Limits...
Perirhinal cortex lesions that impair object recognition memory spare landmark discriminations

View Article: PubMed Central - PubMed

ABSTRACT

Loss of perirhinal cortex spares mirror-imaged landmark discriminations.

Perirhinal cortex lesions do not disrupt latent spatial learning.

Further underlines dissociation between perirhinal and hippocampal function.

Further underlines dissociation between perirhinal and hippocampal function.

No MeSH data available.


Schematic diagram of the square maze with different patterned walls. The inner square shape depicts the pool, the surrounding circle is the larger pool within which the square pool is placed, and the rippled circle represents the curtain used to block distal cues. The broken lines represent striped walls. The small circle represents the platform on which the rat was placed (passive trials). In Probes 1 & 3 (left column), the maze had one striped wall, as was the case in all active and passive training days. In Probes 2 & 4 (right column), the maze had two adjacent striped walls. ‘Passive’ refers to training days when the rat was placed on the escape platform (no swimming). ‘Active’ refers to training days when the rat was placed in the water-maze and swam to find the escape platform.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4998350&req=5

fig0005: Schematic diagram of the square maze with different patterned walls. The inner square shape depicts the pool, the surrounding circle is the larger pool within which the square pool is placed, and the rippled circle represents the curtain used to block distal cues. The broken lines represent striped walls. The small circle represents the platform on which the rat was placed (passive trials). In Probes 1 & 3 (left column), the maze had one striped wall, as was the case in all active and passive training days. In Probes 2 & 4 (right column), the maze had two adjacent striped walls. ‘Passive’ refers to training days when the rat was placed on the escape platform (no swimming). ‘Active’ refers to training days when the rat was placed in the water-maze and swam to find the escape platform.

Mentions: The present study examined the impact of perirhinal cortex lesions on the ability to discriminate mirror-imaged landmarks in order to find a submerged platform in a square water-maze. Mirror-imaged stimuli are of especial interest as they share the same elements and, hence, should be prone to interference. Although a previous study indicated that perirhinal lesions spare mirror-image discriminations [11], the training protocol was very protracted. The present study differed in two key aspects. First, it used a more rapid learning protocol [12], [13]. Second, learning was ‘passive’ in that there was no explicit reinforcement for learning the discrimination. Accordingly, rats were repeatedly placed on a partially submerged escape platform in the corner of a square water-maze where the platform location was signalled by the spatial arrangement of mirror-imaged patterns on adjacent maze walls. The particular discrimination involved those corners where striped walls and white walls met, where their relative left/right position was critical (see Fig. 1). Normal rats then swim to the escape location when first released into the water after passive training, so demonstrating their discrimination between these visual landmarks. As the animals have no experience of swimming to find the escape platform in this location prior to the probe test, this problem can only be solved by learning the correct configuration of spatial cues, rather than by simpler mediating strategies involving individual stimuli (e.g. swim to the striped wall and turn right, see Fig. 1) that could be acquired during active training [12]. The key question was whether perirhinal cortex damage would disrupts rats’ ability to identify the correct configuration given the presence of common cues with shared features.


Perirhinal cortex lesions that impair object recognition memory spare landmark discriminations
Schematic diagram of the square maze with different patterned walls. The inner square shape depicts the pool, the surrounding circle is the larger pool within which the square pool is placed, and the rippled circle represents the curtain used to block distal cues. The broken lines represent striped walls. The small circle represents the platform on which the rat was placed (passive trials). In Probes 1 & 3 (left column), the maze had one striped wall, as was the case in all active and passive training days. In Probes 2 & 4 (right column), the maze had two adjacent striped walls. ‘Passive’ refers to training days when the rat was placed on the escape platform (no swimming). ‘Active’ refers to training days when the rat was placed in the water-maze and swam to find the escape platform.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4998350&req=5

fig0005: Schematic diagram of the square maze with different patterned walls. The inner square shape depicts the pool, the surrounding circle is the larger pool within which the square pool is placed, and the rippled circle represents the curtain used to block distal cues. The broken lines represent striped walls. The small circle represents the platform on which the rat was placed (passive trials). In Probes 1 & 3 (left column), the maze had one striped wall, as was the case in all active and passive training days. In Probes 2 & 4 (right column), the maze had two adjacent striped walls. ‘Passive’ refers to training days when the rat was placed on the escape platform (no swimming). ‘Active’ refers to training days when the rat was placed in the water-maze and swam to find the escape platform.
Mentions: The present study examined the impact of perirhinal cortex lesions on the ability to discriminate mirror-imaged landmarks in order to find a submerged platform in a square water-maze. Mirror-imaged stimuli are of especial interest as they share the same elements and, hence, should be prone to interference. Although a previous study indicated that perirhinal lesions spare mirror-image discriminations [11], the training protocol was very protracted. The present study differed in two key aspects. First, it used a more rapid learning protocol [12], [13]. Second, learning was ‘passive’ in that there was no explicit reinforcement for learning the discrimination. Accordingly, rats were repeatedly placed on a partially submerged escape platform in the corner of a square water-maze where the platform location was signalled by the spatial arrangement of mirror-imaged patterns on adjacent maze walls. The particular discrimination involved those corners where striped walls and white walls met, where their relative left/right position was critical (see Fig. 1). Normal rats then swim to the escape location when first released into the water after passive training, so demonstrating their discrimination between these visual landmarks. As the animals have no experience of swimming to find the escape platform in this location prior to the probe test, this problem can only be solved by learning the correct configuration of spatial cues, rather than by simpler mediating strategies involving individual stimuli (e.g. swim to the striped wall and turn right, see Fig. 1) that could be acquired during active training [12]. The key question was whether perirhinal cortex damage would disrupts rats’ ability to identify the correct configuration given the presence of common cues with shared features.

View Article: PubMed Central - PubMed

ABSTRACT

Loss of perirhinal cortex spares mirror-imaged landmark discriminations.

Perirhinal cortex lesions do not disrupt latent spatial learning.

Further underlines dissociation between perirhinal and hippocampal function.

Further underlines dissociation between perirhinal and hippocampal function.

No MeSH data available.