Abstract
AbstractUsing voltage-sensitive dye optical imaging methods, we visualized neural activity in the rat barrel cortex in response to the deflection of a single whisker in different directions. Obtained data indicates that fast movements of single whiskers in varying directions correlate with different patterns of activation in the somatosensory cortex. A functional map was created based on the voltage-sensitive dye optical signal. This supports prior research that vibrissae deflections cause responses in different cortical neurons within the barrel field according to the direction of the deflection. By analogy with the orientation columns in the visual cortex, directionally-biased single whisker responses to different directions of deflection could be a possible mechanism for the directional selectivity of this important sensory response.
Highlights
Within the past century neuroscientists have discovered many functional maps in the mammalian brain, but until recently, data had led the scientists to assume that detailed maps of directional sensory information from the outside world were located only in the visual cortex (Imamura et al, 2006)
For all eight examined rats voltage-sensitive dye optical signals elicited in response to directional whisker stimulation were observed in a cortical area anatomically corresponding to the barrel field of the left hemisphere
The signal usually appeared just after the frame when the stimulus was presented and reached its peak 20 – 30 ms after stimulus onset. After reaching their maximum value the activated areas decreased until returning to baseline 20 – 40 ms after the stimulus onset. All these properties of directional representation could be reproduced in all rats examined
Summary
Within the past century neuroscientists have discovered many functional maps in the mammalian brain, but until recently, data had led the scientists to assume that detailed maps of directional sensory information from the outside world were located only in the visual cortex (Imamura et al, 2006). Recent studies (Andermann and Moore, 2006; Andermann and Moore, 2008; Boas eat al, 2008 Diamond et al, 2008; Frostig, 2006; Li and Ebner, 2007; Timofeeva et al, 2003) have discovered that the barrel cortex contains a map of directional sensitivity This new map of directional sensitivity has, until now, been studied only using electrophysiological methods (Andermann and Moore, 2006; Borgdorff et al, 2007) which, while very sensitive in time, lack spatial precision for localizing brain activity. Our research group is currently using voltage-sensitive dye optical imaging methods in order to create a functional map of the directional sensitivity of the barrel field This technique has yielded revolutionary results when applied to the visual (Tanaka et al, 2009), auditory (Song et al, 2006; Tsytsarev et al, 2009) and somatosensory (Devor at al., 2005; Civillico and Contreras, 2006; Chen-Bee at al, 2007) systems. We demonstrate that spatially organized neurons in the somatosensory cortex show preference for certain directions of whisker deflection
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