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Biomedical subjects

E M Macphail

Publications and source records attributed to E M Macphail.

15 recordsLinked to original sources
PubMed1989

Medial versus lateral hyperstriatal lesions in pigeons: effects on autoshaping, non-matching-to-sample and spatial discrimination learning at short and long intertrial intervals.

Three experiments contrasted the effects of medial and lateral hyperstriatal lesions in pigeons. Expt. 1 found that both types of lesion obtained slower acquisition of autoshaping, compared to unoperated controls. No group differences in maintained rate of autoshaped responding were found. Expt. 2 found that lateral but not medial lesions disrupted choice performance in a non-matching-to-sample (NMTS) task, in which initial preference was for the correct stimulus; birds with lateral lesions responded more slowly to the sample stimulus than did birds with medial lesions. Expt. 3 found that medial but not lateral lesions disrupted both acquisition and reversal of a spatial discrimination at a long, but not at a short intertrial interval (ITI). Medial lesions damage primarily the hyperstriatum accessorium and lateral lesions, the hyperstriatum ventrale; but no significant correlations between the extent of damage to either of these structures and severity of behavioural disruption were obtained. Implications of these findings for theoretical accounts of hyperstriatal involvement in learning processes are discussed.

Animals↗
PubMed1987

Double dissociation of effects on learning of medial versus lateral hyperstriatal lesions in pigeons.

Three experiments examined the effects of medial and lateral hyperstriatal lesions in two groups of pigeons. In Experiment 1, both hyperstriatal groups were impaired, relative to unoperated and operated control groups, in postoperative performance of preoperatively acquired serial reversal of both spatial and visual discriminations. The deficits of the two hyperstriatal groups appeared both quantitatively and qualitatively similar. Experiment 2 found that performance of spatial reversals was disrupted in the medial, but not in the lateral, hyperstriatal group by a long intertrial interval. Experiment 3 found that acquisition of simultaneous matching-to-sample was disrupted by lateral, but not by medial, hyperstriatal lesions; the lateral group also showed a lower rate of response to the sample stimulus than any of the other groups. Implications of these findings for current theories of hyperstriatal function are discussed.

Animals↗
PubMed1982

Hyperstriatal lesions in pigeons (Columba livia): effects on retention and perseveration.

Two experiments explored the possibility that lesions of avian hyperstriatum, which disrupt reversal learning, might have that effect through a potentiation of the influence of proactive interference. Neither experiment found any evidence to suggest excessive interference in hyperstriatal pigeons, from preceding training on a position (or color) discrimination, on retention of a color (or position) discrimination, and this was true both after a short (30 min) and after a long (6 or 7 day) retention interval. There was, however, evidence of a disturbance, not easily interpreted, in retention following the lesions. There was also convincing evidence, from both experiments, for the disruption by hyperstriatal lesions not only of reversal learning but also of tasks not involving reversals, a disruption that suggests a general tendency to perseverate in hyperstriatal birds.

Animals↗
PubMed1976

Evidence against the response-shift account of hyperstriatal function in the pigeon (Columba livia).

Pigeons with hyperstriatal lesions and unoperated controls were given minimal or extended side-key pretraining prior to acquisition of a position discrimination. Operated birds were impaired following extended, but not minimal, pretraining. The birds then acquired a simultaneous color discrimination with posiversals of the color discrimination, operated birds were impaired, and this was primarily due to an exaggeration of perseverative responding to the former positive stimulus. Analysis of choice latencies found no tendency towards an exaggerated "Mahut effect" in hyperstriatals and indicated that operated subjects used the same solution strategies as normals. These findings directly contradict the response-shift account of hyperstriatal function and indicate a return to the response-inhibition hypothesis.

Animals↗
PubMed1975

Hyperstriatal function in the pigeon: response inhibition or response shift?

Experiment 1 showed that pigeons with lesions of the anterior or posterior hyperstriatum were impaired relative to unoperated controls and to control operates having neostriatal lesions on both acquisition and reversal of a simultaneous position discrimination. The observation that hyperstriatal birds showed more tendency than controls to halt responding altogether in this situation cast doubt on the notion that the reversal deficit was due to a loss of response inhibition. A second experiment supported an alternative hypothesis, that hyperstriatal birds have a deficit in the ability to shift responding to an alternative stimulus as a consequence of nonreinforcement.

Animals↗
PubMed1968

Avoidance responding in pigeons.

Four pigeons were trained in a one-way shuttle box avoidance situation. Three of the birds met the criterion of 90% avoidances; the fourth, although frequently avoiding successfully, was too erratic to meet the criterion. Avoidance responding in two of the birds was subsequently extinguished, showing that the response was true avoidance, and not escape from the buzzer warning stimulus. In Experiment 2, the three birds that had met criterion in Experiment 1 were trained in a two-way avoidance task, and all three met the criterion of 90% avoidances. The shuttle box therefore provides a rapid and reliable method of obtaining avoidance performance in pigeons.

Animals↗