Problemas y conflictos detectados en la promoción de la agenda cultural

Cytoarchitecture and Cellular Neurochemistry

The anterior dorsal ventricular ridge is a pallium-derived structure unique to reptiles (including avian reptiles) (24, 51). It is made up of three concentric zones: a periventricular zone with scarce cells, an intermediate zone of cell clusters, and central cell-poor zone (131-133). In addition, the anterior dorsal ventricular ridge can be divided medially to laterally into three cytoarchitectonic regions. In some species, the medial may not have a clear laminar organization, or may have a narrow periventricular zone and an intermediate zone cell clusters populated with small cells (131-134). The intermediate region has been described as having a wide or narrow periventricular zone, a wide intermediate zone of small cell clusters that have either small, medium or large cell bodies, and a central cell-poor zone (131, 133, 134). The lateral region has been described as having a wide or narrow periventricular zone, a zone of very big cell

clusters, and a narrow deep zone (131, 133, 134). These conflicting descriptions are not

due to interspecific variation as they mostly come from studies on Psammodromus

algirius.

The intermediate and lateral regions are rich in calbindin-expressing neurons in their cell-cluster and deep zones (133). Unlike in the cortical regions, these cells are not GABAergic interneurons, and are likely projection neurons (133). Other neurons, expressing parvalbumin, lie in the deep zone on the border with the striatum and project their axons to the intermediate region (133). A different study found neurons that co- express nitric oxide synthase and parvalbumin; it is unclear whether these represent the same population of neurons (46, 47, 97, 135). Nitric oxide expressing neurons are most abundant in the intermediate region and in the deep zone (97). Other neurons express estrogen, progesterone, serotonin & dopamine receptors, aromatase, acetylcholine,

vitamin D3 receptors, 5-α reductase, somatostatin, the R1α regulatory kinase subunit,

and neuropeptide-Y (37-39, 41, 45, 48, 53, 57, 58, 91, 94, 95, 136).

GABAergic interneurons exist throughout the anterior dorsal ventricular ridge, though they are preferentially found in the lateral region (133). There are three populations of GABAergic neurons: those that co-express parvalbumin, those that co-express calretinin, and those in which a calcium-binding protein was not detected (133). GABAergic neurons in the periventricular zone of the lateral region express calretinin. These neurons have a single long dendrite which projects to the lateral and dorsal cortices (133). There are a few scattered calretinin-expressing cells throughout the rest of the anterior dorsal ventricular ridge (133). Interneurons expressing parvalbumin are preferentially distributed laterally and in the deep zone (133).

Connectivity and Fibrous Neurochemistry

The anterior dorsal ventricular ridge receives projections from the major sensory regions of the brain: The rotund nucleus (visual), the medial nucleus of the thalamus (auditory), and the posterior medial and the posterocentral thalamic nuclei (somatosensory) (132-134, 137). Though the rotund nucleus receives bilateral visual input, the visual region of the anterior dorsal ventricular ridge seems to receive visual information purely from the contralateral eye (137). The globus pallidus sends acetylcholinergic projections to the anterior dorsal ventricular ridge, and serotonergic,

noradrenergic and dopaminergic projections come from the brainstem, including the ventral tegmental area (102, 131). The anterior dorsal ventricular ridge has reciprocal connections with the ventromedial hypothalamus (51, 128). Fibres expressing tyrosine hydroxylase and nitric oxide form dense plexuses in the periventricular and cell cluster zones, particularly around dopamine receptor expressing neurons (53). Other fibres express cholecystokinin, neuropeptide-Y, somatostatin, and neuropeptide-FF (37, 45, 92, 96, 138). Fibres expressing calcitonin gene-related peptide innervate the lateral region, mainly in the periventricular zone (108).

Although the three sensory modalities are largely isolated in the anterior dorsal ventricular ridge, there is some evidence for sensory integration in this region (132). However, the anterior dorsal ventricular ridge is also thought to project multiple sensory modalities caudally to other regions of sensory integration, including to the striatum and the posterior dorsal ventricular ridge (51, 102, 131).

Functional Correlations

The lateral visual region receives topographic visual input into two zones that likely represent the cell-cluster and deep zones, but projections to the putative periventricular zone are not topographic (137). In both topographic zones, the upper visual field is represented anteriorly, and the lower visual field posteriorly (137). The putative cell cluster zone receptive fields, which have an inhibitory surround, are responsive to flashes of light but prefer moving light stimuli. In the putative deep zone, neurons respond to the onset and offset of light, but not to movement. These receptive fields are larger and do not have inhibitory surrounds (137). The putative periventricular region has weaker responses to visual stimuli (137). The receptive fields of neurons in the somatosensory region cover most of the contralateral body, but have regions of high and low sensitivity (137).

Metabolic activity, as measured by cytochrome oxidase expression, increases with age and social experience (139). In a species with temperature-dependent sex-determination, males incubated at a ‘feminizing’ temperature have greater metabolic capacities than males incubated at other temperatures and females incubated at the same temperature (140). Females had higher metabolic capacities, as high as males, when incubated at a

‘masculinizing’ incubation temperature (140). Castration reduces metabolic activity and testosterone implants rescue it in both males and females (141).

Furthermore, metabolic capacity is elevated in male lizards in both the central visual region and the lateral somatosensory region after repeated viewing of an individual displaying aggressive behaviours (69). Castration reduces metabolic activity and testosterone implants rescue it in both males and females (141). The anterior dorsal ventricular ridge was described as part of the “functionally connected” “sensory aggression network” which includes both the central and lateral regions as well as the rotund nucleus (69). The anterior dorsal ventricular ridge varies in volume, relatively to the rest of the pallium, across reptiles (24). This variation seems to be positively correlated with complexity in novel behaviour and social cognition (24).

Neurogenesis

Like all brain regions bordering the lateral ventricle, the anterior dorsal ventricular ridge shows neurogenesis in adults (29, 82, 85, 87, 88, 122). Neurons in the periventricular zone co-express PSA-NCAM, Tbr-1 and doublecortin (76, 79). Neurogenesis is constitutive and is similar to neurogenesis in the medial cortex, including seasonal variation in cell proliferation (82, 83). However, neuronal recruitment may be limited to the periventricular zone (75). The rate of neurogenesis in the anterior dorsal ventricular ridge, relative to neuronal density, is the highest in the telencephalon (75).