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Addition of fornix transection to frontal-temporal disconnection increases the impairment in object-in-place memory in macaque monkeys.

Wilson CR, Baxter MG, Easton A, Gaffan D - Eur. J. Neurosci. (2008)

Bottom Line: If the contribution of the fornix to scene learning is via interaction with or modulation of frontal-temporal interaction--that is, if they form a unitary system--then Fx should have no further effect when added to frontal-temporal disconnection.However, if the contribution of the fornix is to some extent distinct, then fornix lesions may produce an additional deficit in scene learning beyond that caused by frontal-temporal disconnection.The increased impairment following the addition of Fx provides evidence that the fornix and frontal-inferotemporal interaction make distinct contributions to episodic memory.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, University of Oxford, Oxford, UK. charles.wilson@psy.ox.ac.uk

ABSTRACT
Both frontal-inferotemporal disconnection and fornix transection (Fx) in the monkey impair object-in-place scene learning, a model of human episodic memory. If the contribution of the fornix to scene learning is via interaction with or modulation of frontal-temporal interaction--that is, if they form a unitary system--then Fx should have no further effect when added to frontal-temporal disconnection. However, if the contribution of the fornix is to some extent distinct, then fornix lesions may produce an additional deficit in scene learning beyond that caused by frontal-temporal disconnection. To distinguish between these possibilities, we trained three male rhesus monkeys on the object-in-place scene-learning task. We tested their learning on the task following frontal-temporal disconnection, achieved by crossed unilateral aspiration of the frontal cortex in one hemisphere and the inferotemporal cortex in the other, and again following the addition of Fx. The monkeys were significantly impaired in scene learning following frontal-temporal disconnection, and furthermore showed a significant increase in this impairment following the addition of Fx, from 32.8% error to 40.5% error (chance = 50%). The increased impairment following the addition of Fx provides evidence that the fornix and frontal-inferotemporal interaction make distinct contributions to episodic memory.

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Related in: MedlinePlus

Histological sections displaying the lesions in all three monkeys. Top half: coronal sections of the actual and reconstructed lesions of the three monkeys. The first column shows four actual Cresyl violet-stained sections at different levels taken from monkey M1. The second column shows a reconstruction coloured in red of the extent of this ablation represented on Cresyl violet-stained sections taken from a normal macaque brain. The remaining columns show similar sections and reconstructions for monkeys M2 and M3. Bottom half: detail from a coronal section from the brain of a normal monkey (Norm) where the arrow indicates the intact fornix, and similar sections from monkeys M1–M3 where the fornix has been completely transected at the level of the interventricular foramen.
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fig02: Histological sections displaying the lesions in all three monkeys. Top half: coronal sections of the actual and reconstructed lesions of the three monkeys. The first column shows four actual Cresyl violet-stained sections at different levels taken from monkey M1. The second column shows a reconstruction coloured in red of the extent of this ablation represented on Cresyl violet-stained sections taken from a normal macaque brain. The remaining columns show similar sections and reconstructions for monkeys M2 and M3. Bottom half: detail from a coronal section from the brain of a normal monkey (Norm) where the arrow indicates the intact fornix, and similar sections from monkeys M1–M3 where the fornix has been completely transected at the level of the interventricular foramen.

Mentions: Figure 2 illustrates the lesions in the three monkeys. The upper section of the figure shows four actual sections and their corresponding reconstructions on a normal monkey brain from monkey M1, along with reconstructions from monkeys M2 and M3 at the same anterior–posterior level. This method of displaying the histology better illustrates the size of the lesions, in particular the removed sulci that may not be obvious from the original sections due to collapse of overlying cortex. This upper section of Fig. 2 shows the unilateral frontal and inferotemporal ablations. These reconstructions show that, whilst there was slight sparing of posterior medial prefrontal cortex (PFC) in monkeys M1 and M3, the overall extent of the frontal ablations was as intended. With the exception of partial sparing of the lower bank of the superior temporal sulcus in monkey M1, the lesions to the inferotemporal cortex were also complete. Hence the ablations at stage FLxIT were as intended and shown in Fig. 1.


Addition of fornix transection to frontal-temporal disconnection increases the impairment in object-in-place memory in macaque monkeys.

Wilson CR, Baxter MG, Easton A, Gaffan D - Eur. J. Neurosci. (2008)

Histological sections displaying the lesions in all three monkeys. Top half: coronal sections of the actual and reconstructed lesions of the three monkeys. The first column shows four actual Cresyl violet-stained sections at different levels taken from monkey M1. The second column shows a reconstruction coloured in red of the extent of this ablation represented on Cresyl violet-stained sections taken from a normal macaque brain. The remaining columns show similar sections and reconstructions for monkeys M2 and M3. Bottom half: detail from a coronal section from the brain of a normal monkey (Norm) where the arrow indicates the intact fornix, and similar sections from monkeys M1–M3 where the fornix has been completely transected at the level of the interventricular foramen.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2327205&req=5

fig02: Histological sections displaying the lesions in all three monkeys. Top half: coronal sections of the actual and reconstructed lesions of the three monkeys. The first column shows four actual Cresyl violet-stained sections at different levels taken from monkey M1. The second column shows a reconstruction coloured in red of the extent of this ablation represented on Cresyl violet-stained sections taken from a normal macaque brain. The remaining columns show similar sections and reconstructions for monkeys M2 and M3. Bottom half: detail from a coronal section from the brain of a normal monkey (Norm) where the arrow indicates the intact fornix, and similar sections from monkeys M1–M3 where the fornix has been completely transected at the level of the interventricular foramen.
Mentions: Figure 2 illustrates the lesions in the three monkeys. The upper section of the figure shows four actual sections and their corresponding reconstructions on a normal monkey brain from monkey M1, along with reconstructions from monkeys M2 and M3 at the same anterior–posterior level. This method of displaying the histology better illustrates the size of the lesions, in particular the removed sulci that may not be obvious from the original sections due to collapse of overlying cortex. This upper section of Fig. 2 shows the unilateral frontal and inferotemporal ablations. These reconstructions show that, whilst there was slight sparing of posterior medial prefrontal cortex (PFC) in monkeys M1 and M3, the overall extent of the frontal ablations was as intended. With the exception of partial sparing of the lower bank of the superior temporal sulcus in monkey M1, the lesions to the inferotemporal cortex were also complete. Hence the ablations at stage FLxIT were as intended and shown in Fig. 1.

Bottom Line: If the contribution of the fornix to scene learning is via interaction with or modulation of frontal-temporal interaction--that is, if they form a unitary system--then Fx should have no further effect when added to frontal-temporal disconnection.However, if the contribution of the fornix is to some extent distinct, then fornix lesions may produce an additional deficit in scene learning beyond that caused by frontal-temporal disconnection.The increased impairment following the addition of Fx provides evidence that the fornix and frontal-inferotemporal interaction make distinct contributions to episodic memory.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Psychology, University of Oxford, Oxford, UK. charles.wilson@psy.ox.ac.uk

ABSTRACT
Both frontal-inferotemporal disconnection and fornix transection (Fx) in the monkey impair object-in-place scene learning, a model of human episodic memory. If the contribution of the fornix to scene learning is via interaction with or modulation of frontal-temporal interaction--that is, if they form a unitary system--then Fx should have no further effect when added to frontal-temporal disconnection. However, if the contribution of the fornix is to some extent distinct, then fornix lesions may produce an additional deficit in scene learning beyond that caused by frontal-temporal disconnection. To distinguish between these possibilities, we trained three male rhesus monkeys on the object-in-place scene-learning task. We tested their learning on the task following frontal-temporal disconnection, achieved by crossed unilateral aspiration of the frontal cortex in one hemisphere and the inferotemporal cortex in the other, and again following the addition of Fx. The monkeys were significantly impaired in scene learning following frontal-temporal disconnection, and furthermore showed a significant increase in this impairment following the addition of Fx, from 32.8% error to 40.5% error (chance = 50%). The increased impairment following the addition of Fx provides evidence that the fornix and frontal-inferotemporal interaction make distinct contributions to episodic memory.

Show MeSH
Related in: MedlinePlus