). We find that sensory-evoked population activity can propagate in the form of a distinct propagating wave, robustly in either crossmodal direction. In single trials, the waveforms changed continuously during propagation, with dynamic variability from trial to trial, which we interpret as evidence for cortical involvement in the spreading process. To further characterize the functional anatomy of PA, we also studied the propagation of spontaneous sleep-like waves in this area. Using a novel flow-detection algorithm, we detected a propagation bias within PA of spontaneous waves--these tend to propagate parallel to the crossmodal axis, rather than orthogonal to it. Taken together, these findings demonstrate that intracortical networks show pre-attentive crossmodal propagation of activity, and suggest a potential mechanism for the establishment of crossmodal integration.
Takagaki
Kentaroh
K
Department of Physiology and Biophysics, Georgetown University, Washington, DC 20057, United States. kt62@georgetown.edu
Zhang
Chuan
C
Wu
Jian-Young
JY
Lippert
Michael Thomas
MT
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D004396:Coloring Agents; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D019579:Neocortex / Q000033:anatomy & histology / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology; D014738:Vibrissae / Q000294:innervation; D014793:Visual Cortex / Q000502:physiology
D004396:Coloring Agents