Neuroscience 2002 Abstract
| Presentation Number: | 657.4 |
|---|---|
| Abstract Title: | Optical imaging of contrast-dependent direction selectivity in visual cortex. |
| Authors: |
Zhan, C.*1
; Ledgeway, T.2
; Baker, C. L.1
1Dept of Opthalmology, McGill University, Montreal, Canada 2Dept of Psychology, University of Nottingham, Nottingham, United Kingdom |
| Primary Theme and Topics |
Sensory Systems - Vision -- Extrastriate visual cortex: Funtional organization and circuitry |
| Secondary Theme and Topics | Techniques in Neuroscience<br />- Data analysis, physiological methods, statistics |
| Session: |
657. Visual cortex: motion II Poster |
| Presentation Time: | Wednesday, November 6, 2002 11:00 AM-12:00 PM |
| Location: | Hall A2-B3 F-55 |
| Keywords: | Intrinsic Signal, Cat A18 |
While spatial maps obtained with optical imaging have been shown to correspond to results from single unit recording, the quantitative relationship between the magnitudes of electrophysiological and optical responses is open to question. Single neurons in cat A18 typically show direction-selective contrast response functions which are sigmoidal or even non-monotonic (saturating, or declining, at higher contrasts) - (Ledgeway & Baker, SFN Abst 164.3, 2001). We have used intrinsic signal optical imaging (720 nm, responses averaged over ca 8.5 sec stimulus durations) from cat A18 to measure responses to drifting sinewave gratings at contrasts ranging from 10-80 %. We calculated average difference images for pairs of oppositely moving sinewave gratings at each contrast level tested, and employed a novel strategy to find the optimized smoothing filter for noise reduction. The contrast response functions of magnitudes of direction-selective optical responses were monotonic and convex, quite unlike the saturating functions seen for single neuron responses. The disagreement with single unit results might be due to a nonlinearity in the mechanism of the optical response, or alternatively the recruitment of a larger pool of neurons responding more weakly, due either to higher contrast thresholds or non-optimal tuning to the stimulus. In any case, the results indicate that magnitudes of single unit and optical responses may not necessarily be linearly coupled.
Supported by Canadian CIHR grant MOP 9685 to CLB
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2002 Neuroscience Meeting Planner. Orlando, FL: Society for Neuroscience, 2002. Online.
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