Crossmodal propagation of sensory-evoked and spontaneous activity in the rat neocortex

Department of Physiology and Biophysics, Georgetown University, Washington, DC 20057, United States.
Neuroscience Letters (Impact Factor: 2.03). 03/2008; 431(3):191-6. DOI: 10.1016/j.neulet.2007.11.069
Source: PubMed


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.

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Available from: Kentaroh Takagaki
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    • "The onset delay for contralateral visual responses during down states was 98.43 ± 19.05 ms (ranging between 56.7 and 141.0 ms, n = 25), almost five times longer than the onset response to whisker stimulation (19.78 ± 3.42 ms, Figure 1F) and similar to previously reported visual responses (Schulz et al., 2009, 2011). Such delays are expected when comparing to the long and variable delays (50–130 ms) described for visual responses in mouse visual cortex (Niell and Stryker, 2008; Takagaki et al., 2008). In order to verify the occurrence of cortical visual responses, we obtained extracellular recordings (LFP) in V1 simultaneously with the striatal whole-cell recordings (n = 16, Figures 3C and 3D). "
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    • "Part of the explanation might be that the dye signal in vivo reflects synaptic activity at the mesoscopic scale, whereas the action potential recordings capture the activity of single neurons (Lippert et al., 2007; Eriksson et al., 2008). Nevertheless, in several studies one can follow how net increases in the synaptic activity propagate over the cortical areas when the cortex is perturbed by a sensory transient (Senseman, 1996; Prechtl et al., 1997; Senseman and Robbins, 2002; Slovin et al., 2002; Grinvald and Hildseheim, 2004; Roland et al., 2006; Ferezou et al., 2007; Lippert et al., 2007; Xu et al., 2007; Ahmed et al., 2008; Han et al., 2008; Takagaki et al., 2008; Yoshida et al., 2008; Harvey et al., 2009; Ayzenshtat et al., 2010; Meirovithz et al., 2010; Ng et al., 2010; Polack and Contreras, 2012; Harvey and Roland, 2013). This synaptic dynamics may show some order in the feed-forward propagation of net-excitation for example between V1 and V2 in monkeys, rats and turtles, between the barrel field and the motor cortex in the mouse, and between visual areas 17, 18 and 19, 21 in the ferret. "
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