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  Discussion on Research Summary: Could cribbing be due to lesions in the brain?
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DrO

Posted on Tuesday, Apr 29, 2008 - 8:25 am:

This is a fascinating study into cribbing horses that indicates that horses with the disorder have impaired learning ability and may be related to an undefined dysfunction of the stratum medium of the brain.

Behav Brain Res. 2008 Mar 16;
Impaired instrumental choice in crib-biting horses (Equus caballus).

Parker M, Redhead ES, Goodwin D, McBride SD.

School of Psychology, University of Southampton, Highfield, Southampton, Hampshire SO17 1BJ, UK.

Horses displaying an oral stereotypy were tested on an instrumental choice paradigm to examine differences in learning from non-stereotypic counterparts. Stereotypic horses are known to have dysfunction of the dorsomedial striatum, and lesion studies have shown that this region may mediate response-outcome learning. The paradigm was specifically applied in order to examine learning that requires maintenance of response-outcome judgements. The non-stereotypic horses learned, over three sessions, to choose a more immediate reinforcer, whereas the stereotypic horses failed to do so. This suggests an initial behavioural correlate for dorsomedial striatum dysregulation in the stereotypy phenotype.


The association of dysfunction of specific areas of the brain with sterotypical behaviors in horses is new to me so I probed this a bit deeper and found a huge body of research that associates this and other areas to learning, type of learning, and the ability to relearn. This was one of the easier to understand summaries:

The Contribution of the Medial Prefrontal Cortex, Orbitofrontal Cortex and Dorsomedial Striatum to Behavioral Flexibility

Michael Ragozzino
Psychology, University of Illinois at Chicago, 1007 West Harrison Street, Chicago, Illinois, 60607, United States

Behavioral flexibility refers to the ability to shift strategies or response patterns with a change in environmental contingencies. The frontal lobe and basal ganglia are two brain regions implicated in various components for successfully adapting to changed environmental contingencies. A series of experiments are discussed that investigate the contribution of the rat prelimbic area, infralimbic area, orbitofrontal cortex and dorsomedial striatum to behavioral flexibility. Orbitofrontal cortex inactivation did not impair initial learning of discrimination tests, but impaired reversal learning due to perseverance in the previously learned choice pattern. Inactivation of the prelimbic area did not affect acquisition or reversal learning of different discrimination tests, but selectively impaired learning when rats had to inhibit one strategy and shift to using a new strategy. Comparable to orbitofrontal cortex inactivation, strategy switching deficits following prelimbic inactivation resulted from a perseverance of the previously relevant strategy. There is some evidence suggesting the infralimbic region supports reversal learning by maintaining the reliable execution of a new choice pattern. Dorsomedial striatal inactivation impaired both reversal learning and strategy switching. The behavioral deficits following dorsomedial striatal inactivation resulted from the inability to maintain a new choice pattern once selected. Taken together, the results suggest that orbitofrontal and prelimbic subregions differentially contribute to behavioral flexibility, but are both critical for the initial inhibition of a previously learned strategy while the dorsomedial striatum plays a broader role in behavioral flexibility and supports a process that allows the reliable execution of a new strategy once selected.


We can only hope that such work may lead to practical therapeutic options for this troublesome problem with horses.
DrO
Member:
aannk

Posted on Tuesday, Apr 29, 2008 - 10:38 am:

Funny, all the cribbers I've known have been noticeably smarter than the non cribbers.
Alicia
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