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The anterior thalamus provides a subcortical circuit supporting memory and spatial navigation.

Jankowski MM, Ronnqvist KC, Tsanov M, Vann SD, Wright NF, Erichsen JT, Aggleton JP, O'Mara SM - Front Syst Neurosci (2013)

Bottom Line: The extensive direct and indirect hippocampal-anterior thalamic interconnections and the presence of theta-modulated cells in both sites further support the hypothesis that these structures constitute a neuronal network crucial for memory and cognition.Here, we discuss the electrophysiological properties of cells in the ATN with an emphasis on their role in spatial navigation.In addition, we describe neuroanatomical and functional relationships between the ATN and hippocampal formation.

View Article: PubMed Central - PubMed

Affiliation: Trinity College Institute of Neuroscience, Trinity College Dublin Dublin 2, Ireland.

ABSTRACT
The anterior thalamic nuclei (ATN), a central component of Papez' circuit, are generally assumed to be key constituents of the neural circuits responsible for certain categories of learning and memory. Supporting evidence for this contention is that damage to either of two brain regions, the medial temporal lobe and the medial diencephalon, is most consistently associated with anterograde amnesia. Within these respective regions, the hippocampal formation and the ATN (anteromedial, anteroventral, and anterodorsal) are the particular structures of interest. The extensive direct and indirect hippocampal-anterior thalamic interconnections and the presence of theta-modulated cells in both sites further support the hypothesis that these structures constitute a neuronal network crucial for memory and cognition. The major tool in understanding how the brain processes information is the analysis of neuronal output at each hierarchical level along the pathway of signal propagation coupled with neuroanatomical studies. Here, we discuss the electrophysiological properties of cells in the ATN with an emphasis on their role in spatial navigation. In addition, we describe neuroanatomical and functional relationships between the ATN and hippocampal formation.

No MeSH data available.


Related in: MedlinePlus

The color-coded diagram presents the main direct connections of the anterodorsal (AD), anteroventral (AV), and anteromedial (AM) thalamic nuclei in the rat brain. Black arrows depict reciprocal connections, green efferents, and red afferents of the three anterior thalamic nuclei (ATN). Structures in blue contain head direction cells, and so constitute a part of the hierarchically organized head direction system (Clark and Taube, 2012). The various indirect connections of the ATN, along with the connections between other highlighted structures, are not included in this scheme.
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Figure 2: The color-coded diagram presents the main direct connections of the anterodorsal (AD), anteroventral (AV), and anteromedial (AM) thalamic nuclei in the rat brain. Black arrows depict reciprocal connections, green efferents, and red afferents of the three anterior thalamic nuclei (ATN). Structures in blue contain head direction cells, and so constitute a part of the hierarchically organized head direction system (Clark and Taube, 2012). The various indirect connections of the ATN, along with the connections between other highlighted structures, are not included in this scheme.

Mentions: The ATN sits in the middle of a complex array of cortical and subcortical connections (Figure 2). Examples include the widespread links with frontal cortical areas, much of the cingulate cortex, and the hippocampal formation (Amaral and Cowan, 1980; Hicks and Huerta, 1991; Van Groen and Wyss, 1995). Many of these connections are reciprocal (Shibata and Naito, 2005). Especially dense inputs to the ATN arise from the retrosplenial cortex, the subiculum, and the mammillary bodies (Wright et al., 2010); the latter reach the thalamus via the mammillothalamic tract. The mammillary body inputs are particularly notable as it appears that almost every neuron within the structure projects to the ATN (Hopkins, 2005; Vann et al., 2007; Aggleton et al., 2010). However, the various projections to the ATN are often topographically specific (Wright et al., 2013). Previous rodent and primate studies had indicated that separate cell groups in the subiculum project to either the mammillary bodies or the anterior thalamus (Naber and Witter, 1998; Ishizuka, 2001; Aggleton et al., 2005). Wright et al. (2010) investigated this specificity and found distinct bands of projection to each area, i.e., the inputs are segregated. This same pattern of segregation extends to the inputs to the anteroventral and anteromedial nuclei, which often arise from the same structure but rarely from the same cells (Wright et al., 2013). The finding that the direct hippocampal projections to the mammillary bodies and ATN rely on the fornix (Aggleton et al., 2005, 2010; Saunders et al., 2005) is important as it has a direct bearing on how the impact of fornix damage upon cognition is interpreted (Tsivilis et al., 2008). A brief summary of some of the connections involving the different nuclei in the rodent anterior thalamus is summarized as follows (see also Figure 2):


The anterior thalamus provides a subcortical circuit supporting memory and spatial navigation.

Jankowski MM, Ronnqvist KC, Tsanov M, Vann SD, Wright NF, Erichsen JT, Aggleton JP, O'Mara SM - Front Syst Neurosci (2013)

The color-coded diagram presents the main direct connections of the anterodorsal (AD), anteroventral (AV), and anteromedial (AM) thalamic nuclei in the rat brain. Black arrows depict reciprocal connections, green efferents, and red afferents of the three anterior thalamic nuclei (ATN). Structures in blue contain head direction cells, and so constitute a part of the hierarchically organized head direction system (Clark and Taube, 2012). The various indirect connections of the ATN, along with the connections between other highlighted structures, are not included in this scheme.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3757326&req=5

Figure 2: The color-coded diagram presents the main direct connections of the anterodorsal (AD), anteroventral (AV), and anteromedial (AM) thalamic nuclei in the rat brain. Black arrows depict reciprocal connections, green efferents, and red afferents of the three anterior thalamic nuclei (ATN). Structures in blue contain head direction cells, and so constitute a part of the hierarchically organized head direction system (Clark and Taube, 2012). The various indirect connections of the ATN, along with the connections between other highlighted structures, are not included in this scheme.
Mentions: The ATN sits in the middle of a complex array of cortical and subcortical connections (Figure 2). Examples include the widespread links with frontal cortical areas, much of the cingulate cortex, and the hippocampal formation (Amaral and Cowan, 1980; Hicks and Huerta, 1991; Van Groen and Wyss, 1995). Many of these connections are reciprocal (Shibata and Naito, 2005). Especially dense inputs to the ATN arise from the retrosplenial cortex, the subiculum, and the mammillary bodies (Wright et al., 2010); the latter reach the thalamus via the mammillothalamic tract. The mammillary body inputs are particularly notable as it appears that almost every neuron within the structure projects to the ATN (Hopkins, 2005; Vann et al., 2007; Aggleton et al., 2010). However, the various projections to the ATN are often topographically specific (Wright et al., 2013). Previous rodent and primate studies had indicated that separate cell groups in the subiculum project to either the mammillary bodies or the anterior thalamus (Naber and Witter, 1998; Ishizuka, 2001; Aggleton et al., 2005). Wright et al. (2010) investigated this specificity and found distinct bands of projection to each area, i.e., the inputs are segregated. This same pattern of segregation extends to the inputs to the anteroventral and anteromedial nuclei, which often arise from the same structure but rarely from the same cells (Wright et al., 2013). The finding that the direct hippocampal projections to the mammillary bodies and ATN rely on the fornix (Aggleton et al., 2005, 2010; Saunders et al., 2005) is important as it has a direct bearing on how the impact of fornix damage upon cognition is interpreted (Tsivilis et al., 2008). A brief summary of some of the connections involving the different nuclei in the rodent anterior thalamus is summarized as follows (see also Figure 2):

Bottom Line: The extensive direct and indirect hippocampal-anterior thalamic interconnections and the presence of theta-modulated cells in both sites further support the hypothesis that these structures constitute a neuronal network crucial for memory and cognition.Here, we discuss the electrophysiological properties of cells in the ATN with an emphasis on their role in spatial navigation.In addition, we describe neuroanatomical and functional relationships between the ATN and hippocampal formation.

View Article: PubMed Central - PubMed

Affiliation: Trinity College Institute of Neuroscience, Trinity College Dublin Dublin 2, Ireland.

ABSTRACT
The anterior thalamic nuclei (ATN), a central component of Papez' circuit, are generally assumed to be key constituents of the neural circuits responsible for certain categories of learning and memory. Supporting evidence for this contention is that damage to either of two brain regions, the medial temporal lobe and the medial diencephalon, is most consistently associated with anterograde amnesia. Within these respective regions, the hippocampal formation and the ATN (anteromedial, anteroventral, and anterodorsal) are the particular structures of interest. The extensive direct and indirect hippocampal-anterior thalamic interconnections and the presence of theta-modulated cells in both sites further support the hypothesis that these structures constitute a neuronal network crucial for memory and cognition. The major tool in understanding how the brain processes information is the analysis of neuronal output at each hierarchical level along the pathway of signal propagation coupled with neuroanatomical studies. Here, we discuss the electrophysiological properties of cells in the ATN with an emphasis on their role in spatial navigation. In addition, we describe neuroanatomical and functional relationships between the ATN and hippocampal formation.

No MeSH data available.


Related in: MedlinePlus