From:
Sukie Crandall
Date: 2007-12-12 03:02:43 UTC
Subject: [ferrethealth] Abstracts of two visual cortex and hemisphere interaction studies
To: ferrethealth@yahoogroups.com
> Cereb Cortex. 2007 Dec 7 [Epub ahead of print]
> Stimulus-Dependent Interaction between the Visual Areas 17 and 18 of
> the 2 Hemispheres of the Ferret (Mustela putorius).
>
> Makarov VA, Schmidt KE, Castellanos NP, Lopez-Aguado L, Innocenti GM.
> Department of Applied Mathematics, School of Optics, Universidad
> Complutense de Madrid, 28037 Madrid, Spain.
> To study how the visual areas of the 2 hemispheres interact in
> processing visual stimuli we have recorded local field potentials in
> the callosally connected parts of areas 17 and 18 of the ferret
> during the presentation of 3 kinds of stimuli: 2.5 degrees squares
> flashed for 50 ms randomly in the visual field (S1), 4 full-field
> gratings differing in orientation by 45 degrees and identical in the
> 2 hemifields (S2) and gratings as above but whose orientation and/or
> direction of motion differed by 90 degrees in the 2 hemifields (S3).
> The gratings remained stationary for 0.5 s and then moved in 1 of
> the 2 directions perpendicular to their orientation for 3 s. We
> compared the responses in baseline conditions with those obtained
> whereas the contralateral visual areas were inactivated by cooling.
> Cooling did not affect the responses to S1 but it modified those to
> S2 and to S3 generally increasing early components of the response
> while decreasing later components. These findings indicate that
> interhemispheric processing is restricted to visual stimuli which
> achieve spatial summation and that it involves complex inhibitory
> and facilitatory effects, possibly carried out by interhemispheric
> pathways of different conduction velocity.
> PMID: 18065720 [PubMed - as supplied by publisher]
>
> : Cereb Cortex. 2007 Dec 7 [Epub ahead of print]
> Dynamic Properties of the Representation of the Visual Field Midline
> in the Visual Areas 17 and 18 of the Ferret (Mustela putorius).
>
> Nakamura H, Chaumon M, Klijn F, Innocenti GM.
> Department of Neuroscience, Karolinska Institutet, S-17177
> Stockholm, Sweden.
> In mammals, the visual field is split along the midline, each
> hemisphere representing the contralateral hemifield. We determined
> that, in the ferret, an 8- to 10-deg-wide strip of visual field near
> the midline is represented in both hemispheres. Bright squares (1.5
> deg) were flashed at different azimuths within the central 20 deg of
> the visual field. Stimuli were flashed either alone or sequentially,
> and the responses were analyzed with the voltage-sensitive dye (VSD)
> RH 795 and/or by recording local field potentials (LFPs). In both
> VSD and LFP experiments, each stimulus evoked a cortical response
> field that extended over visual areas 17 and 18 up to a surface of
> 1-1.5 mm(2) and then shrank again. Amplitude of the responses
> decreased approaching the visual midline and the latency increased.
> These positional differences are likely to originate from the
> spatiotemporal structure of the peripheral response fields (PRFs)
> that form a mosaic in areas 17 and 18, interrupted near the visual
> midline. Unexpectedly, interhemispheric connections appear not to
> modify these PRFs' effects and may not contribute to the responses
> to discrete, flashed stimuli.
> PMID: 18065721 [PubMed - as supplied by publisher]
>
Sukie (not a vet)
Recommended ferret health links:
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http://ferrethealth.org/archive/
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http://www.miamiferret.org/fhc/
http://www.ferretcongress.org/
http://www.trifl.org/index.shtml
http://homepage.mac.com/sukie/sukiesferretlinks.html
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