Mammillothalamic tracts and representational memory.

Thomas, Garth J.; Gash, Don M.

doi:10.1037/0735-7044.99.4.621

Cited by 38 publications

(27 citation statements)

References 12 publications

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“…Instead, the results of the present study encourage the conclusion that MTT lesions have a disproportionate in¯uence on the encoding of visuo-spatial information (Vann & Aggleton, 2003) rather than resulting in a general de®cit in encoding or using contextual information per se (see Jaffard et al, 1991). The ®nding that MTT lesions result in an initial impairment in learning a visuo-spatial contextual discrimination is consistent with studies showing that rats with MTT lesions are impaired on a variety of spatial tasks (Krieckhaus & Randall, 1968;Field et al, 1978;Thomas & Gash, 1985;Vann & Aggleton, 2003), but appear inconsistent with at least two other studies (Gabriel et al, 1995;Sziklas et al, 1996). In one of these studies, rats with mammillary body lesions were unimpaired in learning a conditional discrimination with a clear spatial component (Sziklas et al, 1996).…”

Section: Discussionsupporting

confidence: 90%

“…The finding that MTT lesions result in an initial impairment in learning a visuo‐spatial contextual discrimination is consistent with studies showing that rats with MTT lesions are impaired on a variety of spatial tasks (Krieckhaus & Randall, 1968; Field et al ., 1978; Thomas & Gash, 1985; Vann & Aggleton, 2003), but appear inconsistent with at least two other studies (Gabriel et al ., 1995; Sziklas et al ., 1996). In one of these studies, rats with mammillary body lesions were unimpaired in learning a conditional discrimination with a clear spatial component (Sziklas et al ., 1996).…”

Section: Discussionmentioning

confidence: 99%

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Lesions of the mammillothalamic tract impair the acquisition of spatial but not nonspatial contextual conditional discriminations

Vann

Honey

Aggleton

2003

Eur J of Neuroscience

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This study examined the influence of selective mammillothalamic tract lesions in rats on the acquisition of two kinds of contextual conditional discrimination: one involving two contexts (A and B) that differed in their visuo-spatial properties and another involving two contexts (C and D) that differed in temperature. In contexts A (and C) presentations of a tone were paired with food whereas presentations of a clicker were not; and in contexts B (and D) presentations of the clicker were paired with food whereas those of the tone were not. Mammillothalamic tract lesions disrupted initial acquisition of the conditional discrimination involving visual contexts (A and B), but not the formally equivalent discrimination involving thermal contexts (C and D). These results provide support for the suggestion that mammillothalamic tract lesions disrupt visuo-spatial encoding.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Lesions of the mammillothalamic tract impair the acquisition of spatial but not nonspatial contextual conditional discriminations

Vann

Honey

Aggleton

2003

Eur J of Neuroscience

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“…memory versus habit (Mishkin and Petri, 1984). and working versus reference memory (Olton and Papas, 1979: see also Kesner and Dimattia, 1987;Thomas and Gash, 1985). In each case, the former of the 2 principles refers to the type of memory mediated by the hippocampus, and the latter refers to some unknown substrate.…”

Section: Discussionmentioning

confidence: 99%

Differential effects of fornix and caudate nucleus lesions on two radial maze tasks: evidence for multiple memory systems

1989

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The present experiments were designed to examine the hypothesis that the mammalian brain contains anatomically distinct memory systems. Rats with bilateral lesions of caudate nucleus or fimbria-fornix and a control group were tested postoperatively on 1 of 2 versions of the radial maze task. In a standard win-shift version, each of the 8 arms of the maze was baited once, and the number of errors (revisits) in the first 8 choices of each trial was recorded. Fimbria-fornix rats were impaired in choice accuracy, while caudate animals were unimpaired relative to controls. Different groups of rats with similar lesions were tested on a newly developed win-stay version of the radial maze, in which the location of 4 randomly selected baited arms was signaled by a light at the entrance to each arm, and which required rats to revisit arms in which reinforcement had been previously acquired within a trial. Rats with fimbria-fornix lesions were superior to controls in choice accuracy on the win-stay radial maze task, while caudate animals were impaired relative to controls. The results demonstrate a double dissociation of the mnemonic functions of the hippocampus and caudate nucleus. Some implications of the presence of 2 memory systems in the mammalian brain are discussed.

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“…Several studies have shown that the mammillary bodies contribute to spatial memory. The mammillothalamic tracts, which connect the mammillary bodies of the brainstem with the anterior thalamic nuclei of the forebrain, are an integral segment of Papez's circuit and are critical areas in rats for discrimination that depends on representational memory (Thomas and Gash, 1985). In humans, neural structures comprising the hippocampus, the fornix, the mammillary bodies, and the anterior thalamic nuclei are considered to form an extended hippocampal system, and damage to this system results in amnesia (Aggleton and Saunders, 1997).…”

Section: Possible Significance Of C-fos Expression In the Ce And Sum mentioning

confidence: 99%

Is there tonic activity in the endogenous opioid systems? A c-Fos study in the rat central nervous system after intravenous injection of naloxone or naloxone-methiodide

2000

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This study examined the possibility that a tonic activity in the endogenous opioid systems (EO systems) exists in animals under normal conditions. In a first set of experiments, concurrent changes in behavioral responses and in the numbers of c-Fos-like immunoreactive (Fos-LI) neurons in 58 structures of the brain and lumbosacral spinal cord were analyzed in rats after systemic administration of the opioid antagonist naloxone (NAL; 2 mg/kg). Possible roles of the EO systems were inferred from changes in the numbers of Fos-LI neurons between normal rats that received either NAL or the same volume of saline. Free-floating sections were processed immunohistochemically for c-Fos protein using standard avidin-biotin complex methods. After NAL, the numbers of Fos-LI neurons were significantly increased in the area postrema; in the caudal, intermediate, and rostral parts of the nucleus tractus solitarii; in the rostral ventrolateral medulla; in the Kölliker-Fuse nucleus; in the supramammillary nucleus; and in the central nucleus of the amygdala. In a second set of experiments examining changes in c-Fos expression in the latter structures, similar increases were found after NAL but not after an equimolar dose of NAL-methiodide, a preferential, peripherally acting opioid receptor antagonist. Therefore, Fos-LI was likely triggered after blockade of central opioid receptors, but not peripheral opioid receptors, releasing neurons from EO system-mediated inhibition. The results of this study suggest the existence of a tonic activity of the EO systems exerted on a restricted number of brain regions in normal rats. This tonic activity of the EO systems may control part of the neural networks involved in cardiorespiratory functions and in emotional and learning processes.

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Mammillothalamic tracts and representational memory.

Cited by 38 publications

References 12 publications

Lesions of the mammillothalamic tract impair the acquisition of spatial but not nonspatial contextual conditional discriminations

Lesions of the mammillothalamic tract impair the acquisition of spatial but not nonspatial contextual conditional discriminations

Differential effects of fornix and caudate nucleus lesions on two radial maze tasks: evidence for multiple memory systems

Is there tonic activity in the endogenous opioid systems? A c-Fos study in the rat central nervous system after intravenous injection of naloxone or naloxone-methiodide

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