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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Psychological research 35 (1971), S. 46-56 
    ISSN: 1430-2772
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Psychologie
    Notizen: Summary Occlusion of one eye and functional hemidecortication by cortical spreading depression (CSD) were used to examine the relative importance of crossed and uncrossed visual projections for pattern discrimination learning in hooded and albino rats. Whereas functionally hemidecorticate albino rats were unable to learn in 200 trials a horizontal-vertical discrimination when using the eye contralateral to the depressed hemisphere, hooded rats needed under similar conditions three times as many trials to criterion (167) than when using opposite eye and hemisphere (59). An engram established in intact animals with both eyes could be retrieved in functionally hemidecorticate rats of both strains even with the eye ipsilateral to the intact hemicortex, but retraining required about twice as many trials as when using the contralateral eye. Retrieval of monocularly acquired engrams was less efficient under similar conditions. Pattern discrimination formed through crossed or uncrossed visual projections during monocular occlusion and contralateral or ipsilateral CSD was completely lateralized, since relearning with naive eye and hemisphere proceeded at the same rate as the original learning. On the contrary, a black-white discrimination trained with the eye contralateral to the depressed hemisphere could be partly retrieved by the untrained eye and hemisphere. It is concluded that the ipsilateral visual projection is more effective in hooded than in albino rats and that it can be more efficiently used for retrieval than for acquisition.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 12 (1971), S. 238-249 
    ISSN: 1432-1106
    Schlagwort(e): Spreading depression ; Slow potentials ; Diffusion in brain tissue ; Potassium chloride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Cortical spreading depression (CSD) was evoked in anaesthetized rats by intracortical microinjection of 3.4·10−8 mol KCl (the single injection threshold T1). With two simultaneous injections at 1 mm tip separation 59% T1 had to be applied to each point to elicit CSD. For interfocal distances 2, 3 and 4 mm the double injection thresholds T1,2 were 65%, 74% and 97% of T1 respectively. The spatial summation effect was still significant at 3 mm and undetectable at 4 mm tip separation. Recording electrodes placed 1–3 mm from the point of injection detected local slow potential changes which attained with subthreshold KCl injections 16% of the maximum CSD negativity at the 1.5 mm distance. The threshold amount of KCl required to trigger CSD at different intervals (30–480 sec) after initial injection of 0.8 T1, exponentially increased with time from 28.2% t1 at 30 sec to 88.9% at 480 sec with the slope 16.8% T1 for a twofold increase of the interinjection interval. Quantitative analysis of results based on equations describing diffusion from an instantaneous point source indicates that the critical volume of depolarization is reached 61 sec after injection. According to the value of the diffusion coefficient of potassium the critical K+ concentration lies between 45 and 12 mequ/l and is reached at a distance of 600–950 μ from the injection.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Psychopharmacology 20 (1971), S. 57-65 
    ISSN: 1432-2072
    Schlagwort(e): Memory ; Consolidation ; Cortical Spreading Depression ; Potassium Chloride ; Pattern Discrimination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of prolonged cortical spreading depression (PCSD) on the retention of a visual discrimination was examined in 213 hooded rats. PCSD was maintained for 5 h by repeated application of 25% KCl onto the exposed cortical surface. Behavioral tests were performed 24 or more h before and/or after the treatment. A single application of 25% KCl did not affect subsequent acquisition of a horizontal-vertical discrimination, the learning of which took 140% and 125% to-criterion trials 1 and 3 days after PCSD. Whereas a single application of 25% KCl did not impair retention of the pattern discrimination learnt in a single session 24 h earlier, PCSD caused severe amnesia under the above conditions and partial amnesia even for pattern discriminations overlearned in 3 sessions. The amnesic effect nearly disappeared, however, when the habit was overlearned for 14 days, or when the engram established in a single session was allowed to consolidate for 2 weeks. When PCSD was applied 24 h after a single learning session amnesia was more marked on day 3 after treatment, and retrieval hardly improved over 2 weeks. In an experiment in which 14 sessions of black-white discrimination training were followed by a single session of horizontal-vertical training, PCSD evoked 24 h after acquisition of the pattern discrimination caused complete amnesia for the latter habit without affecting retrieval of the former one. The relevance of these findings to the consolidation hypothesis is discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 15 (1972), S. 29-38 
    ISSN: 1432-1106
    Schlagwort(e): Ventromedial hypothalamus ; Single units ; Spontaneous and stimulated activity ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The relationship between mean firing rate and activity pattern was studied in 177 neurons in the ventromedial hypothalamus of rats immobilized by Remyolan. Stationary epochs of spontaneous or stimulated activity containing at least 512 interspike intervals were analyzed with the LINC computer. The most frequently encountered interval histograms (IHs) were of the exponential (35%) or gamma 2 (25%) type. The IH shape remained unchanged even if the average firing rate was varied over a wide range (from 20/sec to 2/sec) by polarization through the recording microelectrode (2–5 nA, 1–10 min) or by intracarotid injection of glucose (0.1 ml, 10–25%). The coefficient of variation (CV = SD/ mean interval) was 1.03 for the spontaneous and 0.90 or 0.95 for the activity influenced by polarization or glucose, respectively. Since according to other studies sensory stimulation decreases CV by reorganization of the synaptic input, it is suggested that polarization and glucose affect predominantly the postsynaptic elements without significantly changing the presynaptic activity pattern.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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