DPB - Artículos
https://hdl.handle.net/10481/51775
2024-03-29T15:41:10ZRapid decay of spatial memory acquired in rats with ventral hippocampus lesions
https://hdl.handle.net/10481/89799
Rapid decay of spatial memory acquired in rats with ventral hippocampus lesions
Jiménez Ramos, Juan Manuel
Several memory consolidation theories have proposed that following a learning situation the hippocampus gradually stabilizes labile recent memories into long-lasting remote memories. Most work in this field has focused on the dorsal hippocampus (DHip), giving little consideration to a possible contribution by the ventral hippocampus (VHip), particularly when spatial paradigms are used. However, in recent years a growing number of studies have suggested the existence of a functional continuum, related to spatial processing and navigation, along the dorsoventral hippocampal axis. For this reason, in the present study we compare the effect of DHip vs. VHip lesions on long-term spatial memory retention. Using a four-arm plus-shaped maze, rats with lesions in the DHip, VHip or sham-lesioned learned to criterion a place discrimination task based on allothetic cues. During two retraining phases (2 days and 24 days after learning) retention of the spatial information learned during the acquisition phase was evaluated. The main findings revealed no deficit 2 days after learning, but 24 days after learning both lesioned groups showed a profound impairment compared to control animals (expt. 1). In contrast, when rats learned a cue-guided navigation task in the acquisition phase, both lesioned groups performed the two retention tests, 2 days and 24 days after learning, at the same level as the control group (expt. 2). These results suggest not only that the DHip is vital, but also that normal VHip activity is critical during the post-learning period in order for a recent spatial memory to become a stable long-term memory.
Disconnection of the perirhinal and insular cortices severely disrupts taste neophobia
https://hdl.handle.net/10481/86813
Disconnection of the perirhinal and insular cortices severely disrupts taste neophobia
Jiménez Ramos, Juan Manuel
It is well known that the perirhinal (Prh) and insular (IC) cortices are reciprocally connected,
mainly through ipsilateral projections. Although some studies have demonstrated that
excitotoxic lesions to these regions, each separately, disrupt taste neophobia, it is not yet known
whether the two regions have functional interactions with one another. To find out if they form
a functional unit, we examined the effects of crossed excitotoxic lesions to the Prh and the
contralateral IC (contralateral group). This group's performance was compared to that of rats
with ipsilateral Prh and IC lesions (ipsilateral group) and to that of control-operated rats. All the
animals received a 0.3% saccharin solution for fifteen minutes on five consecutive days. Rats
with contralateral Prh-IC lesions drank significantly higher amounts of saccharin than the other
groups during the first encounter with the novel taste, indicating a disruption in neophobia.
However, the lesions did not disrupt attenuation of neophobia, with the contralateral group
reaching asymptote in trial 2 and the rest of the groups after 3-5 days of exposure to the
saccharin. These findings suggest that both Prh and IC play a necessary role in taste neophobia.
Additionally, the two cortices function interdependently and their interaction is critical for
normal expression of taste neophobia.
This work was supported by a grant from the Spanish Subdirección General de Proyectos de Investigación, Ministerio de Economía y Competitividad (Madrid, Spain) and the European Regional Development Fund – ERDF (PSI2013-41098-P).
Ventral hippocampus lesions and allocentric spatial memory in the radial maze: Anterograde and retrograde deficits
https://hdl.handle.net/10481/86741
Ventral hippocampus lesions and allocentric spatial memory in the radial maze: Anterograde and retrograde deficits
Jiménez Ramos, Juan Manuel; Morón Henche, Ignacio
Although the dorsal hippocampus (DHip) has been clearly implicated in spatial learning and memory, there is
currently debate as to whether the ventral hippocampus (VHip) is also necessary in allocentric-based navigation
tasks. To differentiate between these two subregions of the hippocampal dorsoventral axis, we examined the
effect of neurotoxic lesions to the DHip and VHip in different learning situations, using a four-arm plus-shaped
maze. In experiment 1 a spatial reference memory task was used, with results showing an acquisition deficit in
DHip-lesioned rats but perfect learning in VHip-lesioned rats. However, in experiment 2 an acquisition deficit
was found in VHip-lesioned rats using a doubly marked training protocol. In this case the position of the goal arm
during training was marked simultaneously by the extramaze constellation of stimuli around the maze and an
intramaze cue. The main results indicated that DHip and VHip groups presented significantly more allocentric
errors in the probe test than the control rats. In experiments 3 and 4, animals with their brains still intact learned,
respectively, a spatial reference memory task or a purely cue-guided navigation task, and DHip and VHip lesions
were made 2–3 days after reaching learning criterion. Results indicated a profound retrograde deficit in both
lesioned groups but only with regard to allocentric information. So, depending on the training protocol used, our
results point to increased integration and cooperation throughout the hippocampal dorsoventral axis when
allocentric learning and memory is involved. These data support the existence of a functional continuum from
the dorsal to the ventral hippocampus.
Relationship between prandial drinking behavior and supersensitivity of salivary glands after superior salivatory nucleus lesions in rats
https://hdl.handle.net/10481/86701
Relationship between prandial drinking behavior and supersensitivity of salivary glands after superior salivatory nucleus lesions in rats
Jiménez Ramos, Juan Manuel; Castillo, María Elena; Puerto Salgado, Amadeo
Prandial drinking, an increase in the number of drinking responses and secondary or non-homeostatic polydipsia
in the presence of dry food, is typically associated with a deficit in salivary secretion. This study investigates the
degree of salivary gland supersensitivity to pilocarpine administration after lesions to the superior salivatory
nucleus (SSN), the site of origin of the parasympathetic preganglionic neurons that innervate the submandibularsublingual (S-S) salivary glands. The main aim was to determine if there is a relationship between the degree of
glandular supersensitivity, as an index of secretory deficit, and the development of prandial drinking in lesioned
rats. Results showed that following SSN lesions two subgroups of rats were obtained. One subgroup exhibited
prandial drinking but the other was similar to the control group. The SSN-lesioned prandial drinking subgroup
presented significantly greater supersensitivity than the SSN-lesioned non-prandial drinking rats; the nonprandial drinking subgroup, in turn, presented significantly more supersensitivity than controls. Additionally, SS supersensitivity observed in rats that exhibited prandial drinking due to the sectioning of chorda tympani
efferent axons was compared to that observed in rats exhibiting prandial drinking due to SSN lesions. It was
found that both groups presented the same S-S supersensitivity curve. These results indicate that SSN lesions
produce a gradation of S-S supersensitivity values that appear to run parallel to the degree of glandular secretory
deficit caused by the lesions. Thus, only the rats with greater secretory deficit (greater supersensitivity) develop
prandial drinking. These data support the idea that there is in fact a functional link between the lateral reticular
formation of the brainstem (the region associated with the SSN) and S-S salivary glands.
Ministerio de Economía y Competitividad (Madrid, Spain) and the European Regional Development Fund- ERDF (PSI2010–14979 and PSI2013–41098-P)
Perirhinal cortex supports both taste neophobia and its attenuation
https://hdl.handle.net/10481/86681
Perirhinal cortex supports both taste neophobia and its attenuation
Jiménez Ramos, Juan Manuel
Rats are often reluctant to consume novel tastes because they lack knowledge about the postingestive effects the
new foods might have. This paper examines the effect of excitotoxic lesions and temporary inactivation of the
perirhinal cortex (Prh), a key region in the recognition memory system, on taste neophobia and its attenuation.
Using a two-bottle choice paradigm (saccharin vs water), excitotoxic lesions were found to disrupt taste neophobia to 0.3% and 0.5% saccharin. However, the lesions had no effect when using a concentration of 0.7%, which
is qualitatively aversive (expt. 1a-1c). In a second series of experiments the same animals were able to acquire a
flavor preference learning on the basis of a flavor-taste association. Lesioned and control rats showed, during a
choice test, a clear preference for the flavor associated with saccharin (expt. 2a-2c). Finally, in a third series of experiments, Prh inactivation with lidocaine after trial 1 (expt. 3) and after trials 1-3 (expt. 4) delayed attenuation
of the neophobia. These findings suggest that Prh lesions do not significantly affect taste processing/ perception.
Prh thus appears to play an essential role in taste neophobia and its attenuation.
This work was supported by a grant from the Spanish Subdirección General de Proyectos de Investigación, Ministerio de Economía y Competitividad (Madrid, Spain) and the European Regional Development Fund – ERDF (PSI2013-41098-P).