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B Glenn

Publications and source records attributed to B Glenn.

5 recordsLinked to original sources
PubMed1992

Violations of Listing's law after large eye and head gaze shifts.

1. Kinematic constraints were examined in static eye and head positions after large gaze shifts to visual targets. Three-dimensional eye and head rotations were measured in six adult human subjects by the use of the magnetic field search coil technique. 2. Eye positions in space were found to obey Donder's law; i.e., for any given gaze direction there was a unique three-dimensional orientation. In other words, angular eye positions in space (expressed as quaternions) were constrained to a two-dimensional surface. 3. When only the eye moved (head stationary), the shape of this surface resembled a plane and thus the eye position in space obeyed Listing's law. However, after gaze shifts involving both the eye and the head, the eye in space surface became twisted and thus nonplanar. This twist was similar to that achieved by a Fick gimbal model of rotations in which the horizontal axis is nested within a fixed vertical axis. During oblique gaze shifts, the head made predominantly horizontal movements whereas the eye made predominantly vertical movements. This, combined with the fact that the eye is mounted within the head, causes the eye in space surface to resemble that of a Fick gimbal. 4. The angular position of the head in space was also constrained to a two-dimensional surface. This surface was also not planar (Listinglike) and twisted in a manner similar to that of the eye in space. 5. Whereas the angular position of the eye in head was found to obey Listing's law after head-fixed gaze shifts, violations of Listing's law occurred after head-free gaze shifts. These violations showed significant intersubject variation in their magnitude and character. 6. Given that the eye in space violates Listing's law after head movements, the supposition that Listing's law serves the perceptual purpose of maintaining radial constancy is untenable. The Fick gimballike behavior of the head in space and eye in space may hold several advantages over a Listing's system. When the head in space behaves like a Fick gimbal, a horizontal line through the eyes remains parallel to the horizon. By having the eye in space behave like a Fick gimbal, the work done against gravity may be minimized by having the eye contribute more to vertical gaze shifts than does the head.

Adult↗
PubMed1991

Behavioural effects of selective tachykinin agonists in midbrain dopamine regions.

The effects of selective NK-1, NK-2 and NK-3 tachykinin agonists in midbrain dopamine cell containing regions were investigated in the rat. The NK-3 agonist senktide induced locomotion, rearing and sniffing following infusion into the substantia nigra pars compacta, and to a lesser extent in the ventral tegmental area. These behavioural responses were not seen following infusion of the selective NK-1 agonist [Sar9,Met (O2)11]SP or the NK-2 agonist [N1e10]NKA4-10. In contrast, grooming was induced only by the NK-1 agonist administered into the substantia nigra. Yawning, chewing mouth movements and wet dog shakes were all seen following infusion of senktide into the ventral tegmental area. These findings suggest that (i) dopamine-mediated behavioural responses seen following tachykinin administration into the midbrain are dependent upon stimulation of NK-3 tachykinin receptors, (ii) tachykinin-induced grooming is mediated by stimulation of NK-1 receptors and (iii) some of the previously described 5-HT mediated behaviours seen following administration of NK-3 tachykinin agonists are probably generated by stimulation of 5-HT cell bodies in the ventral tegmental area.

Animals↗
PubMed1987

Evidence that the amygdala is involved in benzodiazepine and serotonergic effects on punished responding but not on discrimination.

Interactions between the benzodiazepines (BZs) chlordiazepoxide (CDP) and midazolam (MDZ), the BZ antagonist R0 15-1788, the inverse BZ receptor agonists CGS 8216 and FG 7142, gamma-aminobutyrate (GABA), serotonin (5-HT), the 5-HT2 antagonist methysergide and the putative 5-HT agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) were investigated using peripheral and intra-amygdaloid treatments. A multiple schedule consisting of rewarded, nonrewarded (Time out: TO) and conflict periods was used to compare in parallel effects on successive discrimination between rewarded and nonrewarded periods and punished responding. The three components were presented in both a fixed order (Experiment 1) and a random order (Experiments 2 and 3). Intra-amygdaloid treatments with GABA and the BZs selectively increased rates of punished responding. CDP given systemically, on the other hand, increased both TO and conflict rates, suggesting an additional impairment of discrimination, which was more marked in the random than the fixed order condition. R0 15-1788, CGS 8216 and FG 7142 given by both routes counteracted the anti-conflict effects of CDP given centrally or systemically. However increases in TO rates induced by IP CDP were antagonized only by IP treatments with these compounds. The two inverse agonists, but not R0 15-1788, also counteracted increases in punished responding which were found after intra-amygdaloid GABA infusions. In Experiments 2 and 3 where baseline rates of pressing in Conflict periods were sufficiently high to detect decreases, CGS 8216 and FG 7142 reduced responding below control level, suggesting a specific anxiogenic activity. Evidence for effects of R0 15-1788 by itself was inconclusive. 5-HT injected into the amygdala also reduced punished responding below control level, whereas methysergide increased it with both central and peripheral treatment. Effects of 8-OH-DPAT varied according to route of administration. With IP treatment Conflict rates were increased, but after amygdaloid infusion both TO and Conflict rates were marginally reduced below control level, with a more consistent depression of punished responding. These results provide evidence that effects of BZs on punished responding are mediated by a GABAergic system which includes the lateral/basolateral amygdala, but which does not participate in BZ-induced disruption of discrimination. They also indicate that the antagonistic effects of CGS 8216 and FG 7142 involve a decrease in GABA transmission, and that these compounds may also be anxiogenic.(ABSTRACT TRUNCATED AT 400 WORDS)

Amygdala↗