Biomedical subjects

B B Bessette

Publications and source records attributed to B B Bessette.

7 recordsLinked to original sources

PubMed1990

Behavioral effects of chronic imipramine treatment in genetically nervous pointer dogs.

The genetically nervous pointer dog has been proposed as a model for human anxiety disorders. In a double-blind placebo-controlled study, seventeen nervous pointer dogs were treated for four weeks with imipramine hydrochloride (10 mg/kg), a potent antipanic agent in humans. Although three of the dogs demonstrated marked improvement to imipramine but not placebo treatment after short-term administration, chronic imipramine failed to modify the aberrant behavior in any of the dogs. These findings are discussed in the context of the nervous pointer dog as a model for human anxiety disorders.

Animals↗

PubMed1989

Intensity, color, and pattern discrimination deficits after lesions of the core and belt regions of the ectostriatum.

Pigeons were trained to discriminate visual stimuli that differed in intensity, color, or pattern, after which lesions were made in the ectostriatum, either the core region (EC), the belt region (EB), or both (EC + EB). Control lesions were made in the lateral neostriatum. After surgery, the birds were again trained to discriminate the stimuli. On the basis of a quantitative analysis of the lesion reconstructions, each pigeon was assigned to one of five groups: EC, EB, moderate (EC + EB), slight (EC + EB), or control. Postoperative savings scores, based on the number of preoperative and postoperative sessions required to discriminate the stimuli, were calculated. An analysis of variance indicated a significant effect of lesion location on the extent of postoperative savings or loss. Only the moderate (EC + EB) group was significantly different from the neostriatum controls. A multiple regression analysis of performance on the individual discrimination tasks indicated that the extent of damage to EC predicted the initial performance deficit on the intensity and one of the two pattern discrimination tasks (vertical versus horizontal bar). The color discrimination deficit, which was modest in extent and of short duration, was predicted only by the damage to (EC + EB) that was at least moderate in extent (20-40% of the volume of (EC + EB].

Animals↗

PubMed1989

Head orientation in pigeons: postural, locomotor and visual determinants.

We have determined the pigeon's head orientation for two postures and two locomotor activities that do not involve a specific visual stimulus. Using a high-speed cine camera, we filmed four pigeons (Columba livia) while (1) flying, (2) walking, (3) perching and (4) standing on a flat surface. Under these conditions, the head orientation is relatively constant, allowing us to estimate the normal horizon of the visual field and thus the horizontal meridian of the retina. Measurements of the lateral semicircular canal showed that the canal is tilted slightly up with respect to the horizon in the head orientation determined by the film analysis. In contrast to their relatively stable head posture during locomotion, the pigeons consistently altered their head orientation when presented with seed targets, apparently to fixate each seed with a small portion of the visual field around the bill tip.

Animals↗

PubMed1988

Intensity difference thresholds after lesions of ectostriatum in pigeons.

Seven pigeons were trained to perform in a psychophysical procedure to determine the smallest difference in luminous intensity (intensity difference threshold) that they could discriminate. When their performance stabilized, lesions were made in the ectostriatum in 4 birds and in the neostriatum in the remaining 3 birds. After surgery, the pigeons with ectostriatum lesions showed markedly elevated thresholds. The neostriatum control cases showed only trivial threshold changes as a consequence of the surgery. A psychophysical scaling analysis showed that the ectostriatum-lesioned pigeons had lost from 50% to 83% of their preoperative capacity to discriminate differences in the intensity of visual stimuli. A multiple-regression analysis based on quantitative reconstructions of the lesions revealed that only damage to the core region of the ectostriatum contributed to the postoperative threshold changes.

Animals↗

PubMed1986

Size-threshold changes after lesions of the visual telencephalon in pigeons.

Fifteen pigeons were tested in a psychophysical procedure that determined the limits of their ability to detect differences in the sizes of stimuli. The results indicated that intact pigeons can reliably discriminate an annulus 3.0 mm in diameter from one that is 3.9 mm in diameter. In the first experiment, pigeons with lesions of the ectostriatum that spared the medial 15% were unimpaired in their size-discrimination ability. Those cases in which the lesions involved both the medial and lateral regions of the ectostriatum were greatly impaired. In a second experiment, these findings were replicated. In some cases, the electrode trajectory was varied to rule out possible effects from non-ectostriatal structures. In addition, the second study indicated that destruction of the medial ectostriatum with the lateral regions intact had no measurable effect on size-difference thresholds. The medial region of ectostriatum is part of the termination field of a second tectofugal pathway to the telencephalon. This pathway passes from the optic tectum to nucleus dorsolateralis posterior thalami and then to the neostriatum intermedium, including the medial ectostriatum. An examination of the data of the present experiment and those of other behavioral studies of the ectostriatum suggest that the medial ectostriatum may be involved in the processing of visual information with low spatial-frequency components and the lateral ectostriatum may be processing information about the high-frequency composition of stimuli.

Animals↗

PubMed1986

Interocular transfer in parallel visual pathways in pigeons.

Pigeons were trained to perform intensity, color and pattern tasks monocularly. After their training was completed, a unilateral electrolytic lesion was made either in the nucleus rotundus or in the nucleus opticus principalis thalami (OPT). The lesion was made in the trained hemisphere (contralateral to the trained eye) in half of the subjects and in the untrained hemisphere in the other half. After a 7-day recovery period the birds were retrained on the same tasks with the previously untrained eye. A rotundal lesion, on either side, resulted in the loss of interocular transfer of discrimination, whereas neither contralateral nor ipsilateral OPT lesions affected discrimination. These results suggest that the tectofugal visual pathway plays a crucial role in the interhemispheric transfer of visual information in pigeons.

Animals↗

PubMed1985

Normative data for pigeon vision.

Normative data are reported for the visual acuity, luminance-difference threshold and size-difference threshold of pigeons (Columba livia). The mean visual acuity was 12.66 c/deg or 2.53 min (N = 54), the mean log luminance-difference threshold was 0.11 (N = 105) and the mean size-difference threshold was 0.94 mm (N = 20).

Animals↗