analysis:course-w16:week13
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| Local field potentials and related quantities such as the EEG ultimately result from the spatiotemporal summation of electrical currents across the cell membrane of neurons. Thus, in general, it is expected that spiking activity should be related to LFPs somehow. However, the exact nature of this relationship has proven to be far from trivial, and depends on many factors such as the three-dimensional arrangement of neurons, ion channel distributions, and more rapid dynamics arising from the interaction of multiple inputs. Accordingly, measures that characterize the relationship between spikes and LFPs have painted a surprisingly rich picture of how individual neurons participate in population- and systems-level activity (see e.g. Womelsdorf et al. 2005, Benchenane et al. 2010 and many others for striking examples). | Local field potentials and related quantities such as the EEG ultimately result from the spatiotemporal summation of electrical currents across the cell membrane of neurons. Thus, in general, it is expected that spiking activity should be related to LFPs somehow. However, the exact nature of this relationship has proven to be far from trivial, and depends on many factors such as the three-dimensional arrangement of neurons, ion channel distributions, and more rapid dynamics arising from the interaction of multiple inputs. Accordingly, measures that characterize the relationship between spikes and LFPs have painted a surprisingly rich picture of how individual neurons participate in population- and systems-level activity (see e.g. Womelsdorf et al. 2005, Benchenane et al. 2010 and many others for striking examples). | ||
| - | A different, practical issue is that LFPs are susceptible to //volume conduction//, that is, they can be recorded some distance away from their source. The exact amount distance depends on numerous factors, but even intracranially in the rat the hippocampally-generated theta rhythm can be recorded several millimeters away in the cortex (Sirota et al. 2008). Thus, is is not a priori clear that a LFP recorded from a particular brain structure is generated there (is locally relevant) raising the possibility of attributing properties of the recording to the wrong site! One of the major ways to determine if a LFP is locally relevant is to establish if it is related to spiking activity, which as a fast and relatively local signal does not volume-conduct nearly as far. | + | A different, practical issue is that LFPs are susceptible to //volume conduction//, that is, they can be recorded some distance away from their source. The exact amount distance depends on numerous factors, but even intracranially in the rat the hippocampally-generated theta rhythm can be recorded several millimeters away in the cortex (Sirota et al. 2008), and gamma oscillations in the ventral striatal LFP [[ http://biorxiv.org/content/early/2017/04/13/127126|originate in the nearby piriform cortex]]. Thus, is is not a priori clear that a LFP recorded from a particular brain structure is generated there (is locally relevant) raising the possibility of attributing properties of the recording to the wrong site! One of the major ways to determine if a LFP is locally relevant is to establish if it is related to spiking activity, which as a fast and relatively local signal does not volume-conduct nearly as far. |
| In this module, we will examine basic measures of spike-field relationships useful for both approaches. | In this module, we will examine basic measures of spike-field relationships useful for both approaches. | ||
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| </code> | </code> | ||
| - | Notice that the contents of ''data_trl'' now have multiple cells (88) corresponding to trials, rather than just one for the entire session as before. | + | Notice that the contents of ''data_trl'' now have multiple cells (88) corresponding to trials, rather than just one for the entire session as before. (Also, a more transparent trialification method can be seen in [[http://ctnsrv.uwaterloo.ca/vandermeerlab/doku.php?id=analysis:course-w16:week7|this module]].) |
| Now, we can compute the STA for specific task segments, defined relative to task event time zero, the nosepokes into the reward receptacle: | Now, we can compute the STA for specific task segments, defined relative to task event time zero, the nosepokes into the reward receptacle: | ||
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